Pd/C-catalyzed Transfer Hydrogenation of N-H Indoles with Trifluoroethanol and Tetrahydroxydiboron as Hydrogen Source

Under the guidance of the known mechanism on hydrogenation of indoles and transfer hydrogenation with tetrahydroxydiboron (B2(OH)4), Pd/C catalyzed transfer hydrogenation of N-H indoles with trifluoroethanol and tetrahydroxydiborane as hydrogen source has been developed. It provides an efficient strategy and catalysis system for the reduction of un-activated N-H indoles. And N-H indolines are obtained with good to excellent yields. In addition, a series of the isotopic labelling experiments are carried out to probe the mechanism.