Direct α,β-C-H Difunctionalization of Piperidines for the Construction of the N,O-Acetal Skeleton via 1,5-Hydride Transfer.

Abstract

Herein, we describe an unprecedented Lewis acid-catalyzed annulation of phenols with o-aminobenzaldehydes via a cascade coupling/1,5-hydride transfer/cyclization sequence. The α- and β-positions of cyclic amines were functionalized utilizing enamines generated in situ. A series of complex N,O-acetal derivatives are synthesized in moderate to good yields in one step. The methodology features high atom and step economy, excellent diastereoselectivity, and water as the sole byproduct.