Cycloaddition of cross-conjugated trienes to halogenated quinones

Article abstract of DOI:10.1055/s-1994-25553

The chemoselectivity of [4+2] cycloadditions involving electron-rich cross-conjugated trienes and halogenated quinones has been examined. The approach provides improved preparations of 6-acetyl-2,3,7-trihydroxyjuglone, solorinic and norsolorinic acids, and averythrin. It also confirms the structure proposed for haematommone and 3,8-dihydroxy-4-methoxy-2-methoxycarbonyl-1-methylanthraquinone but invalidates that of sopheranin.