Hydroesterification, alkene

Oxo or Hydroformylation and Hydroesterification. Reactions of alkenes with hydrogen and formyl groups are cataly2ed by HCo(CO)4... 

Directed ruthenium-catalyzed hydroesterifications of alkenes, employing 2-pyridylmethyl formate, leads to esters (Equation (136)). With vinyl ethers a-adducts are obtained (Equation (137)). 

Similar 0—4 generations silica-supported Pd-PAMAM dendrimers with various spacer lengths were used by Alper et al. as recyclable catalysts for the hydroesterification reaction of alkenes (55) and the oxidation of terminal alkenes to methyl ketones (56). The hydroesterification experiments (Scheme 16) showed that (PPh3)2Pd-PPh2-PAMAM-Si02 complexes were highly active catalysts for styrene derivatives and linear long-chain alkenes (numbers of turnovers up to 1200). 

Platinum complexes have so far proved to be of only limited value as carbonylation catalysts. H2PtCl6 in the presence of SnCl2 acts as a hydroesterification catalyst for terminal alkenes (equation 141).5... 

So far, very little work has been carried out on asymmetric carbonylation. Existing studies all concern the hydroesterification of alkenes (equation 145). Depending on the structure of the alkene and the regioselectivity of the reaction, one or two asymmetric carbon atoms may be present in the product (equation 145).S74... 

Both mechanisms are predicted to show syn addition of hydride and caiboxylate to the alkene. In the metal hydride mechanism (equation 36) alkene insertion is syn and CO insertion proceeds with retention of configuration at carbon. In the metal carboxylate mechanisms (equation 37) alkene insertion is syn and cleavage of the metal-carbon bond can take place with retention at carbon. The palladium-catalyzed hydroesterification reaction produces the erythro ester from (Z)-3-methyl-2-pentene (equation 38) and the threo ester from ( )-3-methyl-2-pentene (equation 39).w... 

Table 5 Hydroesterification Reaction of 1 -Alkenes with Methanol... 

High enantiomeric excesses in the hydroesterification of alkenes have not been achieved. The reaction carried out with unbranched 1-alkenes or internal alkenes gives products in less than 20% enantiomeric excess (equation 59). The low enantiomeric excesses are due, in part, to the relatively high temperatures necessary to effect the reaction. 

The presence of catalytic amounts of halide salts (e.g. BU4NI) was found to enhance dramatically the efficiency of hydroesterification of alkenes (e.g. cyclohexenone) and alkynes catalysed by [(CO)i2Ru3] in the presence of the chelating 2-pyridylmethyl formate (2-C5H4NCH2OCHO). On the basis of IR and NMR studies, the halide effect... 

The 1,2-addition of H and CO2H, or CO2R to alkenes and alkynes is called hydrocarboxylation, or hydroesterification, and proceeds with catalytic amounts of... 

Hydroesterification is one of the Reppe reactions in which carbon monoxide, an alcohol, and an alkene react to esters (Scheme 21). This reaction is also called alkoxycarbonylation, hydroalkoxycarbonylation, and hydrocarbalkoxylation. 

The hydroesterification of alkenes is a versatile method for obtaining carboxylic esters from alkene, CO, and alcohol (Eq. 11.13) [45, 46]. 

Depending on the oxidative reaction conditions, besides dicarboxylated products, unsaturated carboxylic acid derivatives or in the case of hydroesterification ff-alkoxy esters could be formed [32]. Thus, linear 1-alkenes afford in principle /9-alkoxy esters under neutral oxidative conditions, but under more basic conditions, e.g., sodium butyrate buffer, 1,2-diesters predominate [36]. 

The synthesis of an ester by addition of carbon monoxide and an alcohol to an alkene, i.e. hydroesterification, has a fairly obvious relationship to the hydrocarboxylation described in Section 4.1.5, where water replaces the alcohol and a carboxylic acid is formed. Not surprisingly, therefore, the same types of catalysts, [Co2(CO)s], [H2PtCl6] and [Pd(PPh3)2Ch], are effective for both reactions. Unfortunately, the reaction usually requires very high pressures (200 bar) and necessitates the use of an autoclave. By varying the catalyst and reaction conditions a variety of linear, branched and cyclic alkenes can be carbonylated under these conditions to give the product in good yield (equation 32). Improved selectivity to the linear ester can be obtained by addition of SnCU to the catalyst system. 

Palladium salts can bring about oxidative carbonylation of alkenes in the presence of copper(II) salts which can reoxidize Pd° to Pd . Oxidative carbonylation is favored over simple hydroesterification by the presence of bases and by low temperatures (25 C) and low pressures (3-15 bar). The products can be a, -unsaturated esters, dicarboxylic acid esters or -alkoxy esters. By careful optimization of the conditions (25 °C, 4 bar CO, methanol solvent, CuCh reoxidant and sodium butyrate buffer) high yields of diesters can be obtained (equation 35). ... 

Asymmetric induction in the palladium-catalyzed hydroesterification of z-methylstyrene, styrene and other alkenes in the presence of ligands with rigid 5//-dibenzophospholyl units linked to chiral cyclobutane, dioxolane or cyclohexane skeletons (CBDBP, DIPHOL, CHDBP) is compared with the effect of the analogous diphenylphosphane ligands18 23. 

In a manner similar manner, the hydrocarbalkoxylation (commonly called hydroesterification) of alkenes in the presence of alcohols can be effected by the nickel, cobalt, platinum, and palladium catalysts described above (Eq. 

Homologation. The hydroesterification of alkenes using Pd(OAc)2, CO, Ph,P, and an alcohol under pressure also works when the clay-supported catalyst is used. ... 

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