Direct Oxidative Cyanation of Alcohol to Nitrile over CoOx/MnO2 with Aqueous Ammonia

Highly direct oxidative cyanation of alcohols provides a promising synthesis route for the cyanide-free synthesis of organic nitriles. It is challenging to explore a noble metal-free catalyst for direct conversion of alcohol to nitrile under ammonia conditions because it is a three-step consecutive reaction. In the present work, the CoOx/MnO2 catalyst was developed for direct oxidative cyanation of benzyl alcohol to benzonitrile with a yield of 86% and a selectivity of 91% with aqueous ammonia. The selectivity to benzonitrile and benzamide can be tuned via water accelerating the transformation of benzonitrile to benzamide. In addition, the kinetic studies reveal that the first step of the oxidation of benzyl alcohol is the rate-determining step for the consecutive reactions. It is found that Mn species are the main active sites while Co species are the co-catalyst for the titled reaction. Moreover, the starting substrates employed in the present catalytic system can be expanded to aliphatic, benzylic, allylic, and heterocyclic alcohols, which demonstrates a sustainable strategy for the direct synthesis of nitrile from alcohol while avoiding the use of the conventional toxic cyanide.