Synthesis of a ditopic cyclophane based on the cyclobutane ring by chalcone photocycloaddition

The intramolecular photocycloaddition of chalcones to give cyclobutanes has proven to be a fast and simple method to shrink a cyclophane ring to a tricyclic system, in order to prepare potential ditopic receptors. In particular, the chalcone , having dioxyethylene chains as spacers, is converted in high yield to the cyclobutane . NOESY spectroscopy indicates that the formation of occurs by a head-to-head syn ring closure.