The rearrangement of allylic phosphines

Abstract

Reduction of the allylic phosphine oxides, Ph₂P(O)CR¹R²·CH:CH₂, with phenylsilane followed by rapid distillation gives the crude allylic phosphines, Ph₂P·CR¹R²·CH:CH₂, which rearrange at 210° to the more stable phosphines Ph₂P·CH₂CH:CR¹R². This rearrangement is catalysed by traces of silanes or silanols; the pure allylic phosphines do not rearrange under these conditions. Diphenyl-1(1-phenylallyl)phosphine gave with methyl iodide the prototropically rearranged methyldiphenyl-(1-phenylprop-1-enyl)phosphonium iodide.