Synthesis, Structure, and Transannular pi-pi Interaction of Novel [3.3] Cyclophanes

(1)合成并表征了多桥[3_n]环番[3_6](1，2，3，4，5，6)环番1的合成、结构及跨环pi-pi相互作用。我们期望1具有令人着迷的化学和结构特征；基于半经验分子轨道计算，预测了1到2的光化学异构化反应。对于1的合成，我们考察了从[3_3](1，3，5)环番开始的分步合成方法。成功合成1的关键在于利用乙酰基和假取代甲酰基之间的分子内羟醛缩合来构建额外的桥。该反应以很高的产率提供了烯酮，并且烯酮很容易通过酮被还原为三亚甲基桥。然而，六桥基酮不能被各种金属氢化物还原，但在1…存在下，SmI_2在四氢呋喃中的应用更多的N水溶液成功地生成了醇，该醇很容易被LiAlH4-AlCl3还原为所需的1.[3_n]环番(n=6，5，4，3)1，2，3，4的电子吸收带及其与四氰乙烯(TCNE)在CHCl_3中的电荷转移(CT)带随着三亚甲基桥数的增加而向长波方向移动.这些结果表明，随着三亚甲基桥数目的增加，1-4具有更强的跨环pi-pi相互作用。在[M.N]环番和多桥苯酚与TCNE的CT络合物中，1(710 Nm)的CT谱带是最长的。在1(甲苯-d_8)的变温~1H核磁共振谱中，估计了1(甲苯-d_8)的反转过程的能垒为9.8kcal/mol。化合物1对光敏感，光产物的分离鉴定正在进行中。(2)含两个15，16-二甲基二氢芘骨架的双层环烯的合成研究作为研究跨环pi-pi相互作用的模型化合物，我们发现7，15-二叔丁基-4，12-二甲基[2，2]偏环芳烃可以通过光合乙酸光照射转化为2，7-二叔丁基-1-15，16-二甲基二氢芘。用低压汞灯照射环烷二聚体的醋酸溶液，观察到目标化合物的甲基质子的~1H核磁共振信号。对该产品的表征正在进行中。较少

(1) Synthesis, Structure, and Transannular pi-pi Interaction of Multibridged [3_n] cyclophanes[3_6] (1,2,3,4,5,6) cyclophane 1, which is one of the ultimate compound in the field of [3.3] cyclophane chemistry has been synthesized and characterized. We expect 1 to have the fascinating chemical and structural features ; the photochemical isomerization of 1 to propella [3_6] prismane 2 has been predicted based on semiempirical MO calculations. For the synthesis of 1, we examined a stepwise approach starting from [3_3] (1,3,5) cyclophane. The key to the successful synthesis of 1 lay in employing intramolecular aldol condensation between an acetyl group and a pseudogeminally substituted formyl group to construct an additional bridge. This reaction provided enones in very high yields and the enones were readily reduced to trimethylene bridges by way of ketones. Hexabridged ketone, however, could not be reduced by various metal hydrides, but the employment of SmI_2 in THF in the presence of 1 … More N aqueous KOH successfully gave the alcohol, which was readily reduced by LiAlH_4-AlCl_3 to give the desired 1.Electronic absorption bands of [3_n] cyclophanes (n=6,5,4,3) 1,2,3,4 and their charge transfer (CT) bands with tetracyanoethylene (TCNE) in CHCl_3 shift to longer wavelength region with the increase of the number of trimethylene bridges. These results suggest that 1-4 tend to have stronger transannular pi-pi interaction as the number of trimethylene bridges increases. The CT band of 1 (710 nm) is the longest wavelength among those of the CT complexes, of [m. n] cyclophanes and multibridged benzenophanes with TCNE.In the variable temperature ^1H NMR spectra of 1 (toluene-d_8), the energy barriers for the trimethylene bridge inversion process are estimated to be 9.8 kcal/mol. The compound 1 is sensitve to light, and the isolation and identification of the photo-product is in progress.(2) A Synthetic Study of Double-layred Annulene Containing Two 15,16-Dimethyldihydropyrene SkeletonsIn a synthesis of double-layred annulene containing two 15,16-dimethyldihydropyrene skeletons as a model compound for the study of transannular pi-pi interaction, we found that 7,15-di-t-butyl -4,12-dimethyl [2,2] metacyclophane is converted to 2,7-di-t-buty1-15,16-dimethyldihydropyrene in good yield by photo-irradiation in acetic acid. When acetic acid solution of a dimer of the cyclophane, a precursor to the desired double-layred annulene, was irradiated with a low-pressure Hg lamp, the characterictic ^1H NMR signal of the methyl protons of the desired compound was observed. The characterization of the product is in progress. Less