[O:1]1[C:6]2[CH:7]=[CH:8][CH:9]=[CH:10][C:5]=2[O:4][CH2:3][CH:2]1[CH2:11][N:12]1[CH2:17][CH2:16][CH2:15][CH:14]([C:18]([NH2:20])=O)[CH2:13]1>S(Cl)(Cl)=O>[O:1]1[C:6]2[CH:7]=[CH:8][CH:9]=[CH:10][C:5]=2[O:4][CH2:3][CH:2]1[CH2:11][N:12]1[CH2:17][CH2:16][CH2:15][CH:14]([C:18]#[N:20])[CH2:13]1Thionyl chloride (20 ml) was added under cooling to 1-(2,3-dihydrobenzo[1,4]dioxin-2-ylmethyl)-piperidine-3-carboxylic acid amide (2.34 g, 8.46 mmol). The reaction mixture was refluxed for 3 h. Excess of thionyl chloride was evaporated. Water was slowly added to the residue, the mixture was made alkaline with aq NaOH and extracted with DCM (3×5 ml). The combined organic phases were dried (Na2SO4), filtered and the filtrate was evaporated to give the title compound, which was purified by column chromatography (DCM/MeOH, 90:10).
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