Reaction OF E-1,2-bis[triphenyl(trifluoromethanesulfonyloxy)phospho]ethylene, Ph₃PCHCHPPh₃·20Tfwith bases: Unusual products and evidence for C₂-dlylide, Ph₃PCCPPh₃, formation

E-1,2-di[triphenyl(trifluoromethanesulphonyloxy)phospho]ethylene 4 reacts with Et₃N or NaH in wet CH₃CN affording phosphineoxides 6 and 7 as a result of phenyl migration and related rearrangements in hydrolysed phosphonium moieties. The reaction of 4 with t-BuLi in CH₂Cl₂ results in nucleophilic vinylic substitution of the phosphonium group by the t-Bu anion. Evidence for the intermediate formation of the C₂-diylide 3 is obtained in the reaction of 4 with n-BuLi in CH₂Cl₂ via trapping with 3,4-dichlorobenzaldehyde.