GENERAL METHOD: To a tetrahydrofuran (THF, 6 mL) solution of 4-methoxy-o-phenylenediamine (400 mg, 3.67 mmol) and N-cyano-4-methyl-N-phenylbenzenesulphonamide (998 mg, 3.67 mmol) was slowly added a hexane solution of 1 M lithium bis(trimethylsilyl)amide (LiHMDS) at 0°C (3.67 mL, 3.67 mL 3.67 mmol). The reaction mixture was stirred at 0°C to room temperature (rt) for 1 hour. Subsequently, the reaction mixture was poured into ice water and stirring was continued for 15 min. The reaction mixture was extracted with ethyl acetate (EtOAc) and the organic layer was separated. The organic layer was washed with saturated brine solution, dried over anhydrous sodium sulfate (Na2SO4), filtered and concentrated under reduced pressure. The crude product was purified by silica gel column chromatography to afford pure 5-methoxy-1H-benzimidazol-2-amine in 90% yield (471 mg).
