Multiple pathways in rhodium-catalyzed reactions of 1-alkynes with 3-butenoic acid

Article abstract of DOI:10.1016/0022-328X(90)87255-C

Rhodium(I) complexes have been shown to catalyze the reaction of 1-alkynes with 3-butenoic acid in alcoholic solvents at 85 deg C.Various pathways, involving rhodium-bonded vinylidene, α-vinyl, β-vinyl or alkynyl group as intermediates, have been uncovered under slightly different conditions.The stereo- and regiochemisty of these reactions provide evidence for the intermediacy of vinylidene-rhodium complexes when tertiary phosphine ligands are used.Subsequent protonation leads to β-vinylrhodium complexes.In contrast, α-vinylrhodium intermediates are involved in the case of di- or tri-alkyl or -aryl-phosphite ligands.The latter ligands also favour the formation of alkynylrhodium complexes at lower temperatures.Some mechanistic aspects are discussed.