[CH3:1][N:2]1[C:6]2[CH:7]=[C:8]([C:15]([O:17]C)=[O:16])[C:9]([C:11]([O:13]C)=[O:12])=[CH:10][C:5]=2[N:4]=[C:3]1[CH3:19].[OH-].[K+].O>CO>[CH3:1][N:2]1[C:6]2[CH:7]=[C:8]([C:15]([OH:17])=[O:16])[C:9]([C:11]([OH:13])=[O:12])=[CH:10][C:5]=2[N:4]=[C:3]1[CH3:19]A mixture of dimethyl 1,2-dimethyl-5,6-benzimidazoledicarboxylate (2.80 g, 10.7 mmol), potassium hydroxide (1.49 g; 26.7 mmol), water and methanol is stirred at room temperature for 16 hours and then concentrated in vacuo. The resultant residue is taken up in a minimal amount of water, cooled, acidified to pH 3 with hydrochloric acid and filtered to give the title product as pink crystals (2.28 g, 91.2%), mp 308°-312° C.
Wird geladen…