Alkali Metal–Promoted Facile Synthesis of Secondary Amines from Imines and Carbodiimides

Abstract

AbstractWe present here an efficient method for the hydroboration of aldimines (‐C=N‐) with pinacolborane (HBpin) using an alkali metal catalyst, potassium benzyl. The reaction was accomplished with unprecedented catalytic efficiency under mild and solvent‐free conditions to afford the high yield of the corresponding N‐boryl amines up to 97%. Various functionalities on aldimines were incorporated for hydroboration. The corresponding boryl amines were subjected to further hydrolysis to yield the corresponding secondary amines with good yields up to 89%. This protocol for the reaction demonstrates an atom‐economic and green method with diverse imines that bears excellent functional group tolerance. Chemoselective reduction of imines was also attained, with good yields of 74–89%. We also propose the most plausible mechanism involving the formation of metal hydride as the active pre‐catalyst.