(Salen)Ti(IV)-Catalyzed Asymmetric Ring-opening of meso Epoxides Using Dithiophosphorus Acid as the Nucleophile

As an important strategy for the formation of 1,2-bifunctionalized systems theasymmetric ring-opening of epoxides with different nucleophiles has drawn muchattention from the organic chemists. A wide variety of nucleophiles are utilized in theaforemention…     

Synthetic and mechanistic studies on asymmetric cyanohydrin synthesis using a titanium(salen) bimetallic catalyst

A bimetallic titanium(salen) complex 1 was found to catalyse the asymmetric addition of ethyl cyanoformate to aldehydes. Best results were obtained using 5 mol% of the catalyst at −40 °C and under these conditions, both aromatic and aliphatic aldehydes were converted into cyanohydrin carbonates with up to 99% enantiomeric excess. The same catalyst could also be used to catalyse the asymmetric addition of potassium cyanide to aldehydes in the presence of propionic anhydride, leading to cyanohydrin esters. Mechanistic studies showed that the enantiomeric excess of the product increased during the early stages of this reaction. However, by adding a ‘sacrificial aldehyde’ this effect could be eliminated. The structure of the catalyst in solution was investigated using variable concentration, variable temperature and variable solvent NMR studies. These experiments showed that the catalyst exists as a mixture of monometallic 4 and bimetallic 1 species, a result which is consistent with previous mechanistic studies on the asymmetric addition of trimethylsilyl cyanide to aldehydes and ketones catalysed by the same catalyst. A mechanistic rationale for all of these observations is reported.     

聚类卟啉金属配合物

为模拟天然卟啉所具有的特殊生理活性,结构与性能各异的多种金属卟啉被合成并应用于许多领域。实际上,天然金属卟啉是在特定天然高分子-蛋白质营造的空穴中才能发挥其独特的性质,因此,类卟啉金属配合物的高分子化逐渐受到关注,并在载氧、催化、导电等领域取得重要成果。基于结合方式不同,高分子类卟啉金属配合物可分为高分子担载类卟啉金属配合物与聚类卟啉金属配合物。其中,后者以稳定的类卟啉环作为高分子链,不但使高分子骨架稳定,而且活性中心与类卟啉金属配合物之间有效间隔,同时活性中心相对密集,使其表现出较高的稳定性与活性。线形与平面型聚金属卟啉与金属酞菁表现出良好的导电性与催化活性;手性Salen席夫碱易于聚合得到线形或网状聚Salen希夫碱金属配合物,其表现出较强的催化活性、高ee值和可循环性。异双核聚类卟啉金属配合物也表现出较强的催化活化分子氧性能。     

水溶性Pt(Ⅱ)-Salen配合物的合成、表征和光催化制氢研究

本文合成了一种水溶性的Pt(II)-Salen配合物(Salen=双5-磺酸钾水杨醛合邻苯二胺席夫碱),将其用于光催化制氢.研究发现在光催化制氢体系中仅存在Pt(II)-Salen配合物和三乙胺(TEA)而没有额外加入催化剂时,在可见光照射下有氢气产生.进一步的研究表明,Pt(II)-Salen配合物在体系中既是光敏剂,又是催化剂Pt纳米粒子的前体.同时,制氢体系中除了TEA外没有使用有机溶剂.该结果为简化多组分制氢体系提供了新思路.     

Trinuclear Cobalt(II) and Zinc(II) Salamo‐type Complexes: Syntheses,Crystal Structures,and Fluorescent Properties

Two trinuclear Co^II and Zn^II complexes, [(CoL)₂(OAc)₂Co] and [(ZnL)₂(OAc)₂Zn], with an asymmetric Salen‐type bisoxime ligand [H₂L = 4‐(N,N‐diethylamine)‐2,2′‐[ethylenediyldioxybis(nitrilomethylidyne)]diphenol] were synthesized and characterized by elemental analyses, IR, UV/Vis, and fluorescent spectroscopy. The crystal structures of the Co^II and Zn^II complexes were determined by single‐crystal X‐ray diffraction methods. The Co^II atom is pentacoodinated by N₂O₂ donor atoms from the (L)^2– unit and one oxygen atom from the coordinated acetate ion, resulting in a trigonal bipyramid arrangement. With the help of intermolecular hydrogen bonding C–H ··· O and C–H ··· π interactions, a self‐assembled continual zigzag chain‐like supramolecular structure is formed. The Zn^II atom is pentacoodinated by N₂O₂ donor atoms from the (L)^2– unit and one oxygen atom from the coordinated acetate ion, resulting in an almost regular trigonal bipyramid arrangement. A self‐assembled continual 1D supramolecular chain‐like structure is formed by intermolecular hydrogen bonding C–H ··· O and C–H ··· π interactions. Additionally, the photophysical properties of the Co^II and Zn^II complexes were discussed.     

Some new Schiff base ligands giving a NNOS coordination sphere and their nickel(II) complexes: Synthesis,characterization and complex formation

Some new tetradentate ligands with a NNOS coordination sphere were prepared and their corresponding nickel(II) complexes were synthesized and characterized by elemental analysis, IR, ¹H NMR, UV–Vis and mass spectrophotometry. The thermodynamic formation constants of the complexes were measured spectrophotometrically, at a constant ionic strength of 0.1 M (NaClO₄) at 25 °C in DMF solvent. The trend of the complex formation for nickel is as follows:     

Activation of 1-halonaphthalenes by electrogenerated [Co-salen]

We report in this paper an electroanalytical study of the reaction of 1-halonaphthalenes with electrogenerated [Co^I-salen]. With 1-iodonaphthalene, the reaction observed is a substitution, with a release of the iodide ion. Conversely, the reaction is much slower with 1-bromonaphthalene, and the intermediate adduct is observed at the time scale of cyclic voltammetry. The corresponding rate constants have been determined.     

Synthesis of a new class of keto-linked bis heterocycles

A new class of keto-linked bis heterocycles have been prepared by 1,3-dipolar cycloaddition of tosyl methyl isocyanide, nitrile imines and nitrile oxides to unsymmetrical bischalcones.     

手性Salen配合物水解拆分环氧氯丙烷的动力学

在立体控制合成有机化合物方面,环氧化合物是一类极有价值的中间体,其中以外消旋混合物形式存在的端基环氧化合物因其价廉易得更是备受关注. 在试图获得高光学纯形式环氧化物的研究中,Jacobsen等[1]对消旋的端基环氧化物的水解动力学拆分(HKR)反应,取得了令人鼓舞的结果,获得了高立体选择性和高产率的手性环氧化物(Y=44%,e.e.＞98%)和1,2-二醇化合物(Y=50%,e.e.=98%). 在该项研究中,水是唯一的试剂,手性Salen-CoⅢ显示出良好的催化性能,并得到反应速率与催化剂浓度的平方成正比的反应动力学结果. Jacobsen等[2]又将手性Salen-CoⅢ催化剂固载于聚苯乙烯树脂和硅胶上,用于催化HKR反应,产物的对映选择性又获得进一步提高(Y=41%,e.e.=99%);他们提出了与Salen-CrⅢ配合物催化TMSN3(三甲基叠氮基硅烷)开环环氧化物相似的双金属协同作用机理[3]. 近年来,Salen金属催化的HKR反应广泛地用于高光学纯药物中间体和天然产物的制备. 首先,Jacobsen等[4,5]成功地利用HKR反应高选择性地制备合成出多种β-肾上腺素的关键中间体,并完成了天然产物Muconin的首次全合成. 随后,Gurjar等[6]和Gandour等[7]也通过HKR反应合成了一些在天然产物及药物分子不对称合成中有广泛应用的中间体. 在国内,上海有机化学所的戴立信等[8]利用HKR反应成功地合成了三种β-肾上腺素的构建模块. 吴毓林等[9,10]则通过HKR反应完成了天然番茄枝内酯类化合物4-Deoxyannomontacin的全合成. 所有这些工作,或是重在提高产物的对映体过量及催化剂的活性,或是重在HKR反应在天然产物及药物化学合成中的应用. 由于对外消旋环氧化物的水解拆分反应机理缺乏详细的研究,从而限制了对新型催化剂的开发及对现有催化剂的改进. 本文以各类手性Salen金属配合物为催化剂,通过对水解拆分环氧氯丙烷反应动力学的研究,考察了浓度、温度、催化剂种类对HKR反应的影响,得到一些反应动力学规律;根据动力学实验数据,进一步证实了环氧氯丙烷的水解拆分反应属于双金属催化的过程.     

Stress resultants and moments around holes in unsymmetrical composite laminates subjected to remote uniform loading

Stress resultants and moments around the holes of infinite unsymmetrical composite laminates under remote uniform loading are analyzed using the complex potential approach developed by Chen and Shen [Mech. Res. Commun. 28 (4) (2001) 423; 28 (5) (2001) 513]. In the analysis, the authors’ previous work has been modified to determine the complex constants B_k appeared in the complex potential functions of Chen and Shen [Mech. Res. Commun. 28 (5) (2001) 513]. Herein B_k are the unknown quantities related to the remote loading conditions. The effect of bending extension coupling has been discussed for several laminates such as [0/90]_T, [45/−45]_T and [0/90/45/−45]_nT. Results indicates that the coupling between bending and extension significantly affects the stresses around the hole of an unsymmetrical laminate containing one sub-laminate only. Such the effect rapidly decreases as the number of the sub-laminates increases. The results confirm the validity of the developed complex potential approach.