C(OC([N:8]1[CH2:17][C:16]2[CH:18]=[C:19]([Cl:22])[CH:20]=[CH:21][C:15]=2[N:14]2[C:10](=[N:11][N:12]=[C:13]2[Br:23])[CH2:9]1)=O)(C)(C)C.Cl>[OH-].[Na+]>[Br:23][C:13]1[N:14]2[C:10]([CH2:9][NH:8][CH2:17][C:16]3[CH:18]=[C:19]([Cl:22])[CH:20]=[CH:21][C:15]=32)=[N:11][N:12]=1A solution of 1-bromo-8-chloro-4H,6H-2,3,5,10b-tetraaza-benzoazulene-5-carboxylic acid tert-butyl ester (3.0 g, 7.6 mmol) in 1.25 M methanolic hydrogen chloride solution (60 ml, 76 mmol) was heated at 50° C. for 10 min. The reaction mixture was poured on 1 M aqueous sodium hydroxide solution (200 ml) and extracted with ethyl acetate. The organic layer was washed with brine, dried over anhydrous sodium sulfate and concentrated in vacuo to give the title compound (1.9 g, 84%) as light yellow solid. MS m/e: 255 (M+H+).
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