Hydrochloric Acid → 2-[(E)-1-(1,2-dimethyl-5-methoxy-3-indolyl)ethylidene]-3-isopropylidene succinic anhydride

Participants

Reaction Steps

To a solution obtained by dissolving 76 g of diisopropylamine in 750 ml of tetrahydrofuran, 350 ml of n-butyllithium was added at low temperatures (-10°~-40° C.), and 91 g of diethylisopropylidene succinate obtained in Reference Example 1 (4) and 81 g of 3-acetyl-5-methoxy-1,2-dimethylindole were added dropwise thereto in 30 minutes with stirring. After reacting for further 8 hours with stirring, the reaction solution was made acidic by pouring 1050 ml of 10% HCl thereinto, followed by extraction 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 to carry out the reaction for 15 hours under reflux. After the reaction, the reaction solution was made acidic with HCl. A precipitate produced was dissolved in chloroform. After removing the solvent from the resulting chloroform solution by distillation, acetyl chloride was added to the residue to carry out a ring closing reaction. 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-(1,2-dimethyl-5-methoxy-3-indolyl)ethylidene]-3-isopropylidene succinic anhydride of the formula: ##STR30## wherein Me is methyl, in yield of 5%.

Provenance & Evidence