Triphenylallenyllead: A facile preparation and its use as a propargylating reagent

Article abstract of DOI:10.1021/om00017a081

Triphenylallenyllead, which is easily prepared by reaction of the readily available Ph₃PbMgBr (in situ, via 3 PhMgBr + PbCl₂ in THF) with propargyl bromide, reacts with aldehydes in the presence of a Lewis acid (BF₃·OEt₂ or TiCl₄) to give homopropargylic alcohols, RCH(OH)CH₂C≡CH, in good yield. Propargylation of ketones requires transmetalation of PH₃PbCH=C=CH₂ with PhLi to CH₂=C=CHLi and reaction of the latter with the ketone.