95-23-8

93-84-5

95-23-8

Step: 21b Synthesis of 5-amino-1,3-dihydrobenzimidazol-2-one. Pd/C catalyst (140 mg) was added to a mixed solution of methanol and ethyl acetate containing 5-nitro-1,3-dihydrobenzimidazol-2-one (1.4 g, 7.8 mmol) and the hydrogenation reaction was carried out for 6 hours. The progress of the reaction was monitored by thin layer chromatography (TLC, the unfolding agent was a chloroform solution of 10% methanol). After completion of the reaction, the reaction mixture was filtered through a bed of diatomaceous earth and the filtrate was concentrated to give the target product 5-amino-1,3-dihydrobenzimidazol-2-one (1 g, 86% yield).