Ligand-Controlled Highly Regioselective and Asymmetric Hydrogenation of Quinoxalines Catalyzed by Ruthenium N-Heterocyclic Carbene Complexes

摘要

Optically active six-membered rings such as cyclohexanes and piperidines play an important role as biologically active building blocks and key intermediates in organic chemistry. Catalytic asymmetric hydrogenation of aromatic and hetero-aromatic compounds is one of the most straightforward routes for the formation of these saturated or partially saturated molecules. Recently, tremendous progress has been made in asymmetric reduction of bicyclic heteroaromatic compounds such as quinoxalines, quinolines,and indoles, and excellent yields and enantioselectivities have been obtained. However, in all these cases, only the reduction of the nitrogen-containing ring was reported, which creates a stereogenic center in the 2- or 3-position.