(NHC)Mn(I) complex catalyzed selective transfer hydrogenation of epoxides, azoarenes and nitroarenes utilizing ammonia borane

Abstract

Herein, we have reported an effective protocol for the regioselective transfer hydrogenation (TH) of epoxides by utilizing a phosphine-free bis-NHC-Mn(I) complex and ammonia borane. By employing this strategy, aromatic epoxides were selectively converted to primary alcohols whereas secondary alcohols were obtained exclusively from aliphatic epoxides. The protocol was further extended for the TH of azoarenes and nitroarenes to hydrazoarenes and anilines respectively. Notably, a library of substrates with different functional groups were screened which resulted in the corresponding transfer hydrogenated product in good to excellent yields. A series of mechanistic investigations were carried out to understand the catalytic process.