N([O-])=[O:2].[Na+].N[C:6]1[C:15]2[C:10](=[CH:11][C:12]([O:16][CH3:17])=[CH:13][CH:14]=2)[C:9](=[O:18])[NH:8][C:7]=1[C:19]1[CH:24]=[CH:23][C:22]([O:25][CH3:26])=[CH:21][CH:20]=1.[N-]=[N+]=[N-].[Na+]>O.C(O)(=O)C.S(=O)(=O)(O)O>[OH:2][C:6]1[C:15]2[C:10](=[CH:11][C:12]([O:16][CH3:17])=[CH:13][CH:14]=2)[C:9](=[O:18])[NH:8][C:7]=1[C:19]1[CH:24]=[CH:23][C:22]([O:25][CH3:26])=[CH:21][CH:20]=1At 0° C., a solution of sodium nitrite (24.8 mg, 0.36 mmol) in water (0.5 mL) is added slowly to a solution of 4-amino-7-methoxy-3-(4-methoxyphenyl)isoquinolin-1(2H)-one (100 mg, 0.33 mmol) dissolved in acetic acid (1 mL) and sulphuric acid (0.5 mL). The mixture is left under stirring under cold conditions for 30 minutes then sodium azide (25.7 mg, 0.39 mmol) dissolved in a minimum amount of water (0.2 mL) is introduced slowly. Stirring, still under cold conditions, is maintained for another 3 hours, then water (10 mL) is poured onto the reaction mixture and the solid residue formed is collected by filtration. Silica gel column chromatography using a gradient of ethanol (0 to 2%) in CH2Cl2 as eluent makes it possible to isolate the compound possessing the greatest mobility which corresponds to the expected compound 41 (31 mg, 31%) in the form of a white solid, 1H NMR (CDCl3) 7.91 (1H, d), 7.74 (1H, d), 7.41 (2H, d), 7.16 (1H, dd), 6.85 (2H, d), 6.75 (1H, br s), 4.60 (1H, br s), 3.98 (3H, s), 3.78 (3H, s); MS 295 (M−2H).
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