Addition of diethyl and dimethyl acetylenedicarboxylates to catechol- synthesis of benzodioxole derivatives

Abstract

2-Ethoxycarbonylmethyl-2-ethoxycarbonyl- (VI) and 2-methoxycarbonylmethyl-2-methoxy-carbonyl-(VII)-benzodibxoles are obtained in high yields by the addition of catechol to diethyl and dimethyl acetylenedicarboxylate. Alkaline hydrolysis of VI affords, besides the expected diacid IX, the rearranged benzodioxane acid X. The alkali-induced interconversions of IX and X are likely to be mediated by phenoxy-maleic acid XVIII and fumaric acid XIX. Pyrolysis of ammonium salts of diacid IX1 yields the novel spirosuccinimides XXX and XXXI. LAH reduction of XXXI results in the formation of a bimolecular product of likely structure XXXIX, besides the expected spiropyrrolidine XXVI.