Hydrochloric Acid → (e)-2-[1-(2,5-Dimethyl-3-furyl)ethylidene]-3-isopropylidenesuccinic anhydride

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To a suspension of 700 ml of benzene with 52.8 g of sodium hydride, 118 g of a mixed solution 76 g of 3-acetyl-2,5-dimethylfuran (mfd. by Sldrich Chemical Co., Inc.) and 118 g of the diethylisopropylidene succinate obtained in Reference Example 1 (4) was added dropwise in 2 hours with stirring. After reacting for further 7 hours with stirring, the reaction solution was poured into 2 kg of ice. The water layer was separated, made acidic with 690 ml of 5M HCl, and extracted with 1.5 liters of ethyl acetate. The resulting organic layer was concentrated. To the residue, 1.85 liters of 5 w/v% ethanolic potassium hydroxide was added and reaction was carried out for 15 hours under relux. After the reaction, the reaction solution was made acidic with HCl. A precipitate produced was dissolved in chloroform. The solvent was removed from the resulting chloroform solution by distillation. To the residue, acetyl chloride was added and ring closing reaction was carried out. After the reaction, excess acetyl chloride was removed by distillation. The residue was purified by column chromatography (filler: Wakogel C-300, eluent: a mixed solvent of n-hexane and ethyl acetate) to give pale yellow crystals of 2-[(E)-1-(2,5-dimethyl-3-furyl) ethylidene]-3-isopropylidene succinic anhydride of the formula: ##STR26## wherein Me is a methyl group, in yield of 15%.

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