C1(P(C2C=CC=CC=2)C2C=CC=CC=2)C=CC=CC=1.N(C(OCC)=O)=NC([O-])=O.O[N:31]([C:46]1[CH:51]=[CH:50][CH:49]=[CH:48][CH:47]=1)[C:32]([C:34]1[CH:35]=[N:36][C:37]2[C:42]([C:43]=1[OH:44])=[CH:41][C:40]([F:45])=[CH:39][CH:38]=2)=[O:33]>CN(C)C=O>[F:45][C:40]1[CH:39]=[CH:38][C:37]2[N:36]=[CH:35][C:34]3[C:32](=[O:33])[N:31]([C:46]4[CH:51]=[CH:50][CH:49]=[CH:48][CH:47]=4)[O:44][C:43]=3[C:42]=2[CH:41]=1Into a mixture of 8.81 g of triphenylphosphine and 50 ml of dimethylformamide, 5.58 g of ethyl azodicarboxylate were poured at 10°-15° C. and after continued stirring for 15 minutes, 6.68 g of the product of Step A were added in small fractions. Stirring was maintained for 2 hours at 0° C. and for 16 hours at ambient temperature and the crystallized product was separated. The filtrate was poured into iced water, and extracted with dichloromethane. The organic phase was washed with water, dried and the solvent was eliminated. The residue was chromatographed on silica and eluted with a methylene chloride-ethyl acetate mixture (9-1) to obtain 0.92 g of 8-fluoro-2-phenylisoxazolo(4,5-c)quinolin-3-(2H)-one melting at 174° C.
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