Pyridine → tert-Butyl 3-isopropoxy-4,4-dimethoxypiperidine-1-carboxylate

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Reaction Conditions

Reaction Steps

tert-Butyl 3-acetoxy-4,4-dimethoxypiperidine-1-carboxylate obtained in Example (147a) (1.58 g, 4.94 mmol) was dissolved in toluene (22.5 mL), tetrahydrofuran (7.5 mL) and pyridine (0.75 mL), followed by cooling to −40° C. Tebbe's reagent (0.5 M solution in toluene, 25 mL, 12.5 mmol) was added at the same temperature, and the mixture was stirred at −10 to −40° C. for 1.5 hours. A 1 N aqueous sodium hydroxide solution and dichloromethane were added, and the precipitate was filtered off. The organic layer was dried over magnesium sulfate, and then the solvent was evaporated under reduced pressure. Methanol was added to the resulting residue, and the precipitate was filtered off again. 10% palladium-carbon (wet, 3.0 g) was added to the resulting solution, which was catalytically hydrogenated at room temperature for three hours. The catalyst was filtered off, and then the solution was concentrated under reduced pressure. The resulting residue was purified by silica gel column chromatography (elution solvent: hexane/ethyl acetate) to obtain 701 mg of the title compound as a colorless solid (47%).

Provenance & Evidence