Studies on the Syntheses of Multilayered [2. 2] Paracyclophanes

Abstract

It is well-known that a number of double-layered compounds such as [2. 2]paracyclophane show anomalous physical and chemical properties due to the transannular π-electronic interaction between the stacked aromatic rings.²) Moreover, the interaction significantly increases with an increase of the layers as observed in a series of multilayered [2. 2]paracyclophanes³) and thereby it is of great interest to search a possibility of an organic semiconductor or its suitable model in them or their derivatives. However, such a study has been severely limited by great difficulty on the syntheses of the layered cyclophanes. While a number of synthetic methods have been developed for cyclophanes,²) only 1,6-Hofmann elimination method has so far been adopted to the preparation of multilayered [2.2]paracyclophanes.³) In practice, however, the yield is very low and becomes markedly poor with the increasing layers. Now we have studied some practical improvements on the preparation of multilayered [2.2]paracyclophanes.