Hydroesterification

In the reaction of aHyl alcohol with carbon monoxide using cobalt carbonyl, Co(CO)g as the catalyst, in the presence of a small amount of hydrogen and carbon monoxide under pressure, 9.8 MPa (1420 psi), at 100°C, intramolecular hydroesterification takes place, yielding y-butyrolactone [96-48-0] (16). 

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

Hydro carbonylation of olefins, hydroformylation, hydroesterification and hy-droxycarbonylation are reactions which appear to be of particular interest. Indeed, they allow the simultaneous creation of a new C - C bond as well as the introduction of a functional group (aldehyde, ester and acids). One or two new stereogenic centres can thus be formed at the same time (Scheme 26). Despite the difficulty of using high carbon monoxide pressure, the aheady existing industrial processes prove that such reactions can be performed on a very large scale [107]. 

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

Table 35 Homogeneous WGS, hydroesterification, hydroformylation-acetalization rates for cw-[Rh(CO)2(amine)2PF6 over 4 hours174... 

E.2. Supported Dendritic Catalysts for Carbonylation, Hydroesterification, Oxidation, and Heck Reactions... 

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). 

From the hydroesterification of 1-decene the cluster [Co3(H)2py5(CO)9] has been isolated.405 In the presence of 2-vinylpyridine, intermediates having the partial structure (94) were detected by NMR spectroscopy. This was believed to be an intermediate in the catalytic hydroesterification of 2-vinylpyridine to methyl 3-(2-pyridyl)propionate (equation 79). 

In presence of a mild base such as Na2C03 or NaOAc, a hydroesterification to furanones is possible (equation 89).437 RhCl3-3H20 or a binary carbonyl was used as catalyst. Indanont derivatives were obtained as by-products. The mechanism probably involves the formation of ar alkoxycarbonyl intermediate (Scheme 29). 

In the hydroesterification of styrene (equation 123) the isomer distribution was found to be very dependent on the phosphorus ligand used. 

When the cluster [Pd4(C0)4(02CMe)4]-2MeC02H was dissolved in styrene and treated with methanol under an atmosphere of carbon monoxide, methyl cinnamate was formed.516 This reaction was also believed to occur by an alkoxycarbonyl route. The reaction became catalytic when [Pd(OAc)2] (106) was used in presence of NaOAc and a stoichiometric amount of copper(II) as reoxidant for the palladium(O) formed. Stille and co-workers have investigated this reaction, sometimes called carboalkoxylation, in detail. A basic difference between this reaction and the hydroesterification described above is that the oxidative nature of carboalkoxylation permits double functionalization of a double bond. Thus (E)- and (Z)-2-butene react readily with CO and methanol in the presence of a catalytic amount of PdCl2 and a stoichiometric amount of CuCl2 to give methyl 3-methoxy-2-methylbutanoate (equation 124).517,518... 

The hydroesterification of dienes gave both the unsaturated monoesters and saturated diesters.524 In some cases, y-ketoesters were obtained and carbonylation of 1,5-cyclooctadiene in absence of alcohol gave a ketone.525 [PdI2(PBu3)2] was used as catalyst. If the catalyst contained a halide anion, butadiene underwent normal hydroesterification. When halide-free catalysts were used, the reaction took a different course. Dimerization of the diene occurred to give the ester of 3,8-nonadienoic acid as the major product (equation 128).526-528... 

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... 

With [Pd(DBA)2] (105) in the presence of (+)-neomenthyldiphenylphosphine, the hydroesterification of styrene with CO and methanol gave a best optical yield of 52% for the methyl 2-phenylpropionate formed.578 The reactions were carried out in presence of trifluoroacetic acid. Other acids were of far lesser value. It was believed that the complex [PdH(02CCF3)PPh2 (neomenthyl)] was formed. 

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