Théodore Vanbésien

Jérôme Le Nôtre

Eric Monflier

Frédéric Hapiot
email: frederic.hapiot@univ-artois.fr

Prof. Frédéric Hapiot

Hydroaminomethylation of oleochemicals: a comprehensive overview

Keywords: hydroaminomethylation, vegetable oils, fatty acid methyl esters, catalysis FAME, fatty acid methyl esters, HAM, hydroaminomethylation, HHM, hydrohydroxymethylation

The present review explores the historical background of the rhodium-catalyzed hydroaminomethylation (HAM) of vegetable oils and the recent developments in this field. The reaction conditions are especially discussed and commented upon. Various amines have been grafted onto alkyl chains of vegetable oils, thus giving rise to a wide range of bio-based HAM-products. A focus is on bifunctional HAM-products as they have potential as monomers in polymer chemistry. The nature of the ligands stabilizing the rhodium catalytic species is also discussed. The catalytic results obtained with phosphanes and amines are analyzed and compared. The goal of this review is to convince the reader that HAM of vegetable oils is a simple and effective synthetic pathway to access valuable functionalized bio-based compounds with industrial potential.

Introduction

Transition to green economy prompted chemists to valorize biomass resources. 1,[START_REF] Deuss | Homogeneous catalysis for the conversion of biomass and biomass-derived platform chemicals[END_REF][START_REF] Appels | Biomass valorization to energy and value added chemicals: The future of chemical industry[END_REF][START_REF] Sheldon | Green chemistry, catalysis and valorization of waste biomass[END_REF] However, competitiveness with petroleum products imposes chemical transformations of bio-sourced products in cost effective ways. In this context, the functionalization of feedstock through a maximum of two steps is highly desirable to access valuable products. Due to their long-chain methylene sequences and multiple functionalities, oleochemicals are promising platforms to obtain readily a wide range of bio-sourced building blocks. Given their structure, their derivatives could find applications in the field of polymers for which both aliphatic backbone and reactive functionality are often required. Countless functionalizations of oleochemicals have already been implemented. [START_REF] Behr | Homogeneous Catalysis with Renewables[END_REF] The carbon-carbon double bonds of fatty acids, fatty esters and triglycerides have especially been converted into epoxy, [START_REF] Findley | Epoxidation of Unsaturated Fatty Materials with Peracetic Acid in Glacial Acetic Acid Solution[END_REF][START_REF] Sonnet | Reactions of dioxiranes with selected oleochemicals[END_REF][START_REF] Kuo | Kinetics and mechanism of the catalyzed epoxidation of oleic acid with oxygen in the presence of benzaldehyde[END_REF][START_REF] Crivello | Epoxidized triglycerides as renewable monomers in photoinitiated cationic polymerization[END_REF][START_REF] Rüsch Gen Klaas | Lipase-catalyzed preparation of peroxy acids and their use for epoxidation[END_REF][START_REF] Pfister | Recent Advances in Vegetable Oil-Based Polyurethanes[END_REF][START_REF] Marks | The conjugation and epoxidation of fish oil[END_REF][START_REF] Uyama | Enzymatic synthesis and curing of biodegradable epoxidecontaining polyesters from renewable resources[END_REF] hydroxyl, [START_REF] Alagi | Vegetable Oil-Based Polyols for Sustainable Polyurethanes[END_REF][START_REF] Harry-O'kuru | Synthesis, rheological characterization, and constitutive modeling of polyhydroxy triglycerides derived from milkweed oil[END_REF][START_REF] Harry-O'kuru | Synthesis and characteristics of polyhydroxy triglycerides from milkweed oil[END_REF][START_REF] Eren | Hydroxymethylation and polymerization of plant oil triglycerides[END_REF][START_REF] Petrović | Structure and properties of polyurethanes prepared from triglyceride polyols by ozonolysis[END_REF][START_REF] Desroches | From vegetable oils to polyurethanes: Synthetic routes to polyols and main industrial products[END_REF][START_REF] Zhang | Substituting soybean oil-based polyol into polyurethane flexible foams[END_REF][START_REF] Latham | Process to prepare open cell foams made with natural oil based polyols and poly(propylene oxide) polyols[END_REF] formyl, [START_REF] Frankel | Catalytic hydroformylation of unsaturated fatty derivatives with cobalt carbonyl[END_REF][START_REF] Vanbésien | Supramolecular emulsifiers in biphasic catalysis: The substrate drives its own transformation[END_REF][START_REF] Mendes | Studies on the experimental variables effects on rhodium catalyzed hydroformylation of unsaturated fatty esters and comparison of [RhH(CO)(PPh3)3] and [RhCl3.3H2O] as starting catalytic precursors[END_REF][START_REF] Behr | Isomerizing hydroformylation of fatty acid esters: Formation of aldehydes[END_REF][START_REF] Kandanarachchi | Kinetics of the hydroformylation of soybean oil by ligandmodified homogeneous rhodium catalysis[END_REF],27 acrylate, [START_REF] Li | Synthesis and characterization of cast resin based on different saturation epoxidized soybean oil[END_REF][START_REF] Khot | Development and application of triglyceride-based polymers and composites[END_REF][START_REF] Scala | The effect of fatty acid composition on the acrylation kinetics of epoxidized triacylglycerol[END_REF] or cross-metathesis derivatives, [START_REF] Rybak | Cross-metathesis of fatty acid derivatives with methyl acrylate: renewable raw materials for the chemical industry[END_REF][START_REF] Malacea | Renewable materials as precursors of linear nitrile-acid derivatives via cross-metathesis of fatty esters and acids with acrylonitrile and fumaronitrile[END_REF][START_REF] Miao | A Direct Route to Bifunctional Aldehyde Derivatives via Self-and Cross-Metathesis of Unsaturated Aldehydes[END_REF] to name only a few. The functionalization of the carbon-carbon double bonds by amino groups is also of great interest. Indeed, the high nucleophilicity of nitrogens can be exploited in many reactions, especially in polymer chemistry. Additionally, it was reported that amino substituents grafted on vegetable oils are able to catalyze the condensation between alcohols and isocyanate to form polyurethane. [START_REF] Zhao | Natural oil based autocatalytic polyols[END_REF] Amino substituents are also interesting as the protonation of the nitrogen doublet gives ammonium salts with a hydrophilic character that could counterbalance the hydrophobic character of the alkyl chains to form amphiphilic species. [START_REF] Foley | Derivation and synthesis of renewable surfactants[END_REF] There are different approaches to synthesize amino-substituted vegetable oils (Scheme 1). Scheme 1. Most common approaches to synthesize amino-substituted vegetable oils. Amino vegetable oils are mainly being synthesized through epoxy ring-opening of epoxidized oils. [START_REF] Badran | The modification of epoxidized oils with amines-II. The modification of epoxidized linseed oil with aromatic amines[END_REF][START_REF] Lee | Modification of soybean oil for intermediates by epoxidation, alcoholysis and amidation[END_REF][START_REF] Liu | Conversion of soybean oil into ion exchange resins: Removal of copper (II), nickel (II), and cobalt (II) ions from dilute aqueous solution using carboxylatecontaining resin[END_REF][START_REF] Liu | Development of soy composites by direct deposition[END_REF][START_REF] Liu | [END_REF][START_REF] Dahlke | Polyhydroxy fatty acids and their derivatives from plant oils[END_REF][START_REF] Caillol | Synthesis of new polyester polyols from epoxidized vegetable oils and biobased acids[END_REF][START_REF] Biswas | Synthesis of diethylamine-functionalized soybean oil[END_REF][START_REF] Lu | Novel polymeric materials from vegetable oils and vinyl monomers: Preparation, properties, and applications[END_REF][START_REF] Liu | Solid freeform fabrication of epoxidized soybean oil/epoxy composites with di-, tri-, and polyethylene amine curing agents[END_REF] However, as the ringopening reaction does not proceed readily with internal epoxide, high reaction temperatures and catalysts are often required. [START_REF] Kandanarachchi | The hydroformylation of vegetable oils and model compounds by ligand modified rhodium catalysis[END_REF][START_REF] Li | Synthesis and characterization of cast resin based on different saturation epoxidized soybean oil[END_REF][START_REF] Malacea | Renewable materials as precursors of linear nitrile-acid derivatives via cross-metathesis of fatty esters and acids with acrylonitrile and fumaronitrile[END_REF][START_REF] Miao | A Direct Route to Bifunctional Aldehyde Derivatives via Self-and Cross-Metathesis of Unsaturated Aldehydes[END_REF][START_REF] Zhao | Natural oil based autocatalytic polyols[END_REF][START_REF] Radojčić | Study on the reaction of amines with internal epoxides[END_REF][START_REF] Liu | Green" composites from renewable resources: Preparation of epoxidized soybean oil and flax fiber composites[END_REF][START_REF] Singh | Synthesis of -Amino Alcohols from Methyl Epoxy Stearate[END_REF] Another approach to obtain amino vegetable oils consists in a four-steps procedure where the C=C double bonds are first converted into polyhydroxy oils which then undergo oxidization to yield polyketones. Conversion of polyketones with primary amines give polyimines, which are eventually reduced into polyamines. [START_REF] Harry-O'kuru | Polyamine triglycerides: Synthesis and study of their potential in lubrication, neutralization, and sequestration[END_REF] A more effective two-steps methodology was recently developed by Meier et al. Keto-FAME are directly synthesized from methyl oleate or erucate by cocatalyst-free Wacker oxidations using oxygen as sole re-oxidant. The resulting keto-FAME are then converted into amino derivatives by reductive amination. [START_REF] Winkler | Highly efficient oxyfunctionalization of unsaturated fatty acid esters: an attractive route the synthesis of polyamides from renewable resources[END_REF] Concurrently to tandem metathesis/hydrogenation, [START_REF] Miao | Tandem Catalytic Acrylonitrile Cross-Metathesis and Hydrogenation of Nitriles with Ruthenium Catalysts: Direct Access to Linear α,ω-Aminoesters from Renewables[END_REF][START_REF] Abel | Cross-metathesis approach to produce precursors of nylon 12 and nylon 13 from microalgae[END_REF] one of the easiest way to access amino oleochemicals is undoubtedly hydroaminomethylation (HAM). [START_REF] Chen | Recent progress in rhodiumcatalyzed hydroaminomethylation[END_REF][START_REF] Crozet | Recent advances in amine synthesis by catalytic hydroaminomethylation of alkenes[END_REF][START_REF] Petricci | Domino Reactions Triggered by Hydroformylation[END_REF] The HAM reaction has already been widely described and finds application in the synthesis of pharmaceuticals or natural compounds. [START_REF] Kalck | Tandem Rhodium Carbonylation Reactions[END_REF][START_REF] Crozet | Recent advances in amine synthesis by catalytic hydroaminomethylation of alkenes[END_REF][START_REF] Gehrtz | Carbonylations of alkenes in the total synthesis of natural compounds[END_REF] It consists in domino steps involving hydroformylation of the C=C double bond, subsequent condensation of the resulting formyl group with a primary or secondary amine to form an enamine, and hydrogenation of the enamine C=C double bond to yield amino oleochemicals (Scheme 1). As oleochemicals contain internal carbon-carbon double bonds, optimizing the regioselectivity of HAM is impractical. Accordingly, HAM products consist of a 1:1 mixture of two different regioisomers whose similar polarity prevent their separation. On the other hand, the chemoselectivity of the HAM reaction is greatly dependent upon the catalyst system. The aim of the present review is to highlight the progress that has been made during the past 17 years on HAM of oleochemicals.

Results and Discussion

The first scientific paper related to HAM of oleochemicals was published in 2000. Behr and Eilbracht reported the Rh-catalyzed HAM of oleic acid ethyl ester and oleyl alcohol with a wide range of primary and secondary amines. 59 Scheme 2. HAM of methyl oleate. HAM reactions were carried out at 140 °C under 100 bar CO/H2 (1:1) for 20 h with 0.5 mol-% [Rh(cod)Cl]2.

Using 1.5-fold excess of hexylamine with respect to oleic acid ethyl ester, the corresponding HAM product were isolated in 97% yield. Excess oleic acid ethyl ester drove the nitrogen of the amine to react twice, resulting in two oleic acid ethyl esters connected to each other by a tertiary amine (74% yield). Replacing hexylamine by other primary amines (1.5-fold excess) such as benzylamine or valinol led to slightly lower yields of products (91% and 95%, respectively). Conversely, a moderate 68% yield was obtained using aspartic acid diethyl ester as primary amine. Secondary amines gave very different results depending on the environment of the nitrogen. The best yield (99%) was measured with morpholine. Because of the rigid structure of morpholine, the nitrogen lone pair was fully available and readily reacted with the formyl groups to form an enamine, which was subsequently reduced into a tertiary amine. On the other hand, the worst yield (<5%) was obtained using diisopropylamine because the hindered isopropyl groups prevented the nitrogen lone pair to reveal its nucleophilicity. Interestingly, alcohols were mainly formed under these conditions. However, the authors did not comment on this in the publication. As we will explain later in the review, diisopropylamine probably coordinated to rhodium to form a hydrogenating catalytic species capable of reducing the aldehydes into alcohols. While a very high yield was obtained in HAM of oleic acid ethyl ester with morpholine, the same reaction with oleyl alcohol only gave 47% yield. No explanation was given at this stage on the significant loss in yield. Astonishingly, nothing was published on HAM of oleochemicals from 2000 to 2013, except reviews including the previous detailed work by Behr. 60,61 In 2013, in the continuity of their previous work, the same group reinvestigated the homogeneous catalyzed HAM of oleyl alcohol (Scheme 3). 62 Scheme 3. HAM of oleyl alcohol with diethyl amine.

They identified two side reactions as a source of conversion loss. Oleyl alcohol could be hydrogenated into octadecanol. Besides, amination of oleyl alcohol was also observed over 6 h. In this study, the HAM reaction was carried out using a 1:1 oleyl alcohol/diethylamine ratio, 0.5 mol% [Rh(cod)Cl]2, and 5 mL solvent under 30 bar CO/H2 (1:1) for 4 h. The synthesis of trialkylamine featuring two ethyl groups and a branched fatty alkyl chain depended upon the nature of the solvent. Polar protic solvent such as methanol led to a low 26% conversion while 64% oleyl alcohol were converted using polar aprotic solvent such as benzonitrile. The conversion reached 88% when the reaction temperature rose from 120 to 150 °C. At 150 °C, 79% of the expected trialkylamine product were isolated. A high 90% conversion was even obtained using PPh3 as a ligand. However, aldehydes were mainly formed under these conditions (58%), suggesting that the hydrogenating ability of the Rhcatalyst was too low. The issue could be overcome using bis (ditertiobutylphosphinomethylene)benzene (1,2-DTBPMB) as a ligand. In that case, the equilibriums were shifted to hydrogenating Rh-species and the expected product was obtained in 77% yield. However, the conversion was reduced to 79%. Better results were obtained at higher CO/H2 pressure. As predicted by the Henry's law, higher partial pressure of CO and H2 improved the gas availability in the solution with beneficial effect on the catalytic activity. In the presence of 1,2-DTBPMB under 40 bar CO/H2 (1:1), 98% oleyl alcohol were converted in 89% tertiary amine. The reaction was then transposed in thermomorphic multicomponent solvents (TMS) to enable the recyclability of the expensive Rh-catalyst (and possibly the ligand, if applicable). TMS are mixtures of solvents with varying degrees of polarity. At reaction temperature, they form a homogeneous phase while they separate into two phases at room temperature (Scheme 4). 63,64 Scheme 4. Principle of a thermomorphic multicomponent solvent (TMS) system.

In combination with alkanes, benzonitrile proved to be inappropriate because the miscibility gap was too low and did not allow a good phase separation. Accordingly, methanol was chosen as a polar solvent. However, the yields in tertiary amines were low (49-55%). Additionally, using methanol/decane mixtures, the lixiviation of the catalyst in the nonpolar phase was significant (176/154 ppm Rh/P). The amphiphilic character of the HAM products was incriminated to explain the Rh-catalyst leaching. In 2014, Vorholt and Behr reported the synthesis of carboxylic diesters through HAM of methyl oleate with proline and subsequent esterification (Scheme 5). 65 Scheme 5. HAM of methyl oleate with proline in MeOH.

The reactions were carried out in methanol using 1 eq proline and 1 eq methyl oleate at 130 °C under 30 bar of CO/H2 (1:1) for 4 h. Increasing the amount of catalytic precursor [Rh(cod)Cl]2 from 0.5 to 2 mol% logically led to higher conversions (Table 1, entries 1-3). However, yields in expected HAM products were limited because of the ratedetermining hydrogenation step of the enamine.

Table 1. HAM of methyl oleate with proline.

Addition of phosphanes such as BISBI (2,2'bis

((diphenylphosphino)methyl)-1,1'-biphenyl), BIPHEPHOS (6,6'-[(3,3'-di-tert-butyl-5,5'- dimethoxy-1,1'-biphenyl-2,2'- diyl)bis(oxy)]bis(dibenzo[d,f][1,3,2]dioxaphosphepi n)) or DPPB (1,4-bis(diphenylphosphino)butane)
amplified the effect as Rh-phosphanes are well known to be good hydroformylating catalysts but bad hydrogenating species (entries 4-6). The use of phosphanes also lowered the esterification step, as at best 6% diesters were isolated. To overcome the issue, addition of 1 eq methanesulfonic acid (MSA) instead of phosphane proved to be much more effective. The conversion of methyl oleate reached 77% along with a 77% selectivity in HAM-products (entry 7). Both the effect of MSA on the catalytic effect of the acid on the esterification and the hydrogenation of intermediate enamines were incriminated to explain the results. However, the stoichiometric methyl oleate/MSA proportions disqualified the process in the viewpoint of sustainability. Although lower quantities of MSA could be considered, the conversions were then dramatically affected. The catalyst could be efficiently recycled using TMS systems with methanol as the polar component and n-alkanes as non-polar solvents (1:1 volume ratio) in 70 mL batch autoclave. Increasing the alkane chain length gave higher conversions (from 54% with hexane to 67% with dodecane) and higher yields in HAM product (up to 55%). However, mass transfer problems were identified using dodecane, resulting in higher proportion of intermediate aldehydes. Leaching was also reduced (to 9 ppm with decane) with long alkyl chain solvents. As high amounts of HAM products were detected in the polar catalyst phase, sodium carbonate was used to neutralize the reaction mixture and subsequently allow the separation of catalyst and product. However, it should be noted that a salt precipitated in the methanol/decane mixture. A substantial erosion of the conversion (from 59 to 43%) and the percentage of the desired HAM-product (from 46 to 33%) was observed over 3 consecutive recycling runs, with a rhodium loss <10 ppm. Note that scaling up the process also yielded higher proportions of hydrogenated products (up to 13%). Vorholt further extended the potential of TMS systems to recycle Rh-catalyst in HAM of methyl oleate in the presence of 3-(methylamino)propionitrile (Scheme 6). 66 Scheme 6. HAM of methyl oleate with 3-(methylamino)-propionitrile.

The aim was to orient the HAM reaction specifically to the amino function, and subsequently hydrogenate the nitrile into an amino group to form an amino ester (precursor of polyamide). This strategy prevents the use of diamines, which would lead to amino-bridged methyl oleates. The HAM reaction was performed using [Rh(cod)Cl]2 (1 mol%) as rhodium precursor under 30 bar CO/H2 (1:1) at 120 °C for 4 h in a 40 mL autoclave . With acetonitrile as solvent, the use of BIPHEPHOS improved the conversion of the carbon-carbon double bonds (Table 2, entry 2).

Table 2. HAM of methyl oleate with 3-(methylamino)-propionitrile.

However, simply increasing the CO/H2 pressure to 40 bar led to higher conversions and advantageously prevented the use of phosphane (entry 3). As described previously, the choice of the non-polar and polar phases was crucial to form a biphasic system at room temperature and a monophasic system at high temperature. The highest content of HAM-product was obtained using heptane/acetonitrile mixtures (entry 8). However, whatever the proportions of each solvent, HAM-products were partitioned between the two immiscible phases, thus impeding the recovery of the reaction products and the Rhcatalyst. Indeed, 42% of HAM-products remained in the catalyst-containing phase. The best conversion (73%) was obtained under 50 bar CO/H2 (1:1) in a 2:3 (v/v) heptane/acetonitrile mixture (5 mL) (entry 9). In that case, the percentage of desired HAMproduct reached 64% with a selectivity of 95% and a Rh-catalyst loss in heptane of 0.6%. Scaling-up the process in a 300 mL autoclave did not significantly affect neither the yield for HAM-products (61-65%) nor the Rh-catalyst leaching (0.9-1.1%). Accordingly, TMS appears as an interesting but limited approach for HAM of methyl oleate. The process greatly suffers from the amphiphilicity of the HAMproducts. Recently, Suarez and coworkers reported the tandem hydroformylation/condensation reaction of soybean FAME using ionic liquid-based biphasic catalytic system. 67 The reaction was carried out with 1-butyl-3-methylimidazolium hexafluorophosphate as ionic liquid (IL) in the presence of n-butylamine with HRhCO(PPh3)3 (~0.1 mol%) as a catalyst precursor under 40 bar of CO/H2 (2:1) at 100 °C in a 100 mL stainless steel autoclave. Under such catalytic conditions, no amine was detected. The use of a 2:1 CO/H2 ratio seems odd, as a 1:2 CO/H2 is preferably required for HAM reactions. While the authors incriminated phosphanes and ILs to justify the absence of HAM-products, the 2:1 CO/H2 ratio is mainly responsible for the low hydrogenating ability of the Rh-species. Accordingly, the reaction should be qualified as "hydroiminomethylation" instead of "HAM". Concurrently to the previous approaches, we also developed catalytic systems for HAM of bio-based substrates. Our strategy was motivated by the need to find appropriate reaction conditions to convert the carbon-carbon double bonds of triglycerides into both amines and alcohols through a one-pot procedure. Based on previous studies showing that bio-sourced triglycerides underwent hydrohydroxymethylation (HHM) in the presence of a rhodium precursor and tertiary amines (Table 3, entry 1), 68,69 we anticipated that the formation of triglyceride-grafted tertiary amines resulting from HAM could act as ligand for rhodium catalyst capable of reducing the remaining formyl groups to primary alcohols (Scheme 7). 70,71 Scheme 7. HAM/HHM cascade reactions of triglycerides.

Knowing that tertiary amines are unable to react with formyl group, we made use of secondary amines to produce triglyceride-grafted tertiary amines by condensation with aldehydes. HAM proceeded under homogeneous conditions using triolein as a model substrate, [Rh(CO)2(acac)] (1.5 mol%) as a rhodium precursor, and toluene as a solvent under 80 bar of CO/H2 (1:1) at 80 °C for 18 h. One of the main advantage of the catalytic system lies in the absence of phosphane. Indeed, the hydroformylating and hydrogenating Rh-species were stabilized either by carbonyl or amine ligands as described on Scheme 8. Scheme 8. Equilibrium between hydroformylating and hydrogenating Rh-species.

After HAM, triglycerides were substituted by aminomethyl and hydroxymethyl groups in variable proportions depending upon the nature of the secondary amine (Table 3). Table 3. Rh-catalyzed hydroaminomethylation (HAM) of T in the presence of amines.

Using overstoichiometric ratio of diethylamine with respect to the carbon-carbon double bonds, Tgrafted tertiary amines were preferentially produced along with a significant reduction of aldehydes and hydrogenated products (entry 2). Conversely, low amounts of diethylamine preferably yielded triolein (T)-grafted primary alcohols (entry 5). Kinetic considerations clearly demonstrated that T-grafted tertiary amines preceded the formation of T-grafted primary alcohols, thus confirming our hypothesis that Tgrafted tertiary amines coordinated to rhodium to give Rh-species able to reduce the remaining aldehydes into alcohols. Using 1 equivalent N,Ndibutylamine with respect to C=C, HAM-products were substituted by one (10 mol%), two (32 mol%) or three (42 mol%) N,N-dibutylaminomethyl groups. Small proportions of diglycerides (11 mol%) and estolides (5 mol%) were also produced by transesterification of the triglyceride ester functions. The amine/alcohol ratio also varied over time. T-grafted tertiary amines resulting from HAM were mainly produced during the first 20 min while high proportions of amino-hydroxylated derivatives were formed over longer reaction times. Other reaction parameters such as the solvent or the CO/H2 pressure had little impact on the selectivity. On the other hand, changing the H2 and CO partial pressures strongly modify the proportions of Tgrafted amines and alcohols. Decreasing the H2 pressure gave higher proportions of amines. For example, the amine/alcohol ratio was 83/11 under a pressure of CO/H2 in a 2/1 ratio. Conversely, it was more balanced (45/47) with a 1/4 CO/H2 pressure. Higher proportions of amines were also obtained when increasing the reaction temperature to 110 °C, suggesting that the condensation/hydrogenation steps proceeded more easily. Condensation of primary amines resulted in T-grafted secondary that subsequently reacted intramolecularly with formyl groups to give T-grafted tertiary amines in a cyclic structure. Of interest, the HAM/HHM cascade reaction was successfully applied to commercial vegetable oils. Olive and sunflower behaved as triolein as they mainly contained monounsatured chains (~86%). On the contrary, amines, hydrogenated and conjugated isomers were produced with sesame oil which consisted of linoleic and linolenic chains (3.75 C=C per triglyceride on average). Less than 1% alcohols was detected in that case, suggesting that the hydrogenating properties of Rh-species was impeded by the formation of stable π-allyl rhodium complexes.

Conclusions

HAM is by far the most effective synthetic route to access amino vegetable oils as six consecutive steps are performed in one go. HAM-products are of great interest as they could be protonated to form cationic biosourced tensides or used as synthons in polymer chemistry. Amino vegetable oils substituted by other functions are also of interest as they can further react to give a wide range of bifunctional compounds. Such compounds could find application in the development of new biobased materials with specific properties. Although many investigations have already been devoted to HAM of vegetable oils, a great deal of work still lies ahead, especially to recycle the Rh-catalyst. We hope that, through the recent substantial progresses that have been, this review will stimulate the creativity and interest of chemists in HAM of vegetable oils. Conditions: 1 mmol triolein (T), 3 mmol amine, 0.015 mmol Rh(CO)2(acac), 5 mL toluene, 80 bar CO/H2 (1:1), 80 °C, 18 h.

Figures with legends

Scheme

  Scheme 1. Most common approaches to synthesize amino-substituted vegetable oils.

3 O 5 .Scheme 6 .

 356 Scheme 1. Most common approaches to synthesize amino-substituted vegetable oils.

Table 1 .

 1 HAM of methyl oleate with proline. a Conditions: n(methyl oleate)=3 mmol, methyl oleate:proline 1:1, [Rh(cod)Cl]2, 30 bar CO/H2 1:1, 5mL methanol, 1000 rpm, 130°C, 4 h, selectivity=diester yield/conversion; BISBI, 2,2'bis((diphenylphosphino)methyl)-1,1'-biphenyl; BIPHEPHOS, 6,6'-[(3,3'-di-tert-butyl-5,5'-dimethoxy-1,1'biphenyl-2,2'-diyl)bis(oxy)]bis(dibenzo[d,f][1,3,2]dioxaphosphepin);DPPB, 1,4bis(diphenylphosphino)butane. b with 1 eq. methyl sulfonic acid with respect to proline.

	Entry	Ligand	nRh (mol%)	Conv. (%)	Diester yield (%)	Selectivity (%)
	1	-	0.5	42	1	2
	2	-	1.0	75	15	20
	3	-	2.0	85	15	18
	4	BISBI	0.5	54	6	11
	5	BIPHEPHOS	0.5	49	6	12
	6	DPPB	0.5	61	1	2
	7 b	-	0.5	77	59	77

a

Table 2 .

 2 HAM of methyl oleate with 3-(methylamino)-propionitrile. a

	Entry	Non-polar	Non-polar	Conv. (%)	Yield (%)	Leaching	Ratio of HAM product
		solv.	solv./MeCN Vol%				non-polar:polar phase
	1	-	0:1	66	56	n.d.	n.d.
	2 b	-	0:1	76	65	n.d.	n.d.
	3 c	-	0:1	87	78	n.d.	n.d.
	4	octane	1:1	35	25	0.5	1.2
	5	cyclooctane 1:1	35	23	0.5	1.2
	6	decane	1:1	37	24	0.5	1.1
	7	dodecane	1:1	38	26	0.6	0.6
	8	heptane	1:1	38	25	0.6	1.4
	9 d	heptane	2.3	73	64	0.6	1.4
	a Conditions: 3 mmol methyl oleate, 3 mmol 3-(methylamino)-propionitrile, 1 mol% [Rh(cod)Cl]2, 4 mol%
	ligand, T=120°C, 30 bar CO/H2 (1:1), 5mL solvent, 4 h. b with BIPHEPHOS=6,6'-[(3,3'-Di-tert-butyl-5,5'-
	dimethoxy-1,1'-biphenyl-2,2'-diyl) bis(oxy)]bis-(dibenzo[d,f][1,3,2]dioxaphosphepin). CO/H2 pressure=40
	bar. d CO/H2 pressure=50 bar.

Table 3 .

 3 HAM of triolein (T) in the presence of amines. a

	entry amine	N/C=C	conv.	aldehyde	tertiary	alcohol (%) b hydrog. prod.
			ratio	(%) b	(%) b	amine (%) b		(%) b
	1	NBu3	1	100	0	-	96	4
	2	HNEt2	2	100	0	78	13	9
	3	HNEt2	1	100	0	65	27	8
	4	HNEt2	0.6	100	12	50	39	4
	5	HNEt2	0.3	100	35	19	48	2
	6	HNBu2	1	100	0	63	26	11
	7	HNHex2		100	0	63	28	5
	8	HNOct2	1	100	0	67	26	12

This work was performed, in partnership with the SAS PIVERT, within the frame of the French Institute for the Energy Transition (Institut pour la Transition Energétique (ITE) P.I.V.E.R.T.) (http://www.institutpivert.com) selected as an Investment for the Future ("Investissements d'Avenir"). This work was supported, as part of the Investments for the Future, by the French Government under the reference ANR-001-01.

The authors have declared no conflict of interest.

References --

59

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