C([Si](C(C)C)(C(C)C)[O:5][C:6]1[CH:14]=[CH:13][CH:12]=[C:8]([C:9]([OH:11])=[O:10])[C:7]=1[NH2:15])(C)C.[F:22][C:23]1[CH:31]=[CH:30][CH:29]=[C:28]([F:32])[C:24]=1[C:25](Cl)=O.C(NC1C=CC2N=C(C3C(F)=CC=CC=3F)OC(=O)C=2C=1)(=O)C.Cl>C1COCC1.C(OCC)(=O)C.C(N(CC)CC)C.C1(C)C=CC=CC=1>[F:22][C:23]1[CH:31]=[CH:30][CH:29]=[C:28]([F:32])[C:24]=1[C:25]1[O:11][C:9](=[O:10])[C:8]2[CH:12]=[CH:13][CH:14]=[C:6]([OH:5])[C:7]=2[N:15]=13-Triisopropylsilyloxyanthranilic acid (0.8 g), 2,6-difluorobenzoyl chloride (0.71 mL) and triethyl amine/toluene (1/1) (25 mL) were reacted as described under (10). Reaction time 2 days. Extraction between ethyl acetate (100 mL) and HCl (1N,100 mL), followed by separation of the organic layer, drylng over MgSO4, filtering and evaporation gave a crude product which was dissolved in warm THF (20 mL) and precipitated with hexane. The resulting mixture was further purified on a silicagel column using dichloromethane as eluent. The isolated fraction (80 mg) was hydrolysed with 1% HCl in ethanol by stirring for 2 days at RT, and further hydrolysis after addition of HCl (4N, 5 mL) and ethyl acetate (10 mL). The organic layer was separated, evaporated and dried resulting in 2-(2,6-difluoro-phenyl)-8-hydroxy-benzo[d][1,3]oxazin-4-one (32 mg), mp.190-198. LC-MS showed the purity 86% with the corresponding O-triisopropylsilylated product as the impurity.
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