Homogeneous gold catalysis: The role of protons

Recent reports have shown that some homogeneous gold catalyzed reactions might in fact be proton-catalyzed. Here, the knowledge on the role of Bronsted acids in gold-catalyzed reactions is summarized.     

Highly Enantioselective Catalytic Alkynylation of Ketones – A Convenient Approach to Optically Active Propargylic Alcohols

The development of highly enantioselective catalysts involving Cu(OTf)₂ and chiral camphorsulfonamides for the alkynylation of ketone is described. The influences of Lewis acids, reaction conditions and chiral ligands on the outcome of the reaction are discussed. The best enantioselectivity (up to 97 % ee) was obtained in the alkynylation of 2′‐chloroacetophenone. The scope of the reaction is also examined.     

Buchwald-Type Ligands on Gold(I) Catalysis

Dialkyl biarylphosphine ligands, presented in the context of Pd-catalyzed cross-coupling reactions, have been extensively applied in gold(I) catalysis giving rise to numerous transformations and reaction pathways otherwise inaccessible under the action of other gold(I) catalysts. This review emphasizes how this privileged ligand class, as well as recent modifications on the biarylphosphine motive, have triggered the discovery of new reactivities in our research program. Finally, the introduction of chiral information on the ligand scaffold provides new solutions to challenging gold(I)-catalyzed enantioselective transformations.     

激光催化氧化甲烷合成化合物的研究进展

天然气储量丰富,日益成为重要的清洁能源之一,而从其主要成分甲烷合成高附加值化合物更是研究前沿。由于甲烷结构稳定,CH键能很高,因而活化甲烷需要的条件非常苛刻。本文首先介绍了普通光催化氧化甲烷合成化合物的反应原理、研究进展、催化反应器和存在不足,然后综述了激光催化氧化甲烷合成化合物的反应原理、研究进展和催化反应器。指出激光光源具有提高光催化剂量子效率和缩短催化反应时间等诸多优势,接下来在深入研究激光催化反应机理的基础上,通过设计科学合理的激光反应体系,并遴选高效的光催化剂,有望显著提升包括甲烷氧化在内的激光催化反应性能,从而具有重要的学术意义和实践价值。今后的重点研究方向是通过激光催化氧化的方法使甲烷在温和的条件下活化,并合成高附加值化合物。     

Development of New Gold (I)-Catalyzed Carbocyclizations and their Applications in the Synthesis of Natural Products

For many years, gold was considered inactive to catalyze organic transformations. In the last two decades, gold(I/III) complexes have emerged as efficient catalyst for the formation of C−O, C−N and C−C bonds. In particular, monomeric organogold complexes whose binding affinity for alkenes, allenes and alkynes opened new directions in organic synthesis. More recently, dimeric gold species were used as photocatalyst in light-enabling processes. Taking advantage of the gold unique reactivity, we describe the development of novel transformations catalyzed by gold and their applications in the synthesis of natural products.      

Synergistic Gold(I)/Trimethylsilyl Catalysis: Efficient Alkynylation of N,O‐Acetals and Related Pro‐Electrophiles

We report a unique mechanism‐guided reaction that enhances and expands the chemical space that readily generated gold(I) acetylides currently operate in. Our strategy exploits the propensity of gold(I) carbophilic catalysts with specific counteranions (LAuX – X=triflate or triflimidate) to efficiently activate and desilylate trimethylsilylalkynes, thereby mediating the in situ formation of equal and catalytic quantities of a silyl Lewis acid (TMSX) of tunable strength and a nucleophilic gold(I) acetylide. This unprecedented manifold opens avenues for developing synergistic silyl‐gold(I)‐catalyzed alkynylation strategies of diverse pro‐electrophiles which were heretofore unattainable, the proof of concept being principally exemplified herein with the first catalytic alkynylation of N,O‐acetals. The reaction proceeds at low catalyst loading, employs mild reaction conditions, is easily scalable, and affords propargylic lactam products in good to excellent yields. Furthermore, it is fully amenable to a diverse array of structure and function substrates, and also expands to other pro‐electrophiles beyond N,O‐acetals. Control experiments have been carried out that strongly support our dual reaction mechanism proposal which, furthermore, itself outlines an inextricable link between the strength of the ancillary silyl Lewis acid (TMSOTf versus TMSNTf₂) and the coordinating ability of the gold counter anion employed. This underlying feature of our system underscores its significant potential and flexibility, which indeed manifests with the demonstration that by carefully selecting the gold counter ion, it is possible to manipulate the strength of the ancillary silyl Lewis acid so that it can be tailored to the ionizing ability of a particular pro‐electrophile.

     

An efficient reaction protocol for the ruthenium‐catalysed epoxidation of methyl oleate

The transition metal catalysed epoxidation of methyl oleate 1 by hydrogen peroxide was investigated using Ru(acac)₃/dipicolinic acid as catalyst. Under optimised reaction conditions, the epoxidised methyl oleate 2 was obtained with a quantitative yield in short reaction time and under mild reaction conditions. Practical applications: Epoxidised fatty acids and their derivatives are produced by the Prilezhaev reaction and used in various applications in the chemical industry. Due to the known drawbacks of epoxidation with peroxy acids, such as hazardous handling of peracids in large quantities or the decrease of epoxide selectivity due to the formation of undesired by‐products in the acidic medium, the epoxidation of fatty acid derivatives using more convenient oxidants is still a subject of research interest. Herein, we present a simple procedure for the transition metal catalysed epoxidation of methyl oleate 1 by hydrogen peroxide in quantitative yields, and under mild reaction conditions, as a potential alternative for the production of epoxidised fatty acid derivatives.     

Ionic Liquids as Surfactants in Aqueous Multiphase Systems for the Pd-Catalyzed Hydrocarboxylation

The suitability of ionic liquids (alkylmethylimidazolium bromides) as surfactants in an aqueous multiphase system for the Pd-catalyzed hydrocarboxylation of 1-dodecene is discussed. Attention is paid to the influence of these ionic liquids on the reaction performance and the phase separation. All tested ionic liquids are suitable as surfactants, but their concentration has a strong impact on the reaction performance. The resulting product concentrations are crucial for the phase behavior and so for the phase separation. In recycling experiments, the Pd-catalyst is successfully separated and reused.     

催化氢酯基化反应的研究进展

介绍了氢酯基化反应及其特点,分别综述了均相催化氢酯基化反应和多相催化氢酯基化反应的研究现状,并对不对称催化氢酯基化的研究提出了建议。     

Selective propylene dimerization to 2,3-dimethylbutenes by homogeneous catalysts prepared by oxidative addition of α-nitroketones to nickel(0) complexes in the presence of phosphine ligands and organoaluminium co-catalysts

Novel nickel catalysts, prepared in situ by oxidative addition of α-nitroketones to nickel(0) complexes, in the presence of a phophine ancillary ligand and activated by organoaluminium co-catalysts were investigated in propylene oligomerization with the aim to selectively obtain 2,3-dimethylbutenes (DMB). In particular, the effect of the nature of the α-nitroketonate ligand as well as of the basicity and bulkiness of the phosphine on catalyst performances were studied. Finally, the influence of the type of organoaluminium co-catalyst and reaction temperature were examined.In particular, when the Ni(cod)₂/tricyclohexylphosphine (PCy₃)/α-nitroacetophenone (naph)/methylalumoxane (MAO) catalytic system was employed, the highest up to now reported regioselectivity within C₆ cut (>90%) was achieved. Moreover, the use of balanced mixtures of MAO and Et₂AlCl allowed to optimize the catalyst performances up to an overall yield to DMB of almost 70%, a significant productivity being also achieved (TOF=4500 h⁻¹).     

过渡金属化合物多壳空心球的制备及其应用研究进展

过渡金属化合物多壳空心球密度低、比表面积大,同时具有较高的光俘获效率,相对于传统的简单中空结构材料在应用中具有更显著的优势,其形状、大小、组成和壳层数可控的中空结构具有独特的性能优势。本文主要介绍了过渡金属化合物多壳空心球的不同制备方法,如硬模板法、软模板法和无模板法;概述了不同反应条件对过渡金属化合物形貌的影响;总结了其应用在锂电池、染料敏化太阳能电池、超级电容器和传感器等领域时表现出的优异性能;并对过渡金属化合物多壳空心球的可控合成进行了前景展望。     

极谱法测定金矿石中的砷

在氢氧化钠-硼砂的底液体系中对金矿石进行极谱测定,在峰电位-0.35 V,砷的质量浓度在2～400μg/mL之间时砷的浓度与峰电流成线性关系。选用含有甘露醇的氢氧化钠硼砂的底液测定砷,精度好,准确度高,检出限为0.002μg/mL。     

New Paradigms and Future Critical Directions in Heterogeneous Catalysis and Multifunctional Reactors

Heterogeneous catalysis is a key pillar of the global industrial chemical and petrochemical sector, and 85% of all chemical products are produced with at least one catalytic step. Indeed, catalysis and catalytic reactors are a critical underpinning science for energy, environmental, and economic security. This paper reviews some future critical directions for research in catalysis science, toward a greener and more sustainable future. We believe that even a relatively mature field as heterogeneous catalysis and nanomaterials can be vitalized and spurred by major discoveries, but an outside-the-box thinking and a focused effort in a large plurality of disciplines is necessary. Thus, critical research needs in several areas, including heterogeneous and homogeneous catalysis, biocatalysis, photocatalysis, electrochemical conversions, and computational catalysis, are reviewed. The research needs of the future lie at the intersection of synthesis of novel nanostructured materials with tunable pore size distribution, controlled porosity, and high surface area; development of new catalytic applications for such materials; and the science of advanced characterization including in situ spatiotemporal analysis. In the area of computational catalysis, we believe that the future lies in the development of hybrid methods (parallel and serial) which can model the typical multiscale phenomena that are typically encountered in protein translocation and signal transduction, charge transport, enzymatic catalysis, surface chemistry, and self-assembly in complex fluids. As we promulgate the new directions to the catalysis fraternity, some prior research areas will unfortunately need to be relegated to obsolescence, to maintain a healthy balance on the research forefront.     

挥发性有机物燃烧催化剂的研究进展

挥发性有机物（VOCs）是主要大气污染物质,也是形成PM_2.5和臭氧的重要前体。强化挥发性有机物控制,是改善大气环境的重要途径。催化燃烧（氧化）被认为是去除VOCs最有效的方式之一,本文综述了VOCs催化燃烧常用的贵金属催化剂、非贵金属催化剂。其中,贵金属催化剂主要包括基于Pd、Pt、Ru等的催化剂,非贵金属催化剂主要包括Mn、Co、Ce、Zr等的氧化物,通常贵金属催化剂具有比非贵金属更高的氧化活性和稳定性,但对于含氮VOCs非贵金属催化剂（Mn、Cu）具有更好的氮气选择性,Cr基催化剂对于含氯VOCs燃烧具有更好的效果。此外,还重点讨论了载体、分散度、催化剂制备方法对贵金属催化剂性能的影响,并对发展VOCs氧化催化剂的研究提出了展望。     

Gold(I)-Catalysis for the Synthesis of Terpenoids: From Intramolecular Cascades to Intermolecular Cycloadditions

Gold(I)-catalyzed cycloisomerizations of 1,n-enynes proceed through electrophilic intermediates that can be trapped intra- or intermolecularly by a variety of hetero- and carbon nucleophiles to form complex skeletons in a single step. This review covers the efforts of our group towards the development of new reactions that have been successfully applied in the total synthesis of several natural terpenoids and related carbocyclic structures, as well as for the ready access to challenging linear acenes.     

Tailoring polymeric composite gel beads-encapsulated microorganism for efficient degradation of phenolic compounds

Phenol and its derivatives are highly toxic pollutants in industrial wastewater for the ecological environ-ments, so there is essential attention to develop effective means of removing these harmful substances from water. In this work, the microorganism was immobilized into polymeric composite gel beads pre-pared by the effective recombination of natural abundant chitosan (CS) and industrial polyvinyl alcohol (PVA) for treating phenolic compounds. The degradation rate of 99.5％ can be achieved to treat 100 mg·L-1 of phenol at 30 ℃ using the fresh resultant immobilized microorganism, where only 21.1％degradation rate was obtained by the free microorganism under the identical conditions. The recycling experiments of repeated 90 times to treat 100 mg·L-1 of phenol displayed that the degradation rate of phenol was stable to 99％with the appearance of beads unchanged significantly, indicating the immobi-lized microorganism possessed excellent operating stability. Moreover, while the phenol derivatives of 100 mg·L-1 were treated catalytically including p-methylphenol, catechol, and o-aminophenol for 24 h by the immobilized microorganism, the degradation rates were all above 95％. The immobilized microor-ganism into PVA-CS polymeric composite with excellent operating stability and degradation activity would provide a feasible solution for treating phenolic compounds in water in industrial applications.     

Recent Advances in Amphiphilic Polymers as the Stabilizers of Colloidal Gold Nanoparticles

Gold nanoparticles (AuNPs) exhibit high catalytic activity as catalysts and have potential applications in biomedicine. To prevent the aggregation of colloidal AuNPs, the stabilizers including organic small molecules, organic ligands, inorganic ligands, and polymers, are necessary to be added in the synthesis of colloidal AuNPs. Among these stabilizers, amphiphilic polymers have attracted significant attention from scientists in the development of polymerization and modification methods. To date, numerous efforts are employed to develop amphiphilic polymers as the stabilizers of colloidal AuNPs but are not well‐summarized yet. In this review, four parts (amphiphilic linear polymers, amphiphilic graft polymers, amphiphilic hyperbranched polymers, and amphiphilic dendrimers) according to the polymer architectures will be discussed. Comprehensive understanding of amphiphilic polymers that are used for stabilizing colloidal AuNPs is provided.     

Self-assembly of gold nanoparticles to silver microspheres as highly efficient 3D SERS substrates

Herein we report a simple, one-pot, surfactant-free synthesis of 3D Ag microspheres (AgMSs) in aqueous phase at room temperature. The 3D AgMSs act as supports to fix the gold nanoparticles (GNPs) in 3D space via the interaction between the carboxyl groups of GNPs and the Ag atoms of AgMSs. The ensemble of AgMSs@GNPs with high surface-enhanced Raman scattering (SERS) activity and sensitivity can be an ideal 3D substrate choice for practical SERS detection applications. The simple self-assembly strategy may be extended to other metallic materials with great potentials in SERS, catalysis, and photoelectronic devices.     

Gold/iron carbonyl clusters as precursors for TiO2 supported catalysts

A series of supported gold/iron catalysts has been prepared from bimetallic carbonyl clusters and characterized to determine how the nature of the precursors and the thermal treatment conditions affected the dispersion of the active phase and the catalytic activity. The chemical–physical characterization, and the catalytic tests carried out, evidenced that the deposition of bimetallic Au/Fe carbonyl clusters on a titania support, and their following controlled decomposition, is a way to obtain stable catalysts, active in the decomposition of toluene.     

Nuclear microanalysis: An efficient tool to study intercalation compounds containing lithium

Lithium can intercalate easily into graphite leading to the LiC₆ compound but the synthesis of a ternary compound associating lithium with a second element seems to be difficult. Recently, graphite-lithium-calcium compounds were obtained by reaction of a pyrographite platelet in a molten Ca-Li alloy at 350 °C. Chemical analyses, electron microprobe, SEM and TEM give the C/Ca ratio but do not allow to determine the lithium concentration and its distribution in these compounds. Therefore, the nuclear microprobe was used to characterise more precisely these ternary intercalation compounds. Using a 3.1 MeV proton beam, the three elements can be quantified simultaneously from the ⁷Li(p,α)⁴He nuclear reaction for lithium and from elastic scattering for calcium and carbon. Among the three synthesised compounds, one of them (α phase) opposes great heterogeneities in lithium and the amount of lithium in the β phase is very high (C/Li ratio approaches 2).