152628-03-0

152628-01-8

152628-03-0

Example 4: Methyl 3-methyl-4-butyrylamino-5-nitrobenzoate (II) (10 g, 0.036 mol) was suspended in 60 ml of water and heated to 70-80 °C. A suspension of sodium dithionite (21.75 g, 0.124 mol) in 60 ml of water was added slowly and heated to 90-100 °C. Upon completion of the reaction, the pH of the reaction mixture was adjusted to 10-11 and the temperature was maintained with continued stirring until TLC detection showed complete disappearance of methyl 3-methyl-4-butyrylamino-5-nitrobenzoate. Subsequently, the pH of the reaction mixture was adjusted to 6-6.5. The resulting solid was filtered and dried at 45-50 °C to afford 2-n-propyl-4-methyl-6-carboxybenzimidazole (7.5 g, yield: 96.4%).