Reaction of 2-acetoxy-3-chloro naphthoquinones towards the 1,3-dioxy diene (2) and the 1,1,3-trioxy diene (9) was examined. The competing influence of the acetoxy and chloro substituents was assessed from the regiochemistry of the resulting Diels–Alder chemistry, as was competition between that process and Michael addition/elimination. Reaction of the same dienes towards the less reactive 2,3-diacetoxy naphthoquinone (25) was also investigated.
Oxy-substituted homophthalic anhydrides have been synthesized by cycloaddition of di- and tri-oxy butadienes to the allenic diester (1). By base-catalysed cycloaddition to appropriate benzoquinones they have afforded new syntheses of viocristin (19), isoviocristin (20) and analogous 1,4-anthraquinones. Related chemistry has led to the naphthalene (34) and the anhydride (35), intermediates in published syntheses of semivioxanthin and 6- methylpretetramid respectively.