[C:1]([O:5][C:6]([N:8]1[CH2:13][CH2:12][C:11](=[O:14])[CH2:10][CH2:9]1)=[O:7])([CH3:4])([CH3:3])[CH3:2].N1CC[CH2:17][CH2:16]1.O.ICC>C1C=CC=CC=1.C1(C)C=CC(S(O)(=O)=O)=CC=1>[C:1]([O:5][C:6]([N:8]1[CH2:9][CH2:10][C:11](=[O:14])[CH:12]([CH2:16][CH3:17])[CH2:13]1)=[O:7])([CH3:4])([CH3:2])[CH3:3]A solution of 4-oxo-piperidine-1-carboxylic acid tert-butyl ester (5 g, 25.1 mmol), pyrollidine (5 mL) and p-toluenesulfonic acid (25 mg) in benzene (100 mL) was heated at reflux for 16 h with azeotropic distillation of water. The resulting enamine solution was cooled to rt and concentrated. The crude enamine was dissolved in acetonitrile (50 mL); iodoethane (4.67 g, 30.1 mmol.) was added and the mixture was heated at 100° C. for 0.5 h, cooled to rt and concentrated. The mixture was dissolved in ethyl acetate (200 mL), washed with 1 N hydrochloric acid, saturated aqueous sodium bicarbonate, and brine. The extract was dried over magnesium sulfate, filtered and concentrated. The crude compound was purified by silica gel chromatography (80% hexanes/20% ethyl acetate) to afford 3-ethyl-4-oxo-piperidine-1-carboxylic acid tert-butyl ester (680 mg).
加载中…
