Total Syntheses of Cinchona Alkaloids via Photoredox-Catalyzed Deoxygenative Arylation.

Abstract

Metallaphotoredox-enabled deoxygenative arylation of alcohols is a recently developed robust synthetic strategy for sp2-sp3 coupling by MacMillan. Inspired by this method, we report herein its first utilization in natural product total synthesis through realizing the coupling of 4-bromo-quinoline or 4-bromo-6-methoxyquinoline with quincorine or quincoridine, respectively. The alcohols were de novo synthesized in racemic form by a key step of the intramolecular Diels-Alder reaction or in an enantioselective manner by Ir/amine dual-catalyzed allylation. All members of the cinchona alkaloids could be prepared efficiently.