Dual catalyst control in the chiral diamine-dipeptide-catalyzed asymmetric Michael addition

By example of conjugate addition of 2-nitropropane to 2-cyclohexen-1-one, it is shown that the combination of H-Leu-His-OH and (1R,2R)-(+)-1,2-diphenylethylenediamine as co-catalysts in a suitable ratio can lead to a new catalytic system for the C-C bond formation reactions. Although neither co-catalyst is Sufficiently effective independently in terms of yield or enantioselectivity, their combination results in a drastic increase in yields (up to 86%) and absolute selectivities (up to 91% ee).