Methyl 3-amino-4-(methylamino)benzoate (3.3 g) was dissolved in 96 ml of formic acid, 4 ml of water was added, and the reaction mixture was stirred at 90°C for 3 hours. After completion of the reaction, the reaction solution was concentrated under reduced pressure and the residue was dissolved in ethyl acetate. The organic phase was washed sequentially with saturated sodium bicarbonate solution and dried over anhydrous sodium sulfate. The organic phase was concentrated under reduced pressure to give methyl 1-methyl-1H-benzimidazole-5-carboxylate (3.4 g, 97% yield). The structure of the product was confirmed by 1H NMR (DMSO-d6, δ ppm: 3.8 (s, 3H), 3.8 (s, 3H), 7.6 (d, 1H), 7.9 (dd, 1H), 8.2 (d, 1H), 8.3 (s, 1H)) and ESI/MS (m/z: 191 [M+H]+).
