[NH:1]1[C:10]2[C:5](=[CH:6][CH:7]=[CH:8][CH:9]=2)[N:4]=[CH:3][C:2]1=[O:11].[H-].[Na+].Br[CH2:15][CH:16]1[O:20][CH2:19][CH2:18][O:17]1.Cl>O.C(OCC)(=O)C.CN(C)C=O>[O:17]1[CH2:18][CH2:19][O:20][CH:16]1[CH2:15][N:1]1[C:10]2[C:5](=[CH:6][CH:7]=[CH:8][CH:9]=2)[N:4]=[CH:3][C:2]1=[O:11]To 20 mL of an N,N-dimethylformamide suspension containing 2.0 g of quinoxalin-2(1H)-one, 0.82 g of 60% sodium hydride was dividedly added at room temperature, and the mixture was stirred at 40° C. for 15 minutes. Thereto was added 2.1 mL of 2-bromomethyl-1,3-dioxolane, and the mixture was stirred at 60° C. for 30 minutes, and stirred at 110 to 120° C. for 1 hour. Thereto was added 2.1 mL of 2-bromomethyl-1,3-dioxolane, and the mixture was stirred at 110 to 120° C. for 5 hours. The reaction mixture was cooled to room temperature, ethyl acetate and water were added, and the resultant solution was adjusted to pH 2.0 with 6 mol/L hydrochloric acid. The organic layer was separated, and the aqueous layer was extracted with ethyl acetate. The organic layer and the extract were combined, the resultant solution was washed sequentially with water and an aqueous saturated sodium chloride solution and dried over anhydrous magnesium sulfate, and the solvent was removed under reduced pressure. The residue thus obtained was purified by silica gel column chromatography [eluent; hexane:ethyl acetate 1:2] to obtain 1.5 g of a light brown oily substance, 1-(1,3-dioxolan-2-ylmethyl)quinoxalin-2(1H)-one.
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