Photochemistry of Epoxyquinone. 4. Primary Dimers in the Photochemical Reaction of 2,3-Dimethyl-2,3-epoxy-2,3-dihydro-1,4-naphthoquinone

Article abstract of DOI:10.1021/jo01298a027

Photolysis of a benzene solution of 2,3-dimethyl-2,3-epoxy-2,3-dihydro-1,4-naphthoquinone (1) (0.1 M) gave the primary dimers 2a and 2b in 65 and 20 percent yields, respectively.Upon further irradiation, the primary dimers underwent photoisomerization to give alkylidenephthalide dimers 3a and 3b quantitatively.On the other hand, photolysis of an extremely dilute solution of 1 (<0.1 mM in benzene) gave different phthalides, 4a and 4b, and triketone 5.Reversible inner C-C bond opening of the oxirane ring was suggested on the basis of a product distribution change dependent upon the concentration of 1.