[Cl:1][C:2]1[C:11]2[C:6](=[C:7]([F:14])[C:8]([F:13])=[C:9]([F:12])[CH:10]=2)[N:5]=[C:4]([O:15]CC)[CH:3]=1.Cl.C(O)(=O)C>O>[Cl:1][C:2]1[C:11]2[C:6](=[C:7]([F:14])[C:8]([F:13])=[C:9]([F:12])[CH:10]=2)[NH:5][C:4](=[O:15])[CH:3]=1A suspension of 4-chloro-2-ethoxy-6,7,8-trifluoroquinoline (70.4 g) in 35% strength aqueous hydrochloric acid solution (170 cc), acetic acid (420 cc) and water (250 cc) is heated with stirring to a temperature in the region of 100° C. for 2 hours and a half. After cooling to approximately 20° C., the reaction mixture is poured into water (1100 cc) at approximately 5° C. and stirred for 15 minutes at this temperature and the insoluble matter is then drained and washed with water (3×220 cc). 4-Chloro-6,7,8-trifluorocarbostyril (61 g) is obtained in the form of a cream-colored solid, m.p. 213° C., which is used without further purification for the subsequent steps.
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