Trifluoroacetic acid → 3,3-Dimethyl-2-oxa-8-azaspiro[4.5]decan-1-one

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Reaction Steps

Trifluoroacetic acid (50 mL) was added to a solution of 1-(1,1-dimethylethyl) 4-ethyl 4-(2-methyl-2-propenyl)-1,4-piperidinedicarboxylate (Description 89, 10.86 g, 35 mmol) in dichloromethane (10 mL) and the mixture was stirred at 50 C for 8 hours. The mixture was cooled and the solvent was evaporated under reduced pressure. Ether (50 mL) was added and the mixture was extracted with hydrochloric acid (1M, 3×50 mL). The combined aqueous fractions were washed with ether (2×50 mL), adjusted to pH 12 with aqueous sodium hydroxide (4M) and the mixture was extracted with ethyl acetate (6×50 mL). The combined organic fractions were dried (MgSO4) and the solvent was evaporated under reduced pressure. The residue was dissolved in ethanol (50 mL), cooled in ice and and ethereal hydrogen chloride (1M, 35 mL) was added slowly. The solvent was evaporated under reduced pressure, ethanol (75 mL) was added and the mixture was heated under reflux for 15 minutes. The mixture was cooled and the solid was collected and dried in vacuo to give the title compound as a colorless solid (5.59 g, 73%), m.p.>280° C. m/z (ES+) 184 (M+1).

Provenance & Evidence