Recent advances in organothorium and organouranium catalysis

In this critical review we summarize the latest results obtained during the last decade concerning the catalytic activities of organoactinide complexes. We begin with a brief summary of the synthesis and characterization of uranium and thorium complexes that later will be used as catalysts for demanding chemical transformations. Hydroamination, hydrosilylation of terminal alkynes, coupling of terminal alkynes with isonitriles, catalytic reduction of azides and hydrazines, ring opening polymerization of cyclic esters and polymerization of alpha-olefins are covered in this review (118 references). The topics covered in this review regarding organoactinide chemistry will be of interest to inorganic, organic and organometallic chemists, material and catalytic scientists due to its unique mode of activation as compared to late transition-metals. In addition, the field of organoactinide complexes in catalysis is steadily growing, because of the complementary reactivity of organoactinides as compared to other early or late transition complexes, in demanding chemical transformations.     

Recent advances in water-mediated multiphase catalysis

Water is the most sustainable solvent, making it the obvious choice to replace organic solvents in various synthesis techniques. However, its applications in the chemical and pharmaceutical industries are often restricted by the low solubility of organic compounds in water. Essentially, the reactions of organic compounds in water are multiphase systems. Therefore, this review classifies aqueous-phase organic reactions into liquid–liquid, liquid–solid and gas–liquid–solid phase from the perspective of phase interfaces of multiphase reactions, and summarizes the research progress and breakthroughs in recent years, including the application of micellar catalysis, Pickering emulsion catalysis, micro-nanobubble/foam catalysis and “dry water” catalysis, as well as the unique advantages of using water as a medium. Finally, we point out the current challenges and future perspectives on multiphase catalysis in aqueous-phase reactions.     

Recent advances on carborane-based ligands in low-valent group 13 and group 14 elements chemistry

Carboranes are a class of polyhedral boron-carbon molecular clusters, they can serve as versatile ligands in stabilizing low-valent main group element compounds, due to their exceptionally thermal and chemical stabilities, easy modifications at the cage carbon vertices, as well as large spherical steric effects. These carborane-based ligands provide interesting opportunities for the synthesis of low-valent main group element compounds with novel structure and reactivity, which indeed enrich the ...     

Recent advances in asymmetric phase-transfer catalysis

The use of chiral nonracemic onium salts and crown ethers as effective phase-transfer catalysts have been studied intensively primarily for enantioselective carbon-carbon or carbon-heteroatom bond-forming reactions under mild biphasic conditions. An essential issue for optimal asymmetric catalysis is the rational design of catalysts for targeted reaction, which allows generation of a well-defined chiral ion pair that reacts with electrophiles in a highly efficient and stereoselective manner. This concept, together with the synthetic versatility of phase-transfer catalysis, provides a reliable and general strategy for the practical asymmetric synthesis of highly valuable organic compounds.     

Recent advances in the transition metal-catalyzed twofold oxidative C-H bond activation strategy for C-C and C-N bond formation

The direct functionalization of heterocyclic compounds has emerged as one of the most important topics in the field of metal-catalyzed C-H bond activation due to the fact that products are an important synthetic motif in organic synthesis, the pharmaceutical industry, and materials science. This critical review covers the recent progresses on the regioselective dehydrogenative direct coupling reaction of heteroarenes, including arylation, olefination, alkynylation, and amination/amidation mainly utilizing transition metal catalysts (113 references).     

Recent advances in the diversification of chromones and flavones by direct C-H bond activation or functionalization

Chromone and flavone are both central backbones of natural products and clinical medicines. Synthesis of diversely functionalized chromones and flavones constitutes significant research contents of the modern synthetic science because abundant molecular libraries of such types are crucial in providing candidate compounds for the discovery of new pharmaceuticals and functional materials. The direct C-H bond activation or functionalization on these heterocyclic backbones provides highly powerful tools for the rapid accesses to densely functionalized chromone and flavone derivatives. Considering the importance of the functionalized chromone and flavone compounds as well as the notable advances in the synthesis of such products by direct C-H activation or functionalization, we review herein the research advances in the C-H bond activation and functionalization reactions of chromone and flavones, in hope of showing the current states and promise of the research domain.     

Recent advances in the diversification of chromones and flavones by direct CH bond activation or functionalization

Chromone and flavone are both central backbones of natural products and clinical medicines. Synthesis of diversely functionalized chromones and flavones constitutes significant research contents of the modern synthetic science because abundant molecular libraries of such types are crucial in providing candidate compounds for the discovery of new pharmaceuticals and functional materials. The direct CH bond activation or functionalization on these heterocyclic backbones provides highly powerful tools for the rapid accesses to densely functionalized chromone and flavone derivatives. Considering the importance of the functionalized chromone and flavone compounds as well as the notable advances in the synthesis of such products by direct CH activation or functionalization, we review herein the research advances in the CH bond activation and functionalization reactions of chromone and flavones, in hope of showing the current states and promise of the research domain.     

光热协同催化去除挥发性有机化合物和CO的研究进展

随着社会和经济的快速发展,环境污染和能源短缺等问题,尤其是空气污染,已经影响了人类的可持续发展.挥发性有机化合物(VOCs),如苯、甲苯、甲醛和丙酮是主要的空气污染物,它们主要来源于油漆、有机化学品、石油化工产品、药物和工业生产过程.大多VOCs具有特殊的气味,而且具有一定的毒性、致畸性和致癌作用,尤其是苯、甲苯和甲醛...     

Electron transfer and bond breaking: Recent advances

After a reminder of concerted/stepwise mechanistic dichotomy and other basic concepts and facts in the field, a series of recent advances is discussed. Particular emphasis is laid on the interactions between the fragments formed upon bond cleavage. These interactions may persist even in polar solvents and have important consequences on dissociative electron transfer kinetics and on the competition between concerted and stepwise pathways. Cleavage of ion radicals and its reverse reaction are examples of single electron transfer reactions concerted with bond cleavage and bond formation, respectively. The case of aromatic carbon–heteroatom bonds is particularly worth examination since symmetry restrictions impose circumventing a conical intersection. Reductive dehalogenases are involved in ‘dehalorespiration’ of anaerobic bacteria in which the role of dioxygen in aerobic organisms is played by major polychloride pollutants such as tetrachloroethylene. They offer an interesting illustration of how the coupling of electron transfer with bond breaking may be an important issue in natural processes. Applications of dissociative electron transfer concepts and models to mechanistic analysis in this class of enzymes will be discussed.     

Recent advances in oxidation catalysis using ionic liquids as solvents

Ionic liquids are an interesting alternative to classical solvents presenting several advantages. A variety of catalysts show good or even enhanced activities when applied in ionic liquids. Oxidation catalysis represents a large segment of industrial chemistry, providing both bulk chemicals and intermediates for high value added special products and pharmaceuticals. Particularly for the latter products organometallic and inorganic catalysts are being developed that can be applied in systems consisting of or containing ionic liquids. This work provides an overview on recent developments in this field.     

1，1’—联—2—萘酚在不对称催化中的应用新进展

光学活性的1，1’—联—2—萘酚(BINOL)及其衍生物作为优异的手性配体应用 于不对称催化中已取得了巨大进展，显示出广阔的应用前景．对BINOL小分子和高 分子在各种不对称催化反应中的最新进展和发展方向进行了评述，并介绍了有关 BINOL的几种新型催化策略．     

Recent advances in heterogeneous catalysis for the nonoxidative conversion of methane

The direct conversion of methane to high-value chemicals is an attractive process that efficiently uses abundant natural/shale gas to provide an energy supply. The direct conversion of methane to high-value chemicals is an attractive process that efficiently uses abundant natural/shale gas to provide an energy supply. Among all the routes used for methane transformation, nonoxidative conversion of methane is noteworthy owing to its highly economic selectivity to bulk chemicals such as aromatics and olefins. Innovations in catalysts for selective C–H activation and controllable C–C coupling thus play a key role in this process and have been intensively investigated in recent years. In this review, we briefly summarize the recent advances in conventional metal/zeolite catalysts in the nonoxidative coupling of methane to aromatics, as well as the newly emerging single-atom based catalysts for the conversion of methane to olefins. The emphasis is primarily the experimental findings and the theoretical understanding of the active sites and reaction mechanisms. We also present our perspectives on the design of catalysts for C–H activation and C–C coupling of methane, to shed some light on improving the potential industrial applications of the nonoxidative conversion of methane into chemicals.

The direct conversion of methane to high-value chemicals is an attractive process that efficiently uses abundant natural/shale gas to provide an energy supply.     

Recent advances in the synthesis of 1,1-diarylalkanes by transition-metal catalysis

1,1-Diaryl moieties are core structures in a wide range of bioactive and pharmaceutical compounds.Transition-metal catalysis is a convenient approach to accessing these invaluable compounds affording high yields and enantioselectivities.This review summarizes 1,1-diarylalkanes synthesis through transition metal catalysis.Particular focus is given to recent developments,such as reductive cross-electrophile couplings,benzylic C–H bond arylation,transformations involving metal migration,asymmetric hydrogenation of 1,1-diarylalkenes and three-component coupling reactions.     

Selective ethylene oligomerization: Recent advances in chromium catalysis and mechanistic investigations

Selective production of linear α-olefins is of significant commercial interest. Recently discovered catalytic systems based on titanium, tantalum, and chromium show remarkable selectivity and productivity for the oligomerization of ethylene to 1-hexene or 1-octene. Chromium-based catalysts are the most selective and active and show the highest structural diversity. This paper discusses the most recent advances in chromium chemistry related to selective olefin oligomerization. Aspects regarding ligand design, catalyst generation, selectivity for different products, and reaction mechanism are presented. Isotopic labeling protocols designed to distinguish between various mechanisms of catalysis are reviewed.     

Gas-expanded liquids for sustainable catalysis and novel materials: Recent advances

Employing a multiscale systems-based research approach, chemists and chemical engineers at the Center for Environmentally Beneficial Catalysis (CEBC) are collaboratively addressing major grand challenges facing the sustainable manufacture of fuels and chemicals from both traditional and renewable feedstocks. By judiciously combining the principles of green chemistry and green reactor engineering, augmented by valuable insights from industrial partners, CEBC researchers are developing alternative technology concepts that minimize the environmental footprint of chemical manufacturing processes including the reduction of carbon emissions. Such collaborations have resulted in several remarkable discoveries as follows: CO₂-expanded liquids (CXLs) as reaction media for selective and inherently safe O₂ oxidations including that for terephthalic acid production from p-xylene with potentially reduced solvent burning (i.e., reduced carbon footprint); propylene oxide production with environmentally benign solvents and oxidant, exploiting the compressibility of propylene at ambient temperatures for process intensification; a novel pressure-intensified ethylene oxide process virtually eliminating CO₂ formation as a byproduct; highly selective hydroformylation of higher olefins employing CXLs and soluble polymer-supported homogeneous Rh-based catalysts that are easily retained in solution while the product is isolated by membrane filtration; and creation of nanoparticles of transition metal complexes with unique functional properties such as reversible oxygen binding and room-temperature nitric oxide disproportionation. Quantitative economic and environmental impact analyses have been employed to benchmark CEBC's novel technology concepts against conventional processes and to guide research and development. Examples of such advances in green processing are discussed in this review.     

平面手性二茂铁的合成及其在不对称催化反应中应用 的最新进展

平面手性二茂铁由于其独特的立体结构和电子效应,在不对称催化反应中已成为一类优良的手性配体。合成高光学纯度的平面手性二茂铁已受到高度重视,将成为设计、合成手性配体研究以及应用中的热点之一。本文综述了近年来其合成方法及其在不对称催化反应中应用研究的进展。     

Recent advances in gold-complex and chiral organocatalyst cooperative catalysis for asymmetric alkyne functionalization

Homogeneous gold catalysis has demonstrated the preponderant capability of realizing a broad range of synthetically versatile alkyne functionalization over the last two decades. Though catalytic asymmetric alkyne transformation has focused on the principle of using gold catalysts either associated with chiral phosphine ligand or combined with chiral counterion, a variety of breakthroughs have been reported with the application of gold-complex and chiral organocatalyst cooperative catalysis strategy, which could enable the challenging transformations that cannot be realized by mono-catalysis with excellent stereoselectivity. This review will cover two general protocols in this field, including relay catalysis and synergistic catalysis, with emphasis on the detailed cooperative catalysts models to illustrate the roles of the two catalysts and highlight the potential synthetic opportunities offered by asymmetric cooperative catalysis.     

Recent advances in hollow metal-organic frameworks and their composites for heterogeneous thermal catalysis

Science China Chemistry - Hollow metal-organic frameworks (HoMOFs) as emerging materials have been arousing great interest in heterogeneous catalysis with respect to the solid counterparts, mainly...     

Recent advances in simple valence-bond theory and the theory of hybrid bond orbitals

The history of important developments in the theory of hybrid bond orbitals and its application in valence-bond theory is reviewed. One of the salient points, the bond strength of a hybrid orbital, is defined as the value of the angular part of the orbital along the bond direction. Characteristic bond angles corresponding to maxima in the bond strength are presented for various basis sets. In order to alleviate computational difficulties in determining the bond strength for complex systems, an approximation to it, the pair-defect-sum approximation, is described. The results of an exhaustive test of the validity of this approximation are presented. Applicaitions of these ideas to coordinate chemistry are provided. Finally, the case is made for the continued viability of valence-bond theory in this age of omnipresent computer terminals.