Reactions of phosphines with acetylenes. Part X. Structure revision of a so-called spirobiphosphole. The rearrangement of a tricycloallylidenephosphorane to a phosph(III)onin

Abstract

1,2,5-Triphenylphosphole and dimethyl acetylenedicarboxylate (2 equiv.) give a stable yellow adduct, which has been shown to be the tricyclo-allylidenephosphorane (12) rather than a stable spirobiphosphole, as previously suggested. The phosphorane rearranges in boiling chloroform to give a cis,cis,trans,cis-phosph(III)onin (17d). The stereochemistry, n.m.r. (¹H and ³¹P), u.v., and i.r. spectra are discussed.