Convenient Two-step One-pot Synthesis of Benzimidazoles Using 2-nitroanilines and Thiourea Dioxide

A new convenient method for the conversion of 2-nitroanilines into benzimidazoles by two-step one-pot procedure is reported. The procedure involves the reduction of nitro group followed by the intramolecular cyclisation of the corresponding o-phenylenediamines utilising thiourea dioxide and sodium hydroxide at 70 °C in mixed solvents of H 2 O and EtOH (v/v, 3/1). The yields are good to excellent and the workup is simple.