Study on the preparation and properties of polycyclic compounds bearing extremely bent benzene rings.

1.|.1 |副环环烷的制备及其结构和热力学的理论研究。去年首次在取代衍生物（R=CO_2Me）上完成了双杜瓦苯化合物(1)光化学异构化法制备|.1 |副环环烷(2)。为了进一步探索极应变环烷的化学性质，制备了未取代的1a，并通过1a的光化学异构化成功地生成了2a。根据理论计算，相对的桥头堡碳之间的原子间距离在2.3-2.4A之间非常短，因此2中的两个芳环之间存在强的跨环相互作用。计算还表明，从2a中去除两个电子会导致电子稳定的状态2a^<2+>，其中电子电荷广泛地离域，并且上述原子间距离进一步减小到2.05A，这对于非键碳原子来说是一个异常短的原子间距离。目前正在研究2的动力学稳定性和2^<2+>的生成。功能化四碳链杜瓦苯1.4的光化学反应性研究。对桥接杜瓦苯- bbb4|副环环烷体系作为光化学驱动的分子开关器件的可能性感兴趣。制备了侧链上带有吸电子基团的杜瓦苯衍生物，并对其光化学行为进行了研究。化合物3b和4a分别光化学可逆转化为5b和6a，紫外/紫外吸收光谱延伸至500nm。3a和4b的光化学反应活性与3b和4a明显不同，无法检测到它们异构化成bbb40 |副环烷结构。

1.Preparation of |1.1|paracyclophane and theoretical study on its structure and energetics. The preparation of |1.1|paracyclophane (2) via photochemical isomerization of bis (Dewar benzene) compound (1) was accomplished for the first time on the substituted derivative (R=CO_2Me) last year. To explore the chemistry of extremely strained cyclophanes further, unsubstituted 1a was prepared and 2a was successfully generated from 1a via its photochemical isomerization. According to theoretical calculations the interatomic distance between the opposing bridgehead carbons is exceptionally short at 2.3-2.4A and, thus, strong transannular interactions between the two aromatic rings in 2 is suggested. The calculations also suggest that removal of two electrons from 2a leads to electronically stabilized dication 2a^<2+> in which electronic charge is extensively delocalized and the interatomic distance mentioned above further diminishes to 2.05A,an unusually short interatomic distance for non-bonded carbon atoms. Investigation on the kinetic stabilization of 2 and the generation of 2^<2+> is now underway.Study on photochemical reactivities of Dewar benzenes 1.4-bridged with functionalized four-carbon-chain. Interested in a possibility that bridged Dewar benzene-|4|paracyclophane system may function as a photochemically driven molccular switching device. Dewar benzene derivatives bearing electron-withdrawing groups on the side chain were prepared and their photochemical behaviors were studied. Compounds 3b and 4a underwent photochemically reversible transformation into 5b and 6a, respectively, which exhibited characteristic UV/V is absorption spectra extending to 500nm. The photochemical reactivities of 3a and 4b were strikingly different from those of 3b and 4a, and their isomerization into the |4|paracyclophane structures could not be detected.