Borane-Catalyzed Transfer Hydrogenations of Pyridines with Ammonia Borane

With the use of ammonia borane as a hydrogen source, a borane catalyzed metal-free transfer hydrogenation of pyridines was successfully realized for the first time to furnish a variety of piperidines in 44–88% yields with moderate to excellent <i>cis</i>-selectivities. The ease in handling without requiring high pressure H<sub>2</sub> makes this transfer hydrogenation practical and useful.