Carbonyl and thiocarbonyl compounds. XI. Synthesis of halogenated benzodioxoles by the action of tetrahalo‐o‐benzoquinones on benzophenone hydrazones and their cleavage by nucleophilic reagents

Abstract

Abstractp,p′‐Dichloro‐, p,p′‐dimethyl‐ and p,p′‐dimethoxybenzophenone hydrazones react with tetrachloro‐ and tetrabromo‐o‐benzoquinone to give directly the halogenated benzodioxoles (IIIa‐IIIf), respectively, together with the corresponding tetrahalocatechol. Cleavage of the dioxole ring by nucleophilic reagents depends markedly on the nature of the substituents. The dimethoxyderivatives (IIIc) and (IIIf) proved to be unusually reactive toward cleavage by dilute mineral acids, lithium aluminum hydride, hydrazines and malonitrile, whereas the dichloro analog behaves normally and is not cleaved under the same conditions.