钛硅分子筛催化环己酮液相氨肟化固定床工艺

采用固定床模式,研究了钛硅分子筛催化环己酮制环己酮肟液相氨肟化反应.结果表明,该工艺模式具有可行性与普适性.优化的反应条件为:温度333K,体系氨浓度>2%,酮/H₂O₂摩尔比=5,H₂O₂空速0.083h^-1.此时环己酮转化率、环己酮肟选择性、H₂O₂转化率及其有效利用率分别达18.7%,99.5%,94.7%和98.7%.进一步研究了H₂O₂在该过程中的反应行为,发现固定床工艺模式能有效提高H₂O₂的有效利用率,其主要原因是该模式有利于羟胺的生成及其进一步与酮反应生成肟.适当的空速与氨和酮的浓度是实现H₂O₂高效利用的关键因素.     

以微乳液法制备的锰源合成LiMn2O4

采用CTAB-C₈H₁₈-C₄H₉OH-H₂O微乳体系制备出MnCO₃，将其灼烧成Mn₂O₃之后，与Li₂CO₃混合，800 ℃高温焙烧，获得了颗粒大小为数百纳米，均匀分布的纯相尖晶石LiMn₂O₄。这一材料的电化学性能优秀，0.5C的电流在3～4.2 V之间充放电时，首次放电比容量为124 mAh·g^-1，经过110次循环，保留比容量118 mAh·g^-1，平均每次容量损失<0.05%。该材料的倍率性能尤为优异，10C放电的比容量在110 mAh·g^-1以上，功率约为0.2C时功率的45倍。     

基于去保护机理的新型H2O2荧光探针的制备及应用

合成的3',6'-对戊酰硼荧光素是一种基于去保护机理的高灵敏H₂O₂荧光增强化合物, 能灵敏地检测出样品中H₂O₂的含量. 用IR, ¹H NMR 对该探针的结构进行了表征, 并且讨论了反应时间、溶剂、碱对探针合成的影响. 研究了探针的最佳响应时间, 结果表明检测过程中反应的最佳时间为3 min. 该探针在2.3×10^－12～2.0×10^－8 mol/L H₂O₂溶液范围内呈荧光增强趋势, 检测下限为2.3×10^－12 mol/L. 此探针重现性良好, 在血清中检测H₂O₂的回收率在93.9%～102.2%之间, 结果令人满意, 具有一定的实用价值.     

基于去保护机理的新型H2O2荧光探针的制备及应用

合成的3',6'-对戊酰硼荧光素是一种基于去保护机理的高灵敏H₂O₂荧光增强化合物, 能灵敏地检测出样品中H₂O₂的含量. 用IR, ¹H NMR 对该探针的结构进行了表征, 并且讨论了反应时间、溶剂、碱对探针合成的影响. 研究了探针的最佳响应时间, 结果表明检测过程中反应的最佳时间为3 min. 该探针在2.3×10^－12～2.0×10^－8 mol/L H₂O₂溶液范围内呈荧光增强趋势, 检测下限为2.3×10^－12 mol/L. 此探针重现性良好, 在血清中检测H₂O₂的回收率在93.9%～102.2%之间, 结果令人满意, 具有一定的实用价值.     

金属氧化物与现代微电子学:过渡金属前体化合物及转化为材料的化学过程

金属氧化物薄膜如HfO₂（被称为高k电介质）是现代微电子器件的关键组件,广泛用于计算机（平板电脑,笔记本电脑和台式机）、智能电话、智能电视、汽车和医疗设备中。具有大介电常数（k）的金属氧化物已经取代了介电常数小的SiO₂（k=3.9）,从而使得微电子元件进一步小型化。过渡金属化合物在化学气相沉积（CVD）和原子层沉积（ALD）中被广泛用作前体,通过与O₂、H₂O或O₃的反应生成金属氧化物薄膜。微电子金属氧化物膜是纳米材料最广泛应用的一个领域。本文概观该领域的最新进展,包括我们对d⁰过渡金属配合物与O₂反应的研究。     

Dawson型磷钨杂多阴离子P2W18O626-的电化学性质和对O2还原的电催化作用

用循环伏安、交流伏安和交流阻抗法对Dawson型磷钨杂多阴离子P₂W₁₈O₆₂^6-的电化学性质进行了详细研究, 循环伏安结果显示, P₂W₁₈O₆₂^6-在pH 2.52的0.1 mol·L^-1 Na₂SO₄+NaHSO₄溶液中有两对可逆的单电子还原-氧化波和两对可逆的双电子还原-氧化波. 单电子波的峰电位和电流与溶液的pH无关, 双电子波的峰电位则随溶液pH的增加而负移, 峰电流降低, 表明双电子电极过程有H⁺参与, 其数目为2. 交流阻抗谱表明P₂W₁₈O₆₂^6-的电极过程完全受扩散控制, 实验测定其扩散系数(D_O)为2.5×10^-6 cm²·s^-1. 循环伏安结果表明P₂W₁₈O₆₂^6-的第III对波对O₂还原为H₂O₂具有显著的电催化作用, 催化效率约达300%. 将P₂W₁₈O₆₂^6-应用于PW₁₁O₃₉Fe(III)(H₂O)^4-构成的类电-芬顿过程, 使该过程对硝基苯的降解效率显著提高.     

纳米固体超强酸SO42-/Fe2O3的制备及其催化合成乙酸乙酯

将Fe₂O₃纳米粉体经一定浓度的H₂SO₄浸泡活化后制成纳米固体超强酸SO₄^2-/Fe₂O₃,将其用于催化合成乙酸乙酯以考察其活性。利用均匀设计分析了超强酸制备过程及酯化反应过程中各因素的影响,研究结果表明较好的制备条件是:H₂SO₄浓度:2.5mol·L^-1;浸泡时间:1h;活化温度:167℃;活化时间:1h,此时获得的固体超强酸SO₄^2-/Fe₂O₃的粒径小于50nm。当催化剂用量为冰乙酸质量的5%,n(乙醇)∶n(冰乙酸)为3∶1,反应3.5h后乙酸的转化率高于80%。该催化剂经H₂SO₄溶液浸泡、活化再生后可重新使用,推断出其酸强度H₀<-14.5。     

对苯二甲酸镁作为钠离子电池的有机负极材料

报道了对苯二甲酸镁作为钠离子电池负极材料的研究. 以对苯二甲酸和氢氧化镁为原料,采用酸碱中和反应制备了含结晶水的对苯二甲酸镁（MgC₈H₄O₄·2H₂O）,该材料对钠离子电池表现出了较好的电化学活性、优异的倍率性能以及良好的循环稳定性. 在0.5C（1C=300 mA·g^-1）倍率下循环50 周以后,可逆容量由114mAh·g^-1降至95 mAh·g^-1,容量保持率高达83%;在2C的倍率下有高达90 mAh·g^-1的可逆比容量. 另外,在氮气气氛中,400 ℃进行后续热处理得到了不含结晶水的对苯二甲酸镁（MgC₈H₄O₄）,探讨了结晶水对其电化学性能的影响. 结果表明,MgC₈H₄O₄·2H₂O的比容量、倍率性能以及循环稳定性都明显优于不含结晶水的对苯二甲酸镁.     

表面缺陷α-Fe2O3(001)纳米片双活性位点类芬顿催化剂用于降解污染物

纯Fe₂O₃表面活性位点较少具有较低的催化活性限制了其在多相芬顿催化体系中的应用。通常采用元素掺杂、贵金属负载以及与其它化合物质复合等改性措施来提升催化活性,然而这些措施存在催化剂制备复杂,制备成本高以及催化剂的精细结构难以精准控制等问题。因此,本文提出在α-Fe₂O₃表面引入氧空位缺陷构筑双活性位点（Fe²⁺和氧空位）用于促进H₂O₂分解提高降解污染物降解效率。实验结果发现α-Fe₂O_3-x-330/H₂O₂体系具有较宽的pH使用范围（pH=2~10）。当pH=4时,罗丹明B的降解速率常数为0.834 h^-1,而且催化剂具有磁性,易回收重复使用。催化机理研究表明氧空位缺陷α-Fe₂O_3-x催化剂的氧空位和Fe²⁺两种活性位点均可促进H₂O₂分解,而且氧空位的引入有利于污染物在催化剂表面的吸附进一步提高催化性能。     

四种Keggin型多酸纳米材料的制备及其吸附有机染料的性能

以4种Keggin型多酸作为原料(分别为H₃PW₁₂O₄₀·36H₂O(简写为PW₁₂^a)、H₃PMo₁₂O₄₀·34H₂O(简写为PMo₁₂^a)、H₄SiW₁₂O₄₀·35H₂O(简写为SiW₁₂^a)和H₄GeW₁₂O₄₀·40H₂O(简写为GeW₁₂^a)),采用表面活性剂智能化控制的软化学法制备了相应的4种Keggin型多酸纳米材料,分别为Ag₃PW₁₂O₄₀·36H₂O(简写为PW₁₂^b)、Ag₃PMo₁₂O₄₀·34H₂O(简写为PMo₁₂^b)、Ag₄SiW₁₂O₄₀·35H₂O(简写为SiW₁₂^b)和Ag₄GeW₁₂O₄₀·40H₂O(简写为GeW₁₂^b)。采用IR、UV-Vis、XRD和SEM表征多酸的结构和纳米粒子的形貌。在室内黑暗条件下,100 mg样品可在5 min内把20 mg·L^-1的100 mL亚甲基蓝(MB)染料溶液脱色,使其变为接近无色,吸附效率最高可达96.3%,吸附效率大小为PMo₁₂^b > PW₁₂^b > GeW₁₂^b > SiW₁₂^b。相同条件下,100 mg样品使20 mg·L^-1的100 mL罗丹明B(RhB)染料溶液30 min内脱色完全,脱色效率最高可达96.1%,吸附效率大小为PW₁₂^b > PMo₁₂^b > SiW₁₂^b > GeW₁₂^b。说明该4种多酸纳米材料具有较高的吸附有机染料性能。     

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.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

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.     

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.     

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.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.