[C:1]([O:5][C:6](=[O:19])[NH:7][C:8]1[C:9]([O:16][CH2:17][CH3:18])=[N:10][N:11]2[CH:15]=[CH:14][S:13][C:12]=12)([CH3:4])([CH3:3])[CH3:2].C([Li])CCC.[Br:25]C(F)(F)C(F)(F)Br.[Cl-].[NH4+]>C(O)(=O)C.CCCCCC.C1COCC1>[C:1]([O:5][C:6](=[O:19])[NH:7][C:8]1[C:9]([O:16][CH2:17][CH3:18])=[N:10][N:11]2[C:15]([Br:25])=[CH:14][S:13][C:12]=12)([CH3:4])([CH3:3])[CH3:2]
To a THF (150 mL) solution of (6-ethoxy-pyrazolo[5,1-b][1,3]thiazol-7-yl)-carbamic acid tert-butyl ester (16.5 g, 61.4 mmol), was added a 2.77M n-hexane solution of n-butyllithium (15.9 mL, 44 mmol) while stirring at −78° C. The mixture was stirred at −78° C. for one hour, and then 1,2-dibromotetrafluoroethane (2.61 mL, 22 mmol) was added, and the mixture was stirred while heating to room temperature for three hours. A saturated aqueous solution of ammonium chloride was added and acetic acid was added, and the mixture was extracted with ethyl acetate and washed with brine, dried over magnesium sulfate, and the solvent was distilled off under reduced pressure. The residue was purified by medium pressure silica gel column chromatography (n-heptane/ethyl acetate: 0% then 30%) to obtain 4.95 g (13.7 mmol) of the title compound.
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