Air Stable Iridium Catalysts for Direct Reductive Amination of Ketones.

Abstract

Half-sandwich iridium complexes bearing bidentate urea-phosphorus ligands were found to catalyze the direct reductive amination of aromatic and aliphatic ketones under mild conditions at 0.5 mol % loading with high selectivity towards primary amines. One of the complexes was found to be active in both the Leuckart-Wallach (NH4 CO2 H) type reaction as well as in the hydrogenative (H2 /NH4 AcO) reductive amination. The protocol with ammonium formate does not require an inert atmosphere, dry solvents, as well as additives and in contrast to previous reports takes place in hexafluoroisopropanol (HFIP) instead of methanol. Applying NH4 CO2 D or D2 resulted in a high degree of deuterium incorporation into the primary amine α-position.