Li Jun-Li, Li Hao-Yuan, Zhang Shan-Shan, Shen Shigang, Yang Xiu-Long, Niu Xiaoying
Key Laboratory of Analytical Science and Technology of Hebei Province, Key Laboratory of Medicinal Chemistry and Molecular Diagnosis of the Ministry of Education, Key Laboratory of Chemical Biology of Hebei Province and College of Chemistry and Materials Science, Hebei University, Baoding 071002, P. R. China.
Postdoctoral Research Station of Chemistry Affiliated College of Chemistry and Materials Science, Hebei University, Baoding 071002, P. R. China.
J Org Chem. 2023 Nov 3;88(21):14874-14886. doi: 10.1021/acs.joc.3c01078. Epub 2023 Oct 20.
An efficient oxidant-free, photoredox-mediated cascade cyclization strategy for the synthesis of 1,3,4-oxadiazoles by using an organo acridinium photocatalyst and a cobaloxime catalyst has been developed. Various acylhydrazones have been transformed into the corresponding 1,3,4-oxadiazole products in up to 96% yield, and H is the only byproduct. Mechanistic experiments and density functional theory (DFT) calculation studies indicate carbon-centered radicals rather than oxygen-centered radicals as π-radicals produced by the oxidation of photoexcited Mes-Acr* along with deprotonation, which is responsible for this transformation. The practical utility of this method is highlighted by the one-pot gram-scale synthesis starting directly from commercially available aldehydes and acylhydrazides.
已经开发出一种高效的无氧化剂、光氧化还原介导的级联环化策略，用于使用有机吖啶鎓光催化剂和钴肟催化剂合成1,3,4-恶二唑。各种酰腙已被转化为相应的1,3,4-恶二唑产物，产率高达96%，且唯一的副产物是氢气。机理实验和密度泛函理论（DFT）计算研究表明，由光激发的Mes-Acr*氧化并伴随去质子化产生的π-自由基是以碳为中心的自由基而非以氧为中心的自由基，这一过程导致了这种转化。直接从市售醛和酰肼开始的一锅法克级合成突出了该方法的实用性。
