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

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Reaction Steps

Into a 250-mL round-bottom flask, was placed a solution of tert-butyl 4-(4-chlorophenyl)-4-hydroxypiperidine-1-carboxylate (compound 42.1, 9.00 g, 28.9 mmol) in pyridine (50 mL). With stirring, phosphoroyl trichloride (7.93 mL, 84.8 mmol) was added drop-wise. The resulting mixture was stirred overnight at room temperature and then concentrated under reduced pressure. The residue was diluted with ethyl acetate (20 mL) and carefully quenched by slow addition of aqueous sodium bicarbonate. The layers were separated and the organic layer was washed with aqueous sodium bicarbonate (2×30 mL), dried (Na2SO4), filtered, and concentrated under reduced pressure. The residue was purified by silica gel column chromatography with ethyl acetate/petroleum ether (1:100 to 1:10) to yield the title compound as a colorless oil (6.1 g, 72%).

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