4-Carbamoyl-4-N-anilinopiperidine

A mixture of 4-carbamoyl-4-N-anilinopiperidine and formamide is heated for 12 hours at 170°C. After cooling, the reaction mixture is divided between 100 parts water and 900 parts chloroform. The organic layer is separated, dried over MgSO, filtered and the filtrate is evaporated. The semisolid residue is stirred in ethyl acetate. The undissolved part is filtered off, washed with ethyl acetate, and dried, yielding 1-oxo-4-phenyl-2,4,8-triazaspiro-(4.5)decane. 

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