Transition-metal-mediated fluoroalicylation is a hot research topic in current organofluorine chemistry. In the past five years, due to the development of new perfluoroallcylation reagents and methodologies, significant progress has been made in the field of transition-metal-mediated perfluoroalkylation. Compared with perfluoroallcylation, di- and monofluoroalkylation can not only introduce fluorine atom(s) into a molecule, but also install a non-fluorinated moiety simultaneously; therefore, in organic synthesis, these reactions are of higher step economy than the direct fluorination reactions. Although analogous to transition-metal-mediated perfluoroallcylations, the di- and monofluoroallcylation have been relatively less developed; therefore, there are still many opportunities for their development. In this review, we have made a survey on transition-metal-mediated di- and monofluoroalkylation reactions that were published in the past nearly 30 years. To our knowledge, this is the first rather comprehensive
Chiral transition metal complexes-catalyzed asymmetric hydrogenation is one of the most efficient methods for the synthesis of optically active compounds, and has been intensively investigated in the past decades. This review presents a brief overview on the progress in the transition metal-catalyzed asymmetric hydrogenation since the beginning of this new century from three aspects: (1) chiral ligands and catalysts; (2) new catalytic asymmetric hydrogenations; (3) new methods and new strategies in asymmetric hydrogenations. Chiral monodentate phosphorus ligands have been a renaissance from the beginning of new century, and many efficient chiral monophosphoramidites such as MonoPhos, SiPhos, DpenPhos have been developed. The chiral phosphine ligands with a chirality on the phosphorus atom (P-chirality), such as BenzP*, ZhanPhos, and TriFer, have also been explored. Chiral ligands with a spiro skeleton have been a highlight of design and synthesis of chiral ligands. The chiral spiro ligands such as SDP, SiPhos
Emerging as a relatively new class of porous materials, metal-organic frameworks (MOFs), possessing diversified, designable and tailorable structures as well as ultrahigh surface area, have captured broad research interest and shown potential applications in many fields in recent years. In particular, MOFs have attracted intensive attention in catalysis. In the first two parts of this review, according to the origin of active sites, for examples, coordinatively unsaturated metal centers, functional organic linkers, functional sites chemically grafted onto the framework, as well as metal complexes or metal nanoparticles (MNPs) encapsulated inside the MOFs, etc., we have summarized the recent progress in heterogeneous catalysis over MOFs and their composites in recent several years. In addition, the MOF-based photocatalysis and electrocatalysis have also been briefly introduced in the subsequent two parts. Finally, the further development and challenge in MOF catalysis are discussed.
Transition metal catalyzed asymmetric reaction is a hot issue and a frontier of the research in current organic chemistry. The design and synthesis of new type of efficient chiral ligands and chiral catalysts, esspecially those with novel skeleton is the focus of research in asymmetric catalysis. Since 1990's, chiral ligands based on spiro skeletons have received increasing attention and gradually developed into a new type of chiral ligands with distinctive characteristics. The skeletons of the chiral spiro ligands developed from spiro[4.4] nonane with three chiral stereocenters to spirobiindane and spiro[4.4] nonadiene with only one axial chirality, as well as other types of spiro skeletons. Nowadays, the library of chiral spiro ligands contains a wide range of chiral spiro ligands with different skeletons, including chiral spiro monophosphorus ligands, diphosphine ligands, phosphine-nitrogen ligands, dinitrogen ligands, and etc. Many of these chiral spiro ligands and related catalysts not only have shown hi
The concept of the molecular orbital composition is often involved in quantum chemistry literatures. However, no enough emphasis has been placed on the corresponding calculation methods, and even there exist some serious misunderstandings. In this article, the basic concepts and calculation methods of composition of basis functions, atomic orbitals and atoms in molecular orbitals are discussed in detail, the differences between various methods are analyzed and compared with examples, meanwhile, the problems in calculations and analyses that need to be noticed are pointed out, the suggestions for choosing appropriate calculation methods are also given.
Bases, either organic bases or inorganic ones, are very often added in transition-metal catalyzed organic reactions to promote the catalytic reaction efficiency and increase the yields of products. As a common practice for most published papers, a reaction condition screening table is given, listing a number of bases and the respective yield of products. However, no discussion or a little in some cases is provided on why one base works well to give a high yield formation of the product, but other bases afford no or low yields of the product. Furthermore, in many cases a certain base works well for one reaction but may not work for another. Indeed, for a complicated reaction mixture containing several different components, it is very difficult to analyze and understand the roles of certain bases. Yet there are sporadic discussions and rationalization on the roles of bases in the literature. The role of bases has been reported to be straightforward in some cases, for examples, to abstract protons or to neutrali
Graphene, a monolayer of carbon atoms packed into a two-dimensional crystal structure, attracted intense attention owing to its unique structure and optical, electronic properties. Raman spectroscopy is a quick and precise method in material science and has been employed for many years to investigate material properties. It can be used to investigate the electronic band structure, the phonon energy dispersion and the electron-phonon interaction in graphene systems. In probing graphene's properties, Raman spectroscopy is considered to be a reliable method. In this review, we highlight recent progress of studying graphene structure using Raman spectroscopy. First, on the basis of systematically analyzing the phonon dispersion of graphene, the typical Raman scattering features of graphene, such as G band, G' band, and D band, and the basic physical process are introduced. Using these Raman fingerprints, we can quickly and directly distinguish the layer thickness of graphene, determine the edge chirality and moni
Homogeneous gold catalysis has experienced rapid development since 2004 and generally exhibited high efficiency and good functional group tolerance. On the other hand, catalytic dearomatization reactions provide a unique and straight approach to the construction of highly functionalized molecules with diverse three-dimensional structures from simple aromatic compounds. In this perspective, recent examples on gold-catalyzed dearomatization reactions are summarized in two main categories: gold-catalyzed rearrangements and gold-catalyzed hydrofunctionalizations of alkynes and allenes. In the first category, intra-and inter-molecular dearomatization reactions were achieved via gold-catalyzed rearrangements of propargylic ester and its derivatives. Although this area is still at its early stage, several outstanding asymmetric examples have been reported by Shi and Toste. In the second category, an array of dearomatization reactions via gold-catalyzed hydrofunctionalizations of alkynes and allenes were presented. A
The incorporation of fluorine atoms or fluorinated moieties into organic molecules can often lead to significant changes of their physical, chemical, or biological properties. Consequently, fluorinated organic molecules are widely used in areas of pharmaceuticals, agrochemicals and materials. Traditional approaches for the incorporation of fluorinated moieties into organic molecules include nucleophilic, electrophilic, and radical pathways. Among them, radical fluoroalkylations under visible-light photoredox catalysis have attracted much attention because of the mild reaction conditions and broad functional group tolerance. In our previous work, the radical fluoroalkylation of isocyanides with fluorinated sulfones as the fluoroalkyl radical precursors via Rf-SO2Ar bond cleavage has been achieved under visible-light photoredox catalysis (Rong, J. et al. Angew. Chem., Int. Ed. 2016, 55, 2743). Herein, as a logical extension of our previous research, we report the radical fluoroalkylation of aryl alkenes with fl
With a significantly high Hansch's hydrophobicity parameter (pi=1.44), electron-withdrawing trifluoromethylthio group (CF3S-) has been considered as one of the most lipophilic substituents and privileged fragments that are able to improve drug molecules' pharmacokinetic and physicochemical properties such as lipophilicity and metabolic stability. It is well-known that incorporation of the trifluoromethylthio group into small molecules greatly enhances its ability to cross lipid membranes and in vivo absorpotion rate. In addition, the high electronegativity of the trifluoromethylthio group significantly improves the small molecule's stablity in acidic environments. Not surprisingly, the trifluoromethylthio group has been of special attention not only from the academia but also from pharmaceutical and agrochemical industry for their use in isostere-based drug design. Development of highly efficient methods for the introduction of the trifluoromethylthio group into small molecules, thereafter, has become a subje
Amides are a class of easily available compounds, and widely serve as versatile intermediates in organic synthesis medicinal chemistry. Amide-based transformations could lead to many useful compounds and intermediates including various amines, ketones and enaminones. Though direct transformation of amides is of high demand, many current chemoselective transformations are only achieved in multistep approaches. In recent years, direct transformation of amides is emerging as an exciting area. A number of recent progresses on nucleophilic addition to amide carbonyl group that led to new C-C bond formation are highlighted in this review, including (1) in situ amide activation with trifluoromethanesulfonic anhydride (Tf2O) followed by addition of pi- and s-nucleophiles or reactive organometallic reagents; (2) direct transformation of N-alkoxyamides; (3) direct transformation of amides using Schwartz reagent; and (4) catalytic reductive C-C bond forming reactions of amides, and metal catalyzed coupling of amides.
Palladium-catalyzed allylic substitution is one of the most important methodologies for the construction of C-C and C-X bonds, and has been widely applied in the synthesis of bioactive natural and pharmaceutical products. Tremendous progress has been made towards the development of increasingly elaborate nucleophiles and catalysts to facilitate the aforementioned reaction. Despite significant advances, Pd-catalyzed allylic substitution reactions remain limited to substrates possessing a good leaving group such as a carboxylate, carbonate, phosphate, or other related derivatives on the allylic moiety. Allylic alcohols and amines have also gained attention for use as substrates for Pd-catalyzed allylic substitutions, because of their use in aiding waste minimization and sustainability. Allyl groups containing allylic C-H bond(s) widely are present in numerous commercially available organic Compounds and various kinds of intermediates for chemical synthesis. There is no doubt that the transformation of allylic C
Catalytic asymmetric hydrogenation of unsaturated substrates is one of the most important transformations in organic chemistry, which provides a significant approach to produce optically active compounds both in academia and chemical industry due to its atom-economy and high efficiency. Since the original work of Knowles and Sabacky in 1960s, transition-metal-catalyzed asymmetric hydrogenation has been well developed with great achievements. However, metal-free asymmetric hydrogenation utilizing molecular hydrogen is extremely challenging, and has long been an unsolved problem. Frustrated Lewis pairs (FLPs) with a combination of sterically encumbered Lewis acids and Lewis bases preclude the formation of classical Lewis acid-base adducts via dative bonds due to the steric effects, and they therefore possess novel and interesting properties and reactivities. Since frustrated Lewis pairs was first disclosed to enable heterolytic cleavage of H-2 reversibly by Stephan and co-workers in 2006, its applications on ac
In this work, we demonstrate the microwave-assisted synthesis of naphthalene diimide-based polymers via three-component polymerization (TCP) of diynes, dialdehydes and dibenzylamine, and the applications of such polymers as cathode interfacial layers for polymer solar cells. The TCP of diynes (1a similar to 1c), dialdehydes (2a similar to 2b) and dibenzylamine catalyzed by InCl3 could be performed smoothly under microwave irradiation in very short reaction time, yielding soluble polymers P1 similar to P4 with high molecular weights. The chemical structures of these resulting polymers were confirmed by nuclear magnetic resonance spectroscopy. The thermal stability, photophysical and electrochemical properties of the resulting polymers were also investigated. Besides, the effects of chemical environment of amine groups on the resulting polymers' electrode modification capability and self-doping behavior were explored by conducting scanning Kelvin probe microscopy and electron paramagnetic resonance (EPR) spectr
The 3,4-dihydroisoquinolinones are a privileged class of heterocyclic motifs and widely found in numerous biologically active compounds. Thus, the development of more efficient and practical methods for their synthesis is highly desirable. Traditional methods are typically focused on transition-metal catalyzed C-H functionalization. Inspired by the recent process of the visible light photocatalytic generation and exploration of N-radicals in organic synthesis, our group in 2014 developed a visible light-induced photocatalytic strategy for direct conversion of the N-H bonds of beta,gamma -unsaturated hydrazones into N-centred radicals for the first time, and used them in intramolecular radical hydroamination, enabling efficient synthesis of 4,5-dihydropyrazole derivatives. By employing suitable additives or changing reaction parameters, we also successfully achieved highly regioselective 6-endo N-radical cyclization and oxyamination reactions based on N-centred radicals, providing the valuable 1,6-dihydropyrad
The localized surface plasmon resonance of metal nanoparticles is the collective oscillation of electrons on particle surface. The localized electromagnetic interaction brings a series of novel functions and applications. Plasmonic nanomaterials have been the significant part of nanophotonics, since its' localized surface plasmon resonance (LSPR) can focus incident phonons on the nanoscale surface. The unique plasmonic property is highly sensitive to their size, shape, coupling between particles as well as local dielectric environment. These properties can be utilized for the development of new biosensing and bioimaging applications. To date, many LSPR sensing strategies have been developed with outstanding measurement capabilities, enabling detection down to the single-molecule level, including LSPR-based sensing, surface-enhanced Raman scattering, metal-enhanced fluorescence, dark-field light-scattering, metal-mediated fluorescence resonance energy transfer. Moreover, the unique optical stability of plasmon
Transition-metal-catalyzed asymmetric transformations are among the most powerful and straightforward strategies to access various enantioenriched compounds. Hence, considerable efforts have been focused on the development of novel chiral ligands capable of highly efficient and enantioselective catalysis. The importance of olefin as ligand in transition -metal-catalyzed reactions wasn't realized until the report of the Zeise' salt in 1827. Nevertheless, application of chiral olefins as ligands for asymmetric catalysis has been overlooked for quite a long time owing to their relatively weak binding affinity toward the central metal. Since the groundbreaking work of Hayashi and Carreira in 2003-2004, chiral dienes as steering ligands in asymmetric catalysis have emerged as a fascinating new field. Given the weak coordination ability of olefins to transition-metals, functional groups with high coordination ability were considered to incorporate into the olefin framework to create a new type of hybrid olefin liga
In recent years, visible-light-promoted photoredox catalytic activation of organic molecules has been flourishing vigorously. This kind of methodology usually takes advantage of transition-metal complexes and organic dyes as photosensitizers, which can directly react with organic substrates through a single-electron-transfer (SET) progress under visible light irradiation. It's operable to construct C-X (X= C, N, 0 ...) bond via the radical or radical ion generated during the SET process. On the basis of different key intermediates, this highlight gives a brief summary on the recent development of visible light promoted benzylic C-sp3-H activation and functionalization.
The carboxyl and alkoxyl radicals generated from visible light photoredox reactions are important reaction intermediates in organic synthesis, which have witnessed conceivable progress recently. In this review, we focus on visible-light-induced photoredox methods to generate carboxyl radicals from carboxylate derivatives and carboxylates, as well as alkoxyl radicals from alcohol derivatives and alcohols, and briefly discuss their synthetic applicatication