Borane-Catalyzed Asymmetric Reduction of 2-Alkylpyridines†

Abstract

Herein, a method for the enantioselective reduction of unprotected 2-alkylpyridines is reported for the first time. By using pinacolborane and an amide as reducing agents, a large number of 2-alkylpiperidines were synthesized with high yields and excellent enantioselectivities via a cascade process involving 1,4-hydroboration and subsequent transfer hydrogenation. The resulting products can be easily converted to natural alkaloids.