94. Synthesen von Dibenzodioxin-2,3-chinonen, einschliesslich der Ecklonochinone A und B sowie der Isoecklonochinone A und B

Article abstract of DOI:10.1002/hlca.19850680407

Syntheses of Dibenzo<1,4>dioxin-2,3-quinones Including the Ecklonoquinones A and B and the Isoecklonoquinones A and B.Oxidation of monomesyloxy-substituted pyrocatechols with MnO2 in toluene using phase-transfer conditions leads in high yield to monomesyloxy-substituted dibenzo<1,4>dioxin-2,3-quinones with loss of one mesyloxy group.In this way, ecklonoquinone A (2), ecklonoquinone B (3), isoecklonoquinone A (43), and isoecklonoquinone B (44) were prepared.Their structures are based on X-ray analyses of ecklonoquinone-A leucoacetate (45) and the mesyloxy-substituted quinone 20.The reddish-violet dibenzodioxin-diquinone 49 was prepared from an intermediate of the iso-series.The parent compound 1 has been synthesized in yields better than 50percent from pyrocatechol and methyl 2,5-dioxo-2,5-dihydrobenzoate as oxidant and 2-methoxypyridin as catalyst.To rationalize the specific effect on the dimerisation step of the mesyloxy group, the intermediacy of 1,4-quinone monoacetals is proposed.This also applies to a proposed biogenetic scheme.