Photoreactive furan derivatives

Several furan compounds bearing conjugated trans CC plus carbonyl moieties appended at the C2 position of the heterocycle were synthesized and characterized. Near-UV irradiation in bulk and in concentrated solutions induced their dimerization through a [π2 + π2] cycloaddition reaction between an excited and a ground state molecule. In dilute solutions, the excited species underwent predominantly trans–cis isomerization to give the equilibrium mixture of the isomers.