LAUSR

Abstract A method for the synthesis of silicon-containing macrocyclic compounds, using intramolecular [2 + 2] photocycloaddition reactions of bis-dimethylsilyl-linked styrene or stilbene derivatives, is described. Photoirradiation of benzene solutions of o- and m-bis(dimethylsilylmethyl)benzene derivatives, containing two styrene units, promotes efficient formation of intramolecular [2 + 2] photocycloadducts. In contrast, photoreaction of the corresponding para-substituted analog generates only dimers. Photoreactions of bis(dimethylsilylmethyl)benzene derivatives, possessing two stilbene units produce intramolecular [2 + 2] photocycloadducts along with products of cis-trans photoisomerization. The efficiencies of these intramolecular photoreactions depend on the distances between two double bonds undergoing [2 + 2] cycloaddition. Triplet-sensitized photoreactions of the stilbene derivatives lead to cis-trans isomerization exclusively. Finally, photoreactions of the stilbene derivatives in the presence of molecular oxygen produce phenanthrene derivatives as side products.