Rhodium-catalyzed CC coupling of allenes with 3-butenoic acid

Abstract

Allenes react with 3-butenoic acid under the catalytic action of rhodium(I) complexes to give dienoic acids. While 3-butenoic acid reacts selectively at the terminal carbon atom, allenes can react both at the central and at the terminal carbon atoms of the allenic system. The most important synthetic aspect is that, unlike terminal 1,3-dienes, higher homologues of allene can be caused to react preferentially at the terminal position, thus giving rise to linear 3,6-dienoic acids. Furthermore, the regioselectivity can be reversed using phosphites as ligands in place of phosphines, the major products being branched 3,5-dienoic acids.