Solvent Effect on the Product Distributions in the Photocycloaddition of Electron-rich Olefins to 1,2-Naphthoquinone
Irradiation of 1,2-naphthoquinone in the presence of electron rich olefins such as 2-methoxypropene, ethyl vinyl ether, or 2,3-dihydrofuran, afforded two isomers of cycloadducts, i.e., dihydrodioxins and dihydrofuran derivatives. The distributions of these two products strongly depended on the solvent polarities. In the reaction in benzene, dihydrodioxins were almost exclusively obtained, whereas in acetonitrile or methanol dihydrofuran derivatives were exclusively produced in high yields.