[NH2:1][C:2]([NH2:4])=[O:3].[F:5][C:6]([F:17])([F:16])[C:7](=O)[CH:8](Cl)[C:9]([O:11][CH2:12][CH3:13])=[O:10]>CN(C=O)C.O>[NH2:1][C:2]1[O:3][C:8]([C:9]([O:11][CH2:12][CH3:13])=[O:10])=[C:7]([C:6]([F:5])([F:17])[F:16])[N:4]=1To a suspension of urea (13.5 g) in DMF (50 mL) was added ethyl 4,4,4-trifluoro-2-chloroacetoacetate (10 mL) and the resulting reaction mixture was heated at 120° C. for 3 days. Then, the reaction mixture was cooled to RT and diluted with H2O (100 mL). Then, the reaction mixture was stirred at 0° C. for 1 h. The resulting precipitate was filtered, washed with H2O and dried in vacuo to yield ethyl 2-amino-4-trifluoromethyloxazole-5-carboxylate (A-1) as a white powder (9.8 g, 74% yield). LCMS (ESI) calcd for [M+1]+ 225.1. found 225.1.
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