In situ generated aminodiborane as a reagent for deoxygenative reduction of carboxamides to amines

Abstract

Herein, we report a new method for the synthesis of aminodiborane (μ-NH₂B₂H₅) by the reaction of NH₃BH₃ and elemental iodine (I₂). The in situ generated aminodiborane is used as a reagent for the reduction of carboxamides to amines. This method is applicable to obtain various secondary amides, tertiary amides, and trifluoroamides, with yields in the range of 67–94%. This protocol is also useful for preparing galipinine, cinacalcet and tetracaine hydrochloride, which are pharmaceutically important compounds. Control experiments and DFT studies have been carried out to explore the mechanistic pathway. These studies indicate that the active reagent in the reduction of secondary amides is aminodiborane and in the case of tertiary amides, aminodiborane and polyaminoborane.