[H-].[Na+].C(O)(C)(C)C.[CH3:8][O:9][C:10]([CH2:12][O:13][C:14]1[CH:25]=[CH:24][CH:23]=[CH:22][C:15]=1[O:16][CH2:17][C:18](OC)=[O:19])=[O:11].C(O)(=O)C>C1(C)C(C)=CC=CC=1>[O:19]=[C:18]1[CH:12]([C:10]([O:9][CH3:8])=[O:11])[O:13][C:14]2[CH:25]=[CH:24][CH:23]=[CH:22][C:15]=2[O:16][CH2:17]1To a mixture of 4.1 g of 60% sodium hydride in 150 ml of xylene is added 0.3 ml of tert-butanol, and a solution of 10 g of methyl 2-methoxycarbonylmethyloxyphenoxyacetate in 100 ml of xylene is added dropwise to the mixture at 140°-150° C. (for 8 hours). To the reaction mixture 7 g of acetic acid is added and the precipitates are filtered off. The filtrate is concentrated under reduced pressure, and the residue is purified by column chromatography on silica gel (eluant: hexane:ethyl acetate=3:1 2:1), to give 6.5 g of methyl 3-oxo-3,4-dihydro-2H-1,5-benzodioxepin-2-carboxylate as a colorless oil. Mass spectrum m/e: 222 (M+). IR νmaxneat cm-1 : 1750. NMR (CDCl3) δ: 3.75(3H, singlet, OCH3), 4.68 (2H, double doublet, C4 --H), 5.32 (1H, singlet, C2 --H).
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