SELECTIVE CODIMERIZATION OF ACETYLENES AND ALLYL HALIDES CATALYZED BY PALLADIUM COMPLEXES

The reaction of various acetylenes and ally! halides with palladium complexes selectively gives substituted 1, 4-diene codimers. The PdX2(PhCN)2 complex is the most active catalyst. In contrast to substituted acetylenes, the reaction of acetylene itself and altyl halides gives a l-halogeno-l, 3, 6-heptatriene cotrimer besides codimers. The catalytic reaction proceeds via Pd-halogen bond recycle; initially acetylene inserts into a Pd-halogen bond and subsequently allyl halide inserts into a Pd-vinyl bond, followed by the β-halogen elimination to give a codimer. The successive insertions of acetylene and allyl halide into the Pd-vinyl bond give a cotrimer. This codimerization provides a very convenient synthetic method for halogeno-substituted mono-and/or diolefins. © 1979, American Chemical Society. All rights reserved.