Gansu International Scientific and Technological Cooperation Base of Water-Retention Chemical Functional Materials, College of Chemistry and Chemical Engineering, Northwest Normal University, Lanzhou, Gansu, 730070, China.
Department of Chemistry and Centre for Scientific Modeling and Computation, Chinese University of Hong Kong, Shatin, Hong Kong, China.
Org Biomol Chem. 2022 Jun 29;20(25):5139-5144. doi: 10.1039/d2ob00847e.
Visible-light-promoted cyclization and aromatization of chalcones with 2-mercaptobenzimidazoles have been successfully developed to obtain diverse imidazo[2,1-]thiazoles, and C-S and C-N bonds were constructed in one step. The reaction uses oxygen in the air as an oxidant, and the method does not need an external photocatalyst or a transition metal catalyst. The strategy features mild conditions, a simple system, readily accessible feedstocks, and a friendly environment. UV absorption spectroscopy and control experiments have shown that the reaction mechanism involves the formation of an electron-donor-acceptor (EDA) complex from thiolate anions and chalcones. In order to verify the mechanism, we studied the structure and HOMO/LUMO of the EDA complex by density functional theory (DFT) calculations. The results show that the π-π stacking between chalcones and 2-mercaptobenzimidazoles will cause a red shift of the UV absorption wavelength in the presence of CsCO, and also provide a theoretical basis for the electron transfer of EDA complexes.
可见光促进的查尔酮与 2-巯基苯并咪唑的环化和芳构化反应已成功开发，可获得多种咪唑并[2,1-]噻唑，并且可以一步构建 C-S 和 C-N 键。该反应使用空气中的氧气作为氧化剂，该方法不需要外部光催化剂或过渡金属催化剂。该策略具有条件温和、体系简单、原料易得和环境友好等特点。紫外吸收光谱和控制实验表明，反应机理涉及硫醇阴离子和查尔酮形成电子给体-受体（EDA）配合物。为了验证该机理，我们通过密度泛函理论（DFT）计算研究了 EDA 配合物的结构和 HOMO/LUMO。结果表明，在 CsCO3 的存在下，查尔酮和 2-巯基苯并咪唑之间的π-π堆积会导致 UV 吸收波长的红移，这也为 EDA 配合物的电子转移提供了理论依据。
