金属络合物不对称催化硫醚氧化研究现状

手性亚砜是重要的手性中间体和辅剂、手性配体和催化剂、手性药物。手性金属络合物催化硫醚的不对称氧化是合成手性亚砜最有效的方法。文章简要的介绍了钛,钒,铌,铁四种金属的络合物不对称催化硫醚氧化的一些最新的研究现状。     

钛催化的不对称硫醚氧化研究进展

手性亚砜是重要的手性中间体和辅剂、手性配体和催化剂、手性药物.手性亚砜可以采用生物方法和化学方法来合成,化学方法包括手性辅剂诱导、手性氧化剂氧化、手性拆分和不对称催化等.手性金属络合物催化硫醚的不对称氧化是合成手性亚砜最有效的方法.理性设计各种手性金属络合物催化剂应用于催化对映选择性氧化潜手性硫醚反应中,近年来引起了化学家们较大的关注.作者简要综述了钛络合物催化剂在不对称硫醚氧化反应制备手性亚砜中的应用.     

手性叔胺催化不对称串联反应构建氧化吲哚螺环化合物的研究进展

近年来,有机小分子催化的串联反应已成为众多有机化学家们的研究热点,是合成手性化合物的有效方法。在众多不同催化体系中,手性叔胺催化的不对称串联反应得到了空前的发展。氧化吲哚螺环骨架是很多具有药理活性分子普遍存在的结构形式,含有该骨架的化合物是众多药物及有机化学家们的目标产物,不对称催化串联反应是合成氧化吲哚螺环化合物的重要理论基础和有力学术支撑。本文对近四年手性叔胺催化的不对称串联反应构建氧化吲哚螺环化合物的研究进行介绍。     

硫醚水相催化氧化研究进展

硫醚催化氧化制备亚砜和砜是有机合成中的一类重要反应。水作为一种廉价安全的绿色溶剂,在硫醚催化氧化反应中备受青睐。主要针对硫醚水相催化氧化反应中的重要金属基催化剂和有机酸催化剂的研究进行综述。在水相体系中,铁和锰等金属基催化剂、多金属氧酸盐及有机酸催化剂在硫醚催化氧化反应中均有良好的催化性能,多数硫醚类化合物转化率和选择性均达到90%以上。最后展望了硫醚水相催化氧化的发展方向,指出以来源广泛的O_2为氧化剂将是未来实现工业化应用的发展趋势。     

硫醚氧化为亚砜和砜的研究进展

亚砜和砜是两类重要的化合物,在化学和生物领域有广泛的应用。虽然有很多方法合成亚砜和砜,但通过控制硫醚的化学选择性氧化是合成亚砜和砜的常用途径之一;常见氧化剂如空气/氧气、双氧水、单过硫酸氢钾复合盐（Oxone）、高碘酸钠等均可以实现硫醚的选择性氧化。本文依据氧化剂的种类对氧化反应进行分类,综述了近年来硫醚氧化制备亚砜和砜的研究进展。     

废气甲硫醚的氧化处理

本文介绍生产甲硫醇副产甲硫醚废气的处理方法。文中列举了五种处理方法,详细地介绍了过氧化氢氧化法的实验步骤及结果。过氧化氢对甲硫醚的分子比为1.0～1.1:1,温度控制在25～35℃。经处理后,二甲亚砜选择率约95％,粗二甲亚砜精馏后纯度达99.9％,甲硫醚的总去除率达99.97％。     

不对称小分子催化合成的最新进展及其在药物合成中的应用

本文以药物合成的热点问题“手性有机小分子催化”为研究对象,介绍小分子催化反应的分类即“亲核性催化”和“亲电性催化活化”;在药物合成方法中主要有外消旋体拆分法、化学-酶合成法、酶催化手性药物合成法、不对称催化法,在药物合成中以形成非共价键活化底物的方式达到催化作用。     

不对称催化合成手性泛解酸内酯的研究进展

泛解酸内酯是合成D-泛酸钙和D-泛醇的重要中间体,国内主要采用生物拆分法,虽取得一定进展,但存在底物浓度偏低、反应条件苛刻、光学纯度不高和催化剂活性不强等问题。化学不对称合成法成为近年来制备手性泛内酯的研究热点。根据手性源的不同,介绍过渡金属配合物催化不对称还原酮基泛内酯,过渡金属配合物催化羟醛缩合反应,有机小分子及其衍生物不对称催化羟醛缩合反应并经还原内酯化合成泛内酯以及光学活性化合物作为反应底物或非手性底物中加入手性助剂的合成手性泛内酯工艺。其中,有机小分子催化乙醛酸酯与醛的反应表现出良好的催化效果,且催化剂易得,反应条件温和,操作简单。缩合产物的收率和对映选择性均不高,设计具有高活性和高选择性的有机小分子手性催化剂是今后研究的重点。     

聚芳硫醚新型中间体4-(苯硫基)苯甲亚砜(PSO)的合成

以廉价的二苯硫醚为起始原料,经氯磺化(Reed)反应并还原芳基磺酰氯合成了4-(苯硫基)苯硫醇,进一步以四丁基碘化铵(TBAI)催化端基硫醇,再与硫酸二甲酯发生甲基化反应,最终将甲基苯基硫醚高选择性地氧化成亚砜,得到聚芳硫醚合成的关键中间体4-(苯硫基(苯甲亚砜(PSO);考察了磺化试剂、磺酰氯还原体系(二氯二甲基硅烷-锌)、甲基化试剂、催化剂、溶剂和反应时间等对产率的影响,并对工艺进行了优化。该方法与其他路线相比,解决了使用液溴、硝酸等物质导致设备腐蚀问题的同时,大大提高了产率与纯度。     

手性催化在有机合成中的应用研究

介绍了手性催化在有机合成,特别是手性化合物合成方面的重要作用,并详细介绍了酶催化、手性金属络合物催化和手性有机小分子催化的手性催化的三种形式,并简要介绍了相关研究进展,同时也总结了手性催化所面临的各方面的挑战和亟待我们解决的相关难题。     

Chirality – Beyond the Structural Effects

Usually, when one refers to chirality, one focuses on the structural properties of the molecules. This review focuses on the interesting electronic properties of these molecules, and specifically, on the interrelation between the spin of the electrons transmitted through molecules and the chiral structure of these molecules. This relation is expressed in the chiral-induced spin selectivity (CISS) effect, which is described, including some of its implications. Specifically, several applications are described, in spintronics, in spin-specific reactivity, and in spin-controlled multiple-electron oxidation processes. In the latter, experimental results are described that demonstrate that by coating the anode of a photoelectrochemical cell with chiral molecules, the overpotential of the water-splitting process can be reduced.     

Analysis of the Molecular Structure at the PPS/Copper Interphase and its Role in Adhesion

X-ray photoelectron spectroscopy (XPS) was used to examine the interfacial chemistry in polyphenylene sulfide (PPS)/copper bonded laminates. Several surface pretreatments were studied including a simple methanol wash, two acid etches, thermal oxidation and chemical oxidation. Peel test analysis showed poor adhesion to the methanol-washed and acid-etched foils, giving a peel strength of only 3-5 g/mm. XPS analysis of the failure surfaces revealed a large amount of inorganic sulfide at the interface with reduction of the copper oxide. Chemical oxidation using an alkaline potassium persulfate solution gave a matt-black surface consisting of primarily cupric oxide. These samples showed improved adhesion and XPS analysis of the failure surfaces revealed fracture through a mixed PPS/cuprous oxide layer. A simple thermal oxidation yielded a cuprous oxide surface layer and laminates bonded to these surfaces showed a more than ten-fold increase in peel strength. XPS analysis of the failure surfaces showed much lower amounts of interfacial copper sulfide and it was postulated that excess sulfide at the interface was responsible for the poor adhesion observed for other pretreatments.     

Adsorption of Iodine and Bromine by Polyethylene Sulfide Containing Cotton Fabric

The adsorption of iodine and bromine by polyethylene sulfide-containing fabrics was investigated. It was found that the halogens could be adsorbed from aqueous solution as well as from a saturated halogen atmosphere. Adsorption was attributed to complexation by the sulfide bonds in the polymer. Adsorption from aqueous solution led to the formation of a complex with a molar ratio of halogen molecules (X₂) to ethylene sulfide units of 1:1, while that from gaseous iodine a ratio of 2 was obtained. Complexation was accompanied by a little degradation of the polysulfide which was attributed to halogenation of the polyethylene sulfide. High adsorption of bromine led to complete degradation of the cotton fabric due to oxidation of the cellulose. The adsorption of polyethylene sulfide in the fabric was much higher than that of homopolyethylene sulfide itself under comparable conditions.     

Recognition of chiral carboxylic anions by artificial receptors

Many carboxylic molecules, ranging from drugs to flavors and fragrances, contain chiral centers. As a consequence, research has been carried out in order to design and synthesize artificial receptors for carboxylic anions. Many problems have to be solved for binding anions. The results obtained in the binding of carboxylic anions by guanidine, secondary ammonium and metal-center have been selected. The last part of this review focuses on chiral recognition of carboxylic anions by organic and metal-based chiral receptors.     

Investigation of 3,3′,5,5′-tetra-tert-butyl-4,4′-stilbenequinone-based catalyst in the reaction of liquid-phase oxidation of inorganic sulfides

In this paper, the intermediate and final reaction products of catalytic oxidation of inorganic sulfides in the presence of oxygen dissolved in the kerosene fraction and 3,3′,5,5′-tetra-tert-butyl-4,4′-stilbenequinone were investigated. The thiosulfate and sulfate are major products of the oxidation of sodium sulfide under these conditions. The intermediate and final products in the catalytic oxidation of sulfide sulfur do not affect the rate of its oxidation. The yield of catalytic oxidation products depends on the nature of the sulfide and on the pH of the solution. The catalytic cycle for sulfide oxidation in the presence of 3,3′,5,5′-tetra-tert-butyl-4,4′-stilbenequinone is shown. The role of 3,3′,5,5′-tetra-tert-butyl-4,4′-stilbenequinone is to create a new and a more effective way of electron transfer from the reducing agent (sulfide) to the oxidant (oxygen).     

Alkaline earth metal catalysts for asymmetric reactions

The group 2 alkaline earth metals calcium (Ca), strontium (Sr), and barium (Ba) are among the most common elements on Earth, abundant in both the sea and the Earth's crust. Although they are familiar in our daily lives, their application to organic synthesis has, so far, been limited. Some particularly useful properties of these elements include (i) low electronegativity, (ii) a stable oxidation state of +2, meaning that they can potentially form two covalent bonds with anions, and (iii) the ability to occupy a variety of coordination sites due to their large ionic radius. Furthermore, the alkaline earth metals, found between the group 1 and group 3 elements, show mild but significant Lewis acidity, which can be harnessed to control coordinative molecules via a Lewis acid-base interaction. Taken together, these characteristics make the metals Ca, Sr, and Ba very promising components of highly functionalized acid-base catalysts. In this Account, we describe the development of chiral alkaline earth metal catalysts for asymmetric carbon-carbon bond-forming reactions. Recently prepared chiral alkaline earth metal complexes have shown high diastereo- and enantioselectivities in fundamental and important chemical transformations. We chose chiral bisoxazoline (Box) derivatives bearing a methylene tether as a ligand for chiral modification. These molecules are very useful because they can covalently coordinate to alkaline earth metals in a bidentate fashion through deprotonation of the tether portion. It was found that chiral calcium-Box complexes could successfully promote catalytic asymmetric 1,4-addition and [3 + 2] cycloaddition reactions with high diastereo- and enantioselectivities. Both the calcium-Box complexes and chiral strontium-bis-sulfonamide and chiral barium-BINOLate complexes could catalyze asymmetric 1,4-addition reactions with high enantioselectivities. Furthermore, we designed a calcium-neutral coordinative ligand complex as a new type of chiral alkaline earth metal catalyst. We found that pyridinebisoxazolines (Pybox) worked well: they served as excellent ligands for calcium compounds in 1,4-addition reactions and Mannich reactions. Moreover, they were successful in 1,4-additions in concert with enantioselective protonation, affording the desired products in good to high enantioselectivities. Our results demonstrate that alkaline earth metals are very useful and attractive catalysts in organic synthesis. Moreover, their ubiquity in the environment is a distinct advantage over rare metals for large-scale processes, and their minimal toxicity is beneficial in both handling and disposal.     

Catalytic Wet Air Oxidation of Sodium Sulfide Solutions. Effect of the Metal-Support and Acidity of the Catalysts

This work evaluates the catalytic wet air oxidation of sulfide present in spent caustic wastes generated during petroleum refining. Operating conditions were 70 °C and atmospheric pressure, with and without catalyst. Two supports (silica and clinoptilolite) and two metal oxides (vanadium and copper) were employed to produce different catalysts. The sulfide oxidation without catalyst displays a short induction period and complete oxidation of sulfide at 210 min. The most active catalysts were Cu/silica (CS) and V/clinoptilolite (VC), which improved the sulfide oxidation, achieving complete oxidation in 20 and 26 min, respectively.     

氧化铁/活性炭负载型硫化氢脱除剂制备及性能评价

为提高硫化氢脱除剂性能,利用活性炭吸附表面积大的特点,合成具有吸附性能的氧化铁负载型硫化氢脱除剂。为便于不同硫化氢脱除剂性能评价,设计和搭建了一种用于快速评价气体硫化氢脱除剂脱除效果的评价方法与实验装置。结果表明,吸附型脱硫剂加入反应型脱硫组分后,脱硫速率的持续性优于吸附型脱硫组分,氧化铁负载质量分数为5%时,脱除剂初始脱硫速率较高。