3,6-Dioxocyclohexa-1,4-diene-1,2,4,5-tetracarboxylic acid dianhydride, a strong electron acceptor

Abstract

3,6-Dioxocyclohexa-1,4-diene-1,2,4,5-tetracarboxylic acid dianhydride (V) has been prepared by oxidation of the corresponding 3,6-dihydroxy-derivative (IV) with nitrogen oxides in the presence of Molecular Sieve 4A. The dihydroxy-compound was made via self-condensation of diethyl acetonedicarboxylate. The quinone dianhydride was characterised as a deep red 1 : 1 complex with benzene; it is a strong electron acceptor, dissolving in the methylbenzenes to give coloured solutions. It has a very low solubility in most solvents, and reacts with many in which it is slightly soluble. Further properties of compounds (IV) and (V) are reported and the role of the molecular sieve in the oxidation is discussed.