DFT study on the effects of β-cyclodextrin in synthesis of 2-phenylbenzimidazole via benzaldehyde and o-phenylenediamine.

The conversion of 2-phenylbenzimidazole using o-phenylenediamine and benzaldehyde can be improved significantly under β-cyclodextrin (β-CD). The density functional theory (DFT) method was applied to study the whole process. According to energy parameters (binding energy, deformation energy) and structural deformation, entry models and the reaction process can be pinpointed, with o-phenylenediamine embedding β-CD from a wide rim, and then benzaldehyde passing into the inclusion from the narrow rim. Subsequently, natural bonding orbital (NBO), Mulliken charge, frontier orbital, FuKui function and nuclear magnetic resonance (NMR) methods were employed to reveal the mechanism of electron transfer. The results illustrate that β-CD plays a catalytic role in synthesis reaction mechanism on the secondary side, improving the reactivity and selectivity of the process. Graphical Abstract Density functional theory study of the effects of β-cyclodextrin in synthesis of 2-phenylbenzimidazole via benzaldehyde and o-phenylenediamine.