Brice Laurent

David Pontille

Madeleine Akrich

Stève Bernardin

Jérôme Denis

Liliana Doganova

Félix Talvard

Towards a study of city experiments

Introduction

In 2016, Singapore National Research Foundation (NRF) announced the launch of a partnership with Dassault Systems in the development of 'Virtual Singapore', a 'dynamic three-dimensional (3D) city model and collaborative data platform'. This platform would 'enable users from different sectors to develop sophisticated tools and applications for testbedding concepts and services, planning and decision-making, and research on technologies to solve emerging and complex challenges for Singapore.' 1 The same year in San Francisco, the Municipal Transportation Authority (SFMTA) was testing the new features of its mobile application, called MuniMobile, in partnership with a non-profit organization, yet closely tied to investment funds City Innovate Foundation. These new features would allow it to optimize the gathering of data related to mobility practices in San Francisco, and possibly use them to introduce incentives designed to nudge people into using transportation systems in such a way that it would alleviate pervasive congestion problems.

These two examples can be seen as almost perfect illustrations of the current trend to try and create smart cities. These initiatives are based on the production, manipulation and circulation of large amounts of data. They are tied to new understanding of how to act on the city, by targeting urban issues, and providing solutions to challenges, such as pollution and waste management, ageing and health services, or public transportation and mobility practices. As they rely on close associations between public bodies and private entities, these initiatives might redefine not only the city's modes of governing, but also the urban political identities, as citizens in Singapore might be offered new ways to intervene in issues that matter to them, and San Francisco inhabitants might be turned into economic agents optimizing their choices according to the incentives that their transportation app provides them. The 'smartness' of these examples is problematic though. Are these projects connected to concrete realizations or mere flagship announcements that serve window dressing objectives? In what ways are the data on which they rely being used in a 'smart' manner? As we encountered these cases in the context of a research project on urban innovation, 2 we gradually displaced the problematic 'smart' label in order to be able to ask other questions: How to analyze them, not as standalone innovative projects, but as components of a wider evolution in urban policies? How are these initiatives connected to the political and economic ordering of the city? What do they tell us about potential alternatives being left out in that process? In this chapter, we argue that a way to approach these questions is to set aside, at least temporarily, the 'smart' label, and study cases such as Virtual Singapore or San Francisco's transportation app as 'city experiments'. We use the expression 'city experiments' to point to situations of urban life where experiments are conducted which directly engage the nature of the city itself. A growing literature has been focusing on 'urban experimentations' [START_REF] Evans | The Experimental City[END_REF], and is an invitation to analyze the means through which experiments can be empirical and theoretical entry points for the study of contemporary urban transformations. The focus on city experiments, we argue, is a way of studying these transformations without taking the claim of novelty at face value, while also reflecting on the possibility for replication, extension, and possibly widespread deployment. This chapter builds on the two case studies briefly introduced above to explore the analytical interest of the study of city experiments. We start by discussing why these two initiatives can be considered as 'city experiments', and what the analytical consequences of this notion are. We then break down the components of city experiments, again illustrating them with these two cases. Finally, we discuss the analytical value of studying city experiments.

Investigating city experiments

Two experimental situations

The vocabulary of experiments has become a pervasive trope in the contemporary urban discourse. The two examples briefly introduced above can be seen as illustrations of this trend. 'Virtual Singapore' is expected to provide a digital infrastructure through which 'concepts and services' can be 'test-bedded'. Singapore National Research Foundation states that this project offers possibilities for 'virtual experimentation' (e.g. exploring 4G coverage), and 'virtual test-bedding to validate the provision of services' (e.g. modelling crowd dispersion). 3 Here, the simulated environment can be used to test possible scenarios and/or explore in virtual ways the consequences of a particular situation. For instance, as the person in charge of Virtual Singapore showed us during an interview: the Dassault Systems' 3D Experience tool is meant to simulate a variety of situations such as a leak in the natural gas network supply and its spreading in a building (meant to determine, by drawing on various behavioural models, the best evacuation plan that would be implemented depending on the profile of inhabitants in the area); a shorttime sales operation in a mall (requiring testing the speed and direction of escalators); the positioning of rooftop solar panels (to find out their profitability according to their exposure to certain weather conditions). (A.P., Dassault Systems, 15 February 2017) In these virtual experiments, 3D visualization is key to envision a series of scenarios generated by the combination of various datasets. When we met the people in charge of Virtual Singapore at Dassault Systems, they also underlined another dimension of the test, namely that the platform itself, and its components, was experimented with in the process. In San Francisco, the language of experiments is a recurrent part of the official discourse of public bodies like the SFMTA. The experimental dimension of the MuniMobile App was explicit in the initial testing phase, which was managed by a dedicated private company, and during which self-registered users tested a beta version and offered feedback to the SFMTA. 4But the experiment extends far beyond the initial testing phase of the app. Once in place, the app offers a platform gathering data, which can be used to test various mechanisms related to pricing and incentives. As the person in charge of innovation at the SFMTA said to us during an interview:

We're experimenting with what the customers actually care about -what they care about is getting free things. We call that gamification. We don't have the money to pay for these things so we think the right approach is to partner with the private sector and have them do it.

(T.P., SFMTA Office of Innovation, 10 February 2016) For all their differences, Virtual Singapore and Muni Mobile share a dual dimension of the experimental platform. On the one hand, they are meant to serve as infrastructures on which various tests can be conducted. On the other hand, they are also meant to be tested as platforms supposed to be designed to optimize urban interventions.

Experiments as an analytical category

In these two cases, the language of experiments is that of the actors involved. We see this pervasiveness as an invitation to theorize the notion of experiments, and use it as an analytical category. While this move can build on the recent literature of cities and urban innovation [START_REF] Gieryn | City as Truth-Spot: Laboratories and Field-Sites in Urban Studies[END_REF][START_REF] Halpern | Test-bed urbanism[END_REF][START_REF] Laurent | A Field Test and its Displacements. Accounting for an Experimental Mode of Industrial Innovation[END_REF]Tironi and Sànchez Criado 2015;[START_REF] Evans | The Experimental City[END_REF][START_REF] Kitchin | The Ethics of Smart Cities and Urban Science[END_REF], we take our inspiration here from a series of work in STS that has discussed the politics of experiments. Early works in the field considered experiments as operations that simultaneously act on the production of knowledge and social ordering. Shapin and Schaffer's seminal study of the nascent experimental physics in 17th century England [START_REF] Shapin | Leviathan and the Air-Pump: Hobbes, Boyle, and the Experimental Life[END_REF] and detailed studies of practices of testing [START_REF] Pinch | Testing -One, Two, Three … Testing': Toward a Sociology of Testing[END_REF] have been followed by studies that have extended the discussion of experiments to situations where economists test, in vitro or in vivo, their theories or models thereby re-arranging the economy itself [START_REF] Callon | Civilizing Markets: Carbon Trading Between in Vitro and in Vivo Experiments[END_REF][START_REF] Mitchell | The Work of Economics: How a Discipline Makes its World[END_REF], protesters reinvent the forms of political activism [START_REF] Barry | Demonstrations: Sites and Sights of Direct Action[END_REF][START_REF] Doubleday | Despotism and Democracy in the UK: Experiments in Reframing Relations Between the State, Science and Citizens[END_REF], experts test 'technologies of democracy' [START_REF] Lezaun | Consulting Citizens: Technologies of Elicitation and the Mobility of Publics[END_REF][START_REF] Laurent | Technologies of Democracy: Experiments and Demonstrations[END_REF], and users of mundane technologies make sustainable development a matter of personal experience [START_REF] Marres | Material Participation: Technology, the Environment and Everyday Publics[END_REF]. We do not want to provide a detailed review of the rich STS literature on experiments, but rather point to a few lessons that are directly useful for our study of cases, such as Virtual Singapore or San Francisco's MuniMobile. First, experiments associate a sociotechnical apparatus with demonstration practices, for the sake of a learning objective [START_REF] Barry | Demonstrations: Sites and Sights of Direct Action[END_REF][START_REF] Rosental | Toward a Sociology of Public Demonstrations[END_REF]). Crucial to this collective production of knowledge are the ways in which the heterogeneous components of the apparatus are specifically assembled and the demonstration practices are actually performed. Second, experiments can be 'economic' in that they participate in the making of markets [START_REF] Callon | Economic Experiments and the Construction of Markets[END_REF], and 'political' in that they are components of democratic ordering processes [START_REF] Laurent | Political Experiments that Matter: Ordering Democracy from Experimental Sites[END_REF]. Virtual Singapore and MuniMobile can be seen as both 'economic' and 'political' experiments in that they engage both the elaboration of markets and the would-be appropriate mode of intervention of the city's public bodies. Third, the study of experiments is neither 'micro' nor 'macro', but focuses on the association between the apparatus making the test possible and the spaces that are re-ordered to make its validation possible [START_REF] Callon | Unscrewing the Big Leviathan; or How Actors Macrostructure Reality, and How Sociologists Help Them to Do So?[END_REF][START_REF] Latour | Give Me a Laboratory and I Will Raise the World[END_REF][START_REF] Laurent | Political Experiments that Matter: Ordering Democracy from Experimental Sites[END_REF]. Thus, understanding Virtual Singapore as an experiment requires that one connects the test conducted on the platform with the audiences they are expected to convince, including foreign companies that Singapore's government might hope to attract, or investors eager to fund potentially lucrative technological developments. Similarly, San Francisco's MuniMobile cannot be understood as an experiment without accounting for the ecology of actors involved in the design of the app, its successive tests, and the distinct audiences assembled.

City experiments

We use the important body of STS work devoted to experiments to see Virtual Singapore and San Francisco's MuniMobile as 'city experiments'. The expression points to the fact that these initiatives are urban-related projects intended to explicitly serve as tests, arranged to produce new knowledge that remains at least partly uncertain, and tied to public demonstrations.

In the course of these tests, the city itself (or part thereof) is experimented with: whether it is a virtual representation of the city expected to determine future urban organization (e.g. in designing emergency routes), or a transportation test eventually re-routing flows of passengers, any city experiment envisions, explicitly or not, a peculiar definition of the future, and a redesigned and reordered city (e.g. easily manageable, congestion free, etc.) at the core of the test itself. Echoing the ways in which the Chicago School made Chicago a laboratory and a field-site [START_REF] Park | The City as a Social Laboratory[END_REF][START_REF] Gieryn | City as Truth-Spot: Laboratories and Field-Sites in Urban Studies[END_REF]), these projects are entry points for us to develop an analysis of contemporary forms of urban organizations, in their political and economic dimensions. Such an approach comes with descriptive questions orienting the investigations: What is tested in practice? Who are the experimenters? In which site(s) and experimental conditions are the tests conducted? What are the audiences addressed by the public demonstrations? Who is expected to certify results?

The components of city experiments

Analyzing urban initiatives such as Virtual Singapore or MuniMobile as city experiments implies that we account for a series of components of these projects. In this section, we break down city experiments and discuss their components.

Experimenters

All experiments need experimenters, and city experiments are no exception. But the identity of these experimenters might be more distributed in the latter. In San Francisco, the tests developed with MuniMobile not only associate the SFMTA and the City Innovate Foundation, but also a wide range of private transportation providers such as Uber, Lyft and the local group rideshare company Chariot, and service companies as well (such as Waze or other apps). Virtual Singapore associates a private company, Dassault Systems, and a public body, the National Research Foundation, in the development of the platform. Who might then use it to test 'concepts and services' is still uncertain, but may comprise many different actors. Other examples in Singapore have shown that public bodies might be keen to call for diverse actors to use urban data to test technologies. For instance, the Jurong Lake District has been conceived of as a 'smart district' aimed to make data available for companies, start-ups, or individuals to develop technological 'solutions'. 5 The language of 'solutions' here points to problems that are not yet identified, but could be so thanks to the intervention of a wide range of actors having expertise related to housing, transportation, healthcare, etc. For all the possibility of a diversity of experimenters to intervene, city experiments are also strongly dependent on the ability to restrain the perimeter of who is expected to act as experimenters. In Singapore, the circulation of data is problematic. During an interview, a scientist in charge of numerous data production and analysis projects at the Jurong Lake District spoke of an 'Asian point of view'6 as he referred to the ways in which open data protocols were used in Singapore, as he stressed that making urban data available was also counter-balanced by an active control of their circulation and use. Other kinds of tension are visible in San Francisco, as the tests conducted by the City Innovate Foundation are meant to use data provided by private companies eager to benefit from their economic value, and reluctant to make them widely available. While the political value of data is what makes their circulation problematic in Singapore, it is their economic value that makes it so in San Francisco -a tension that has been dealt with by introducing third party contracts to regulate data circulation. 7Experimental subjects and objects Experiments operate on entities that are made experimental, possibly by cutting their ties, standardizing them, making them comparable with each other [START_REF] Latour | Science in Action. How to Follow Scientists and Engineers through Society[END_REF]. In city experiments, the entities that are experimented with might be technical systems of data acquisition, pricing mechanisms, or human behaviors. Thus, city experiments shape political objects, whether market objects [START_REF] Callon | The Economy of Qualities[END_REF] or objects of government [START_REF] Lezaun | Creating a New Object of Government: Making Genetically Modified Organisms Traceable[END_REF], such as testable scenarios and the virtual platform that Virtual Singapore relies on. In doing so, they also manufacture political subjects, such as citizens turned into economic agents expected to make real-time decisions in San Francisco [START_REF] Laurent | Real-Time Democracy. Imagining the City of Permanent Innovation[END_REF], or citizens framed as 'smart, efficient subjects' within the Smart Nation program in Singapore [START_REF] Ho | Smart Subjects for a Smart Nation? Governing (Smart) Mentalities in Singapore[END_REF]. Virtual Singapore can operate only if data are available, and this also involves participating inhabitants. Some data layers of the Virtual Singapore Platform have been completed by distributing 40,000 individual sensors to students. These sensors collected data about the students' geolocalized displacements, the noise they were exposed to, or the wifi coverage and connectivity they experienced from one place to another. Thus, Singapore's inhabitants become part of the experiments, as crucial components of the infrastructure required to make the laboratory work. The MuniMobile app also calls for various kinds of data related to the use of public transport among the municipal network (subways, tramways, buses and trolleys), so that riders can plan their journeys, knowing the transit times of vehicles to a particular stop. To make such data available in real-time, for instance, the precise position of buses is detected with an algorithm calculating an estimation from previous rides on the same line and information remotely provided by the vehicle thanks to GPS tracking tools. Thus, each bus is not a mere transportation vehicle anymore, but also becomes a key data provider, and as such part of the experiment.

Laboratories

The 'laboratorization' of the world [START_REF] Latour | Science in Action. How to Follow Scientists and Engineers through Society[END_REF][START_REF] Callon | Genèse et circulation des faits scientifiques[END_REF]) is particularly well illustrated in the city, as parts of the urban space are turned into testing grounds [START_REF] Karvonen | Urban Laboratories: Experiments in Reworking Cities[END_REF][START_REF] Evans | The Experimental City[END_REF] or entire cities are erected from scratch as test-beds [START_REF] Halpern | Test-bed urbanism[END_REF]). Exploring the laboratories on which city experiments occur means that one is attentive to, at least, the following elements. First, and contrary to scientific laboratories where secluded research is performed [START_REF] Callon | Acting in an Uncertain World: An Essay on Technical Democracy[END_REF], the laboratories where city experiments are conducted are part of what is tested [START_REF] Coletta | Open-Ended and Continuous Urban Experimentation Through Networked Big Data Infrastructures: the Case of LPWANs[END_REF]. Virtual Singapore and MuniMobile are less stable data systems serving as infrastructural background for future tests than sociotechnical apparatus in the making, which might evolve significantly according to the outcomes of city experiments. Second, analyzing the laboratories of city experiments requires an attention to the spatial organization of the city. In San Francisco, it helps point to an emerging understanding of city organization in terms of permanently evolving flows (of people, cars and other means of transportation) that are supposed to be managed in real-time. This 'real-time' reorganization construes the space of the city as a permanently revised outcome of optimization operations [START_REF] Kitchin | The Real-Time City? Big Data and Smart Urbanism[END_REF]. As such, it can be opposed to long-term planning, which sees the spatial organization of the city as a long-term intervention on costly material elements [START_REF] Laurent | Real-Time Democracy. Imagining the City of Permanent Innovation[END_REF]. Virtual Singapore offers an illustration of the articulation between virtual and physical spaces. While the boundaries of the virtual laboratory seem neatly defined, as they separate the virtual world from the material one, the articulation between the two is crucial. Gathering data requires that a network of sensors is extended across the city, possibly through the help of inhabitants (see above). The virtual space is less a digital representation of a physical city than a reconstruction of another space, part virtual and part material, that is meant to be a laboratory. Third, investigating the boundaries of city experiments' laboratories allows us to identify framing operations and subsequent overflowings [START_REF] Callon | An Essay on Framing and Overflowing: Economic Externalities Revisited by Sociology[END_REF], and offer an analytical path to consider entities that do not fit with the standardization process of the tests, and that eventually are cast out [START_REF] Star | Power, Technology and the Phenomenology of Conventions: on Being Allergic to Onions[END_REF]. Organizing Virtual Singapore as a laboratory supposes that elements that cannot be measured by the network of sensors on which it relies are left out. Turning San Francisco into a 'real-time city' makes the whole city a laboratory in a way that imagines the role of public bodies (including above all the municipal transportation authorities) as coordinators able to ensure that supplies and demands of urban services are permanently optimized. To most of these public bodies, such a perspective is often framed as an alternative to costly and controversial long-term public investment in transportation infrastructures [START_REF] Laurent | Real-Time Democracy. Imagining the City of Permanent Innovation[END_REF]. It indeed frames the role of public authorities in a way that excludes long-term action.

Audiences

There is no city experiment without associated demonstrations. City experiments, like other experiments [START_REF] Shapin | Leviathan and the Air-Pump: Hobbes, Boyle, and the Experimental Life[END_REF][START_REF] Barry | Demonstrations: Sites and Sights of Direct Action[END_REF][START_REF] Rosental | Toward a Sociology of Public Demonstrations[END_REF], need to assemble an audience expected to attest that their outcomes have value. Simulations in Singapore offer a virtual platform for the production of public proofs addressed to a community of experimenters made of government bodies eager to ground their intervention in the urban environment on tested (if virtual) facts. The audience of the tests is not limited to government bodies though. Another audience is envisioned by the simulations' designers, namely potential stakeholders of the initiative being tested. Eventually, and in line with longstanding practices of collaboration between foreign companies and Singapore's government [START_REF] Akrich | Can an Island Nation Be a Global Test-Bed? The Politics of Experimentation in Singapore[END_REF], Virtual Singapore also serves as a demonstration addressed to customers and investors whereby Dassault System may publicly prove the value of its expertise. In San Francisco, the MuniMobile experiment is meant to produce proofs for transportation managers to act on pricing mechanisms and transportation administration. In a similar fashion as Dassault Systems, the City Innovate Foundation is also a global actor involved in different places and using interventions in one site as a demonstration of what it can do in another. As such, the tests are also meant for all the experimenters involved to provide demonstrations of their ability to act on the city. Examining the audience component of city experiments offers a way out of two of the difficulties we might encounter when studying smart cities. First, when analyzing audiences, there is little room for asking questions such as whether or not the initiatives at stake are 'mere hype'. As they necessarily comprise the assemblage of public proofs, and an external gaze to witness them, city experiments are necessarily construed as 'hype'. What matters then, for both the actors involved and the analysts studying them, is less whether or not this 'hype' has 'real' grounds than who it manages to convince, convey and eventually transform, and by what means. Second, the study of city experiments' audiences offers an opportunity to avoid questions related to whether the analysis is (or should be) 'micro' or 'macro', 'local' or 'global'. As one cannot understand city experiments without accounting for the audiences that they assemble, they are part of particular spaces within which they are expected to have value. This latter point leads us to our final reflection. We can now get back to our initial questions, and discuss the ways in which the analysis of city experiments offers us a path to answer them.

How do city experiments matter, and to whom?

After having characterized Virtual Singapore and MuniMobile as city experiments, and broken down their components, we can now explore how the analysis of city experiments helps us answer our initial questions: How to analyze city experiments, not as standalone innovative projects, but as components of wider evolutions of urban policies? How are these initiatives connected to the political and economic ordering of the city? What do they tell us about potential alternatives being left out in that process? A way of approaching these questions is to explore how city experiments matter, and to whom. Of course, this is a question raised by the actors themselves, but it is also relevant as an analytical interrogation, in order to identify relevant sites where contemporary cities are transformed. Studying how city experiments matter and to whom is also a way of examining a crucial issue: are these experiments only first steps before larger deployment? Or can one identify a mode of governing cities that would be characterized by a permanent experimental state? San Francisco and Singapore provide elements that lead us to the second half of this alternative, yet in ways that significantly differ.

San Francisco and real-time democracy

The variety of experimenters intervening in the MuniMobile initiative consider it important in that it takes part in a renewed understanding of the urban organization. Indeed, they naturally connect it to a diversity of city experiments in San Francisco. When we interviewed the head of SFMTA's innovation office, he immediately invited us to talk with some of his colleagues at the Office of Civic Innovation at San Francisco city hall. There, he told us, we could complete our understanding of why initiatives such as those he had just presented to us were important in San Francisco. At the Office of Civic Innovation, which was created in 2012 in the wake of the election of the late Edwin Lee as mayor of San Francisco, we were presented with a series of initiatives aimed to test potential solutions to urban problems, through various partnerships with start-ups, thanks to a new Open Data program. In San Francisco, we encountered other initiatives undertaken by the SFMTA, often in partnership with other public bodies, and meant to act in adaptive ways. Programs such as 'pavement to parks', 'a collaborative effort between the San Francisco Planning Department, the Department of Public Works, and the Municipal Transportation Agency',8 seek to involve local inhabitants in the test of small-scale urban infrastructures in dedicated areas of public space. As we studied the experimenters of the MuniMobile experiment, the entities that were being tested, the laboratory that it relied on, and the audiences it assembled, we were drawn to other city experiments. MuniMobile mattered in that it was connected to these other initiatives, which together aim to turn San Francisco into a self-proclaimed 'capital of innovation', where urban problems and solutions are permanently re-defined and re-adjusted. In this context, city experiments are not just primary trials before a definitive extension of a given technical solution, but technologies of government [START_REF] Rose | Political power beyond the State: Problematics of Government[END_REF]. They are the tools whereby public bodies act on people, and which turn them into particular political subjects, namely individual ones expected to contribute to the identifications of urban problems and solutions. Understanding this was not only a way to re-situate city experiments, but also to better understand the nature of the political, economic and material ordering at stake in the 'capital of innovation'. If MuniMobile is indeed a component of a 'real-time city', what the set of initiatives in which it is situated draws is a type of ordering that makes the real-time adjustment of urban problems and solutions the core task for governing the city. One can see here a problematization of the sources of democratic legitimacy, as well as a proposition for the identification of the active participants of urban life -namely those who mobilize to make urban problems explicit, and/or propose solutions to them. The 'real-time democracy' that emerges here [START_REF] Laurent | Real-Time Democracy. Imagining the City of Permanent Innovation[END_REF] is also the outcome of economic ordering processes, as private actors make urban issues a new source of market demand, and, perhaps more fundamentally, as inhabitants are expected to adopt economic modes of reasoning, following incentives, or acting as entrepreneurs to propose new solutions for urban problems.

Singapore and the making of a global laboratory

In Singapore, projects based on simulating the city, or part thereof, in which government bodies are engaged not only comprise Virtual Singapore, but also a modelling tool developed by the French company EDF in collaboration with the House and Development Board (HDB), and various modelling initiatives conducted at the Singapore MIT Alliance for Research and Technology (SMART) in partnership with government bodies such as the Land Transport Authority. The number of these projects, the networks of sensors on which they rely, the sheer amount of data they gather, and their integration into a 'Smart Nation' program might well be components of what a recent book characterizes as a 'smart state' [START_REF] Calder | Singapore: Smart City, Smart State[END_REF], thereby re-affirming what others had claimed in the early days of the smart city trend, that Singapore had the potential to become the model smart city [START_REF] Mahizhnan | Smart Cities: the Singapore Case[END_REF]. Whether or not this is indeed the case is less important here than what the city experiment lens allows us to account for. A first straightforward remark is that alongside Virtual Singapore aimed at simulating the entire city, other projects offer more detailed information on some features, such as the EDF simulation, which aims to serve as a platform for HDB to test building innovation, and for local stakeholders to confront various choices related to building layout. These other simulation projects could be described using the same categories as those discussed in the previous section. We would then be led to examine connections between these various city experiments, as, for instance, public bodies are involved in several of them, or companies compete to attract would be customers or investors. What emerges then is a desirable horizon of intervention for the Singapore public bodies, whereby simulation would offer a technological tool on which to base the government of the city, for the sake of political subjects expected not only to be passive simulated entities, but also contributors to the collection of data and as would-be users of the platform. As real-time democracy in San Francisco is an outcome of both political and economic ordering processes, this type of political ordering is also economic. Indeed, the value of Virtual Singapore for the actors involved is tied to another laboratory that emerges from the collection of city experiments, namely the island of Singapore itself. While global companies use the city of Singapore as a test-bed for experimenting with their technologies (here simulation methods), public bodies deliberately use the characterization of Singapore as a laboratory to attract these companies. The analysis of Virtual Singapore is thus not only that of a single city experiment, but leads us to reflect on the aggregation of them, and eventually on the making of Singapore as the outcome of deliberate experimental strategies. These experimental strategies have been tied to the definition of Singapore as an independent citystate, able to become a global laboratory for multinational corporations to test their technologies. They are now part of a redefinition of Singapore's instruments of government to include virtual tools. Singapore offers yet another case where city experiments are not a first step before mainstreaming, but a central component of how the city is expected to be governed. But whereas San Francisco provided an illustration of techniques of government based on real-time interventions, Singapore makes experiments a condition for the city-state to ensure its long-term stability.

Alternative cities

The political and economic ordering processes that we identified out of the Virtual Singapore and MuniMobile cases are also choices for the desirable city, which have little reason to be consensual and/or uniformly stable. In San Francisco, the affirmation of innovation as an engine for urban life is often met by scepticism, if not violent protest. The city experiments we mention can be contrasted with others, performed by concerned groups and activists (De Kosnik 2014; Maharawal 2014), and perhaps best understood as counter-experiments. Activists protesting the gentrification of the city have been active in the 'anti-eviction mapping project', which gathers data and maps them to illustrate the transformation of the city, and test potential connections with other evolutions, such as the growing role of private actors in transportation. In doing so, they oppose the optimization of flows circulating in the city characteristic of real-time democracy by supporting another type of democratic organization, namely community building. Activists use data to demonstrate the need for political action against the transformations of the city. This demonstration aims to persuade a local audience to join an active community. .Activists' interventions here can be seen as a powerful counter-experiment, and as such offers an alternative vision of the city. Virtual Singapore offers no example of counter-experiments. Yet it is a telling illustration of the problematic transformation of the global island laboratory. The official discourse calls people in Singapore to act as innovators 'and to co-create with business corporate bodies', 9 actively taking part in technological innovation and participating in the identification of urban problems and solutions. Tools such as Virtual Singapore are meant to serve as platforms for various stakeholders to intervene in the urban life. One can identify here a tension between opening up simulation tools to external contributions (for would-be entrepreneurs, or political discussions about city choices, or foreign actors) and maintaining control. This tension is at the heart of the stabilization of city experiments in Singapore. While it might offer entry points to re-thinking the nature of political intervention in the city state (at both descriptive 9 V.N., Deputy Head, Smart Nation Programme Office, 8 February 2017. and normative levels), it also shows that analyzing city experiments is also investigating stabilization processes, and potential sites of friction.

Conclusion

In this chapter, we have proposed to contribute and dialogue with the large amount of works contemplating, urging for, or critically examining the move towards smart cities by focusing on city experiments. Drawing on the STS literature on laboratory and tests practices [START_REF] Latour | Give Me a Laboratory and I Will Raise the World[END_REF][START_REF] Shapin | Leviathan and the Air-Pump: Hobbes, Boyle, and the Experimental Life[END_REF][START_REF] Pinch | Testing -One, Two, Three … Testing': Toward a Sociology of Testing[END_REF], we suggested that a focus on city experiments offers relevant entry points for the study of contemporary urban transformations. Such an STS-inspired approach builds on the recent invitation to explore 'urban experimentations' as an emerging mode of governance [START_REF] Karvonen | Urban Laboratories: Experiments in Reworking Cities[END_REF][START_REF] Evans | The Experimental City[END_REF], and develops it in several ways. As it takes seriously the key role of experiments in smart city projects, it proposes to study the production of knowledge about the city, as it is articulated with processes of economic, material and political reorderings. The 'smart' label might cover a wide range of domains, and leads one to examine what is 'smart' and what is not, what is 'real' and what is 'mere hype'. By contrast, city experiments can be empirically accounted for by carefully examining a series of concrete components (e.g. experimenters, experimental subjects and objects, laboratories, audiences). Such an approach thus provides some insights into the investigation of city experiments in practical and theoretical terms. In addition, the analysis of city experiments connects many elements that comprise, but are not limited to, what are commonly seen as components of smart cities. Not only does the investigation point to a range of actors that is far beyond the key players usually made visible (funders, ICT firms, and local start-ups), but it also stresses the ecology of political and economic reorderings -and their articulation to (international) networks in situated, local urban initiatives -in which city experiments take a significant place.

https://www.nrf.gov.sg/programmes/virtual-singapore

https://www.sfmta.com/sites/default/files/agendaitems/2015/11-3-15%20Item%2010.4%20MuniMobile%20app.pdf

W.S.N., Deputy Department Head, Urban Systems at the Institute for Infocomm Research, A*Star, 14 February 2017.

W.S.N., Deputy Department Head, Urban Systems at the Institute for Infocomm Research, A*Star, 14 February 2017.

Thus, the SFMTA regularly sets up agreement with private companies (e.g. transportation app providers) and public universities, whereby the latter use the data of the former for the benefit of the SFMTA but without disclosing the data.

http://pavementtoparks.org/about/


Benjamin Bois
email: benjaminbois@yahoo.fr

Lucien Wald

Philippe Pieri

Cornelis Van Leeuwen Ac

Loic Commagnac

Philippe Chery

Maxime Christen

Jean-Pierre Gaudillere

Etienne Saur

ESTIMATING SPATIAL AND TEMPORAL VARIATIONS IN SOLAR RADIATION WITHIN BORDEAUX WINEGROWING REGION USING REMOTELY SENSED DATA

Keywords: Solar radiation, remote sensing, Vitis vinifera, cartography, Bordeaux vineyards

major role in evaporative processes, such as evapotranspiration [START_REF] Priestley | On assessment of surface heat flux and evaporation using large-scale parameters[END_REF][START_REF] Bois | Sensitivity analysis of the Penman-Monteith evapotranspiration formula and comparison of empirical methods used in viticulture soil water balance[END_REF]. Solar radiation determines incoming light and photosynthetically active radiations (PAR). For grapevine (Vitis vinifera L.), as for most of the plants, light availability increases dry mass production [START_REF] Buttrose | Vegetative growth of grapevine varieties under controlled temperature and light intensity[END_REF][START_REF] Grechi | Effect of light and nitrogen supply on internal C:N balance and control of root-to-shoot biomass allocation in grapevine[END_REF]. But in hot and dry conditions, photosynthesis can be reduced despite non limiting light conditions [START_REF] Zufferey | A model analysis of the photosynthetic response of Vitis vinifera L. cvs Riesling and Chasselas leaves in the field: I. Interaction of age, light and temperature[END_REF]. Several researches have enlightened the difficulties to separate temperature from light effects on photosynthesis activity and berry maturation in natural conditions, as incoming solar radiation determines both of these climatic variables [START_REF] Crippen | The effects of sun exposure on the compositional development of Cabernet Sauvignon berries[END_REF][START_REF] Schultz | Photosynthetic duration, carboxylation efficiency and stomatal limitation of sun and shade leaves of different ages in fieldgrown grapevine (Vitis vinifera L.)[END_REF][START_REF] Bergqvist | Sunlight exposure and temperature effects on berry growth and composition of Cabernet-Sauvignon and Grenache in the Central San Joaquin Valley of California[END_REF]. Results concerning the influence of sun exposition on berries differ according to locations and experimental conditions. Overexposure to sunlight may decrease anthocyanin contents of berries [START_REF] Bergqvist | Sunlight exposure and temperature effects on berry growth and composition of Cabernet-Sauvignon and Grenache in the Central San Joaquin Valley of California[END_REF] and sugar concentration [START_REF] Kliewer | Influence of cluster exposure to the sun on the composition of thompson seedless fruit[END_REF]). However, sugar concentration level may increase in sun exposed berries due to water loss [START_REF] Crippen | The effects of sun exposure on the compositional development of Cabernet Sauvignon berries[END_REF]. In all experiments, sunlight-exposed fruits are lower in malate concentration and total titrable acidity [START_REF] Kliewer | Influence of cluster exposure to the sun on the composition of thompson seedless fruit[END_REF][START_REF] Kliewer | Influence of temperature, solar radiation and nitrogen on coloration and composition of Emperor grapes[END_REF][START_REF] Crippen | The effects of sun exposure on the compositional development of Cabernet Sauvignon berries[END_REF][START_REF] Dokoozlian | Influence of light on grape berry growth and composition varies during fruit development[END_REF][START_REF] Spayd | Separation of sunlight and temperature effects on the composition of Vitis vinifera cv. Merlot berries[END_REF]. Theses results, sometimes contradictory, highlight the fact that management of incoming solar radiation via vineyard architecture has to be adapted to local conditions (i.e. local climate and soil characteristics). Models have been developed to integrate the quantity of solar irradiation intercepted by leaf area according to vineyard architecture, in order to estimate grapevine transpiration and vineyard soil water balance [START_REF] Riou | Un modèle simple d'interception du rayonnement solaire par la vigne. Vérification expérimentale[END_REF][START_REF] Riou | Water use of grapevines well supplied with water. Simplified expression of transpiration[END_REF][START_REF] Lebon | Modelling the seasonal dynamics of the soil water balance of vineyards[END_REF][START_REF] Oyarzun | A simple approach to modeling radiation interception by fruit-tree orchards[END_REF].

Solar radiation data is seldom available in weather records, for its precise measurement requires steadily maintained fragile devices, such as pyranometers. However,with recent advances in remote sensing and image analysis, it is now possible to retrieve daily solar radiation from satellite data [START_REF] Solanki | Irradiance models[END_REF]. The HelioClim-1 database, elaborated from

Meteosat images analysis provides solar radiation data for Europe and Africa [START_REF] Lefèvre | Using reduced data sets ISCCP-B2 from the Meteosat satellites to assess surface solar irradiance[END_REF]. This database was used to establish the European Solar Radiation Atlas (ESRA, [START_REF] Rigollier | On the clear-sky model of the ESRA -European Solar Radiation Atlas -with respect to the Heliosat method[END_REF], and was coupled to a 2 km resolution Digital Elevation Model (DEM)

to include the effects of relief on solar radiation interception for photovoltaic potential cartography of Africa [START_REF] Huld | Integration of Helioclim-1 database into PV-GIS to estimate solar electricity potential in[END_REF].

Orography has a major effect on incoming solar radiation, especially when close to equinox, between 30° and 60° latitudes (Oke, 1978). Advances in computer technology and development of GIS software allow to easily determine spatial variations of solar irradiation provided by terrain slope and aspect [START_REF] Durand | Cartographie automatique de l'energie solaire en fonction du relief[END_REF][START_REF] Flint | Calculation of solar radiation in mountainous terrain[END_REF][START_REF] Hofierka | The solar radiation model for Open source GIS: implementation and applications[END_REF][START_REF] Kang | Spatial and temporal patterns of solar radiation based on topography and air temperature[END_REF][START_REF] Wang | New calculation methods of diurnal distribution of solar radiation and its interception by canopy over complex terrain[END_REF].

We propose here to combine satellite sensed data and solar irradiation models based upon orography to estimate spatial and temporal variability of solar radiation interception of Bordeaux winegrowing area, France. The results provided by the cartography methods are used as a tool for viticulture zoning.

MATERIAL AND METHODS

Study area

The winegrowing area of Bordeaux is located in Southwest of France, in the province ("département") of Gironde. It is composed of 57 appellations of controlled origin (AOC) covering about 230 000 ha, although only 120 000 ha are actually planted with grapevine.

Bordeaux vineyards are located at 20 to 150 kilometers from the Atlantic Ocean, between 45. 5°N and 44.3°N (figure 1A and 1B). The Bordeaux vineyards can be divided in 5 subregions, as shown on figure 1B and in table 1.

The climate is temperate, with moderately dry summers (200 mm from July to September)

and wet autumn and winter periods. The average annual rainfall is 930 mm (1976-2005 mean) and ranges from 700 to 1300 mm according to the year. The mean annual temperature is 13.8°C, and ranges from 22.3°C in August to 7.8°C in December. The large area of the Bordeaux vineyards provides a considerable diversity of climatic conditions, due to several topographic elements: the Medoc region, (in the north of region I, figure 1B), is caught between the Atlantic Ocean and the Gironde Estuary. In South-East, the eastern Entre-Deux-Mers area is marked by frequent storms during summer. Most of the western side of the Bordeaux winegrowing area is flat, whereas the eastern part is hilly. Some of the vineyards are located within the suburbs of Bordeaux city and benefit from higher temperature, due to urban heat island effects (Oke, 1978).

Grapevine cultivars are mostly Merlot, Cabernet-Sauvignon, Cabernet franc for red varieties, and Sauvignon blanc and Semillion for white varieties.

Solar radiation cartography

Solar radiation on horizontal surfaces

Daily solar irradiation data was taken from the HelioClim-1 database, available at the SoDa Web Service (http://www.soda-is.org, [START_REF] Gschwind | Converting a successful research project into a sustainable service: The case of the SoDa Web service[END_REF]. This database has been obtained by the application of the Heliosat-2 method to reduced data sets ISCCP-B2 Meteosat satellite images [START_REF] Lefèvre | Using reduced data sets ISCCP-B2 from the Meteosat satellites to assess surface solar irradiance[END_REF]. The Heliosat-2 method is based upon the construction of cloud and clear-sky indexes, for each pixel of a satellite image [START_REF] Rigollier | The method Heliosat-2 for deriving shortwave solar radiation from satellite images[END_REF]. The precision of the method depends mostly on the cloud cover: relative uncertainties are lower during clear-sky days [START_REF] Rigollier | The method Heliosat-2 for deriving shortwave solar radiation from satellite images[END_REF]. The HelioClim-1 database provides root mean squared differences of about 20% of daily pyranometers values for Europe and Africa [START_REF] Lefèvre | Using reduced data sets ISCCP-B2 from the Meteosat satellites to assess surface solar irradiance[END_REF]. Heliosat-2 method does not account for slope and aspect of the terrain.

Daily solar irradiation data was collected for the period 1986-2005. Daily solar irradiation data was downloaded at 418 points, each sampled at an approximate distance of 20 kilometres inside and at neighbouring sites of Gironde.

From daily irradiation data, cloud cover temporal patterns were analyzed using a clearness index (K T ), calculated as follows:

d0 dh T G G = K [1]
where G dh is the daily irradiation on horizontal surface (in MJ m -2 ), G d0 is the daily extraatmospheric irradiation (in MJ m -2 ). G d0 was calculated with astronomical formulae.

Mean daily irradiations on several periods and mean monthly K T values were then interpolated on a 500 m resolution grid, using the ordinary kriging technique. A review on geostatistical techniques can be found in [START_REF] Goovaerts | Geostatistics in soil science: state-of-the-art and perspectives[END_REF]. Kriging was done using the Gstat package of the R statistical software [START_REF] Pebesma | Multivariable geostatistics in S: the gstat package[END_REF]R Development Core Team, 2007).

Linear co-variance models were fitted automatically to experimental semi-variograms, by least squared method.

Terrain integration for incoming solar radiation cartography

Effects of terrain on solar irradiation were taken into account by mean of direct geometrical relations. The solar radiation model r.sun [START_REF] Hofierka | The solar radiation model for Open source GIS: implementation and applications[END_REF], implemented in GRASS Geographical Information System (GIS) was used. The r.sun model estimates beam, diffuse and reflected components of solar incoming radiation on horizontal and inclined surfaces.

Daily solar irradiation is calculated at a 15' time step and cumulated for each day. Mask effects of surrounding orography are taken into account.

Terrain effects on solar radiation interception are considerable during clear-sky days, as most of the incoming radiation is direct, and relationship between irradiation and orography is geometric. During cloudy days, most of the incoming radiation is diffuse. In such situations, except the mask effects produced by surrounding relief, terrain effects are minor. For oceanic climate conditions, such as Bordeaux area, cloudy days frequency is not negligible. For this reason, we used the r.sun model, which integrates diffuse radiation (standard overcast method).

Input data for r.sun are: elevation, slope and aspect (retrieved from a 50 m resolution Digital Elevation Model (DEM)); ground albedo (set to 0.2), horizontal surface irradiation from HelioClim-1 database; Linke turbidity coefficient, whose monthly values were provided by the SoDa Web service; diffuse (k dh ) and beam (k bh ) proportions (i.e. values from 0 to 1) of daily irradiation on horizontal surfaces, estimated with an empirical relationship established at Bordeaux (Pieri and Valancogne, personal communication) :

                        - 1 1.2843 2.6896 1.09 min 3 d0 2 d0 ; G G + G G = k dh dh dh [2] and 0.2 1 d0 < G G if = k dh dh         [3] and dh bh k k - = 1 [4]
where G dh and G d0 have the same signification and units as in equation [1].

The r.sun model provided daily beam, diffuse and reflected solar radiation on inclined surfaces, at the DEM resolution (i.e. 50 m by 50 m). These three variables were then summed to obtain daily irradiation data. The inter-annual differences between horizontal and inclined surfaces were evaluated on a 5 year period, from 2001 to 2005.

RESULTS

Solar radiation climatology in Bordeaux area

Annual mean of daily solar irradiation, annual sunshine duration and annual clear-sky frequency data of Gironde province and Bordeaux winegrowing area are shown in table 2.

Mean daily irradiation ranges from 11.67 to 13.34 MJ m -2 (-5% to 9% of the mean value) for the Gironde province and from 11.67 to 12.83 MJ m -2 in Bordeaux winegrowing area (-3% to 7% of the mean value). The average clearness index is 0.44 for Gironde province and 0.433 for Bordeaux wine growing area. Solar irradiation reaches its maximum in June and July (figure 2). It remains low from October to February (mean daily irradiation below 10 MJ m -2 ).

The spatial variation of solar irradiation is larger for the Gironde province than for Bordeaux winegrowing area (figure 2).

The winegrowing season, spanning a period from April to September, benefits from clearness indices from 0.46 to 0.58 (figures 3A and 3B) in Gironde province. During the autumn period, the proportion of extra-atmospheric global radiation that reaches the ground is lower that during other seasons (figure 3C). This could be explained both by the cloud climatology (weather is globally cloudier from October to February in Gironde province) and the increasing length of solar radiation path throughout the atmosphere, due to sun inclination.

The spatial patterns of clearness index remain similar throughout the year: the Atlantic Ocean coast receives the highest amount of solar radiation. The clearness index decreases from west to east, during spring, summer and winter. During autumn, it decreases from west to east until the center of Gironde province, and then increases again towards east (figure 3C). This particular spatial pattern might be related to the greater diversity of synoptic situations during this period [START_REF] Jones | Using a synoptic climatological approach to understand climate-viticulture relationships[END_REF]. The largest spatial variability is observed during winter.

The western part of Bordeaux winegrowing area receives the highest amount of solar radiation. In Medoc, located in the north-west of Gironde (region I, see figure 1), clearness index is 4 to 8% higher than in the easternmost vineyards, from April to September (figures 3A and 3B).

Bordeaux vineyards zoning

In Bordeaux winegrowing area, veraison of red and white grape varieties generally occur at the end of July or at the beginning of August. The harvest period ranges from mid-September to beginning of October. As climate conditions are crucial from veraison to harvest, mean daily values of solar irradiation from August to September on horizontal surface were calculated. This index is referred hereafter as G mat,h (where mat stands for maturation period, i.e. august to September, and h indicates that G mat is calculated on a horizontal surface). It was used to perform a zoning of Bordeaux winegrowing area, as follows: (a) Mean G mat,h on a 20 year period was calculated for each pixel located in Bordeaux winegrowing area ; (b) all the pixel values were classified in 3 classes with regular interval. Classes obtained correspond to low, middle and high G mat,h values (table 3, figure 4B). The first class ("low") corresponds to a mean daily irradiation (for August and September) ranging from 15.36 to 15.84 MJ m -2 , with a mean value of 15.68 MJ m -2 . For the second class ("medium"), G mat,h ranges from 15.85 to 16.33 MJ m -2 , with a mean value of 16.03 MJ m -2 . For the third class ("high"), G mat,h ranges from 16.33 to 16.81 MJ m -2 , with a mean value of 16.48 MJ m -2 . Whereas the total amplitude of G mat,h observed within the Bordeaux winegrowing equals 8.9% of the mean horizontal value, the difference between the mean values are small (-2.2% between low and medium, and 2.8% between medium and high). Class 1 (low G mat,h value) represent 66% of the total area of Bordeaux vineyards, class 2 (medium) 32% and class 3 (high) 2%.

The western and the southern parts of Bordeaux winegrowing area (region I and II, and the west of region V) are located in the medium G mat,h value zone, and eastern part of Bordeaux winegrowing area (region III and IV) is located in the low G mat,h value zone, as well as the eastern part of region V (figure 4A). A small area, the northwesternmost part of Bordeaux vineyards (region I) is located in high G mat,h value zone.

Terrain integration on solar radiation zoning

Solar daily irradiation data with terrain effects integration was calculated for the period 2001-2005, using the r.sun algorithm, at the DEM cell resolution, i.e. a 50 m by 50 m pixel. This high resolution cartography has a high computational cost: it is both time and hard-disk-space consuming, and the calculation on a 20 years period would have taken several weeks of computer calculations. To reduce computational cost, G mat (i.e. mean daily irradiation from August to September, with terrain effects integration) for the 20 year period was obtained using an empirical correction factor calculated for the period 2001-2005: G mat for the 20 years period was assessed by multiplying G mat,h (1986)(1987)(1988)(1989)(1990)(1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005) by the 5 years average (2001)(2002)(2003)(2004)(2005) of the ratio G mat h /G mat calculated for each 50 m pixel. We assumed that, for each 50 m pixel, having its own terrain characteristics (i.e. slope inclination and aspect), the ratio between G mat (computed using daily irradiation data with terrain integration, at high resolution) and G mat,h (horizontal irradiation data, at 500 m resolution) remained constant. This was verified with the 2001-2005 high resolution data set: The relative difference for each pixel (i.e. (G mat -G mat,h )/ G mat,h ) is almost the same from 2001 to 2005 (figure 5). In other words, the effect of terrain on solar radiation interception during August and September is quasi-identical from one year to another.

A new zoning was achieved, using the high resolution G mat on the period 1986-2005 to classify Bordeaux winegrowing area in the 3 classes ("low", "medium" and "high") previously obtained with G mat,h . The repartition of Bordeaux's appellations of origin before and after the integration of terrain effects on solar radiation interception is shown in table 4.

In the region I, the zoning changes for three appellations of origin areas: 16 to 36% of Listrac, Médoc and Moulis appellations total areas are situated in high G mat class after terrain integration, whereas they were located in medium class in flat terrain zoning. The G mat,h values of these areas are close to the threshold values of medium-high classes, which explains that a small variation in incoming solar radiation induced by terrain modified strongly the zoning. For regions II, III, IV and V, the classification was considerably modified. For example, 93% of Entre-Deux-Mers appellation of origin was classified in low G mat,h zone.

With terrain integration, 63% of the area remains in low G mat zone, one third is classified in medium G mat zone, and 4% of the area is classified in high G mat zone. The well-known area of Saint-Emilion, as well, receives little solar radiation during August and September, compared to the whole Bordeaux winegrowing area. 100% of the total surface area of this appellation was located in low G mat,h area, when considering incoming radiation on horizontal surface.

With terrain effects integration, 8% of the appellation changes of class: 6% of the appellation is classified as a medium G mat area, and 2% as high G mat area. Figure 6B shows that the southexposed slopes close to Saint-Emilion village receive from 1 to 10% more solar radiation than the mean value of the area.

Another example is the appellation of origin Côtes-de-Bourg, where 48% of the area is classified in a low G mat,h area and 52% of the total area is classified in a medium G mat,h area.

After terrain integration, 12% of the total area is situated in low G mat class. G mat within the appellation of origin Côtes de Bourg varies from -14% to +13% of the mean appellation value (figure 6A).

DISCUSSION AND CONCLUSIONS

Satellite sensed solar radiation, from the HelioClim-1 database, combined with terrain information was used to calculate solar irradiation for the large wine growing area, at a high resolution (50m). The studied period is sufficiently long to provide a robust analysis of solar radiation climatology of Bordeaux vineyards. Such study would not have been possible using ground measurement devices, such as pyranometers. Firstly, because pyranometer devices are quite recent and the technology has been improved, so data would have required several recalibration. Secondly, only a small number of weather stations located close to or within Bordeaux vineyards provide solar radiation records, for such a long period (less than 5 stations). However, our high resolution spatialized solar irradiation daily values (50 m) underestimate solar radiation. They have been compared to pyranometer records of the weather station of Villenave d'Ornon (located between regions I and II), for the period 2001-2005. They showed a mean difference (bias) of -1.5 MJ m -2 , indicating a underestimation of 11.1% of the annual mean (table 5). The root mean squared difference was 2.7 MJ m -2 (19.8% of the mean annuel pyranometer value). For G mat , the bias and root mean squared differences are -9.8% and 16.6% of the annual mean, respectively. These errors stay in the range of uncertainties provided by the use of pyranometer measurements [START_REF] Llasat | Data error effects on net radiation and evapotranspiration estimation[END_REF][START_REF] Droogers | Estimating reference evapotranspiration under inaccurate data conditions[END_REF]. Although the relative spatial differences presented in this study have not been affected by this underestimation, the absolute values may be slightly higher.

It has been shown that the western part of Bordeaux vineyards receive more solar radiation than the eastern part, throughout the year. As the ripening of grapevine varieties of Bordeaux area occurs during the August and September, a zoning based on the mean daily irradiation during this period (referred as G mat,h ) was proposed. The Bordeaux winegrowing area was partitioned into three classes: low, medium and high G mat,h values. The southern and the eastern parts of Bordeaux winegrowing region receive the highest amount of solar radiation during berry ripening period. When increasing the resolution of the zoning, using the r.sun model, it has been shown that terrain effects on solar radiation are not negligible, although the Bordeaux winegrowing area could not be considered as a mountainous region. Well exposed (south) slopes of the eastern part of Bordeaux vineyards receive as much solar radiation as flat surfaces in the western part. [START_REF] Failla | Spatial distribution of solar radiation and its effects on vine phenology and grape ripening in an alpine environment[END_REF] have found that slopes that receive a higher amount of solar radiation were associated with earlier phenology, higher sugar content, lower titrable acidity and lower phenolic content in berries, in red cv. Nebbiolo vineyards.

The attempt of the present work was to evaluate solar radiation climatology of Bordeaux winegrowing area, and to propose a new zoning approach for ripening potential of vineyards.

The assumptions made prior to such zoning are multiple: firstly, solar irradiation affects berry ripening [START_REF] Dokoozlian | Influence of light on grape berry growth and composition varies during fruit development[END_REF][START_REF] Bergqvist | Sunlight exposure and temperature effects on berry growth and composition of Cabernet-Sauvignon and Grenache in the Central San Joaquin Valley of California[END_REF]. Secondly, solar irradiation has a major effect on surface and air temperature, which affect grapevine phenology, malate degradation within berries, polyphenolic, sugar and aromatic contents of berries [START_REF] Buttrose | Effect of the temperature on the composition of Cabernet-Sauvignon berries[END_REF][START_REF] Reynolds | Influence of fruit microclimate on monoterpene levels of Gewurztraminer[END_REF][START_REF] Bergqvist | Sunlight exposure and temperature effects on berry growth and composition of Cabernet-Sauvignon and Grenache in the Central San Joaquin Valley of California[END_REF][START_REF] Spayd | Separation of sunlight and temperature effects on the composition of Vitis vinifera cv. Merlot berries[END_REF]. Thirdly, as spatial variation of cumulated incoming solar radiation during berry maturation period depends mainly on vineyard slopes and aspects, it is associated with different water runoff patterns, due to slope intensity. It can be expected that steep slopes will be associated with higher runoff. Finally, solar radiation plays a major role in vineyard transpiration and it is a key parameter of water balance models [START_REF] Trambouze | Measurement and modelling of the transpiration of a Mediterranean vineyard[END_REF][START_REF] Lebon | Modelling the seasonal dynamics of the soil water balance of vineyards[END_REF].

Hence, south-exposed vineyards would certainly be subject to higher evaporative demands.

Increasing G mat index may thus be associated to higher water deficits.

Row orientations and spacing, as well as canopy structure dramatically affect incoming solar radiation distribution between grapevine rows and bare or grass-covered surface [START_REF] Smart | Sunlight interception by vineyards[END_REF]Pieri andGaudillere, 2003, 2005). [START_REF] Oyarzun | A simple approach to modeling radiation interception by fruit-tree orchards[END_REF] recently proposed a solar radiation interception model for horizontal and inclined surface in orchards and vineyards.

Coupling this kind of model to satellite sensed solar radiation, water runoff and water balance models would certainly improve general knowledge about inclined surface effects on grapevine development and berry maturation. for the list of the appellation of origin located in each region).

  Estimating spatial and temporal variations in solar radiation within Bordeaux winegrowing region using remotely sensed dataBenjamin Bois, Lucien Wald, Philippe Pieri, Cornelis van Leeuwen, Loïc Commagnac, Philippe Chery, Maxime Christen, Jean-Pierre Gaudillère, Etienne Saur To cite this version: Benjamin Bois, Lucien Wald, Philippe Pieri, Cornelis van Leeuwen, Loïc Commagnac, et al.. Estimating spatial and temporal variations in solar radiation within Bordeaux winegrowing region using remotely sensed data. Journal International des Sciences de la Vigne et du Vin, 2008, 42 (1), pp.15-25. hal-00363698 1 INTRODUCTION Solar radiation has a large influence on vine growth, berry ripening, and disease development in vineyards. Its effects are numerous, and it affects other climate variables. Hence, vineyard microclimate depends strongly on this variable. Most of the radiative balance is determined by incoming solar radiation. It induces variations of surface and air temperature, and it has a

Figure 1 :

 1 Figure 1: Maps of the study area. A: France, with the Gironde province and the city of Bordeaux. B: The Bordeaux winegrowing area, located in Gironde province. Figures in roman numbers indicate the number of the 5 sub-regions of Bordeaux winegrowing area (see table 1

Figure 2 :

 2 Figure 2: Box-plots of monthly means of daily irradiations, during the period 1986-2005, for Gironde province (A) and Bordeaux winegrowing area (B). Data used to elaborate each box are the mean daily irradiation values of each 500 m pixel. Points outside the boxes represent the minimum and the maximum values observed within each area.

Figure 3 :

 3 Figure 3: Seasonal maps of clearness index of Gironde province(period 1986-2005). The dashed areas represent the 5 sub-regions of Bordeaux winegrowing area (see figure2B). A: "spring", from April to June ; B: "Summer", from July to September ; C: "Autumn", from October to December ; D: "Winter", from January to March.

Figure 4 :

 4 Figure 4: Zoning of Bordeaux winegrowing area based on the mean daily solar irradiation value from August to September (G mat,h ), for the period 1986-2005. A: map of G mat,h classes (horizontal surface zoning); B: box-plot of G mat,h values of the three classes ; C: map of G mat classes (inclined surface zoning) ; D: box-plot of G mat values of the three classes. Points on box-plots figures correspond to the extremes values of each class.

Figure 5 :

 5 Figure 5: Scatter plot comparing, for different years, the values of the relative differences between G mat on horizontal and inclined solar radiation data, of each pixel located in the Bordeaux winegrowing area (N = 948239).

Figure 6 :

 6 Figure 6: Mean daily solar irradiation data from August to September, for the period 1986-2005, of two appellations of origin (A.O.C.) areas of Bordeaux. The data is expressed in percent of the mean value of each whole area. A: A.O.C. Côtes-de-Bourg, B: A.O.C. Saint-Emilion (the circle indicates the localization of Saint-Emilion village.

Table 1 :

 1 Classification by region of appellations of origin of Bordeaux winegrowing area (see figure2)

	Region	Appellations of origin (AOC)
	I	Bordeaux ; Bordeaux Supérieur ; Haut-Médoc ; Listrac ; Margaux ; Médoc ; Moulis ; Pauillac ; Saint-Estèphe ; Saint-Julien
	II	Barsac ; Bordeaux ; Bordeaux Supérieur ; Cerons ; Graves ; Graves Supérieures ; Pessac-Léognan ; Sauternes
		Bordeaux ; Bordeaux Supérieur ; Côtes de Bordeaux ; Saint-Macaire ; Entre-Deux-Mers ;
	III	Haut-Bénauge ; Graves-de-Vayres ; Loupiac ; Premières Côtes de Bordeaux ; Cadillac ;
		Sainte-Croix-du-Mont ; Sainte-Foy Bordeaux
		Bordeaux ; Bordeaux Supérieur ; Côtes de Francs ; Côtes de Castillon ; Lalande de
	IV	Pomerol ; Lussac Saint-Emilion ; Montagne Saint-Emilion ; Pomerol ; Puisseguin Saint-
		Emilion ; Saint-Emilion ; Saint-Georges Saint-Emilion
	V	Blaye ; Blayais ; Bordeaux ; Bordeaux Supérieur ; Canon Fronsac ; Côtes de Bourg ; Fronsac ; Premières Côtes de Blaye ; Côtes de Blaye

Table 2 :

 2 Spatial variations statistics of solar radiation climatological data, on the period 1986-2005, for Gironde province and Bordeaux vineyards. CV = coefficient of variation (mean divided by the standard deviation, σ).

		Gironde Province	Bordeaux vineyards
		Daily irradiation (Wh m-2)	Clearness index (K T )	Daily irradiation (Wh m-2)	Clearness index (K T )
	Min.	11.7	0.42	11.7	0.425
	1st quartile	12.0	0.43	11.8	0.428
	Median	12.2	0.44	11.9	0.431
	Mean	12.3	0.44	12.0	0.433
	3rd quartile	12.5	0.45	12.0	0.435
	Max.	13.3	0.48	12.8	0.463
	σ σ σ σ	0.38	0.01	0.20	0.007
	CV	3.1%	2.9%	1.7%	1.6%

Table 3 :

 3 Statistics of mean solar irradiation (MJ m -2 ) from August to September, for three classes obtained by regular interval clustering, in Bordeaux winegrowing area. CV = coefficient of variation (the mean divided by the standard deviation, σ).

		Horizontal surface classes	Inclined surface classes
		Low	Medium	High	Low	Medium	High
	Mean	15.68	16.03	16.48	15.59	16.05	16.50
	σ	0.10	0.15	0.14	0.22	0.14	0.18
	CV	0.6%	0.9%	0.8%	1.4%	0.9%	1.1%
	Min.	15.36	15.85	16.33	12.38	15.85	16.33
	Max.	15.84	16.33	16.81	15.85	16.33	17.80
	Area (ha.)	156106	77065	3889	127819	92962	16279

Table 4 :

 4 Distribution of appellation of origin areas, within the three solar radiation zones (i.e. classes), before and after integration of terrain. : the figures are given in percent of the total area of each appellation of origin

	Region	Appellation of origin (A.O.C.)	Horizontal surface G mat zones a Low Medium High	G mat zones with terrain effects integration a Low Medium High	Total area (ha)
		Bordeaux ; Bordeaux supérieur	-	99%	1%	-	99%	1%	1472
		Haut-Médoc	-	97%	3%	-	81%	19%	9077
		Listrac	-	73%	27%	-	48%	52%	1393
		Margaux	-	100%	-	-	94%	6%	1856
	I	Médoc	-	70%	30%	-	54%	46%	10419
		Moulis	-	94%	6%	-	60%	40%	1034
		Pauillac	-	100%	-	2%	96%	2%	1600
		Saint-Estèphe	-	100%	-	-	92%	8%	1552
		Saint-Julien	-	100%	-	-	94%	6%	997
		Barsac	-	100%	-	4%	96%	-	860
		Bordeaux ; Bordeaux supérieur	-	100%	-	15%	83%	2%	3131
	II	Cerons ; Graves ; Graves supérieures	-	100%	-	10%	89%	1%	2446
		Graves ; Graves supérieures	-	100%	-	20%	78%	2%	8994
		Pessac-Léognan	-	100%	-	13%	85%	2%	4514
		Sauternes	-	100%	-	22%	75%	3%	2154
		Bordeaux ; Bordeaux supérieur 69%	31%	-	69%	30%	1%	4471
		Côtes de Bordeaux ; Saint-Macaire	25%	75%	-	39%	47%	14%	4498
		Entre-Deux-Mers	93%	7%	-	63%	33%	4%	59325
		Entre-Deux-Mers ; Bordeaux ; Haut-Benauge	99%	1%	-	48%	47%	5%	6809
	III	Graves de Vayres	100%	-	-	89%	11%	-	1370
		Loupiac	-	100%	-	45%	40%	15%	828
		Premières Côtes de Bordeaux	88%	12%	-	60%	33%	7%	4207
		Premières Côtes de Bordeaux ; Cadillac	42%	58%	-	40%	40%	20%	8356
		Sainte-Croix-Du-Mont	-	100%	-	33%	31%	36%	760
		Sainte-Foy Bordeaux	100%	-	-	79%	20%	1%	16425
		Bordeaux ; Bordeaux supérieur 100%	-	-	97%	3%	-	7379
		Bordeaux ; Côtes de Francs	100%	-	-	86%	14%	-	1030
		Côtes de Castillon	100%	-	-	80%	17%	3%	5608
		Lalande de Pomerol	100%	-	-	96%	4%	-	1378
	IV	Lussac Saint-Emilion Montagne Saint-Emilion	100% 100%	--	--	90% 83%	9% 16%	1% 1%	1834 2097
		Pomerol	100%	-	-	100%	-	-	978
		Puisseguin Saint-Emilion	100%	-	-	84%	14%	2%	1041
		Saint-Emilion	100%	-	-	92%	6%	2%	7153
		Saint-Georges Saint-Emilion	100%	-	-	61%	38%	1%	274
		Blaye ; Blayais	66%	34%	-	59%	41%	-	2426
		Bordeaux ; Bordeaux supérieur 98%	2%	-	83%	16%	1%	21498
		Canon Fronsac	100%	-	-	50%	35%	15%	396
	V	Côtes de Bourg	48%	52%	-	48%	40%	12%	7005
		Fronsac	100%	-	-	51%	37%	12%	1311
		Premières Côtes de Blaye ; Côtes de Blaye	53%	47%	-	51%	46%	3%	17111

a

Table 5 :

 5 Comparison of pyranometer and high-resolution spatialized irradiation mean daily data at the weather station of Villenave d'Ornon (44.789°N ; 0.577°E).G dp = pyranometers mean daily values ; Bias = mean error (spatialized -pyranometer), RMSD = Root Mean Squared Difference ; Min. = the minimum daily difference, Max = the maximum daily difference ; N = the number of observations. The values between parentheses indicate the statistical indicator in fraction of the pyranometer values (G dp ). Except for N, the values are given in MJ m -2 .

	Period	G dh	Bias	RMSD	Min.	Max.	N
	January	4.6	-0.5 (-9.9%)	1.0 (22.5%)	-3.3	1.8	155
	February	7.7	-1.4 (-18%)	2.0 (25.8%)	-5.2	3.0	141
	March	12.4	-1.8 (-14.2%)	2.4 (19.7%)	-7.4	1.3	155
	April	16.4	-1.9 (-11.6%)	3.0 (18.3%)	-8.7	8.6	150
	May	20.5	-2.7 (-13%)	4.0 (19.5%)	-10.8	9.3	155
	June	23.3	-1.8 (-7.7%)	3.1 (13.1%)	-11.0	5.2	150
	July	22.2	-2.2 (-9.9%)	3.7 (16.6%)	-10.8	5.3	155
	August	19.6	-1.7 (-8.8%)	3.1 (16%)	-10.4	4.5	155
	September	15.3	-1.7 (-11.2%)	2.7 (17.3%)	-10.4	6.1	150
	October	9.3	-1.9 (-20.9%)	2.5 (27.4%)	-9.4	2.1	155
	November	5.6	-0.3 (-5.8%)	1.3 (22.5%)	-3.4	3.5	150
	December	4.1	-0.1 (-1.8%)	1.0 (25%)	-3.7	2.6	155
	Year	13.4	-1.5 (-11.1%)	2.7 (19.8%)	-11.0	9.3	1826
	Aug. -Sept.	17.5	-1.7 (-9.8%)	2.9 (16.6%)	-10.4	6.1	305

Acknowledgements :

The authors thank the Conseil Interprofessionnel des Vins de Bordeaux for their technical and financial support.


Prof. Dr Jiajun Wu

Christophe Darcel
email: christophe.darcel@univ-rennes1.fr

Tandem Fe/Zn or Fe/In catalysis for the selective synthesis of primary and secondary amines via selective reduction of primary amides

Tandem iron/zinc or iron/indium-catalysed reductions of various primary amides to amines under hydrosilylation conditions are reported under visible light activation. By a simple modification of the nature of the co-catalyst (Zn(OTf)2 vs In(OTf)3), Fe(CO)4(IMes) can promote the high chemoselective reduction of primary amides into primary amines (21 examples, up to 93% isolated yields) and secondary amines (8 examples, up to 51% isolated yields), respectively. Notably, both benzamide and alkanamide derivatives can be reduced.

Introduction

The reduction of carboxamides is among the most important reaction in molecular synthesis mainly for the synthesis of amines, and more particularly of primary amines. [1] Since two decades, numerous catalytic pathways to prepare efficiently amine derivatives have been developed. Representative methodologies were based on aryl halide amination with palladium or copper catalysts, [START_REF] Dorel | [END_REF] hydroamination of olefins, [3] imine, [4] nitro, [5] nitrile, [6] or carboxamide [7] reduction, and amination of alcohols and carbonyl derivatives. [8] It should be underlined that the reduction of carboxamides can be seen as the most difficult reaction to perform due to notably the lack of activity of the amide group and the chemoselectivity issues (C-N vs C-O bond cleavage). [7c] Indeed, using traditional stoichiometric metal hydride species, even if efficient, functional group tolerance was always the main observed drawback, associated with tedious purification procedures. [START_REF] Seyden-Penne | Reductions by Alumino and Borohydrides in Organic Synthesis 2 nd[END_REF] Additionally, when performing the reduction under hydrogenation conditions, mainly using noble metal catalysts, the main limitation is due to the drastic conditions used (elevated pressure, very high temperature…) which limited their use in larger scale. [10] Over the last decade, progresses have been achieved with the development of metal-catalyzed chemoselective hydrosilylation, usually conducted under milder reaction conditions. Noticeably, first row transition metals can be used to perform such reduction. [START_REF] Khalimon | For a review on earth abundant metal catalysed hydrosilylation of carboxamide[END_REF] As representative recent examples, hydrosilylation of primary amides leading to primary amines were performed with manganese [START_REF] Das | For a representative example of hydrosilylation with manganese[END_REF] or nickel based catalysts. [START_REF] Pandey | For hydrosilylation with nickel[END_REF] It should be also underlined that over the last two decades, progresses have been made with the use of iron in homogeneous catalysis, notably in reduction area. [14] The first selective reductions of secondary and tertiary carboxamides to their corresponding amines via deoxygenation were developed under hydrosilylation using iron salts or complexes. [15] Noticeably when performing the hydrosilylation with primary amides, the corresponding nitriles were specifically obtained. [16,15h] Only scarce contributions performing the full reduction of primary amides to primary amines were described at iron. The first one reported by Beller using two different iron complexes in a consecutive manner, [Et3NH][HFe3(CO)11] for the generation of nitriles and Fe(OAc)2/phenanthroline for the reduction of nitriles to primary amines. Similarly, Nagashima has employed an iron/cobalt catalytic system albeit with limited scope. [17] Herein, we report iron-catalysed chemoselective and tandem methodologies to reduce primary carboxamides either to primary amines using a Zn based co-catalyst or to secondary amines with the association of an indium cocatalyst. (Scheme 1) Scheme 1. Iron catalysed tandem reduction of primary carboxamides either to primary or secondary amines with Zn or In co-catalyst.

Results and Discussion

First of all, in order to evaluate the ability of iron(0) based catalysts to reduce primary amides into the corresponding primary amines under hydrosilylation conditions, we began our initial work by performing the reduction of benzamide 1a using 3 equiv. of phenylsilane as the reducing agent in the presence of 5 mol% of Fe(CO)4(IMes) [IMes = 1,3-bis (2,4,6-trimethylphenyl)imidazol-2-ylidene] upon visible light irradiation (using 24 watt compact fluorescent lamp). Even if full conversion was observed, only the dehydration derivative benzonitrile 2a was obtained (95%, Table 1, entry 1). Such results were already described under iron-catalysed hydrosilylation conditions. [15] Thus the effect of the addition of a Lewis acid in order to promote the reduction was evaluated (Table 1). Among the tested metal salts (20 mol%), indium and zinc exhibited interesting reactivities. Whereas indium chloride favored the formation of dibenzylamine 4a (entry 5), zinc salts selectively led to benzylamine hydrochloride salt 5a, resulting from the treatment of the benzylamine 3a by a solution of dry HCl, zinc triflate being the most efficient (85% isolated yield, entry 9). Varying the quantity of Zn(OTf)2 (10 and 30 mol%) had a deleterious effect on the efficiency to produce 5a (75 and 60%, respectively, entries 10 and 11). Similarly, increasing the reaction temperature to 130 °C or decreasing to 100 °C led to 5a in less good yields (entries 12 and 13). Importantly, when the reaction was performed in absence of iron catalyst, with 20 mol% of Zn(OTf)2, full conversion was observed but a mixture of 2a and 3a was obtained (73, 24%, respectively, entry 14). This result clearly demonstrated that the bimetallic association of Fe and Zn surpassed the selectivity of zinc, hydrosilylation with zinc salts being already reported with secondary and tertiary amides. [18] Additionally, different iron catalysts (5 mol%) such as Fe(CO)4(DIPP) [DIPP = 1,3-bis (2,6-diisopropyl-phenyl)imidazol-2-ylidene], [CpFe(CO)2(IMes)][I] or the Knölker catalyst in presence of 10 mol% of Me3NO, were evaluated in the presence of 20 mol% of Zn(OTf)2, but lower efficiencies were obtained (79, 56 and 60% isolated yields, respectively, Table S1, SI).

Table 1. Optimization of the parameters for the selective reduction of benzamide 1a to benzylamine 3a. [a] Entry Additive (mol%)

Conv.(%) [b] Yield (%) 2a [b] 5a [c] 4a [b] 1 Zn(OTf)2 (20) >99 0 71 10 13 [e] Zn(OTf)2 (20) >99 13 56 14

14 [f] Zn(OTf)2 (20) >99 73 24 0

[a] Conditions: Benzamide (0.3 mmol), additive (10-30 mol%), Fe(CO)4IMes (5 mol%), PhSiH3 (3 equiv.), toluene (1 mL), 110 °C for 20 h under argon and visible light activation (using 24 watt compact fluorescent lamp). [b] Conversion and yields of 2a and 4a determined by GC using dodecane as an internal standard; [c] Isolated yield of 5a after acidification of 3a with HCl solution (0.5 M in dioxane). [d] 130 °C. [e] 100 °C. [f] Reaction without iron catalyst.

Among the tested hydrosilanes, tertiary silanes gave either no conversion (iPr3SiH, Table 2, entry 6) or full conversion, but led only to the dehydrated benzonitrile 2a (entries 8-11). By contrast, the use of secondary silanes such as diethylsilane permitted to selectively obtained benzylamine hydrochloride salt 5a with moderate isolated yields up to 64% (entry 5). Finally, the best identified silane was PhSiH3 with an optimized amount of 3 equiv. which permitted to obtain up to 85% of 5a. (entries 1-3).

Additionally, the nature of the solvents was evaluated for this reaction under similar conditions in the presence of 3 equiv. of PhSiH3 (Table S2, SI). Whereas lower conversions were obtained in n-BuOH (10%) and 2-MeTHF (30%), with all the other tested solvents including cyclopentylmethylether, dioxane, and cyclohexane, full conversions were detected and benzylamine 3a were selectively produced. The best efficiency was observed in cyclohexane, 5a being isolated in 93% yield, thus exhibiting higher efficiencies in non-polar solvents.

Table 2. Influence of the nature of the hydrosilane on the reduction of benzamide 1a. [a] Entry Silane (equiv.) Conv.(%) [ b] Yield (%) 2a [b] 5a [c] 4a [b] 1 [a] Conditions: Benzamide (0.3 mmol), Zn(OTf)2 (20 mol%), Fe(CO)4IMes (5 mol%), silane (2-4 equiv.), toluene (1 mL), 110 °C for 20 h under argon and visible light activation. [b] Conversion and yields of 2a and 4a determined by GC using dodecane as an internal standard; [c] Isolated yield of 5a after acidification of 3a with HCl solution (0.5 M in dioxane). *Numerous unidentified by-products were also detected.

With these optimized conditions in hands, we then evaluated the substrate scope and limitation of this transformation. Noticeably, the primary amines 3 were isolated as their chloride ammonium salts 5 by simple addition of a HCl solution (0.5 M in dioxane) at the end of the reaction (Scheme 2). The reduction was successfully conducted with substituted benzamide derivatives bearing electron-donating groups such as methoxy, methyl, or halides, leading to the corresponding ArNH2HCl salts 5b-i in 47-87% isolated yields. It must be underlined that the steric hindrance due to the ortho-substitution of the benzamide derivatives has a significant influence on the reactivity lowering the yields (47-66%, 5d, 5f, 5h, and 5k).

In the case of o-iodobenzamide, even if the full conversion was observed, the main product obtained was the corresponding nitrile compound, with trace amount of amine. The reduction can also be conducted with benzamide derivatives bearing an electron-withdrawing group such as trifluoromethyl thus leading to 5l in 49% yield. Interestingly, terephthamide was efficiently reduced leading to the salt 5n derived from 1,4-phenylenediamine 3n in 87% isolated yield. Additionally, heteroaromatic derivatives such as 2-thiophenecarboxamide led to the corresponding ammonium salt 5o in 70% yield. The reaction can be selectively conducted with cinnamamide: the corresponding salt 5p derived from cinnamylamine was isolated in 68% associated to the fully reduced one derived from 3-phenylpropanamine (14%) showing that under such conditions, the conjugated C=C bond can be also reduced.

Scheme 2. Scope for the hydrosilylation of primary amides leading to primary amines. a Isolated yield. b In toluene. c Fe(CO)4IMes (7.5 mol%), Zn(OTf)2 (30 mol%).

These conditions can be also efficiently applied to alkanamides, and the corresponding ammonium salts 5q-5t were isolated in 62-91% yields. The reduction of 4hydroxybenzamide and 4-aminobenzamide led to a mixtures of products with small amount of the expected amines.

Additionally, 2-phenylethylamine 3u, a monoaminergic and a neurotransmitter in the human central nervous system (CNS) can be efficiently prepared from its corresponding amide and the corresponding salt 5u was obtained in 72% yield. By contrast, when starting from 2-phenylpropanamide, no corresponding product was obtained under such conditions. To demonstrate the synthetic usefulness of this methodology, a gram scale reaction starting from 10 mmol of benzamide 1a led to the benzylamine hydrochloride salt 5a in 79% isolated yield. During the optimization of the reaction, it was observed that when 20 mol% of InCl3 was used, 90% conversion was detected and the selectivity was switched as 41% of dibenzylamine 4a was obtained as the main product in addition to 13% of benzonitrile 2a and 15% of benzylamine 3a (Table 3, entry 1). Noticeably, InBr3 was described as a catalyst specifically for the reductive deoxygenation of tertiary and secondary amines, but only one example of primary amide was reported. [19] The optimization of the reaction performing a screening of salts and conditions was illustrated in Table 3. The decrease of the amount of InCl3 to 10 mol% had a deleterious effect, whereas its increase to 30 mol% did not give better results (Table 3, Entries 2 and3). Noticeably, when performing the reaction at 130 °C, even if full conversion was observed, only 50% of dibenzylamine 4a was obtained. (Table 3, entry 4).

Table 3. Optimization of the parameters for the selective preparation of dibenzylamine 4a from benzamide 1a. [a] Additive (mol%)

Conv.(%)[ b]
Yield (%) 2a [b] 3a [b] 4a [b] 1

InCl3 (20) 90 13 15 41 2 InCl3 (10) 90 31 0 21

3 [c] InCl3 (30) 88 17 13 36 4 [d,c] InCl3 (20) >99 5 Trace 50 5 [d,c] InBr3 (20) >99 0 32 42 6 [d] In(OTf)3 (20) 99 0 Trace 55(51)

7 [e] InCl3 (20) 90 37 0 29

[a] Conditions: Benzamide (0.3 mmol), indium salt (10-30 mol%), Fe(CO)4IMes (5 mol%), PhSiH3 (3 equiv.), toluene (1 mL), 110 °C for 20 h under argon and visible light activation (using 24 watt compact fluorescent lamp). [b] Conversion and yields determined by GC; in parenthesis, isolated yield of 4a. [c] Several by-products were also detected including one corresponding to the formation of secondary amides. [d] 130 °C. [e] Reaction without iron catalyst.

Interestingly, when using InBr3, similar results were obtained, with a significant amount of primary benzylamine 3a (entry 5).

The more efficient identified co-catalyst was In(OTf)3, leading selectively to the dibenzylamine 4a with 51% isolated yield (entry 6). Noticeably, without iron catalyst, even if the conversion can reach 90%, and 29% of 4a can be obtained, several byproducts including N-benzylbenzamide were detected (Entry 7).

In order to illustrate the applicability of this tandem iron/indium catalyzed reactions of primary amides, using the optimized conditions (Table 3, entry 6), various symmetrical secondary amines 4 were prepared in moderate yields from primary amides bearing either electron donating or deficient groups on the aromatic moiety (Scheme 3).

Scheme 3. Selective preparation of symmetrical secondary amines by hydrosilylation of primary amides catalyzed by In/Fe catalysts (Isolated yield).

We then conducted preliminary mechanistic studies to gain insights into these Fe/Zn and Fe/In catalysed transformations, a series of control experiments. (Scheme 4) First of all, benzamide 1a was not selectively reduced by the sole iron catalyst and by the sole zinc or indium additive under light activation (Table 1, entries 1 and 14; Table 3,entry 7). Additionally, the dehydration of primary amide 1 leading to nitrile 2, already described under iron catalysed hydrosilylation conditions, [15h,16] proceeded efficiently using Fe(CO)4IMes under light activation (Table 1, entry 1). Thus, the obtained nitrile 2 should then react with the hydrosilane to lead to the Nsilylimine A, and the disilylated amine B, both Zn(OTf)2 and In(OTf)3 possibly playing a role in activating the amide moiety. Noticeably these two reactions did not proceed in the absence of light activation. [18,[20][21][22] It should be underlined that benzonitrile 2a was not reduced to the corresponding amine 3a using either Zn(OTf)2 or In(OTf)3 as the sole catalyst. (Scheme 4b) It should be underlined that there are only scarce reports dealing with zinccatalyzed hydrosilylation of benzonitrile derivatives, and that only the formation of silylated imines was described when using well defined zinc hydride complexes. [20b,c] Noticeably, the reaction of benzonitrile in the presence of 5 mol% of Fe(CO)4IMes, 20 mol% of Zn(OTf)2 or In(OTf)3 and 3 equiv. of PhSiH3 led exclusively to benzylamine 3a with only trace amount of 4a. (Scheme 4a) [21,22] Importantly, no reaction occurred without light activation. (Scheme 4a) This result with In(OTf)3 as a co-catalyst thus excludes the formation of the secondary amine 4 through a pathway involving the generation of the aldimine C resulting of the condensation of A with B. (Scheme 5) [23, 19a] Additionally, as already described with Fe(0) catalyst in reduction of esters, and highlighted in Scheme 5, visible light activation is a crucial process to generate a 16 e-iron(0) species able to promote the oxidative addition of hydrosilane. [24] In order to rationalize the difference of selectivity when using indium co-catalyst in comparison to zinc one, a plausible pathway through the formation of secondary amide and its subsequent reduction was evaluated. The formation of the secondary amide D from benzylamine 3a and benzamide 1a was catalysed only by the indium salt, even if under the optimized conditions, the efficiency is moderate (22% yield) which may suggest that the species D can be efficiently obtained by the direct condensation of 1a with the disilylated species B. (Scheme 4c) The obtained secondary amide was then efficiently reduced by the Fe/In under hydrosilylation, both catalysts being described as efficient in such transformation. (Scheme 4d) [15,19] Scheme 4. Mechanistic studies. Reactions performed using light activation are highlighted in yellow. Results conducted in the absence of light activation are highlighted in grey.

From a mechanistic point of view, based on the above investigations, plausible pathways are shown in Scheme 5. The pathway explaining the selective formation of primary amines from primary amides involved a dehydration step leading to the nitrile 2 which is reduced thanks to the synergic combination of the iron catalyst and the zinc salt under light activation. An alternative pathway for the formation of the secondary amine 4 is proposed through the formation of secondary amide D via the In(OTf)3 promoted transamidation of 1 by the produced benzylamine 3 or its disilylated precursor B, [START_REF]For selected reviews on catalyzed transamidation reactions[END_REF] reaction which is more difficult with Zn(OTf)2. Finally, the amide D is reduced. Scheme 5. Proposed pathways for the selective formation of primary and secondary amines from primary amides. [START_REF]It should be noted that siloxane O[Si2Ph2(OMe)2(OH)2] was detected by GC-MS analysis of the crude mixture obtained after quenching the reaction with NaOH[END_REF] The yellow light bulb indicated the steps promoted by light activation.

Conclusion

In conclusion, we have developed tandem iron/zinc and iron/indium-catalyzed reductions of primary amides to primary and secondary amines under hydrosilylation conditions. Depending of the nature of the co-catalyst, the selectivity of the reduction was controlled: by using Zn(OTf)2, primary amines were selectively and efficiently produced (21 examples, 47-93% isolated yields) whereas with In(OTf)3, secondary amines can be obtained in moderate yields up to 51%. The potential synthetic application of the preparation of primary amines was demonstrated by a gram-scale reaction.

Experimental Section

Typical for the synthesis of primary amine hydrochloride salts 5. In a dried Schlenk tube with a magnetic bar, Fe(CO)4(IMes) (11.8 mg, 0.025 mmol, 5 mol%), Zn(OTf)2 (36.3 mg, 0.1 mmol, 20 mol%), primary amide (0.5 mmol, 1 equiv.), phenylsilane (162.3 mg, 1.5 mmol, 3 equiv.) and cyclohexane (1.5 mL) were added successively under an argon atmosphere. Then the mixture was stirred upon visible light irradiation (using 24 watt compact fluorescent lamp) at 110 o C for 20 h. After cooling to the room temperature, the mixture was diluted with ethyl acetate and filtrated through aluminum oxide. Then, 0.5 M HCl in solution was added and a precipitation occurred immediately, which was filtered and washed with diethyl ether to obtain the corresponding amine hydrochloride salt 5.

Typical procedure for the synthesis of secondary amines 4. In a dried Schlenk tube with a magnetic bar, Fe(CO)4(IMes) (11.8 mg, 0.025 mmol, 5 mol%), In(OTf)3 (56.2 mg, 0.1 mmol, 20 mol%), primary amide (0.5 mmol, 1 equiv.), phenylsilane (162.3 mg, 1.5 mmol, 3 equiv.) and toluene (1.5 mL) were added successively under an argon atmosphere. Then the mixture was stirred upon visible light irradiation (using 24 watt compact fluorescent lamp) at 130 o C for 20 h. After cooling to the room temperature, the mixture was diluted with ethyl acetate and filtrated through aluminum oxide. The residue was purified by silica gel column chromatography using a mixture of heptane and ethyl acetate as the eluent to afford the desired products 4.

Acknowledgements

This work is supported by the Université de Rennes 1, the Centre National de la Recherche Scientifique (CNRS) and the FR Increase. J. W. thanks the Chinese Scolarship Council for a PhD fellowship.

Entry for the Table of Contents

Insert graphic for Table of Contents here.

Insert text for Table of Contents here. Tandem iron/zinc or iron/indium-catalysed hydrosilylation primary amides is reported under visible light activation. The nature of the co-catalyst (Zn(OTf)2 vs In(OTf)3) played a crucial role for the selectivity of the Fe(CO)4(IMes) catalyzed reduction of primary amides: Zn promoted the formation of primary amines whereas secondary amines were obtained using indium co-catalyst.

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