Iminophosphine-palladium(0) complexes as catalysts in the alkoxycarbonylation of terminal alkynes

In the presence of methanesulfonic acid, the palladium(0)-olefin complexes: [Pd(2-ol)(P–N)] [ol = dimethyl fumarate or fumaronitrile, P–N = 1-(Ph2P)C6H4-2-CH=NR (R = CMe3 or C6H4OMe-4)] catalyse the alkoxycarbonylation of terminal alkynes. Moderately good rates are obtained when the catalysts are promoted with two equivalents of the free P–N ligand and a large excess of acid at 120◦C. The catalytic data suggest that derivatives of the type [Pd(alkyne)(P–N)n] (n = 2–3) are the active catalytic species.