O=P(Cl)(Cl)[Cl:3].CN([CH:9]=[O:10])C.[CH2:11]([O:13][C:14]([N:16]1[CH2:21][CH2:20][CH2:19][CH2:18][C:17]1=O)=[O:15])[CH3:12].C([O-])(=O)C.[Na+]>O>[Cl:3][C:19]1[CH2:20][CH2:21][N:16]([C:14]([O:13][CH2:11][CH3:12])=[O:15])[CH2:17][C:18]=1[CH:9]=[O:10]
POCl3 (2.18 g, 23.4 mmol) was added very slowly to dry DMF (2.7 ml) at 0° C. and the resulting mixture was stirred at 25° C. for 15 min. The reaction mixture was again cooled to 0° C., and N-ethoxycarbonyl piperidone (11.7 mmol) was added. The resulting reaction mixture was stirred at 25° C. for 3 h. It was then stirred with sodium acetate (7 g) and water (8.5 ml) and extracted with benzene. The organic layer was successively washed with water, sodium hydrogencarbonate an brine and was finally dried over sodium sulfate. Evaporation of the organic layer under reduced pressure gave the crude product, which was used directly in the next step without further purification. Yield: 63%.
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