Novel Kinetic Stabilization of the [1.1] Paracyclophane System and Preparation of the Naphthalenophane System

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A kinetic stabilization of the [1.1]paracyclophane system was examined by structurally modifying the methylene bridges. This approach allows introductlon of a variety of substituents on the benzene rlngs of [1.1]paracyclophane. The bis (Dewar benzene) derivative, the precursor of [1.1]paracyclophane, bearing t-BuMe_2SiO groups on the bridges prepared in 21 steps. Photoirradiation to this compound at 77K resulted in the formation of labile [1.1]paracyclophane but accompanied by other byproducts. To investigate the reactivity and stability of this new type of [1.1]paracyclophanes bearing different groups in this position was also prepared.The [1.1]naphthalenophanes exhibiting extended conjugation of the [1.1]paracyclophane π-system were designed in anticipation of the enhanced transannular effect. In the course of preparation of their precursors, a novel benzo-annulation method consisting of [2+2]photocycloaddition of olefins to benzoquinone bis (ethylene ketal), deprotection of ketals and spontaneous aromatization steps was developed. Synthetic study of [1.1]naphthalenophane derivatives is now under way by this methods.