The design of C2-chiral bases with dual basic sites predicted to exceed the range of superbasicity: a computational study

Abstract

A set of C₂-chiral bases with bis-protonation sites (1–9) on dimethyl-binaphthalene derivatives have been explored using the B3LYP/6-311+G(d,p) level and the proton affinities calculated are in the range of superbases for both the sites. This would be the first report to possess a basicity exceeding the range of superbases on either basic site. The pK_a predicted for the designed system (9) in acetonitrile comes in the range of 32–36 at the B3LYP/6-311+G(d,p) level. The molecular electrostatic isopotential surface (MESP) shows that the two basic sites can simultaneously be protonated and the average PA results are also in the superbase region. The isodesmic reactions suggest that the super basicity achieved in these cases is the interplay of the ring strain of unprotonated bases, the steric repulsion, and the strength of intramolecular hydrogen bonding interactions. The kinetic activity predicted from the proton transfer study suggests that such chiral bases can perform as potential catalysts.