Synthesis of Piperidin-4-one Derivatives via -Imino Rhodium Carbene-Initiated 1,2-Aryl/Alkyl Migration and Annulation

Valuable piperidin-4-one derivatives were synthesizedin excellentyields via an & alpha;-imino carbene-initiated cascade reaction involving1,2-aryl/alkyl migration and annulation. The excellent selectivityof alkyl migration was attributed to the neighboring group participationof 2-bromoethyl. Features such as high efficiency, excellent migratingselectivity, broad substrate scope, and convenient one-pot procedurequalified this protocol as an effective tool for piperidine derivativesynthesis. The product could be transformed to a bioactive moleculeeasily. The migration-annulation reaction of & alpha;-imino carbeneprovided a powerful strategy for heterocycle construction.