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. (c) 2013 Elsevier Ltd. All rights reserved.