Electrocatalytic hydrogenation of quinolines with water over a fluorine-modified cobalt catalyst

Abstract

Room temperature and selective hydrogenation of quinolines to 1,2,3,4-tetrahydroquinolines using a safe and clean hydrogen donor catalyzed by cost-effective materials is significant yet challenging because of the difficult activation of quinolines and H2. Here, a fluorine-modified cobalt catalyst is synthesized via electroreduction of a Co(OH)F precursor that exhibits high activity for electrocatalytic hydrogenation of quinolines by using H2O as the hydrogen source to produce 1,2,3,4-tetrahydroquinolines with up to 99% selectivity and 94% isolated yield under ambient conditions. Fluorine surface-sites are shown to enhance the adsorption of quinolines and promote water activation to produce active atomic hydrogen (H*) by forming F−-K+(H2O)7 networks. A 1,4/2,3-addition pathway involving H* is proposed through combining experimental and theoretical results. Wide substrate scopes, scalable synthesis of bioactive precursors, facile preparation of deuterated analogues, and the paired synthesis of 1,2,3,4-tetrahydroquinoline and industrially important adiponitrile at a low voltage highlight the promising applications of this methodology.