Yang Ting, Chen Zheng, Wang Ziqing, Yu Jiayuan, Xia Changjiu, Liu Hongxia, Liu Lei, Peng Xinxin, Luo Yibin, Shu Xingtian
State Key Laboratory of Petroleum Molecular & Process Engineering, Research Institute of Petroleum Processing, SINOPEC, Beijing 100083, China.
Center for Computational Chemistry, College of Chemistry and Chemical Engineering, Wuhan Textile University, Wuhan 430200, China.
Inorg Chem. 2024 Nov 11;63(45):21577-21589. doi: 10.1021/acs.inorgchem.4c03791. Epub 2024 Oct 30.
Disulfide is an important organic reagent and synthetic intermediate that is widely used in organic synthesis, polymers, and other fields, but its synthesis still suffers from many environmental pollution and economic problems. Here, we present an environmentally friendly and efficient base-free aerobic oxidative thiol coupling catalyzed by heterogeneous CoO nanoclusters entrapped in hierarchical silicalite-1 zeolite, synthesized by combining silane pore expansion and metal coordination methods under hydrothermal conditions. It is confirmed that open hierarchical channels favor mass diffusion, and the chemical valence of Co species in CoO/-S-1-H is +2, which is different from that of CoO particles in CoO/-S-1-I. CoO nanoclusters, are strongly fixed in the channels of silicalite-1 zeolite via Co-O-Si bonds, which is of great importance for the high catalytic activity in both symmetrical and unsymmetrical oxidative thiol coupling reactions. After recycling experiments four times, the CoO/-S-1-H used has almost the same chemical state and the same distribution of Co(II) species as the fresh catalysts. Based on DFT calculations and inhibition experiments, the oxidative coupling of thiols undergoes a free radical mechanism in which Co(III) causes RS-H cleavage into RS· and H· species. Subsequently, two RS· radicals are coupled to disulfides, while H· radicals react with the O species to form HO molecules. This work not only provides guidance on catalyst design and parameter optimization for oxidative thiol coupling but also advances the understanding of the aerobic oxidation mechanism.
二硫化物是一种重要的有机试剂和合成中间体，广泛应用于有机合成、聚合物等领域，但其合成仍存在许多环境污染和经济问题。在此，我们展示了一种环境友好且高效的无碱有氧氧化硫醇偶联反应，该反应由包裹在分级硅沸石-1中的非均相CoO纳米团簇催化，通过在水热条件下结合硅烷扩孔和金属配位方法合成。证实开放的分级通道有利于质量扩散，并且CoO/-S-1-H中Co物种的化学价为+2，这与CoO/-S-1-I中的CoO颗粒不同。CoO纳米团簇通过Co-O-Si键牢固地固定在硅沸石-1的通道中，这对于对称和不对称氧化硫醇偶联反应中的高催化活性至关重要。经过四次循环实验后，所用的CoO/-S-1-H与新鲜催化剂具有几乎相同的化学状态和相同的Co(II)物种分布。基于DFT计算和抑制实验，硫醇的氧化偶联经历自由基机制，其中Co(III)导致RS-H裂解为RS·和H·物种。随后，两个RS·自由基偶联形成二硫化物，而H·自由基与O物种反应形成HO分子。这项工作不仅为氧化硫醇偶联的催化剂设计和参数优化提供了指导，还推进了对有氧氧化机制的理解。
