[Br:1][C:2]1[C:15]2[S:14][C:13]3[C:8](=[CH:9][CH:10]=[C:11]([O:16][CH3:17])[CH:12]=3)[NH:7][C:6]=2[CH:5]=[C:4]([O:18][CH3:19])[C:3]=1[OH:20].CI.[C:23](=O)([O-])[O-].[K+].[K+]>CN(C=O)C.O.C(OCC)(=O)C>[Br:1][C:2]1[C:15]2[S:14][C:13]3[C:8](=[CH:9][CH:10]=[C:11]([O:16][CH3:17])[CH:12]=3)[NH:7][C:6]=2[CH:5]=[C:4]([O:18][CH3:19])[C:3]=1[O:20][CH3:23]
To a solution of 4-bromo-2,7-dimethoxy-3-hydroxy-10H-phenothiazine (3.54 g) and methyliodide (2.5 ml) in DMF (20 ml) there was added pulverized potassium carbonate (1.3 g). The reaction mixture was stirred at room temperature. After 15 minutes, another addition of potassium carbonate (1 gram) was made, followed by two other such additions at 15-minute intervals. The final mixture was stirred for a further 15 minutes, then it was diluted with water (100 ml) and ethyl acetate (100 ml). The organic layer was washed twice with water, dried and evaporated down to a solid residue. Crystallization from acetone followed by column chromatography on silica gel eluting with 1:19 ethyl acetate-dichloromethane afforded the pure title compound (1.27 g). m.p. 223°-225° C.
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