Benzyl chloroformate → Benzyl 4-oxopiperidine-1-carboxylate

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Reaction Steps

N-Benzyl-4-piperidone (122.2 g, 0.645 mole) in 500 ml toluene was warmed to 45° C. Benzyl chloroformate (130 ml, 155 g, 0.915 mole) was added in a thin, steady stream, and the reaction mixture heated to reflux for 2 hours, cooled to ambient temperature, diluted with 250 ml H2O and stirred vigorously 0.5 hour. The organic layer was separated, washed 1×400 ml 6N HCl and then 1×100 ml saturated NaCl, dired (MgSO4), treated with activated carbon, and concentrated to an oil. The oil was distributed between 400 ml ethyl acetate and 400 ml of H2O containing 67.0 g NaHSO3, stirred 0.5 hour, and the aqueous layer separated, washed with 3 portions of ether, made basic with aqueous NaOH and extracted with fresh ether. The ether layer was dried and reevaporated to yield purified title product as an oil, 136.1 g.

Provenance & Evidence