Arene-alkene meta photocycloadditions and conjugated enyne photorearrangements

The new advances and synthetic potential of arene-alkene meta photocycloadditions, with the goal of rapid approach to polycyclic molecules, are described. Vinyl cyclohexanecarboxylate has been found to be an efficient alkene moiety to improve the reaction efficiency by reducing formation of polymers during irradiation. Exploration of asymmetric meta photocycloaddition, via chiral auxiliaries, resulted in partial asymmetric induction. Fluorescence studies have led to a better understanding of the reaction mechanism. Intramolecular isotope effect results on meta photocycloaddition remain unexplained. Conjugated enynes undergo a singlet photorearrangement, resulting in a pseudodegenerate rearrangement. The synthesis of starting materials, characterization of products, studies of the reaction reversibility, and studies of the generality of the rearrangement are described. Two possible mechanisms, 1,2-cyclobutadiene and carbene walk, are proposed and discussed