Synthesis of tert-butyl (1H-benzo[d]imidazol-2-yl)methylcarbamate.

tert-Butyl (1H-benzo[d]imidazol-2-yl)methylcarbamate.

Benzene-1, 2-diamine (1.05 g, 9.72 mmol) and N-(tert-butoxycarbonyl)glycine (1.71 g, 9.72 mmol) were dissolved in 30 ml of THF and cooled to 0 °C. Into the above solution was added N, N'-dicyclohexylcarbodiimide (2.41 g, 11.7 mmol ) in batches and the mixture was stirred at 0 °C for half an hour and then at room temperature overnight. The reaction mixture was filtrated and evaporated to afford a brown oil, which was purified by a silica-gel column chromatography (dichloromethane / methanol, 25:1 by volume) to get a yellow solid (2.24 g). The solid was dissolved in 20 ml of acetic acid and the solution was stirred at 72 °C for 8 h. The acetic acid was removed under reduced pressure and the crude compound was purified by a silica-gel column chromatography (dichloromethane / methanol, 25:1 by volume) to afford a white solid. Yield: 82%. m.p. 181-183 °C. IR (KBr) cm-1: 3343 (-NH-), 3058, 2980, 2940 (CH, aliphatic), 1686 (>C=O), 1529 (-C=C-), 736 (-Ar-); 1H NMR (300 MHz, CDCl3, δ ppm): 1.45 (s, 9H, CH3), 4.53-4.55 (d, 2H, J = 6.3 Hz, CH2), 6.12 (brs, 1H, NH), 7.22-7.25 (m, 2H, Ar-H), 7.54-7.60 (m, 2H, Ar-H); HRMS (ESI): [M + H]+ calcd m/z 248.1400, found 248.1397.δ ppm): 1.45 (s, 9H, CH3), 4.53-4.55 (d, 2H, J = 6.3 Hz, CH2), 6.12 (brs, 1H, NH), 7.22-7.25 (m, 2H, Ar-H), 7.54-7.60 (m, 2H, Ar-H); HRMS (ESI): [M + H]+ calcd m/z 248.1400, found 248.1397.