EFFICIENT PALLADIUM CATALYSTS FOR THE CARBONYLATION OF ALKYNES

A class of highly efficient homogeneous palladium catalysts has been developed for the carbonylation of alkynes. One application of interest is the selective production of methyl methacrylate by methoxycarbonylation of propyne. The essential feature of the new catalyst systems is that they are formed by the combination of a ligand containing a 2-pyridylphosphine moiety with a palladium(II) species and a proton source containing weakly coordinating anions. High turn-over numbers of more than 40000 mol (mol Pd)-1 h-1 and selectivities towards methyl methacrylate of up to 99.95% can be obtained under mild conditions. It is suggested that the 2-pyridylphosphine ligand plays an essential role both as a chelating P-N ligand in the selectivity-determining step and as a monocoordinated ligand in the rate-determining step of the catalytic cycle.