Regioselective hydroesterification of 1-alkynes catalyzed by palladium-phosphine complexes

The reaction of 1-alkynes, CO, and methanol (hydroesterification) catalyzed by palladium-phosphine complexes has been studied in acetonitrile media. B ranched alpha,beta-unsaturated ester was mainly produced in the presence of a catalytic amount of a palladium complex containing PPh3. In contrast, dp pf-based palladium complexes showed excellent regioselectivity for the form ation of linear alpha,beta-unsaturated ester. On the other hand, hydroester ification of 1,7-octadiyne with a catalyst system of Pd(OAc)(2)/PPh3/TsOH f ollowed a different path to give a cyclized carbonylation product as the ma jor product. A tentative mechanism involving a Pd-H species has been propos ed for these reactions. (C) 2000 Elsevier Science B.V. All rights reserved.