Chiral alcohols, as significant synthetic building blocks, are extensively applied in domains such as biology, chemical engineering, pharmaceutics, and fragrances. The asymmetric hydrogenation of ketones catalyzed by transition metal represents a crucial approach for the synthesis of chiral alcohols. In recent years, 3d metals have garnered escalating attention owing to their abundant reserves and environmentally friendly attributes. The asymmetric hydrogenation reactions catalyzed by 3d metal complexes have witnessed rapid development. Among them, when serving as the catalytic metal center in asymmetric hydrogenation reactions, cobalt has achieved commendable outcomes. Nevertheless, the reports on asymmetric transfer hydrogenation reactions of ketones catalyzed by cobalt are relatively scarce. The existing few cases suffer from deficiencies such as demanding conditions, low activity, and low enantioselectivity. This work reports an (S,S)-amide-ene (amino) cobalt(II) catalyst, which realizes the asymmetric transfer hydrogenation of ketones with a high turnover number (TON up to 862) under mild conditions. Through the optimization of the structure of P-NH-N-P ligand, the enantioselectivity of the catalyst is enhanced while expanding the substrate scope. This catalyst demonstrates good tolerance towards heterocyclic aryl and exposed amino groups. The transformation of 48 substrates including diaryl ketones, heteroaryl diaryl ketones, and 2'-amino- aryl alkyl ketones is accomplished within 20 min to 24 h, with yields up to>99% and enantiomeric excess (ee) up to 97%. Some of the obtained chiral alcohols are key intermediates for the synthesis of biologically active substances or drug molecules.

Key words: asymmetric transfer hydrogenation, cobalt catalyst, ketones, chiral alcohols, high-enantioselectivity