Reaction of α,β-Unsaturated Acid Chlorides with Tris(triphenylphosphine)chlororhodium(I): Formation of Phosphonium Salts

Article abstract of DOI:10.1021/ja00396a031

The reaction of (E)-cinnamoyl chloride and tris(triphenylphosphine)chlororhodium(I) in equivalent amounts in dichloroethane at 85 deg C gives styryltriphenylphosphonium chloride and bis(triphenylphosphine)chlorocarbonylrhodium in good yields. (E)-2-Butenoyl chloride gives 1-propenyltriphenylphosphonium chloride, and (E)-2-heptenoyl chloride gives a mixture of 1- and 2-hexenyltriphenylphosphonium chlorides. 3-Methyl-2-butenoyl chloride gives only isobutylene.None of these α,β-unsaturated acid chlorides give the expected 1-chloro-1-alkene.Control experiments showed that the phosphonium salts are not formed by secondary reactions.Bis(triphenylphosphine)styryldichlorocarbonylrhodium was shown to be an intermediate in the formation of styryltriphenylphosphonium chloride.A study of the kinetics of decomposition of the intermediate showed that dissociation of chloride ion is the rate-determining step.The observed rate law is -d/dt = kk'-> + k').The significance of these observations for an understanding of the details of the "reductive elimination" reaction is discussed.