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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.

1. temperatureto maintain the internal temperature below 35 degrees
2. stirringThe mixture was stirred for 30 minutes
3. temperaturecooled to −10 to 0 degrees
4. temperatureto maintain the internal temperature at −10 to 0 degrees
5. waitAfter 10 minutes
6. stirringstirred for another 3 hours
7. temperaturecooled to −10 to 0 degrees
8. customThe reaction was quenched by the addition of 200 mL of saturated aqueous sodium bicarbonate
9. additionadded at a rate
10. temperatureto maintain the internal temperature at −10 to 0
11. stirringThe mixture was stirred at room temperature for 10 minutes
12. filtrationfiltered through Celite
13. washwashing with 200 mL of ether
14. extractionThe filtrate was extracted twice with 200 mL of ether
15. dry with materialThe combined organic layers were dried over anhydrous sodium sulfate
16. filtrationfiltered
17. concentrationconcentrated under reduced pressure
18. addition200 mL of hexanes-ether (80:20) was added to the residue
19. customthe resulting solid was removed by filtration
20. concentrationthe filtrated concentrated under reduced pressure
21. distillationThe residue was distilled under vacuum