Cobalt‐Catalyzed Hydrogenation of Ketones and Aldimines with Ammonia Borane.

Efficient hydrogenation of organic compounds employing low‐cost and easy‐to‐synthesize catalysts is highly desirable as the corresponding hydrogenated products have significant importance in pharmaceutical and fine‐chemical industries. Herein, a cobalt(II) complex supported by α‐diimine ligand has been easily prepared by treatment of anhydrous CoCl2 with diimine, which can catalyze the hydrogenation of unsaturated bond with ammonia borane as the hydrogen source. A variety of ketones and aldimines bearing diverse functional groups can be reduced to corresponding alcohols and amines in moderate to excellent yields at ambient conditions. It is noteworthy that several readily reducible functional groups such as nitro and cyano are tolerated under the standard reaction conditions. Furthermore, the gram‐scale reaction has been successfully carried out and the procedure could be handled easily, which both make this methodology general and practical. [ABSTRACT FROM AUTHOR]