Condensations of diketones with aromatic compounds. Part IV. Hexane-2,5-dione and pyrogallol

Abstract

Hexane-2,5-dione reacts with pyrogallol in 70% v/v aqueous sulphuric acid to give 9,10-dihydro-9,10-dimethyl-9,10-ethanoanthracene-1,2,3,5,6,7-hexaol and 5,8-dimethylnaphthalene-1,2,3-triol. The latter exists in the keto-form in the solid state and is oxidised in solution by air to 2,3-dihydroxy-5,8-dimethyl-1,4-naphthaquinone. An attempted synthesis of this quinone starting from hexa-2,4-diene and 1,4-benzoquinone gives instead the corresponding monohydroxynaphthaquinone; the diene reacts with 2,3-dimethoxy-1,4-benzoquinone in the presence of selenium dioxide to form 2,3-dimethoxy-5,8-dimethyl-1,4-naphthaquinone.