Understanding the π-facial diastereoselectivity in the addition of chiral diaminophosphino(silyl)carbenes to activated olefins

The synthesis of a new chiral diaminophosphino(silyl)carbene, based on the use of (R,R)-cyclohexane-trans-1,2-diamine, is described. Its reaction with methyl acrylate afforded a cyclopropane derivative as a single diastereomer. The diastereoselectivity in the addition reactions between olefins and chiral carbenes derived from C2-symmetric diamines has also been studied by theoretical calculations, which establish that it has a steric origin; we report a rationale to predict the absolute configuration of the adducts.