Unraveling the Metal–Ligand Cooperativity in a Phosphine-Free Mn(II)-Catalyzed Transfer Hydrogenation of Nitriles to Primary Amines and Dehydrogenation of Dimethylamine Borane

Selective synthesis of primary amines from nitriles is
challenging
in synthetic chemistry owing to the possible en route formation of
various amines and imines. Herein, we report a well-defined phosphine-free
Mn(II)-pincer complex-catalyzed transfer hydrogenation of nitriles
to the corresponding primary amines with a relatively unexplored hydrogen
source (dimethylamine borane). The protocol proceeds under relatively
mild conditions with a broad substrate scope involving metal–ligand
cooperation. Various control studies have been performed to understand
the mechanism of the present strategy. The gas chromatography analysis
of the reaction mixture revealed the evolution of the H2 gas through the dehydrogenation of dimethylamine borane. Detailed
computational calculations were undertaken to shed light on the possible
intermediates and transition states involved during the present protocol.