Direct reductive amination of ketones with ammonium salt catalysed by Cp*Ir(iii) complexes bearing an amidato ligand

A series of half-sandwich Ir(iii) complexes 1-6 bearing an amidato bidentate ligand were conveniently synthesized and applied to the catalytic Leuckart-Wallach reaction to produce racemic alpha-chiral primary amines. With 0.1 mol% of complex 1, a broad range of ketones, including aryl ketones, dialkyl ketones, cyclic ketones, alpha-keto acids, alpha-keto esters and diketones, could be transformed to their corresponding primary amines with moderate to excellent yields (40%-95%). Asymmetric transformation was also attempted with chiral Ir complexes 3-6, and 16% ee of the desired primary amine was obtained. Despite the unsatisfactory enantio-control achieved so far, the current exploration might stimulate more efforts towards the discovery of better chiral catalysts for this challenging but important transformation.

Automated summary

A series of half-sandwich Ir(iii) complexes were synthesized and applied to catalyze the Leuckart-Wallach reaction to produce racemic alpha-chiral primary amines. Despite attempts at asymmetric transformation, the enantio-selectivity achieved was limited, but the study provides a basis for further efforts in developing better chiral catalysts for this important transformation.