C(N[CH:5]1[CH2:10][CH2:9][N:8]([C:11]([O:13][CH2:14][CH3:15])=[O:12])[CH2:7][CH2:6]1)(=O)C.[C:16](#[N:18])C.S(Cl)(Cl)=O.CC(O)C>C(OCC)(=O)C>[C:16]([CH:5]1[CH2:6][CH2:7][N:8]([C:11]([O:13][CH2:14][CH3:15])=[O:12])[CH2:9][CH2:10]1)#[N:18]A mixture of 4-acetamido-N-ethoxycarbonylpiperidine (17.0 g) and acetonitrile (200 ml) was cooled to 0° C., and 15.5 g of thionyl chloride was added dropwise, under nitrogen, with stirring. The reaction mixture was allowed to warm to ambient temperature. To the reaction mixture was added 2-propanol (20 ml) and the mixture was heated under reflux for 1 hr. Ethyl acetate was added, the layers were separated, and the organic phase was washed with 5% sodium bicarbonate solution, dried over anhydrous magnesium sulfate, filtered, and the filtrate was concentrated. The residue was chromatographed on a preparatory liquid chromatograph, eluting with 4:1-heptane:ethyl acetate. The appropriate fractions were collected and evaporated to give 15 g of residue. A 4-g sample of the residue was distilled to give 3.5 g (84.6%) of product, bp 130° C. (4 mm mercury).
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