Biphilic Organophosphorus Catalysis: Regioselective Reductive Transposition of Allylic Bromides via p~Ⅲ/p~Ⅴ Redox Cycling

摘要

We report that a regioselective reductive transposition of primary allylic bromides is catalyzed by a biphilic organophosphorus (phosphetane) catalyst. Spec-troscopic evidence supports the formation of a penta-coordinate (σ~5-P) hydridophosphorane as a key reactive intermediate. Kinetics experiments and computational modeling are consistent with a unimolecular decomposition of the σ~5-P hydridophosphorane via a concerted cyclic transition structure that delivers the observed allylic transposition and completes a novel P~Ⅲ/P~Ⅴ redox catalytic cycle. These results broaden the growing repertoire of reactions catalyzed within the P~Ⅲ/P~Ⅴ redox couple and suggest additional opportunities for organophosphorus catalysis in a biphilic mode.