Weinreb amide as an efficient reagent in the one pot synthesis of benzimidazoles and benzothiazoles

One pot synthesis of 2-substituted benzimidazoles/benzothiazoles through condensation is followed by cyclization of Weinreb amide with o-diaminoarene or o-aminothiophenol is reported. In the presence of boron trifluoride etherate in 1,4-dioxane solvent, a high yield (75–94%) was achieved within 60 min. Weinreb amide shows high selectivity in the reaction, even in presence of other active functional groups such as carboxyl, halogen, cyano, and methoxy.