P(NMe2)3-Mediatecl Umpolung Alkylation and Nonylidic Olefination of α-Keto Esters

A commercial phosphorus-based reagent (P-(NMe 2 ) 3 ) mediates umpolung alkylation of methyl aroylformates with benzylic and allylic bromides, leading to either Barbier-type addition or ylide-free olefination products upon workup. The reaction sequence is initiated by a two-electron redox addition of the tricoordinate phosphorus reagent with an α -keto ester compound (Kukhtin–Ramirez addition). A mechanistic rationale is offered for the chemoselectivity upon which the success of this nonmetal mediated C–C bond forming strategy is based.