Synthesis of Esters by Functionalisation of CO2

Abstract

The invention relates to a method for (I) producing a carboxylic ester of formula (I). Said method comprises the steps of: a) bringing an organosilane/borane of formula Si or B into contact with CO.sub.2, in the presence of a catalyst and an electrophilic compound of formula (III), the groups R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, Y, and M′ being as defined in claim 1; and optionally b) recovering the compound of formula (I) produced.

##STR00001##

Claims

1. A process for the preparation of a carboxylic ester of formula (I): ##STR00042## wherein: R.sup.1 independently represents a C.sub.1-C.sub.12 alkyl group, a C.sub.2-C.sub.12 alkenyl group, a C.sub.2-C.sub.12 alkynyl group, a C.sub.6-C.sub.10 aryl group, a (C.sub.6-C.sub.10)aryl(C.sub.1-C.sub.4)alkyl group, a 5- to 7-membered heteroaryl group, a 5- to 7-membered heterocycle, a silyl group —Si(R.sup.6).sub.3, a siloxy group —Si(OR.sup.6).sub.3 or an amino group —NR.sup.7R.sup.8, the alkyl, alkenyl, alkynyl, aryl, arylalkyl, heteroaryl and heterocycle groups optionally being substituted by one or more R.sup.9 groups, R.sup.5 independently represents a C.sub.1-C.sub.12 alkyl group, a C.sub.2-C.sub.12 alkenyl group, a C.sub.2-C.sub.12 alkynyl group, a C.sub.6-C.sub.10 aryl group, a (C.sub.6-C.sub.10)aryl(C.sub.1-C.sub.4)alkyl group, a 5- to 7-membered heteroaryl group, a 5- to 7-membered heterocycle, a silyl group —Si(R.sup.6).sub.3, a siloxy group —Si(OR.sup.6).sub.3 or an amino group —NR.sup.7R.sup.8, the alkyl, alkenyl, alkynyl, arylalkyl, aryl, heteroaryl and heterocycle groups optionally being substituted by one or more R.sup.9 groups, the process comprising: a) bringing an organosilane/borane of formula Si or B into contact with CO.sub.2 in the presence of a catalyst and of an electrophilic compound of formula (III): ##STR00043## wherein: R.sup.2, R.sup.3 and R.sup.4 represent, independently of one another, a C.sub.1-C.sub.12 alkyl group, a C.sub.2-C.sub.12 alkenyl group, a C.sub.2-C.sub.12 alkynyl group, a C.sub.1-C.sub.12 alkoxy group, a C.sub.6-C.sub.10 aryl group, a 5- to 7-membered heteroaryl group, a 5- to 7-membered heterocycle, a silyl group —Si(R.sup.6).sub.3, a siloxy group —Si(OR.sup.6).sub.3 or an amino group —NR.sup.7R.sup.8, the alkyl, alkenyl, alkynyl, aryl, heteroaryl and heterocycle groups optionally being substituted by one or more R.sup.10 groups; Y represents a negatively charged organic or inorganic ligand; M represents an organic or inorganic cation; X represents Cl, Br, I, or an —OSO.sub.2R.sup.11 group, or R.sup.5—X, taken in its entirety, represents an oxonium salt; R.sup.6, in each case, independently represents a hydrogen atom, a halogen atom, a C.sub.1-C.sub.6 alkyl group, a C.sub.1-C.sub.6 alkoxy group or a C.sub.6-C.sub.10 aryl group; R.sup.7 and R.sup.8 represent, independently of one another, a hydrogen atom, a C.sub.1-C.sub.6 alkyl group, a C.sub.2-C.sub.6 alkenyl group, a C.sub.2-C.sub.6 alkynyl group, a C.sub.6-C.sub.10 aryl group, a 5- to 7-membered heteroaryl group, a 5- to 7-membered heterocycle, a silyl group —Si(R.sup.6).sub.3 or a siloxy group —Si(OR.sup.6).sub.3; R.sup.9 and R.sup.10 represent, independently of ore another a halogen atom, a C.sub.1-C.sub.6 alkyl group, a C.sub.1-C.sub.6 perfluoroalkyl group, a hydroxyl group, a C.sub.1-C.sub.6 alkoxy group, a nitro (—NO.sub.2) group, a nitrile (—CN) group or a C.sub.6-C.sub.10 aryl group; R.sup.11, in each case, independently represents a C.sub.1-C.sub.6 alkyl or perfluoroalkyl group or a C.sub.6-C.sub.10 aryl group, the aryl group optionally being substituted by one or more C.sub.1-C.sub.6 alkyls, and optionally b) recovering the compound of formula (I) obtained.

2. The process as claimed in claim 1, wherein the catalyst is an organic catalyst, a metal salt or a metal complex.

3. The process as claimed in claim 2, wherein the catalyst is a metal salt or complex.

4. The process as claimed in claim 3, wherein the metal is selected from the group consisting of metalloids of Groups 13-16 of the Periodic Table, alkali metals, alkaline earth metals, transition metals and rare earth metals.

5. The process as claimed in claim 4, wherein the metal is silicon or copper.

6. The process as claimed in claim 1, wherein the catalyst is a metal salt or complex in which the metal is silicon or copper.

7. The process as claimed in claim 1, wherein the catalyst is a complex of a transition metal and of an N-heterocyclic carbene.

8. The process as claimed in claim 1, wherein the catalyst is tetrabutylammonium triphenyldifluorosilicate (TBAT) or chloro- or fluoro[1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene]copper (I) (1PrCu(I)).

9. The process as claimed in claim 1, wherein in stage a) the CO.sub.2 is under pressure.

10. The process as claimed in claim 1, wherein stage a) is carried out at a temperature of between 25° C. and 150° C.

11. The process as claimed in claim 1, wherein the molar ratio of (Si or B) to the compound of formula (Ill) is from 0.5 to 5.

12. The process as claimed in claim 1, wherein the amount of catalyst is between 0.001 and 1 molar equivalent, with respect to the substrate of formula (Si or B).

13. A process for the preparation of labeled carboxylic ester compounds of formula (I′): ##STR00044## the process comprising the stages of: a) bringing together an organosilane/borane of formula Si or B and C*O*.sub.2 in the presence of a catalyst and of an electrophilic compound of formula (HIT ##STR00045## wherein: R.sup.1* and R.sup.5* respectively correspond to R.sup.1 and R.sup.5 as defined in claim 1, and optionally comprise a H*, C*, N*, O*, F*, Si* and/or S*, H* represents a hydrogen atom (.sup.1H), deuterium (.sup.2H) or tritium (.sup.3H), C* represents a carbon atom (.sup.12C) or a .sup.11C, .sup.13C or .sup.14C isotope, N* represents a nitrogen atom (.sup.14N) or a .sup.15N isotope, O* represents an oxygen atom (.sup.16O) or a .sup.18O isotope, F represents a fluorine atom (.sup.19F) or a .sup.18F isotope, Si* represents a silicon atom (.sup.28Si) or a .sup.29Si or .sup.30Si isotope, S* represents a sulfur atom (.sup.32S) or a .sup.33S, .sup.34S or .sup.36S isotope, R.sup.2, R.sup.3, R.sup.4, Y, M and X are as defined in claim 1, where at least one of the compounds Si* or B*, C*O.sub.2* or R.sup.5*—X comprises an isotope from those listed above, and optionally b) recovering the compound of formula (I′) obtained.

14. A process as defined in claim 1 for recovery in value of CO.sub.2 emissions.

Description

EXAMPLES

[0120] Abbreviations:

RT: room temperature

##STR00010##

[0121] 1. Materials and Methods

[0122] The catalytic reaction for the esterification of the organosilanes of the process according to the invention was carried out according to the following experimental protocol:

[0123] 1. The organosilane/borane (1 equivalent), the precatalyst (from 0.001 to 1 equivalent), the additive (from 1 to 3 equivalents), the halide (from 1 to 2 equivalents) and the solvent are introduced under an inert atmosphere, in a glovebox, into a Schlenk tube, which is subsequently sealed by a J. Young valve. The concentration of organosilane/borane and of halide in the reaction mixture is approximately 0.3M (concentration calculated on the basis of the volume of solvent introduced). The order of introduction of the reactants is not important.

[0124] 2. The Schlenk tube is subsequently placed under a CO.sub.2 pressure (from 1 to 3 bar) using a vacuum line and is then heated at a temperature of between 25 and 100° C. until the organosilane/borane has completely converted (reactions of 5 minutes to 72 hours).

[0125] 3. Once the reaction is complete, an Et.sub.2O/H.sub.2O extraction makes it possible to remove the undesirable salts. The organic phase is collected. The remaining volatile compounds in the organic phase are removed under reduced pressure and the reaction mixture is purified by chromatography on silica gel. The use of an ethyl acetate/n-pentane mixture as eluent makes it possible to obtain the analytically pure ester. Alternatively, if the boiling point of the ester of formula (I) is sufficiently low (<200° C.), the ester can be isolated from the reaction mixture by a simple distillation at ambient or reduced pressure.

[0126] 2. Results

[0127] The results obtained are presented below, giving examples of conversions of various hypervalent silanes/boranes and organosilanes/boranes to give esters (determined by NMR) under stoichiometric and catalytic conditions.

##STR00011##

[0128] Different systems were tested for the reaction:

2.1. Stoichiometric Reactions Involving the Catalyst TBAT

[0129]

TABLE-US-00001 TABLE 1 [00012] [00013] Entry R-Hal Conditions Yield (%) 1 n-Prl RT, 40 h 90 2 i-Prl RT, 40 h 85 3 n-Hexl RT, 40 h 93 4 [00014] RT, 40 h 99 5 [00015] 70° C., 23 h 99 6 [00016] 70° C., 3 h 99 7 n-HexBr 70° C., 23 h 93 8 [00017] 70° C., 23 h 58 9 [00018] 70° C., 3 h 99 10 n-HexCl 70° C., 17 h 99

##STR00019## ##STR00020##

2.2. Copper-Based Stoichiometric Reactions

[0130]

TABLE-US-00002 TABLE 2 [00021] [00022] Entry Substrate Yield 1 PhSi(OMe).sub.3 52 2 PhSiMe(OEt).sub.2 46 3 PhSi(OEt).sub.3 53 4 p-MeOPhSi(OEt).sub.3 53 5 p-ClPhSi(OEt).sub.3 60 6 vinylSi(OMe).sub.3 33 7 allylSi(OMe).sub.3 62

2.3. Copper-Based Catalytic Reactions

[0131] PySiMe.sub.2vinyl as substrate

TABLE-US-00003 TABLE 3 [00023] [00024] Entry RX Conditions Yield (%) 1 CH.sub.3I RT, 20 h 86 2 [00025] 70° C., 20 h 20 3 [00026] 70° C., 20 h 17 4 [00027] RT, 20 h 20 5 n-Hexl RT, 20 h 34

[0132] TBAT as substrate

TABLE-US-00004 TABLE 4 [00028] Entry R-Hal Conditions Yield (%) 1 n-Prl 70° C., 18 h 76 2 i-Prl 70° C., 18 h 63 3 n-Hexl 70° C., 18 h 84 4 PhBr 70° C., 18 h 48
3. Copper-Based Catalytic Reactions with Phenyltriethoxysilane as Substrate

[0133] Variation of the Solvent

TABLE-US-00005 TABLE 5 [00029] [00030] Entry Solvent Yield (%) 1 THF 22 2 DMF 10 3 CH.sub.3CN 25

[0134] Variation of the Catalyst

TABLE-US-00006 TABLE 6 [00031] [00032] Entry X Cat. Yield (%) 1 OEt CuC 10 2 OMe CuCl 10 3 Cl CuCl 15 4 F CuCl 82 5 F Cu(0) 35 6 F IPrCuCl 52 7 F IPr + CuF.sub.2 46 8 F IPrCuF 70 9 F SMes + CuI 75 10 F itBu + CuI 50 11 F SiPr + CuI 54 12 F TMEDA + CuCl 20 13 F Bipy + CuCl 10 14 F Dppz + CuCl  5

[0135] Variation of the Electrophile

TABLE-US-00007 TABLE 7 [00033] [00034] Entry R-Hal Yield (%) 1 [00035] 70 2 [00036] 55 3 [00037] 59 4 [00038]  5 5 [00039] 20

[0136] Variation of the Silane

TABLE-US-00008 TABLE 8 [00040] [00041] Entry R X Catalyst Yield (%) 1 Cl OEt CuI 25 2 CF.sub.3 OEt CuI  5 3 Me OEt CuI 10 4 Me F IPrCuF 90