单重态卡宾与甲酰氯环加成反应机理的理论研究

用限制的H artree-Fock从头算分子轨道理论研究了单重态卡宾与甲酰氯环加成反应的机理。在HF/3-21G*基组水平上,计算了反应势能面上各驻点的构型参数、振动频率和能量。计算结果表明,该反应的主反应途径由两步组成:首先,两反应物通过一无势垒的放热反应生成一富能中间体INT a,放出的热量为36.47 kJ.m o-l 1;然后该中间体经过渡态TSa异构化为一三元环产物P,其势垒为23.22 kJ.m o-l 1。该反应途径与其竞争反应途径相比具有很好的选择性。     

聚乙二醇负载氮杂环卡宾钯化合物催化水相中的Suzuki偶联反应

含溴原子的环钯化合物[PdCl{[(η5-C5H5)]Fe[(η5-C5H3)-NC5H3-Br]}(C3N2H2)(C6H3-2C3H7)2](化合物1)与聚乙二醇(PEG)-10000反应,合成出聚乙二醇负载氮杂环卡宾环钯化合物1-PEG(10000).用红外光谱和核磁共振对其结构进行表征.以水为溶剂,K3PO4为碱,1-PEG(10000)能高效催化各种氯代芳烃的Suzuki偶联反应,该催化体系循环使用3次,还能保持较高的催化活性.     

Molecule matters

Divalent carbon compounds which were once considered as highly reactive organic intermediates have been tamed by the modern day synthetic chemist in the form of N-heterocyclic carbenes. The land marks in the history of development of these compounds and their applications as ligands in the Nobel Prize winning work on olefin metathesis catalysts are described. Anil J Elias is a professor at the Department of Chemistry, Indian Institute of Technology, Delhi.     

Recent progress in reactivity study and synthetic application of N-heterocyclic phosphorus hydrides

N-heterocyclic phosphines (NHPs) have recently emerged as a new group of promising catalysts for metal-free reductions, owing to their unique hydridic reactivity. The excellent hydricity of NHPs, which rivals or even exceeds those of many metal-based hydrides, is the result of hyperconjugative interactions between the lone-pair electrons on N atoms and the adjacent σ^*(P–H) orbital. Compared with the conventional protic reactivity of phosphines, this umpolung P–H reactivity leads to hydridic selectivity in NHP-mediated reductions. This reactivity has therefore found many applications in the catalytic reduction of polar unsaturated bonds and in the hydroboration of pyridines. This review summarizes recent progress in studies of the reactivity and synthetic applications of these phosphorus-based hydrides, with the aim of providing practical information to enable exploitation of their synthetically useful chemistry.     

用HMO理论解释卡宾的电子结构与立体结构及其反应

卡宾的基态有单线态和三线态两种状态。本文用HMO法的近似解说明了卡宾是以单线基态还是以三线基态存在的原因,同时也比较满意地解释了卡宾弯曲空间结构的特点,以及环状共轭卡宾的亲核或亲电反应性质。本文认为,卡宾中心碳原子是SP~2杂化。卡宾的基态是单线态还是三线态取决于卡宾中心碳原子的非键P轨道与相邻原子的P轨道的相互作用以及P电子的数目。     

N-heterocyclic carbene-stabilized metal nanoparticles within porous organic cages for catalytic applicationOA

Tuning the surface-embellishing ligands of metal nanoparticles(NPs) is a powerful strategy to modulate their morphology and surface electronic and functional features, impacting their catalytic activity and selectivity. In this work, we report the design and synthesis of a polytriazolium organic cage PIC-T, capable of stabilizing Pd NPs within its discrete cavity. The obtained material(denoted Pd@PCC-T) is highly durable and monodispersed with narrow particle-size distribution of 2.06 ± 0.02 nm,...     

Metal-organic frameworks bonded with metal N-heterocyclic carbenes for efficient catalysisOA

Metal N-heterocyclic carbenes(M-NHCs) on the pore walls of a porous metal-organic framework(MOF)can be used as active sites for efficient organic catalysis. Traditional approaches that need strong alkaline reagents or insoluble Ag₂O are not, however, suitable for the incorporation of NHCs on the backbones of MOFs because such reagents could destroy their frameworks or result in low reactivity. Accordingly,development of facile strategies toward functional MOFs with covalently bound M-...     

含氮杂环化合物作为农用杀菌剂的开发应用

综述了近年来含氮杂环化合物在农用杀菌剂领域的研究开发情况,介绍了属于含氮杂环化合物的五类最常见的农用杀菌剂.根据这些化合物具有的共性,对含氮杂环类化合物作为农用杀菌剂进一步开发的途径进行了讨论.