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

(1)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π-π相互作用本文合成并表征了[3.3]环番化学领域的重要化合物之一。我们期望1具有迷人的化学和结构特征，1的光化学异构化propella [3_6] prismane 2已被半经验分子轨道计算的基础上预测。对于1的合成，我们研究了从[3_3]（1，3，5）环蕃开始的逐步方法。成功合成1的关键在于利用乙酰基和假偕取代甲酰基之间的分子内羟醛缩合来构建额外的桥。该反应以非常高的产率提供烯酮，并且烯酮容易通过酮还原成三亚甲基桥。但六缩酮不能被各种金属络合物还原，而SmI_2在THF中，1 ...更多信息 [3_n]环番（n= 6，5，4，3）1，2，3，4的电子吸收带及其与四氰基乙烯（TCNE）在CHCl_3中的电荷转移（CT）带随着三亚甲基桥数目的增加而向长波区移动。这些结果表明，随着三亚甲基桥数目的增加，1-4倾向于具有更强的跨环π-π相互作用。CT带1（710 nm）是CT复合物中最长的波长，为[m.在1（甲苯-d8）的变温^~ 1H NMR谱中，估计了三亚甲基桥翻转过程的能垒为9.8 kcal/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轮烯的合成研究在作为研究跨环π-π相互作用的模型化合物的含两个15，16-二甲基二氢芘骨架的双层轮烯的合成中，我们发现7，15-二叔丁基-4，12-二甲基[2，2]间环芳烷转化为2，7-二叔丁基-15，16-二甲基二氢芘在乙酸中通过光照射以良好的产率合成。当用低压汞灯照射环蕃二聚体（双层轮烯的前体）的乙酸溶液时，观察到所需化合物的甲基质子的特征性^1H NMR信号。产品表征正在进行中。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