Dioxopyrrolines. XLV. (2+2)Photocycloaddition of 4-ethoxycarbonyl-5-aryl-1H-pyrrole-2,3-dione to cyclopentene derivatives: Formation of dihydropyridones.

Abstract

Photocycloaddition reactions of 4-ethoxycarbonyl-5-aryl-1H-pyrrole-2, 3-dione (1) with cyclopentadiene, indene, and cyclopentene gave the dihydropyridones 8, 11, and 12 as major products, respectively. Formation of them can be rationalized by assuming the formation of a 2s + 2a adduct predicted by the stereoselection rule and subsequent skeletal rearrangement. The stereochemical results seem to support the hypothesis that the donor-acceptor interaction as theoretically deduced by Epiotis plays an important role in determining the stereochemical pathway of photocycloaddition.