Enantioselective Catalytic Dearomative Addition of Grignard Reagents to 4-Methoxypyridinium Ions

ACS Catal. 2021 Jul 16;11(14):8476-8483. doi: 10.1021/acscatal.1c01544. Epub 2021 Jun 28.

Abstract

We describe a general catalytic methodology for the enantioselective dearomative alkylation of pyridine derivatives with Grignard reagents, allowing direct access to nearly enantiopure chiral dihydro-4-pyridones with yields up to 98%. The methodology involves dearomatization of in situ-formed N-acylpyridinium salts, employing alkyl organomagnesium reagents as nucleophiles and a chiral copper (I) complex as the catalyst. Computational and mechanistic studies provide insights into the origin of the reactivity and enantioselectivity of the catalytic process.