Dunnione and related naphthoquinones. II. Synthesis of isodunniol and dl-dunnione

Abstract

Claisen rearrangement of 2-(3,3-dimethylallyloxy)-1,4-naphthoquinone gives two products. One of these is identical with isodunniol, and the other, on treatment with sulphuric acid, gives a compound which is evidently the racemic modification of the natural dextrorotatory pigment dunnione. It is shown that isodunniol must be 2-hydroxy-3-(1,2-dimethylallyl)-1,4-naphthoquinone, and dunnione is ααβ-trimethyl-dihydrofurano-1,2-naphthoquinone. The racemic modifications of α-dunnione and allodunnione are also described.