Templating photodimerization of trans-cinnamic acids with cucurbit[8]uril and γ-cyclodextrin

Cucurbit[8]uril and gamma-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 transcinnamic 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.