1. Methyl 2-amino-3-nitrobenzoate (150.0 g, 0.765 mol) was placed in an autoclave and ethyl acetate (1000 mL) and nickel ruanne (75 g) were added. The reaction mixture was stirred at 12-15 °C for 20-25 h under hydrogen pressure (2-3 kg/cm2). Upon completion of the reaction, the catalyst was removed by diatomaceous earth filtration and the diatomaceous earth was washed with ethyl acetate (150 mL). The filtrate was distilled under reduced pressure and the solvent was completely removed at 45-50 °C.
2. Acetic acid (171 mL) was added to the residue, and raw tetraethyl carbonate (180 g) was added slowly over 30-45 minutes. The reaction mixture was stirred at 25-35 °C for 2-3 hours.
3. Cool the reaction mixture to 0-5 °C and slowly add water (750 mL) over 15-30 min. The precipitated solid was filtered and washed sequentially with water (150 mL) and ethyl acetate (150 mL).
4. The resulting solid was dried at 55-65 °C for 10-12 h to afford methyl 2-ethoxy-1H-benzo[d]imidazole-7-carboxylate (140 g, 83.1% yield).
