催化氧化合成己二酸的清洁方法*

己二酸是一种非常重要的有机合成中间体,由于传统生产工艺的局限性,其绿色合成方法备受研究者的关注。本文综述了近年来用H₂O₂、O₂或O₃作为清洁氧化剂,以环己烯、环己酮、环己醇或其混合物为原料,催化氧化合成己二酸清洁方法的研究进展,重点介绍了含钨化合物-双氧水体系的催化氧化法,也概述了几种新的己二酸合成方法,并从溶剂、产率、后处理等方面探讨了各种方法的优缺点。在这些方法中,负载催化剂-双氧水体系将是未来工业化的最佳选择之一。     

二价镍离子修饰TS-1分子筛纳米片用于有效光催化醇氧化及污染物降解（英文）

以O₂为绿色氧化剂实现高效光催化有机物氧化转化过程如醇等有机物的选择性氧化及污染物降解是当前光催化发展的重要方向之一.成功实现高活性及高选择性的上述转化过程主要在于设计并制备有效的光催化材料.二氧化钛作为最广泛应用的光催化材料被报道用于光催化空气醇氧化选择性转化,但通常活性有限且因其表面催化活性位均为含有Ti-O₆活性中心而具有较低的产物选择性.相比之下,同样作为Ti基材料的钛硅分子筛如TS-1分子筛具有高选择性的Ti-O₄催化中心、丰富的孔结构及良好的稳定性,被广泛用于多种传统催化氧化反应.近年来, TS-1分子筛因具有光催化活性而成为一类具有工业应用潜力的光催化材料,特别是其独特的Ti-O₄催化中心有望实现高选择性的光催化氧化转化.然而,其活性仍受限于较差的光生电荷分离,提升TS-1分子筛的电荷分离是促进其光催化活性的关键.本工作以特定结构的季铵盐表面活性剂为结构导向剂,通过低温水热法成功制备了TS-1分子筛纳米片,并通过离子交换法于TS-1分子筛纳米片的离子交换位引入二价镍离子,显著地提升了其...     

过氧化氢选择性氧化硫醚的研究进展

亚砜和砜类化合物具有广谱生物活性而有广泛的应用前景,同时作为有机合成的重要中间体广泛应用于碳-碳键形成、分子重组反应中.硫醚直接氧化是制备亚砜和砜的主要方法之一.在众多关于硫醚选择性氧化反应的研究中,过氧化氢作为清洁氧化剂备受关注.鉴于此,就过氧化氢选择性氧化硫醚反应中的重要金属催化体系和一些非金属催化体系的研究状况作一综述,简要介绍各类催化氧化体系的催化效果.     

过渡金属盐及络合物在乙苯液相氧化中的催化作用

有机化合物中的C-H键选择性官能团化是有机合成中具有挑战性的课题之一。在不同的氧源(如H₂O₂、NaOCl、TBHP、RCOOOH、O₂等)作用下,许多过渡金属络合物可以选择性氧化有机物[1]。显然,由于分子氧廉价易得并且在氧化过程中对环境没有污染,所以分子氧是氧化反应的最理想的氧源。由于分子氧较难活化以及选择性方面的原因,在温和条件下过渡金属催化的分子氧选择性氧化过程受到了广泛的关注[2]。有关乙苯的液相催化氧化已有一些报道,比较有代表性的有以[W₁₀O₃₂]^4-和 CoC₁₂·6H₂O为催化剂的光催化氧化过程[3,4]、负载型的Ru络合物催化剂[5]以及在己醛存在下以Fe盐或Ru盐为催化剂的氧化过程[6]。本文在温和条件下(常压、110℃), 考察了不同过渡金属盐及络合物在乙苯液相氧化中的催化作用,着重考察了催化反应机理。     

双氧水对于单核铜分子筛催化甲烷直接氧化制甲醇反应性能的利弊（英文）

直接催化甲烷(CH₄)氧化转化制备甲醇(DMTM)是具有较高绿色化学原子经济性的反应过程,且可在常温下进行,是潜在的实现CH₄转化升级的重要过程.作为“圣杯反应”, DMTM性能通常显著受氧化剂影响,使用氧气(O₂)作为氧化剂一步实现DMTM仍然极具挑战性.至今,双氧水(H₂O₂)仍是被报道最多的具有较高CH₄转化速率和甲醇(CH₃OH)选择性的绿色氧化剂.为了深入理解氧化剂如何影响DMTM反应性能,本文基于密度泛函理论计算和微观动力学分析研究了在Cu-ZSM-5, Cu-MOR和Cu-SSZ-13三种具有不同微孔尺寸的单核铜分子筛上DMTM反应机理,以确定H₂O₂作为氧化剂在DMTM反应中的优势和局限性.通过理论计算对比在反应条件下O2和H₂O₂的O–O键活化以及CH₄的C–H键活化过程,发现在单核Cu分子筛中, H     

苯甲醇的绿色选择性氧化

醇的氧化是制备醛和酮的重要反应之一,也是有机化学理论教学和实验教学的一个重点内容。目前,大多数本科生实验教材安排了环己醇氧化合成环己酮的实验。虽然现有实验教材提供了一例将伯醇氧化为醛的方案,即采用Na₂WO₄·2H₂O/（C₄H₉）₄NHSO₄催化体系,在90°C用H₂O₂将苯甲醇选择性氧化为苯甲醛,但是存在着产率低、安全性不高和重金属污染等问题。本文采用Fe（NO₃）₃·9H₂O、4-羟基-2,2,6,6-四甲基哌啶氧化物（4-OH-TEMPO）和乙酸（HOAc）为催化剂、O₂为氧化剂,以H₂O为溶剂,在温和的反应条件下高选择性地将苯甲醇氧化为苯甲醛,分离产率可达91%,这为伯醇的选择性氧化提供了一个低成本且高效绿色的实验教学新方案。同时,在实验过程中引入薄层色谱、气相色谱、快速制...     

SnCl4催化丙酮与过氧化氢反应制取大环过氧化物

H₂O₂与过渡金属构成的催化体系可选择性地氧化烃类化合物,如芳烃的羟基化和烯烃的环氧化等^[1～3],且H₂O₂在应用中无环境污染,是一种颇有前途的氧化剂.有关金属催化H₂O₂与酮类化合物反应的报道很少.     

非贵金属催化剂用于CO选择性氧化脱除的研究

以Co和Ni为催化剂活性组分、活性炭为载体,通过饱和浸渍法制得非贵金属催化剂,采用XRD、SEM和TPD对催化剂性能进行表征,考察了该催化剂用于富氢气中CO选择性氧化活性及H₂O或/和CO₂对催化性能的影响。研究结果表明,催化剂以NiO和高分散的Co₃O₄为主要物相,催化剂吸附O₂的能力随着金属氧化物负载量的增加而增加,且催化剂对O₂分子的吸附能力明显强于CO₂分子。金属氧化物负载量为35%的催化剂表现出较高的CO选择性氧化活性和选择性,在低于473K时O₂氧化选择性达50%以上,此时可将CO浓度降到40×10^-6以下,达到燃料电池对氢燃料气的要求。同时,催化剂表现出较强的抗水蒸气和CO₂的能力。     

TiO2/TiN纳米管异质结用于光电催化CO2还原:氮辅助活性氢机制(英文)

利用太阳能将CO₂转换为高附加值的化学品是解决化石燃料消耗过快与CO₂排放过度问题的可行性方案.光电催化CO₂还原可以模拟自然光合作用将CO₂还原为多碳产物(C₂₊).然而,光电催化剂的带隙与太阳辐射光谱不匹配以及载流子的快速复合是限制人工光合作用效率的关键因素.前期研究表明,缺陷工程可有效地增加催化剂活性位点,减小半导体的带隙并增强对光子的捕获能力;而异质结的构筑则可有效提升载流子的分离效率.因此,构建具有较好可见光响应的高效半导体异质结催化剂有望实现催化材料对CO₂还原能力和产物选择性的提升.本文通过对金属钛板进行电化学阳极氧化,氨气气氛煅烧得到Ti N,然后原位进行部分氧化构筑出结构新颖的Ti O₂/Ti N纳米管异质结材料,再进行配体和钯量子点修饰,得到更加高效的催化电极材料Pd/R-Ti O₂/TiN,并在三电极系统中研究了其光电催化CO₂还原的性能.通过扫描隧道电子显微镜、透射电...     

Ag-ZSM-5催化剂上CH4选择催化还原NOx的研究

摘要研究Ag-ZSM-5催化剂上CH₄选择性催化还原NO_x的反应性能,采用TPD和TPSR技术研究NO和O₂共吸附于Ag-ZSM-5催化剂表面形成的吸附物种及其和CH₄之间的反应。结果表明,Ag-ZSM-5催化剂上CH₄选择性还原NO_x活性和选择性较高。NO和O₂共吸附在Ag-ZSM-5催化剂上形成的NO₃(s)吸附物种能被CH₄还原生成N₂.在NO₃(s)和O₂共存的体系中,CH₄能优先并选择性还原NO₃(s)生成N₂.     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.