Ionic Liquid Hydrogen‐bonding Promoted Alcohols Amination over Cobalt Catalyst via Dihydrogen Autotransfer Mechanism

Higher amines are important high-valuable chemicals with wide applications, and amination of alcohols is a green route to them, which however generally suffers from harsh reaction conditions and use of equivalent base. Herein, we report an ionic liquid (IL) hydrogen-bonding promoted dihydrogen autotransfer strategy for amination of bio-alcohols to higher amines over cobalt catalyst under base-free conditions. Co(BF4)2·6H2O complexed with triphos and IL (e.g., tetrabutylphosphonium tetrafluoroborate, [P4444][BF4]) shows high performances for the reaction, and is tolerate to wide scopes of amines and bio-alcohols, affording higher amines in good to excellent yields. Mechanism investigation indicates that the [BF4]- anion activates alcohol via hydrogen bonding, promoting transfer of both hydroxyl H and a-H of alcohol to cobalt catalyst to form aldehyde intermediate and cobalt dihydride complex, which involve in subsequent reductive amination. This strategy provides a green and effective route for alcohol amination, which may have promising applications in alcohol-involved alkylation reactions.