Hydroesterification butadiene

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... 

Hydroesterification of butadiene with CH3OH employing a Co catalyst can proceed in a stepwise fashion, initially to methyl 3-penteneoate and subsequently, under more rigorous conditions, to dimethyl adipate. Thus hydroesterification of an olefin stream containing 44% butadiene (remainder mostly butenes) with CH3OH, employing Co2(CO)g catalyst and an isoquinoline promoter, gave 98% methyl pent-3-enoate ° after... 

The hydroesterification of butadiene is not well developed, although much effort in many industrial laboratories has been spent to develop this process as a method to prepare adipic add and caprolactam. Because little information on this process has been disclosed in 1he academic literature, this topic is not presented in detail here. Challenges encountered in developing this reaction include the regioselectivity for formation of terminal esters, the potential to form stable allyhnetal intermediates, and the potential to form polymeric or oligomeric products containing multiple diene units. 

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