One-pot, two-step synthesis and photophysical properties of 2-(5-phenylindol-3-yl)benzimidazole derivatives

Abstract

An efficient one-pot, two-step procedure has been successfully applied for the synthesis of a series of 2-(5-phenylindol-3-yl)benzimidazoles. The first step was cyclocondensation–oxidation of 5-bromoindole-3-aldehydes with o-phenylenediamines in 1,4-dioxane, which was promoted by activated carbon and used atmospheric air as a “green” oxidant. The resulting 2-(5-bromoindol-3-yl)benzimidazoles in the pot were in situ coupled with postadded phenylboronic acids, and catalyzed with PdCl₂(dppf) in 1,4-dioxane-H₂O to afford the desired compounds with satisfactorily high yields. The relationship between the synthesized compounds' absorption, and fluorescence spectra with molecular structures has been investigated with experimental data and theoretical calculations.