Photochemical Cycloaddition of Singlet trans-Stilbene with α,β-Unsaturated Esters

Article abstract of DOI:10.1021/jo01294a006

The photochemical cycloaddition reactions of singlet trans-stilbene with five α,β-unsaturated esters and diesters are described.Adduct stereochemistry is influenced more by secondary ?-orbital overlap than by steric effects.The reactivity of the unsaturated esters with singlet stilbene increases with their electron affinity.This trend is consistent with the formation of a charge-transfer-stabilized exciplex intermediate in which singlet stilbene is the electron donor.Cycloaddition quantum yields, however, decrease with increasing electron affinity.This trend isreadily explained by using simple frontier molecular orbital theory.