Mechanistic study on the intramolecular oxa-[4 + 2] cycloaddition of substituted o-divinylbenzenes.

This paper reports a detailed computational study of the mechanisms of formation of oxacyclic derivatives from substituted o-divinylbenzenes by a photoinduced intramolecular oxa-[4 + 2] cycloaddition. The reaction mechanism and chemoselectivity of trans, trans- and cis, trans-substituted ortho-divinylbenzene were studied. Detailed density functional theory calculations show that the reaction system proceeds through two main steps: light-active intramolecular cyclization and Diels-Alder reactions of C=O. Trans, trans-products of cycloaddition of substituted o-divinylbenzenes are more favored than cis, trans-products. Compared with different substituents, the cycloaddition reaction of phenyl ketone has a relatively low activation barrier, and the strong electron-withdrawing group on the benzene ring is more favorable for the intramolecular cycloaddition reaction of substituted o-divinylbenzenes.