Reactions of phosphorus compounds. Part XXII. A reinvestigation of the reactions of activated alkynes with triphenylphosphine hydrobromide. An investigation of the reactions with bases of the vinylphosphonium salts prepared

Abstract

The reaction of triphenylphosphine hydrobromide with phenylpropiolic acid (1b) leads not to (Z)-2-carboxy-1-phenylvinyltriphenylphosphonium bromide (3B), as reported, but to a mixture of the E- and Z-isomers (3A and B). These isomeric vinylphosphonium salts can be converted into the corresponding 2-ethoxycarbonyl derivatives (4A and B) by way of the zwitterionic (E)- and (Z)-3-phenyl-3-triphenylphosphonioacrylates (10A and B). The salt (4A) is also formed by treatment of triphenylphosphine hydrobromide with ethyl phenylpropiolate (1c); again in disagreement with the literature report. The reactions of the salts prepared with alkoxides are reported.