Synthesis of Benzo[a]quinolizidines via an Aza-Michael/Oxidative Mannich Process

Abstract

The synthesis of substituted benzo[a]quinolizidines via aza-Michael addition of tetrahydroisoquinolines to alkyl vinyl ketones, followed by oxidative Mannich cyclization, is described. Various Michael adducts are easily prepared, and subsequent DDQ-mediated oxidations stereoselectively afford the corresponding azacycles efficiently. Furthermore, the one-pot aza-Michael/oxidative Mannich process gave benzo[a]quinolizidines, thus providing a metal-free and practical synthetic route to N-heterocyclic building blocks.