Reactions of a Lewis acidic methylene phosphonium cationic adduct with olefins

Abstract

Efforts to deprotonate the halophosphonium cations [Ph₂P(X)Me]⁺ (X = F, Cl) generated species of the form [Ph₂(X)PC(H)PPh₂Me][X′]. The derivative where X = O₃SCF₃ provides access to a methylene phosphonium cation. The coordinated triflate anion can be replaced by Et₃PO and dimethylaminopyridine (DMAP). In addition, the cation reacts with the olefins R₂CCH₂ (R = Ph, Me) and PhMeCCH₂. While Ph₂CCH₂ was shown to give the species [Ph₂(Ph₂CCH)PCH₂PPh₂Me][O₃SCF₃]₂ with a pendant vinyl group, reactions with methyl substituted olefins undergo additional isomerization to form [Ph₂(RCH₂CCH₂)PCH₂PPh₂Me][O₃SCF₃]₂ (R = Ph, Me) featuring pendant allyl moieties.