FURTHER-STUDIES OF THE PT(II) CATALYZED HYDROMETHOXYCARBONYLATION OF 1-ALKYNES

Pt(II) complexes such as PtCl2(PPh(3))(2), PtHCl(PPh(3))(2), PtHCl(PEt (3))(2), PtH(NO3) (PEt(3))(2), PtCl2(1,4- bis(diphenylphosphino) butan e) are able to catalyze the hydromethoxycarbonylation of phenylacetyle ne. It has been found that the dichloro complexes require the presence of SnCl2 to be active in catalysis, while the hydride species do not require the presence of promoters. Among the catalysts tested PtHCl(PP h(3))(2) displays the highest activity accompanied by a total regiosel ectivity towards the formation of methyl atropate, however the chemose lectivity of the reaction is only approximate to 40-60% owing to forma tion of high molecular weigh by-products due to partial polymerization both of the substrate and of the carbonylation product. It is interes ting to note that working with PtCl2(1,4-bis(diphenylphosphino) butane ) the regiochemistry of the reaction is inverted and the main product is methyl cinnamate. Some aspects of the mechanism are discussed.