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A solution of triphosgene (3.26 g, 0.011 mol) and anhydrous tetrahydrofuran (1000 mL) cooled to −20° C. was treated with pyridine (4.45 mL, 0.055 mol). The resulting cloudy suspension was slowly treated with a solution of 4-(3-trifluoromethyl-phenyl)-piperidin-4-ol (9 g, 0.036 mol) in anhydrous tetrahydrofuran (45 mL) while the internal temperature was maintained between −20° C. to −30° C. The resulting mixture was transferred to an ice bath which was allowed to come to 25° C. overnight to give a light brown solution with a small amount of brown precipitates. The reaction mixture was then concentrated in vacuo to give a brown solid. Flash chromatography (Merck Silica gel 60, 230-400 mesh, 75/25 hexanes/ethyl acetate) afforded 4-hydroxy-4-(3-trifluoromethyl-phenyl)-piperidine-1-carbonyl chloride (6.89 g, 61%) as a clear, viscous oil. The NMR spectrum obtained on the sample is compatible with its structure.

1. temperaturewas maintained between −20° C. to −30° C
2. customThe resulting mixture was transferred to an ice bath
3. customto give a light brown solution with a small amount of brown precipitates
4. concentrationThe reaction mixture was then concentrated in vacuo
5. customto give a brown solid