Syntheses and Properties of Strained Polycyclic Compounds

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Recently much attention has been focused on the design and construction of novel carbon-rich materials with unusual structural, electronic and optical properties. Despite the fascinating structural features, however, π-conjugated carbon-rich macrocycles with a cylindrical structre still remain as a synthetic challenge, although several attempts to prepare related belt-shaped molecules have been reported. In this study we examined the synthesis and characterization of the first [4_6]paracyclophanedodecayne derivative, in which six p-phenylene and butadiyne units are connected alternatively to form a highly unsaturated cylindrical π-conjugated system. A key feature in the present approach is exploitation of a Dewar benzene as an angular p-phenylene synthon. Thus, [4_6]paracyclophanedodecayne derivative has been photochemically generated from the corresponding hexakis(Dewar benzene) compound as a highly strained but isolable compound. The present results clearly demonstrate the high synthetic potential of our Dewar benzene building block approach for the construction of strained phenylene macrocycles that are difficult to prepare from planar benzene derivatives.