Le dimère de la cis dihydroxy-5,6 cyclohexène-2 dione-1,4

The osmic acid catalyzed oxidation of p-benzoquinone by sodium chlorate has long been recognized to yield a dimeric substance. By using progressively more vigorous conditions of acetylation, it has been possible to prepare from it three acetates corresponding to the dimer and to products of increasing degrees of dehydration and aromatization. The compounds have now been identified as the tetraacetates of 1,2,6,7-tetrahydroxydibenzo-p-dioxine (2a), of 2-oxo-1,4a (trans),6,7-tetrahydroxy-1,2,4a,10a-tetrahydrodibenzo-cis-p-dioxinne (3) and of the monohemiacetal dimer of cis-5,6-dihydroxycyclohex-2-ene-1,4-dione(4b). The structure of the dimer in the solid state and in solution is discussed.