Templating Photodimerization of trans-Cinnamic Acids with Cucurbit[8]uril and γ-Cyclodextrin

Cucurbit[8]uril and γ-cyclodextrin are able to align two olefin molecules in a head−head fashion within their large cavities. Excitation of such templated olefins results in syn head−head cyclobutanes in nearly quantitative yields. The methodology revealed here works with trans-cinnamic acids that do not dimerize either in solution or in the solid state and with the ones that yield only anti head−tail dimer in the solid state.