Abstract
Abstract A new preparative method to produce alkyl 2-alkynoates from 1-alkynes in alcohol under atmospheric pressure of CO at room temperature was developed with palladium–phosphine catalysts, using molecular oxygen as an oxidant. On the basis of the behavior of model complexes such as methoxycarbonylpalladium and alkynylpalladium complexes, we propose a mechanism accounting for the catalytic carbonylation of alkynes through an intermediate having the both methoxycarbonyl and alkynyl ligands that liberates methyl 2-alkynoates and a Pd(0) species on reductive elimination. The oxidation of Pd(0) to Pd(II) species in the presence of a halide ion was confirmed to proceed cleanly with molecular oxygen as the oxidant. On the basis of the findings on homogeneous catalysts, a heterogeneous catalytic system using Pd/C has also been developed.
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