NC1[S:3][C:4]2[CH:10]=[C:9]([O:11][C:12]3[CH:17]=[CH:16][C:15]([F:18])=[CH:14][CH:13]=3)[CH:8]=[CH:7][C:5]=2[N:6]=1.[OH-].[K+].C(O)(=O)C>O.C(O)CO>[NH2:6][C:5]1[CH:7]=[CH:8][C:9]([O:11][C:12]2[CH:13]=[CH:14][C:15]([F:18])=[CH:16][CH:17]=2)=[CH:10][C:4]=1[SH:3]22 g of 2-amino-6-(4-fluorophenoxy)benzothiazole (prepared as described in preparation 7) were added to a mixture of a solution of 90 g of potassium hydroxide in 100 ml of water and 28 ml of ethylene glycol, and the mixture was stirred for 2 hours on an oil bath kept at 130° C under an atmosphere of nitrogen. After the mixture had been cooled to room temperature, 90 ml of acetic acid was added dropwise to the resulting homogenous solution to deposit a precipitate: this was extracted with toluene. The toluene extract was dried over anhydrous magnesium sulfate and concentrated by evaporation under reduced pressure, to afford 16 g of the title compound as a pale yellow solid.
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