Nickel-catalyzed transfer hydrogenative cross-coupling of nitriles and amines with B2(OH)4/H2O system

H2O, which is the most environmentally benign solvent and exists widely in nature, usually provides hydrogen as a proton source. However, we found that H2O could serve as a hydride provider in the presence of B2(OH)4; thus, it can offer an expedient and efficient method for the synthesis of deuterated compounds, as D2O is the cheapest and most readily available deuterium source. Herein, we describe the application of a B2(OH)4/H2O system in Ni-catalyzed transfer hydrogenative cross-coupling reactions of nitriles with amines. Under this catalytic system, various interesting secondary amines and 2,3-dihydro-1H-perimidines could be obtained via intermolecular reactions. Moreover, indoles, which are crucial building blocks in pharmaceuticals, natural products and bioactive molecules, could also be obtained via intramolecular reactions with 2-(2-aminoaryl)acetonitriles as substrates.