A Model Theoretical Study for Alkylation in Benzimidazoles: ab initio Electrostatic Potentials

Abstract

Ab initio molecular orbital theory is used to study the protonation of benzimidazole anions. Both kinetically and thermodynamically controlled processes are considered for the unsubstituted and for NH₂, NO₂ and CN substituted systems. Extensive use is made of molecular electrostatic potential (m.e.p.) maps to predict kinetically preferred sites of protonation. Predictions made on this basis are consistent with experimental data on alkylation of these and closely related systems. In contrast, other approaches based on theoretical charges or frontier orbital coefficients do not correlate well with the experimental results.