Stereocontrol in Cyclophane Synthesis:  A Photochemical Method To Overlap Aromatic Rings

To overlap aromatic rings in cyclophanes, the inter- and intramolecular [2 + 2] photocycloaddition of vinylarenes has been developed. It gives cyclophanes, naphthalenophanes, phenanthrenophanes, thiophenophanes, and carbazolophanes in reasonable to excellent yields. The structures and properties of cyclophanes obtained are reviewed; especially the excimer emission of phenanthrenophanes, naphthalenophanes, and carbazolophanes stressed that many intriguing cyclophanes can be obtained through the fine molecular design of precursors.