Allenyl(vinyl)methane photochemistry. Photochemistry of γ-(3-methyl-1-phenyl-1,2-butadienyl)-substituted α,β-unsaturated ester and nitrile derivatives

The direct photolyses of the γ-(3-methyl-1-phenyl-1,2-butadienyl)-substituted α,β-unsaturated esters and nitriles gave the bicyclo[2.1.0]pentanes, cross-conjugated trienes, and several intramolecular products, while the triplet-sensitization led to the former two compounds. It was found that the photochemoselectivity depended on the substituents on the vinyl group and would be controlled by the energy using the triplet sensitizers.