Borenium-Catalyzed Reduction of Pyridines through the Combined Action of Hydrogen and Hydrosilane

Org Lett. 2021 Sep 3;23(17):6617-6621. doi: 10.1021/acs.orglett.1c01892. Epub 2021 Aug 12.

Abstract

Mesoionic carbene-stabilized borenium ions efficiently reduce substituted pyridines to piperidines in the presence of a hydrosilane and a hydrogen atmosphere. Control experiments and deuterium labeling studies demonstrate reversible hydrosilylation of the pyridine, enabling full reduction of the N-heterocycle under milder conditions. The silane is a critical reaction component to prevent adduct formation between the piperidine product and the borenium catalyst.