[N:1]1[CH:6]=[CH:5][CH:4]=[C:3]2[CH2:7][C:8]3[CH:14]=[C:13]([CH2:15][C:16](=[O:18])[CH3:17])[CH:12]=[CH:11][C:9]=3[O:10][C:2]=12.C1(C)C=CC(S(O[CH2:29][CH2:30][O:31][CH3:32])(=O)=O)=CC=1>[Na].C(O)(C)C>[N:1]1[CH:6]=[CH:5][CH:4]=[C:3]2[CH2:7][C:8]3[CH:14]=[C:13]([CH:15]([CH2:29][CH2:30][O:31][CH3:32])[C:16](=[O:18])[CH3:17])[CH:12]=[CH:11][C:9]=3[O:10][C:2]=123 g of 5H-[1]benzopyrano[ 2,3-b]pyridin-7-yl-acetone is dissolved in a solution of 0.32 g of metallic sodium in 15 ml of absolute isopropyl alcohol by warming to 50°-60°C. The solution is cooled to 40°C, 3.5 g of 2-methoxyethyl p-toluenesulfonate is added, and the mixture is stirred under reflux for 1.5 hours. The reaction mixture is concentrated, chloroform and water are added to the residue, and the mixture is stirred. The chloroform layer is separated, dried over anhydrous magnesium sulfate and concentrated. The oily residue is column chromatographed over silica gel (100 g) with a mixture of chloroform and ethyl acetate (10:1) as eluent to give 2.0 g of 3-(5H-[1]benzopyrano[ 2,3-b]pyridin-7-yl)-5-methoxy-2-pentanone as a pale yellow transparent oil. nD28 = 1.5764
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