Mn-Catalyzed Asymmetric Transfer Hydrogenation of Ketones Improved by Cinchona Alkaloid-Derived NNS Ligands.

A novel class of phosphine-free manganese catalysts incorporating cinchona alkaloid-derived NNS ligands (L1-L8) has been successfully developed for asymmetric transfer hydrogenation (ATH). Among these, manganese complex Mn(CO)3(L1)Br demonstrated remarkable catalytic performance in the transfer hydrogenation of various ketone substrates (38 examples), achieving exceptional enantioselectivities of up to 99%. Through combined experimental investigations and density functional theory calculations, we proposed a plausible mechanistic pathway for the manganese-catalyzed ATH.