DFT analysis of a key step in the cinchona-mediated organocatalytic Michael-addition of nitromethane to 1,3-diphenylpropenone

The potential of a series of cinchona-based organocatalyst candidates was investigated by comparative DFT analysis of the crucial bond-forming step of the enantioselective Michael addition of nitromethane to 1,3-diphenylpropenone. It was shown that the applied methods are feasible to investigate the influence of functional groups on the activation electron energy. Besides the well known interaction of the substrates with the urea and quinuclidine moiety the significance of π stacking- and H-bonding interactions between the electrophilic component and the catalyst are also pointed out. Due to the π stacking the replacement of the widely appreciated trifluoromethyl groups by nitro groups allows the interacting rings to get closer lowering the activation barrier of the crucial C–C bond formation step.