An organoantimony nitrate complex with azastibocine framework as water tolerant Lewis acid catalyst for the synthesis of 1,2‐disubstitued benzimidazoles

Abstract

A novel organoantimony complex of 6‐cyclohexyl‐6,7‐dihydrodibenzo[c,f] [1,5]azastibocin‐12(5H)‐yl nitrate (2) was synthesized and systematically characterized by techniques such as NMR spectra, TG‐DSC, and X‐ray diffraction. It was found that the complex 2 exhibits relatively strong Lewis acidity (3.3 < Ho ≤ 4.8) and could be employed as a water tolerant Lewis acid catalyst for the synthesis of synthetically valuable benzimidazole derivatives starting from aldehydes and arylenediamines. This catalytic system shows excellent tolerance toward a wide variety of functional groups, such as methyl, methoxyl, fluoro, chloro, bromo, nitro, cyan, trifluoromethyl, 1‐naphthaldehyde, furfural and n‐butyl, together with facile reusability in 5 times scale enlarged synthesis.