Formamides derived from N-methyl amino acids serve as new chiral organocatalysts in the enantioselective reduction of aromatic ketimines with trichlorosilane

Asymmetric reduction of N-aryl ketimines , , and with trichlorosilane can be catalyzed by new N-methyl l-amino acid-derived Lewis-basic organocatalysts, such as the valine-derived bisamide (10 mol%), in toluene at room temperature with high enantioselectivity (≤92% ee). The structure–reactivity investigation shows that the product configuration is controlled by the nature of the side chain of the catalyst scaffold (e.g., i-Pr vs Me, as in and ), so that catalysts of the same absolute configuration may induce the formation of the opposite enantiomers of the product. Arene–arene interactions between the catalyst and the incoming imine appear to be the prerequisite for asymmetric induction. This metal-free, organocatalytic protocol is competitive with the traditional, metal-catalyzed methodology.