Ligand-enabled silver-catalyzed carbene insertion into the N–H bond of aliphatic and electron-rich aromatic amines

Abstract

Despite the recent flurry of silver catalysis in modern synthetic organic chemistry, silver-catalyzed carbene insertion into the N–H bonds remain scarce and limited to electron-poor aromatic amines. Herein, a ligand-enabled silver-catalyzed carbene insertion into the N–H bond of amines has been described, offering a selective route toward a series of otherwise difficult-to-obtain non-natural α- amino acid derivatives. In this way, we were able to achieve the first silver-catalyzed N–H insertion of aliphatic amines with the tribromo(tripyrazolyl)borate (Tp^Br3) ligand and efficient N–H insertion of electron-rich aromatic amines using the 1,2-diaminocyclohexane (DACH) ligand. The experimental and DFT mechanistic data reported here support an unprecedented mechanism for the silver catalyzed N–H insertion, wherein DACH stabilizes the silver catalyst by lowering its redox potential and amine acts as a proton shuttle in the reaction.