C[O-].[Na+].[CH3:4][C:5]1[NH:6][C:7]2[CH:13]=[C:12]([C:14]([O:16][CH3:17])=[O:15])[C:11]([C:18]([O:20][CH3:21])=[O:19])=[CH:10][C:8]=2[N:9]=1.IC.[C:24](=O)(O)[O-].[Na+]>CO.C(O)(=O)C>[CH3:24][N:9]1[C:8]2[CH:10]=[C:11]([C:18]([O:20][CH3:21])=[O:19])[C:12]([C:14]([O:16][CH3:17])=[O:15])=[CH:13][C:7]=2[N:6]=[C:5]1[CH3:4]
Sodium methoxide (1.96 g, 36.3 mmol) is added to a solution of dimethyl 2-methyl-5,6-benzimidazoledicarboxylate (8.50 g, 34.2 mmol) in methanol. The reaction mixture is stirred 0.5 hour at room temperature, treated with iodomethane (2.15 mL, 34.5 mmol) stirred overnight, acidified to pH 6 with acetic acid, treated with sodium bicarbonate to pH 8 and extracted with chloroform. The extracts are combined, dried (MgSO4) and concentrated in vacuo to yield the title product as a pink solid (6.25 g, 69.7%). A small portion is recrystallized from ethyl acetate to afford the title product as pink crystals, mp 147°-148° C.
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