Chiral thiourea-based bifunctional organocatalysts in the asymmetric nitro-Michael addition: A joint experimental-theoretical study

A highly enantioselective (84-92% ee) organocatalytic Michael addition of acetone to aromatic nitroolefins has been described. The transition state geometries for formation of R and S enantiomers in this Michael addition have been calculated and analyzed. It was shown that only one oxygen atom of the nitro group is bound to the thiourea moiety, in juxtaposition to the working hypothesis known from the literature which involves a bonding of both oxygens. The theoretical and experimental enantiomeric excess values show good agreement, rendering the computations an efficient tool for predicting the ee values in similar reactions.