Photochemical Transformations of 1-Imidazolyl-1,2-dibenzoylalkenes. Steady-State and Laser Flasch Photolysis Investigations

Article abstract of DOI:10.1021/jo00368a003

The photochemistry of a number of 1-imidazolyl-1,2-dibenzoylalkenes and 1-benzimidazolyl-1,2-dibenzoylalkenes has been investigated by steady-state photolysis combined with product analysis and laser flash photolysis.In several cases, the intramolecular phenyl group migration leading to ketene-mediated 3-butenoic acids and esters is observed.In addition, depending on the substituents present in the imidazolyl and benzimidazolyl groups, a variety of phototransformations occur; these include electrocyclic ring-closure reactions leading to dihydrophenanthrene and dihydroisoquinoline derivatives and photofragmentation reactions resulting in the loss of the imidazolyl moieties from the parent dibenzoylalkenes.Plausible mechanisms for these photoreactions are discussed.Laser flash photolysis in several cases gives rise to transient processes related to ketene and zwitterionic intermediates.