Site-Selective Pyridine C-H Alkylation with Alcohols and Thiols via Single-Electron Transfer of Frustrated Lewis Pairs

Angew Chem Int Ed Engl. 2022 Dec 19;61(51):e202213857. doi: 10.1002/anie.202213857. Epub 2022 Nov 22.

Abstract

A unified strategy for the deoxygenative or desulfurative pyridylation of various alcohols and thiols has been developed through a single-electron transfer (SET) process of frustrated Lewis pairs (FLPs) derived from pyridinium salts and PtBu3 . Mechanistic studies revealed that N-amidopyridinium salts serve as effective Lewis acids for the formation of FLPs with PtBu3 , and the generated phosphine radical cation ionically couples with the in situ generated xanthate, eventually affording the alkyl radical through facile β-scission under photocatalyst-free conditions. The reaction efficiency was further accelerated by visible-light irradiation. This method is conceptually appealing by using encounter complexes in FLP chemistry to promote SET, which provides a previously unrecognized opportunity for the selective heteroarylation of a diverse range of alcohols and thiols with various functional groups, even in complex settings under mild reaction conditions.

Keywords: C−H Functionalization; Frustrated Lewis Pairs; Heterocycles; Radicals; Reaction Mechanisms.