[CH3:1][C:2]1[C:7]2[NH:8][CH:9]=[N:10][C:6]=2[C:5]([C:11]([OH:13])=[O:12])=[CH:4][CH:3]=1.[N+:14]([O-])([O-:16])=[O:15].[K+]>OS(O)(=O)=O>[CH3:1][C:2]1[C:7]2[NH:8][CH:9]=[N:10][C:6]=2[C:5]([C:11]([OH:13])=[O:12])=[CH:4][C:3]=1[N+:14]([O-:16])=[O:15]A mixture of 7-Methyl-1H-benzimidazole-4-carboxylic Acid (22) (4.944 g, 28.10 mmol) and concentrated H2SO4 (30 mL) is heated to about 60° C. to obtain a solution which is then cooled to about 0° C. To this solution is added KNO3 (3.12 g, 30.9 mmol) portionwise, so as to maintain the internal reaction temperature <10° C. Following complete addition, the cooling source is removed and the reaction mixture is allowed to warm to ambient temperature, whereupon the mixture is stirred for about 1 hour. The reaction mixture is then added to ice water (100 mL) and held at about 0° C. for about 4 hours. The resulting solids are filtered, washed with water, and dried to provide 7-Methyl-6-nitro-1H-benzimidazole-4-carboxylic Acid (23) as an off white solid (6.12 g, 98% Yield).
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