Xinyuan Sun,Dan Li,Qianqian Niu,Yan Liu,Dandan Zhang,Longjiu Cheng,Baokang Jin
Cyclic azobenzenes are capable of undergoing reversible cis-trans isomerization upon visible light irradiation, making them promising candidates as molecular photoswitches for applications in biological systems. However, their synthesis remains challenging due to their unique structural features. In this study, two eight-membered cyclic azobenzenes, namely 12H-dibenzo[b,f][1,4,5]thiadiazocine ( 13 ) and 12H-dibenzo[b,f][1,4,5] oxadiazocine ( 14 ), were synthesized through electrochemical reduction of 2’-nitrobenzyl-2-nitrophenyl-sulfide ( 1 ) and 1-nitro-2-((2’-nitrobenzyl)oxy)benzene ( 2 ), respectively, in the presence of CO₂. The synthesis yielded high conversion rates ( 13 : 85.98%, 14 : 93.76%). Using in situ infrared spectroscopy, NMR, and MS, detailed reduction mechanisms were elucidated, revealing an irreversible 8-electron transfer process and CO₂ involvement in a four-step reaction pathway. UV-Vis spectroscopic analysis showed that both 13 and 14 undergo trans-to-cis isomerization upon exposure to yellow (520 nm) or red (630 nm) light, in agreement with theoretical calculations. Additionally, S0→S1 excitations of both cis and trans isomers are predominantly governed by n→π* transitions. It is found that the cis conformation of compounds 13 and 14 is more stable than the trans conformation. Under yellow or red light irradiation, they undergo rapid trans-to-cis isomerization. No photochemical fatigue was observed in the cyclic experiments at room temperature, indicating their excellent photostability and potential application in photopharmacology. This work offers a sustainable strategy for the synthesis of cyclic azobenzenes and CO₂ capture.
Octatrimethylsilyl-[8]cycloparaphenylene ([8]CPP-8TMS) was synthesized using the copper(I)-mediated homocoupling reaction of the highly functionalized biphenyl precursor and subsequent platinum-mediated macrocyclization. [8]CPP-8TMS was well characterized by spectroscopic techniques, including NMR, mass, UV–vis absorption, and fluorescence spectroscopy and cyclic voltammetry. Single-crystal X-ray diffraction analysis indicates that [8]CPP-8TMS possesses a highly symmetric structure and adopts an intermolecular tubular packing. [8]CPP-8TMS can serve as a versatile platform for the efficient construction of unprecedented functional nanocarbon structures.
Niu Ben,Xie Ping,Wang Min,Wang Yanjie,Zhao Wannian,Pittman Charles U.,Zhou Aihua
A series of seven- and eight-membered ring – N,O –, – N,N –, and – N,S –sultams were effectively synthesized via tandem reactions involving oxa-, aza-, and thia-Michael addition to vinyl sulfonamides. These reactions are summarized here since they enrich current synthetic methodologies for sultams and provide a good example of sultam diversity-oriented synthesis. All reactions proceeded under relatively mild and environmentally friendly conditions, and all these reactions are quite suitable for the rapid preparation of sultam compound libraries, which are valuable for biological activity explorations.
危险品化学品经营许可证（带存储）