Cl[Si](C)(C)C.Br[C:7]([F:14])([F:13])[C:8]([O:10][CH2:11][CH3:12])=[O:9].[N:15]1([CH2:24]NC2CCCCC2)[C:19]2[CH:20]=[CH:21][CH:22]=[CH:23][C:18]=2N=N1>O1CCCC1.[Zn]>[CH2:11]([O:10][C:8](=[O:9])[C:7]([F:14])([F:13])[CH2:24][NH:15][CH:19]1[CH2:20][CH2:21][CH2:22][CH2:23][CH2:18]1)[CH3:12]To a mixture of 13.7 g (0.21 g-atom) of zinc powder (325 mesh) and 200 mL of anhydrous tetrahydrofuran was added 20 mL (0.156 mole) of chlorotrimethylsilane in one portion. After stirring for 5 minutes, a solution of 20.4 mL (0.156 mole) of ethyl bromodifluoroacetate in 50 mL of tetrahydrofuran was added dropwise at a rate to maintain the internal temperature below 35 degrees. The mixture was stirred for 30 minutes and then cooled to −10 to 0 degrees. A solution of 40 g (0.174 mole) of benzotriazol-1-ylmethyl-cyclohexylamine in 400 mL of tetrahydrofuran was added dropwise at a rate to maintain the internal temperature at −10 to 0 degrees. After 10 minutes, the reaction mixture was warmed to room temperature, stirred for another 3 hours and then cooled to −10 to 0 degrees. The reaction was quenched by the addition of 200 mL of saturated aqueous sodium bicarbonate, added at a rate to maintain the internal temperature at −10 to 0. The mixture was stirred at room temperature for 10 minutes, then filtered through Celite, washing with 200 mL of ether. The filtrate was extracted twice with 200 mL of ether. The combined organic layers were dried over anhydrous sodium sulfate, filtered, and concentrated under reduced pressure. 200 mL of hexanes-ether (80:20) was added to the residue, the resulting solid was removed by filtration and the filtrated concentrated under reduced pressure. The residue was distilled under vacuum to give 12.9 g of 3-cyclohexylamino-2,2-difluoropropionic acid ethyl ester as a colorless oil. bp. 85-90 degrees at 1 mm Hg.
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