Br[Zn][CH2:3][C:4]([O:6][CH2:7][CH3:8])=[O:5].[Cl:9][C:10]1[C:11](=[O:18])[C:12]([Cl:17])=[CH:13][C:14](=[O:16])[CH:15]=1.Cl.C(OCC)(=O)C>C1COCC1>[Cl:9][C:10]1[C:11](=[O:18])[C:12]([Cl:17])=[CH:13][C:14]([CH2:3][C:4]([O:6][CH2:7][CH3:8])=[O:5])([OH:16])[CH:15]=1Under, nitrogen atmosphere, 6 mL of THF was added to 1.22 g (2 mmol, 0.6 equivalent) of (BrZnCH2COOEt.THF)2. A solution of 0.59 g (3.33 mmol) of 2,6-dichloro-p-benzoquinone in 3 mL of THF was added dropwise while stirring at 0˜5° C. The mixture was stirred at 20˜25° C. for 1 hour. 5 mL of 1N hydrochloric acid was added dropwise at 20° C. or lower, followed by dilution with 25 mL of ethyl acetate. Then, the layers were separated. The organic layer was washed successively with 5 mL (×2) of 1N hydrochloric acid, 5 mL of water, 10 mL (×2) of an aqueous saturated sodium bicarbonate solution, and 5 mL (×2) of an aqueous saturated sodium chloride solution. After washing, the organic layer was dried with anhydrous magnesium sulfate. After concentration under reduced pressure, purification with silica gel column (developing solvent; ethyl acetate/n-hexane=1/3) afforded 0.76 g of the desired product (NMR yield 74%; internal standard trioxane). As a purified product, 0.48 g of the desired product was obtained (yield 54%). 1H NMR (CDCl3), (ppm): δ 1.31 (3H, t, J=7.2 Hz), 2.77 (2H, s), 4.21-4.29 (3H, m), 7.15 (2H, s).
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