Diboron-Mediated Rhodium-Catalysed Transfer Hydrogenation of Alkenes and Carbonyls

A diboron-mediated rhodium-catalysed transfer hydrogenation system using water as the hydrogen donor is developed. In addition to a series of alkenes with good functional group tolerance, this rhodium-based catalytic system also effectively reduces aldehydes and ketones. A plausible mechanism involving the Rh-I-catalysed hydrogen generation and Rh-0-catalysed hydrogenation is proposed for the reaction.