A One‐Pot Dearomative Approach to C4‐Alkylated Tetrahydropyridines and Tetrahydroquinolines

Abstract A regioselective one‐pot approach to the synthesis of C4‐alkylated tetrahydropyridines (THPs) and tetrahydroquinolines (THQs) by dearomatization of pyridines and quinolines has been developed. The transformation is achieved by the BF 3 ⋅ OEt 2 ‐mediated, C4‐selective addition of Grignard reagents, followed by a cascade of enamine protonation and the subsequent Et 3 SiH reduction of the resulting iminium ions. This protocol not only provides a facile synthetic approach to C4‐substituted THPs and THQs, but also offers a new strategy for the dearomatization of heteroaromatics.