Triethylamine → 1,1-Dimethylethyl 4-(4-chlorophenyl)-3,6-dihydro-1(2H)-pyridinecarboxylate

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Reaction Steps

4-(4-Chlorophenyl)-1,2,3,6-tetrahydropyridine hydrochloride (Lancaster, 1.00 g, 4.35 mmol), triethylamine (0.92 g, 9.13 mmol), and di-tert-butyl carbonate (Aldrich, 1.04 g, 4.78 mmol) were combined in dichloromethane (100 mL) and stirred at room temperature for 14 hours. The mixture was washed with saturated aqueous ammonium chloride solution (30 mL), water (30 mL), saturated sodium chloride solution (30 mL) and dried over anhydrous magnesium sulfate. The mixture was filtered and concentrated in vacuo to give 4-(4-chlorophenyl)-3,6-dihydro-2H-pyridine-1-carboxylic acid tert-butyl ester (1.41 g, 100%) of as a viscous yellow oil, which was used without further purification. 4-(4-Chlorophenyl)-3,6-dihydro-2H-pyridine-1-carboxylic acid tert-butyl ester (334 mg, 1.14 mmoL) was dissolved in acetone/water (1:1, 10 mL), and N-methylmorpholine-N-oxide (Aldrich, 462 mg, 3.42 mmoL) and a catalytic amount of osmium tetroxide (Aldrich) were added. The mixture was stirred at room temperature for 3 hours. A saturated aqueous solution of sodium sulfite (2 mL) was added, and the mixture was stirred for 30 minutes at room temperature. The mixture was diluted with ethyl acetate (10 mL) and water (5 mL). The organic layer was separated, and the aqueous layer was extracted with ethyl acetate (2×10 mL). The combined organic layers were washed with brine and dried over anhydrous magnesium sulfate. The mixture was filtered and concentrated in vacuo to give cis-[rac]-4-(4-chlorophenyl)-3,4-dihydroxypiperidine-1-carboxylic acid tert-butyl ester (364 mg, 1.11 mmol, 97%) as a yellow oil.

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