Computational study of structure of a catalyst for Darzens asymmetric synthesis

Chiral quaternary ammonium salts, catalysts for chiral Darzens reaction of α-chloroacetic acid esters with benzaldehyde to yield glycidates in phase-transfer catalysis conditions, were studied by using the DFT/B3LYP/6-31G∗∗ calculations. Structure and energetics of several complexes between the chiral Darzens reaction catalysts and α-haloacetic ester carboanion were examined. Based on comparison of the complex stabilization energies and experimental ee values it was shown that the complex interaction energy alone is not a crucial parameter for catalyst to be efficient in asymmetric synthesis. A catalyst design was also tried, however, despite the interaction energy for the designed catalyst increased the geometrical arrangement of the reactant and the catalyst favoured a racemic rather than an asymmetric reaction.