STUDY ON THE OXIDATIVE COUPLING OF METHANE III.CATALYTIC PERFORMANCE OF TiO2-BASED CATALYSTS STUDIED BY CO2-TPD AND TPR-TPO

The effects of surface acidity-basicity and surface oxidation reduction property of Li-La-Mn/TiO2 (I) and Li-La-Mn-W/TiO2 (II) catalysts on oxidative coupling of methane were studied by CO2-temperature programmed desorption (CO2-TPD) and temperature programmed reduction temperature programmed oxidation (TPR-TPO). The results show that there exist strong basic sites on catalysts I and II, but the quantity of these sites on catalyst II is more than that on catalyst I. Besides, the strength of basics site on catalyst II is stronger than that on catalyst I. The surface of catalyst II is easier to reduce and re-oxidize than that of catalyst I. The surface of catalyst II is easier to reduce and re-oxidize than of catalyst I, and the extent of reduction and reoxidation of catalyst II is more intensive than catalyst I, which results in a lowing of the reaction temperature and enhances the activity and C2 hydrocarbon yield as well as gas hourly space velocity(GHSV). Catalyst II is excellent for the oxidative coupling of methane (OCM).     

Polymer-supported lewis acid catalysts. VII. Polystyrene-bonded Ti(IV) chloride catalysts

A polystyrene-bonded Ti(IV) chloride catalyst was synthesized by the reaction of a polystyryl lithium (catalyst I , PS—TiCl₂) or a polystyryl magnesium (catalyst II , PS-TiCl₃) combined with titanium tetrachloride. The catalyst produced is a polymeric organometallic compound containing 0.479 mmol Ti/g catalyst, 0.986 mmol Cl/g catalyst (catalyst I ) and 0.281 mmol Ti/g catalyst, 0.766 mmol Cl/g catalyst (catalyst II ), depending on the method of synthesis. Both catalysts showed very good stability and good catalytic activity in such organic reactions as esterification, acetalation, and ketal formation. They can be reused many times without losing its catalytic activity. © 1993 John Wiley & Sons, Inc.     

Conditional Copper-Catalyzed Azide–Alkyne Cycloaddition by Catalyst Encapsulation

Supramolecular encapsulation is known to alter chemical properties of guest molecules. We have applied this strategy of molecular encapsulation to temporally control the catalytic activity of a stable copper(I)–carbene catalyst. Encapsulation of the copper(I)–carbene catalyst by the supramolecular host cucurbit[7]uril (CB[7]) resulted in the complete inactivation of a copper-catalyzed alkyne–azide cycloaddition (CuAAC) reaction. The addition of a chemical signal achieved the near instantaneous activation of the catalyst, by releasing the catalyst from the inhibited CB[7] catalyst complex. To broaden the scope of our on-demand CuAAC reaction, we demonstrated the protein labeling of vinculin with the copper(I)–carbene catalyst, to inhibit its activity by encapsulation with CB[7] and to initiate labeling at any moment by adding a specific signal molecule. Ultimately, this strategy allows for temporal control over copper-catalyzed click chemistry, on small molecules as well as protein targets.     

乙二醇单乙醚醋酸酯合成用固体催化剂的筛选及催化作用分析

采用自建动态酯化反应实验装置，通过色谱分析测定了不同催化剂上乙二醇单乙醚醋酸酯合成反应的转化率－时间关系曲线。根据多种催化剂的活性及寿命，筛选出一种较为理想的锆基催化剂。该催化剂在实验条件下，反应２ｈ，转化率达９７％，对目标产生的选择性为１００％。     

An in situ generated CuI/metformin complex as a novel and efficient catalyst for C–N and C–O cross-coupling reactions

An in situ generated complex of copper(I) and a biguanide, namely metformin, was found to be a highly efficient homogeneous catalyst in N/O-arylation reactions. The O-arylation of substituted phenols with various aryl iodides and bromides was also achieved using this copper catalyst to afford diaryl ethers in good to excellent yields in DMF. This heterogeneous copper catalyst also promotes the N-arylation of imidazole with a variety of aryl halides (Cl, Br, I) in acetonitrile.     

Cu(I)-catalyzed diamination of conjugated dienes. Complementary regioselectivity from two distinct mechanistic pathways involving Cu(II) and Cu(III) species

Conjugated dienes can be diaminated at the internal and/or terminal double bonds using Cu(I) as catalyst and N,N-di-t-butyldiaziridinone (1) as nitrogen source. The regioselectivity is highly dependent upon the choice of Cu(I) catalyst and the substituents on diene substrates. The diamination likely proceeds via two mechanistically distinct pathways. The N-N bond of N,N-di-t-butyldiaziridinone (1) is first homolytically cleaved by the Cu(I) catalyst to form four-membered Cu(III) species A and Cu(II) radical species B, which are in rapid equilibrium. The internal diamination likely proceeds in a concerted manner via Cu(III) species A, and the terminal diamination likely involves Cu(II) radical species B. Kinetic studies have shown that the diamination is first-order in N,N-di-t-butyldiaziridinone (1), zero-order in olefin, and first-order in total Cu(I) catalyst, and the cleavage of the N-N bond of 1 by the Cu(I) catalyst is the rate-determining step. The internal diamination is favored by use of CuBr without ligand and electron-rich dienes. The terminal diamination is favored when using CuCl-L and dienes with radical-stabilizing groups.     

Conditional Copper‐Catalyzed Azide–Alkyne Cycloaddition by Catalyst Encapsulation

Supramolecular encapsulation is known to alter chemical properties of guest molecules. We have applied this strategy of molecular encapsulation to temporally control the catalytic activity of a stable copper(I)–carbene catalyst. Encapsulation of the copper(I)–carbene catalyst by the supramolecular host cucurbit[7]uril (CB[7]) resulted in the complete inactivation of a copper‐catalyzed alkyne–azide cycloaddition (CuAAC) reaction. The addition of a chemical signal achieved the near instantaneous activation of the catalyst, by releasing the catalyst from the inhibited CB[7] catalyst complex. To broaden the scope of our on‐demand CuAAC reaction, we demonstrated the protein labeling of vinculin with the copper(I)–carbene catalyst, to inhibit its activity by encapsulation with CB[7] and to initiate labeling at any moment by adding a specific signal molecule. Ultimately, this strategy allows for temporal control over copper‐catalyzed click chemistry, on small molecules as well as protein targets.     

Cyclization reaction for the synthesis of polysubstituted naphthalenes in the presence of Au(I) precatalysts

Au(I)-catalyzed cyclization of alkenyl carbonyl compounds leading to a variety of substituted naphthalenes has been developed. This process exploits a dual function of the Au(I) catalyst: (1) the oxophilic nature of the Au(I) catalyst, counterintuitive to the π-acidic reactivities generally associated with Au catalysts, and (2) olefin isomerization supported by the outcome of isotope scrambling experiments. It cannot be completely excluded that TfOH is a true operative catalyst in this protocol. In view of the practicality, the unnecessity of isomerically pure starting material in this reaction is particularly attractive and valuable.     

聚4-乙烯吡啶类高分子铑(I)化合物对甲醇羰化合成乙酸的催化性能

本文将聚4-乙烯吡啶(PVPy)、聚1-甲基-4-乙烯吡啶季铵碘(PVPyMe^+I^-)和4-乙烯吡啶/1-甲基-4-乙烯吡啶季铵碘共聚物[P(VPy-VPyMe^+I^-)]分别与四羰基二氯二铑反应制备成高分子铑(I)催化剂, 并考察了它们各自在甲醇羰化反应中的催化行为。结合IR光谱对这些催化剂结构的分析研究表明, 以上4-乙烯吡啶类高分子链上所含的功能基各自与铑(I)配合物离子之间以不同的链联方式所产生的不同结构的活性物种对催化反应性能有着显著的影响, 具有双配位的螯合型稳定结构的Rh(I)/PVPy催化剂, 表现出较差的催化反应活性, 而离子键合型的Rh(I)/PVPyMe^+I^-和杂键合型的Rh(I)/P(VPy-VPyMe^+I^-)催化剂均表现较佳的反应性能, 特别是Rh(I)/P(VPy-VPyMe^+I^-),由于其形成具有更强亲核性的五配位中间过渡态参与反应过程, 从而在较大程度上提高了催化反应速率。     

Highly cis-selective Rh(I)-catalyzed cyclopropanation reactions

The performance of recently reported highly cis-diastereoselective Rh(I) cyclopropanation catalysts has been significantly improved by a systematic study of different reaction parameters (catalyst activation, solvent, temperature, stoichiometry). The catalyst efficiency and diastereoselectivity were enhanced by changing the activating agent from AgOTf to NaBArf. With this new system, the Rh(I) catalyst was shown to be a highly efficient and cis-diastereoselective cyclopropanation catalyst in reactions between α-diazoacetates and a range of different alkenes and substituted derivatives. Particularly noteworthy is the remarkable reactivity and cis-diastereoselectivity displayed in the reactions between ethyl diazoacetate and cyclopentene, 2,5-dihydrofuran, and benzofuran, with yields up to 99% and cis-selectivities greater than 99%.     

有序介孔有机金属Au(I)催化剂催化水相炔烃水合制备甲基酮

采用表面活性剂自组装、有机金属硅烷与苯基硅烷共聚法制备了有机金属Au(I)嵌于介孔材料孔壁的非均相催化剂Au(I)-PPh2-PMO(Ph).结果表明,Au(I)-PPh2-PMO(Ph)催化剂的活性位分散均匀,孔道不易堵塞,对反应物的扩散与传质影响较小,其催化活性不仅明显高于后嫁接法制得的Au(I)-PPh2-PMO(Ph)-G和均相Au(PPh3)Cl催化剂,且可以重复使用,显示出较好的应用前景.     

Tandem deuteration/hydrosilylation reactions catalyzed by a rhodium carbene complex under solvent-free conditions

The complex [Rh(I(t)Bu)(2)HCl] has been shown to be an active catalyst in the hydrosilylation of carbonyl and imine complexes. This reactivity, combined with the previously reported H/D exchange catalyzed by these complexes allows for a one pot, two step reaction using a single catalyst for both H/D exchange and hydrosilylation. Using triethylsilane, [Rh(I(t)Bu)(2)Cl] catalyst, and D(2) gas, deuterated silyl-ethers can be synthesized in an atom-economical, solvent-free reaction.     

Fe3O4 nanoparticle‐supported copper(I): magnetically recoverable and reusable catalyst for the synthesis of quinazolinones and bicyclic pyrimidinones

A highly efficient, easily recoverable and reusable Fe₃O₄ magnetic nanoparticle‐supported Cu(I) catalyst has been developed for the synthesis of quinazolinones and bicyclic pyrimidinones. In the presence of supported Cu(I) catalyst (10 mol%), amidines reacted with substituted 2‐halobenzoic acids and 2‐bromocycloalk‐1‐enecarboxylic acids to generate the corresponding N‐heterocycle products in good to excellent yields at room temperature in DMF. In addition, the supported Cu(I) catalyst could be recovered at least 10 times without significant loss of its catalytic activity. Copyright © 2012 John Wiley & Sons, Ltd.     

Highly Efficient and Stereoselective Thioallylation of Alkynes: Possible Gold Redox Catalysis with No Need for a Strong Oxidant

Stereoselective thioallylation of alkynes under possible gold redox catalysis was accomplished with high efficiency (as low as 0.1 % catalyst loading, up to 99 % yield) and broad substrate scope (various alkynes, inter‐ and intramolecular fashion). The gold(I) catalyst acts as both a π‐acid for alkyne activation and a redox catalyst for Au^I/III coupling, whereas the sulfonium cation generated in situ functions as a mild oxidant. This novel methodology provides an exciting system for gold redox catalysis without the need for a strong oxidant.     

A recyclable nanosize aminoarenethiolato copper(I) catalyst for C-C coupling reactions

An aminoarenethiolato copper(I) catalyst was attached to a carbosilane dendritic wedge, which had been prepared via a novel convergent synthetic method. Compared with the unsupported complex, this novel dendritic copper(I) catalyst is more robust towards hydrolysis and oxidation and has increased solubility in common organic solvents. The catalytic activity of the dendritic copper catalyst was tested in the 1,4-addition of Et₂Zn to 2-cyclohexenone. In both polar (Et₂O) and apolar (hexane) solvents excellent activity was observed. The fact that the catalytic copper site remains attached to the nanosize dendritic aminoarenethiolate ligand allows separation of this catalyst by means of nanofiltration.     

在无定形二氧化钛上生长纳米钛硅分子筛催化剂

尺寸在1～100nm之间的材料称为纳米材料.纳米材料中表面分子占很大比例,由此产生了不同于常规材料的各种特殊性能.纳米材料在很多领域得到广泛的研究和应用.很多研究者发现纳米结构的催化剂有着与常规催化剂不同的催化活性和选择性.沸石分子筛催化剂是一种结晶的多孔物质,其孔径一般小于1 nm.     

二(三氟乙酸)卤化钕催化体系中卤素对催化共轭双烯烃聚合的影响

众所周知,稀土配位催化剂用于共轭双烯的定向聚合,卤素是形成活性中心的必要条件之一。文献上对卤素在稀土催化剂中的作用曾有研究,但报导的都是非均相催化体系和三元催化体系。均相的二元催化体系中的卤素作用尚未见文献报导。鉴于从可溶性(CF₃COO)₂NdClEtOH-Et₃Al体系中分离出含卤素原子的活性体,研究卤素在该体系中的作用,对于活性催化剂的形成条件和催化聚合反应机制的了解都有意义。     

Preparation of Al2O3-supported nano-Cu2O catalysts for the oxidative treatment of industrial wastewater

Cuprous oxide (Cu₂O) nanoparticles supported on Al₂O₃ prepared using two different methods (hereafter referred to as catalyst I and II, respectively) were characterized by XRD and TEM. The catalytic activities of catalyst I and II during the treatment of industrial wastewater were then investigated. Specifically, the progress of the catalytic oxidation of industrial wastewater was observed by monitoring the time-dependent change in the chemical oxygen demand (COD) of industrial wastewater when the catalysts were applied. The results indicated that the catalytic activity of catalyst II was greater than that of catalyst I. Furthermore, under optimal conditions the COD removal efficiency was 94.59%. Finally, the mechanism by which the oxidative degradation of the industrial wastewater occurred could be explained based on a hydroxyl radical mechanism.     

A sulfonate-based Cu(Ⅰ) metal-organic framework as a highly efficient and reusable catalyst for the synthesis of propargylamines under solvent-free conditions

A new highly efficient and reusable Cu(Ⅰ)-MOF has been developed for the synthesis of propargylamine compounds via the three-component reaction of secondary amines,alkynes.and aromatic aldehydes under solvent-free conditions.The desired propargylamines were obtained in good to excellent yields with a low catalyst loading.The catalyst may be recovered and reused for up to 5 cycles without major loss of activity.This protocol has the advantages of excellent yields,low catalyst loading,and catalyst recyclability.     

A novel and highly efficient polyaniline‐functionalized multiwall carbon nanotube‐supported cu(I) complex for Sonogashira coupling reactions of aryl halides with phenylacetylene

A polyaniline‐functionalized multiwall carbon nanotube‐supported Cu(I) complex was developed as an efficient catalyst for the Sonogashira reactions of aryl halides with phenylacetylene in the presence of potassium hydroxide in dimethylformamide at 135 °C under nitrogen atmosphere. The corresponding products were generated in good to excellent yields using this catalytic system. Moreover, the multiwall carbon nanotube‐supported Cu(I) catalyst was simply recycled and reused for six consecutive runs.