Cyclopropaquinone chemistry

Abstract

The known cyclopropaquinone (45), available from 1,4-benzoquinone in five steps in an overall yield of 79% appears to be a good precursor for higher homologues such as oxygenated 1H-cyclopropa[b]anthracenes (61) and (67). The aim of this study is the synthesis of 1H-cyclopropa[b]anthracene-3,8-dione (61). Interest in synthesying the oxygenated cycloproparenes (66) and (67) has led to investigating the cycloaddition chemistry of (45) and (76). Cyclopropanthraquinone (61) and its precursor endo-adduct (60) have not been isolated. The current study establishes that temperature controls product formation during reaction of cyclopropaquinone (45) with buta-1,3-diene. At 100 °C diadduct (71) is obtained. The structure assignment is supported by isolating (74) from reaction of cyclopropanaphthalene (2) with buta-1,3-diene.