Polystyrene-supported GaCl3: A new,highly efficient and recyclable heterogeneous Lewis acid catalyst for acetylation and benzoylation of alcohols and phenols

A new, simple and highly chemoselective method for both acetylation and benzoylation of alcohols and phenols with acetic anhydride in the presence of polystyrene-supported gallium trichloride (PS/GaCl₃) as a highly active and reusable heterogeneous Lewis acid catalyst is presented. In this catalytic system, primary, secondary and tertiary alcohols as well as phenols were converted to the corresponding acetates and benzoates with high yields. The heterogenized catalyst is of high reusability and stability in the acetylation reactions and was recovered several times with negligible loss in its activity or a negligible catalyst leaching, and also there is no need for regeneration. Remarkably, a selective mono-acetylation of symmetrical diols can be achieved chemoselectively by employing the same catalyst.     

Carbocations as Lewis Acid Catalysts in Diels–Alder and Michael Addition Reactions

In general, Lewis acid catalysts are metal‐based compounds that owe their reactivity to a low‐lying empty orbital. However, one potential Lewis acid that has received negligible attention as a catalyst is the carbocation. We have demonstrated the potential of the carbocation as a highly powerful Lewis acid catalyst for organic reactions. The stable and easily available triphenylmethyl (trityl) cation was found to be a highly efficient catalyst for the Diels–Alder reaction for a range of substrates. Catalyst loadings as low as 500 ppm, excellent yields, and good endo/exo selectivities were achieved. Furthermore, by changing the electronic properties of the substituents on the tritylium ion, the Lewis acidity of the catalyst could be tuned to control the outcome of the reaction. The ability of this carbocation as a Lewis acid catalyst was also further extended to the Michael reaction.     

In situ Generated Ruthenium Catalyst Systems Bearing Diverse N‐Heterocyclic Carbene Precursors for Atom‐Economic Amide Synthesis from Alcohols and Amines

The transition‐metal‐catalyzed direct synthesis of amides from alcohols and amines is herein demonstrated as a highly environmentally benign and atom‐economic process. Among various catalyst systems, in situ generated N‐heterocyclic carbene (NHC)‐based ruthenium (Ru) halide catalyst systems have been proven to be active for this transformation. However, these existing catalyst systems usually require an additional ligand to achieve satisfactory results. In this work, through extensive screening of a diverse variety of NHC precursors, we discovered an active in situ catalyst system for efficient amide synthesis without any additional ligand. Notably, this catalyst system was found to be insensitive to the electronic effects of the substrates, and various electron‐deficient substrates, which were not highly reactive with our previous catalyst systems, could be employed to afford the corresponding amides efficiently. Furthermore, mechanistic investigations were performed to provide a rationale for the high activity of the optimized catalyst system. NMR‐scale reactions indicated that the rapid formation of a Ru hydride intermediate (signal at δ=?7.8 ppm in the ¹H NMR spectrum) after the addition of the alcohol substrate should be pivotal in establishing the high catalyst activity. Besides, HRMS analysis provided possible structures of the in situ generated catalyst system.     

Gold nanoparticles supported on ionic liquid‐modified cellulose as an efficient and recyclable catalyst for the oxidation of alcohols to aldehydes/ketones and reduction of nitroarenes

A novel catalyst of gold nanoparticles supported on cellulose fibres with the ionic liquid framework (Au NPs@CL‐IL) has been shown to be a highly active and recyclable catalyst for the oxidation of primary and secondary alcohols and reduction of nitroarenes in aqueous media. The reusability of this catalyst is high, and it can be reused ten times without a significant decrease in its catalytic activity. Furthermore, transmission electron micrographs of the recovered catalyst show the presence of well‐distributed Au NPs on the CL‐IL fibres without any aggregation.     

Robust CoAl Alloy: Highly Active,Reusable and Green Catalyst in the Hydrogenolysis of Glycerol

CoAl alloy catalyst is found, for the first time, to be highly active, selective and reusable for the synthesis of diols via the hydrogenolysis of glycerol under mild conditions. The products and the catalyst could be self‐separated from the reaction system through a simple reactor.     

Immobilization of the Grubbs second-generation ruthenium-carbene complex on poly(ethylene glycol): a highly reactive and recyclable catalyst for ring-closing and cross-metathesis

A poly(ethylene glycol)-bound Hoveyda-Grubbs Ru catalyst derived from the Grubbs second-generation Ru carbene complex was synthesized and shown to be highly reactive in the ring-closing metathesis of a wide variety of diene substrates, yielding di-, tri-, and tetra-substituted carbocyclic and heterocyclic olefins. The immobilized catalyst also proved to be highly reactive and recyclable in cross-metathesis and ring-opening/cross-metathesis. In all cases tested, the catalyst exhibited a high level of recyclability and reusability.     

Influence of preparative conditions on molecular weight and stereoregularity distributions of polypropylene

The influence of preparative conditions on the molecular weight and stereoregularity distributions of polypropylene was investigated. The stereoregularity distribution is narrowed by using a highly stereospecific catalyst, by decreasing the polymerization temperature, and for the three-component catalyst by keeping the mole proportion of the electron-donating third component at 0.5. The molecular weight distribution can be narrowed by using a highly stereospecific catalyst, a high monomer concentration, and a high polymerization temperature, and by having a lower conversion, particularly at low monomer concentration. The possibility of long-chain branching in polypropylene was indicated by data from the fractionation of tritium-labeled polymers.     

酸性聚乙烯基吡咯烷酮—杂多酸杂化催化剂的合成及其催化酯化反应性能

合成并表征了聚乙烯基吡咯烷酮修饰的杂多酸杂化催化剂PVP-PW,比较了它与其它催化剂上乙酸和正丁醇的酯化反应性能.结果表明,PVP-PW是催化酯化反应的高效多相催化剂,所得酯收率和选择性分别高达98.4%和100%;反应结束后,催化剂通过简单过滤即可分离回收,重复使用6次后,其催化活性没有明显下降.通过改变反应底物羧酸和醇,发现催化剂PVP-PW在众多酯化反应中均具有较高的催化活性.     

高效二氧化碳电催化还原反应花状钴催化剂的制备及性能（英文）

随着工业的不断发展,化石燃料的大量使用导致全球大气二氧化碳浓度逐年升高.通过电还原将二氧化碳转化为燃料是实现碳循环经济最有前景的途径之一.目前,还原二氧化碳常用的方法包括热化学法,光化学法和电化学法.与另外两种方法相比,电催化还原二氧化碳具有条件简便,易于控制,转化率较高,材料易得,易于放大生产等优点,具备潜在的实际应用价值.电还原二氧化碳的催化材料主要分为金属材料,金属氧化物,有机分子,生物分子等.其中,以过渡金属催化剂的研究与应用最为普遍.我们发展了一种新型金属钴催化剂的制备方法,采用快捷,绿色的溶剂热方法,以正丁胺为保护剂,合成了具有花状形貌的金属钴催化剂.这种特殊形貌的金属钴催化剂相比体相的金属钴催化剂与层状的氢氧化钴材料,能够暴露更多的活性位点,在二氧化碳电还原反应中表现出极高的催化活性与选择性.我们采用循环伏安法和线性扫描伏安法(LSV)等电化学表征手段,进一步证明了先前其他课题组已报道过的通过溶剂热法制备得到的钴/钴氧化物二维材料在二氧化碳电催化还原过程中,金属钴/氧化钴界面的存在对二氧化碳还原反应具有决定性作用的观点.X射线衍射表明这种新型金属钴催化剂具有六方密堆积的晶体相,晶粒平均直径为17.3 nm.扫描电子显微镜直观地展示了其不同于体相的金属钴催化剂与层状的氢氧化钴材料,具有特殊的形貌.电化学表征结果显示花状金属钴催化剂比另外两种材料具有更正的起始电位(-0.7 V vs.SCE).不同扫描速度LSV研究表明,甲酸等其他还原产物的形成受二氧化碳传质控制影响.采用核磁共振分析不同电位下10 h恒电位电解产物,发现当电极电势为-0.85 V(vs.SCE)时,还原产物甲酸的法拉第效率达63.4%.另外,循环伏安曲线表明该催化剂不仅对二氧化碳还原反应具有极高的活性,同时,对还原产物的氧化也表现出极低的过电位与极高的反应活性,因此所开发催化剂可视为一类双效电催化剂.     

Didecyldimethylammonium bromide (DDAB): a universal, robust, and highly potent phase-transfer catalyst for diverse organic transformations

Didecyldimethylammonium bromide (DDAB) has been scrutinized in comparison with traditional phase-transfer catalysts in variety of liquid-liquid reactions. It was found to be an exceptionally comprehensive, durable, and highly efficient phase-transfer catalyst (PTC) in a number of representative organic transformations such as C- and N-alkylations, isomerization, esterification, elimination, cyanation, bromination, and oxidation under very mild conditions of temperature and mixing. It was confirmed that DDAB is an exceedingly accessible and concurrently a highly liphophilic phase-transfer catalyst. This unprecedented characteristic renders DDAB to be a multipurpose catalyst that functions effectively both in mass transfer controlled and chemically controlled phase-transfer reactions.     

Highly active, immobilized ruthenium catalysts for oxidation of alcohols to aldehydes and ketones. Preparation and use in both batch and flow systems

A novel, highly active immobilized ruthenium catalyst, which can be successfully used in oxidation of alcohols to aldehydes and ketones, has been developed. In contrast to most immobilized catalysts, the Ru catalyst has activity that is higher than that of the original non-immobilized catalyst. In a batch system, the Ru catalyst was recovered and reused several times without loss of activity. The catalyst was also applied to a flow system, in which excellent conversions and yields were demonstrated. No leaching of Ru was observed in both cases.     

Carbonylative Suzuki coupling and alkoxycarbonylation of aryl halides using palladium supported on phosphorus‐doped porous organic polymer as an active and robust catalyst

Developing highly active catalysts with the combined advantages of molecular and solid catalysis is considered as the “Holy Grail” in the area of catalysis research. Herein, a phosphorus‐doped porous polymer‐immobilized palladium was successfully developed as an efficient, robust, and recyclable catalyst for the carbonylative Suzuki coupling and alkoxycarbonylation reactions of aryl halides. Rather than just as an immobilizing molecular catalyst, palladium supported on phosphorus‐doped porous organic polymer exhibits even better catalytic performances than that of its analogue homogeneous catalysts in both carbonylation reactions. Moreover, the catalyst can be easily separated and reused for at least 5 times without significant loss in reactivity. Importantly, the catalyst was highly stable under carbonylation reaction conditions, and no palladium nanoparticle was observed even after the 5th reuse.     

Single‐Atom Gold Catalysis in the Context of Developments in Parahydrogen‐Induced Polarization

A highly isolated monoatomic gold catalyst, with single gold atoms dispersed on multiwalled carbon nanotubes (MWCNTs), has been synthesized, characterized, and tested in heterogeneous hydrogenation of 1,3‐butadiene and 1‐butyne with parahydrogen to maximize the polarization level and the contribution of the pairwise hydrogen addition route. The Au/MWCNTs catalyst was found to be active and efficient in pairwise hydrogen addition and the estimated contributions from the pairwise hydrogen addition route are at least an order of magnitude higher than those for supported metal nanoparticle catalysts. Therefore, the use of the highly isolated monoatomic catalysts is very promising for production of hyperpolarized fluids that can be used for the significant enhancement of NMR signals. A mechanism of 1,3‐butadiene hydrogenation with parahydrogen over the highly isolated monoatomic Au/MWCNTs catalyst is also proposed.     

Understanding the Reactivity and Selectivity of Fluxional Chiral DMAP-Catalyzed Kinetic Resolutions of Axially Chiral Biaryls

Fluxional chiral DMAP-catalyzed kinetic resolutions of axially chiral biaryls were examined using density functional theory. Computational analyses lead to a revised understanding of this reaction in which the interplay of numerous non-covalent interactions control the conformation and flexibility of the active catalyst, the preferred mechanism, and the stereoselectivity. Notably, while the DMAP catalyst itself is confirmed to be highly fluxional, electrostatically driven π⋅⋅⋅π⁺ interactions render the active, acylated form of the catalyst highly rigid, explaining its pronounced stereoselectivity.     

废弃SCR催化剂的循环再利用及表征分析研究

针对废弃SCR脱硝催化剂常规再利用处理后存在SO_2氧化率高的问题,提出了一种新型的废弃催化剂再利用新工艺,包括酸洗、还原酸浸和活性组分负载等步骤,以有效控制再利用催化剂的SO_2氧化率。实验考察了经不同步骤处理后所得催化剂的组分、脱硝效率和SO_2氧化率的变化情况,并对催化剂进行了深入的分析表征。结果表明,新鲜催化剂、废弃催化剂、常规再利用催化剂、新型再利用催化剂的脱硝效率和SO_2氧化率分别为99.0%和0.43%、77.0%和0.46%、94.2%和0.80%、99.3%和0.48%,采用本方法获得的再利用催化剂不仅脱硝效率完全恢复,而且SO_2氧化率得到了很好的控制。通过对催化剂的分析表征发现,采用常规再利用技术不能有效清除废弃催化剂表面的高聚态钒物种,而本方法则可以有效清理这类高聚态钒物种,并以高度分散的钒物种进行替代,从而有效控制再利用催化剂的SO_2氧化率。     

Acylation of aromatic alcohols and phenols over InCl3/montmorillonite K-10 catalysts

Montmorillonite K-10 clay supported InCl₃ is a highly active catalyst for the acylation of aromatic alcohols and phenols with different acyl chlorides. This catalyst can be reused in reactions a number of times without very significant loss of catalytic activity     

The Highly Controlled and Efficient Polymerization of Ethylene

The highly controlled and efficient polymerization of ethylene is a very attractive but challenging target. Herein we report on a Coordinative Chain Transfer Polymerization catalyst, which combines a high degree of control and very high activity in ethylene oligo- or polymerization with extremely high chain transfer agent (triethylaluminum) to catalyst ratios (catalyst economy). Our Zr catalyst is long living and temperature stable. The chain length of the polyethylene products increases over time under constant ethylene feed or until a certain volume of ethylene is completely consumed to reach the expected molecular weight. Very high activities are observed if the catalyst elongates 60 000 or more alkyl chains and the polydispersity of the strictly linear polyethylene materials obtained are very low. The key for the combination of high control and efficiency seems to be a catalyst stabilized by only one strongly bound monoanionic N-ligand.     

N-alkyl-4-boronopyridinium halides versus boric acid as catalysts for the esterification of alpha-hydroxycarboxylic acids

[reaction: see text] Boric acid is a highly effective catalyst for the dehydrative esterification reaction between equimolar mixtures of alpha-hydroxycarboxylic acids and alcohols. In contrast, N-methyl-4-boronopyridinium iodide (2a) is a more effective catalyst than boric acid for the similar esterification in excess alcohol. A heterogeneous catalyst, such as N-polystyrene-bound 4-boronopyridinium chloride, is also an effective catalyst and can be recovered by filtration.     

Transfer hydrogenation using recyclable polyurea-encapsulated palladium: efficient and chemoselective reduction of aryl ketones

A robust and recyclable palladium catalyst [Pd0EnCat] has been prepared by ligand exchange of polyurea-encapsulated palladium(II) acetate with formic acid, resulting in deposition of Pd(0) in the support material; Pd0EnCat is shown to be a highly efficient transfer hydrogenation catalyst for chemoselective reduction of a wide range of aryl ketones to benzyl alcohols.     

Phosphine-free polystyrene-supported palladium(II) complex as an efficient catalyst for the Heck and Suzuki coupling reactions in water

A palladium complex, 1-phenyl-1,2-propanedione-2-oxime thiosemi-carbazone-functionalized polystyrene resin supported Pd(II), is found to be a highly active catalyst for the Heck reaction of methyl acrylate with aryl halides and Suzuki reaction of phenylboronic acid with aryl iodides and bromides, giving excellent yields. The reactions were performed under phosphine-free conditions in an air atmosphere. The palladium catalyst is easily separated, and can be reused for several times without a significant loss in its catalytic activity.