Synthesis and Applications of 2‐Substituted Imidazole and Its Derivatives: A Review

Imidazole and its derivatives are assigned as an exclusive and multifaceted skeleton because of having a variety of applications in medicinal and synthetic organic chemistry as well as in the field of industrial chemistry. For these perspectives, various elegant methods for imidazoles and its derivatives have been developing over the last years using different types of catalyst to improve selectivity, purity, and yield of the product. Thus, we have reviewed various synthetic routes for the formation of imidazoles and their applications from 2014 to 2016.     

Modified Nucleosides,Nucleotides and Nucleic Acids via Click Azide-Alkyne Cycloaddition for Pharmacological Applications

The click azide = alkyne 1,3-dipolar cycloaddition (click chemistry) has become the approach of choice for bioconjugations in medicinal chemistry, providing facile reaction conditions amenable to both small and biological molecules. Many nucleoside analogs are known for their marked impact in cancer therapy and for the treatment of virus diseases and new targeted oligonucleotides have been developed for different purposes. The click chemistry allowing the tolerated union between units with a wide diversity of functional groups represents a robust means of designing new hybrid compounds with an extraordinary diversity of applications. This review provides an overview of the most recent works related to the use of click chemistry methodology in the field of nucleosides, nucleotides and nucleic acids for pharmacological applications.     

Design and synthesis of bile acid-peptide conjugates linked via triazole moiety

A conjugation of bile acids with peptides via Cu(I)-catalyzed click chemistry has been described. Novel bile acid-peptide conjugates linked via a 1,2,3-triazole moiety based on cholic, deoxycholic and lithocholic acid derivatives were synthesized using Cu(I)-catalyzed 1,3-dipolar cycloaddition ("click" reaction). It was shown that up to three peptide fragments can be attached to a central steroid core, thus forming complex three-dimensional polyconjugate structures, which can find important applications in biochemistry, medicinal chemistry, and coordination chemistry.     

Oxidopyrylium [5+2] cycloaddition chemistry: Historical perspective and recent advances (2008–2018)

The following review article provides an overview of oxidopyrylium [5+2] cycloaddition chemistry, with a particular emphasis placed on seminal historical developments and advancements made over the last decade. It is our hope this review serves as a valuable resource to those interested in the oxidopyrylium cycloaddition chemistry, and helps inspire future advancements.     

Azulene-based organic functional molecules for optoelectronics

Design and synthesis of new organic functional materials with improved performance or novel properties are of great importance in the field of optoelectronics. Azulene, as a non-alternant aromatic hydrocarbon, has attracted rising attention in the last few years. Different from most common aromatic hydrocarbons, azulene has unique characteristics, including large dipole moment, small gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO). However, the design and synthesis of azulene-based functional materials are still facing several challenges. This review focuses on the recent development of organic functional materials employing azulene unit. The synthesis of various functionalized azulene derivatives is summarized and their applications in optoelectronics are discussed, with particular attention to the fields including nonlinear optics (NLO), organic field-effect transistors (OFETs), solar cells, and molecular devices.     

A One-Pot Approach to Novel Pyridazine C-Nucleosides

The synthesis of glycosides and modified nucleosides represents a wide research field in organic chemistry. The classical methodology is based on coupling reactions between a glycosyl donor and an acceptor. An alternative strategy for new C-nucleosides is used in this approach, which consists of modifying a pre-existent furyl aglycone. This approach is applied to obtain novel pyridazine C-nucleosides starting with 2- and 3-(ribofuranosyl)furans. It is based on singlet oxygen [4+2] cycloaddition followed by reduction and hydrazine cyclization under neutral conditions. The mild three-step one-pot procedure leads stereoselectively to novel pyridazine C-nucleosides of pharmacological interest. The use of acetyls as protecting groups provides an elegant direct route to a deprotected new pyridazine C-nucleoside.     

Preparation and synthetic applications of alkene complexes of group 9 transition metals in [2+2+2] cycloaddition reactions

The [2+2+2] cycloaddition reaction has become an invaluable tool for the synthetic chemistry in recent years, due to the increase of complexity of the accessed target molecules by this methodology. Over several decades, the members of group 9 of the periodic table have contributed significantly to the development and understanding of this particular cycloaddition reaction. On the other hand, catalyst complexes containing alkenes as ligands are widely used today as either catalysts or as precursor molecules for the facile generation of catalytically active metal species. In this tutorial review we want to describe the catalytically relevant chemistry of group 9 metal-alkene complexes and compile some recent applications in [2+2+2] cycloaddition reactions.     

The emerging utility of ketenes in polymer chemistry

The continued evolution of functional materials that contribute to pressing societal challenges requires the development of powerful synthetic methodologies in polymer systems. Since their discovery by Staudinger in the early 20th century, the unique chemistry of ketenes have fascinated synthetic chemists and been the driver of revolutionary applications in photolithography, medicinal chemistry, and commodity materials. The versatile chemistry of ketenes, specifically their ability to act as an electrophile and/or undergo cycloaddition reactions, has recently been shown to provide a powerful platform for the design of next‐generation materials. This Highlight focuses on the history of ketenes in materials science and their recent renaissance in polymer chemistry, with specific focus being given to methodologies that provide reliable access to this important functional group in polymer systems. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 3769–3782     

Growing Impact of Intramolecular Click Chemistry in Organic Synthesis

Click Chemistry, a modular, rapid, and one of the most reliable tool for the regioselective 1,2,3-triazole forming [3+2] reaction of organic azide and terimal alkyne is widely explored in various emerging domains of research ranging from chemical biology to catalysis and medicinal chemistry to material science. This regioselective reaction from a diverse range of azido-alkyne scaffolds has been well performed in both intermolecular as well as intramolecular fashions. In comparison to the intermolecular metal (Cu/Ru/Ni) variant of ‘Click Chemistry’, the intramolecular click tool is little addressed. The intramolecular click chemistry is exemplified as a mordern tool of cyclization which involves metal-catalyzed (CuAAC/RuAAC) cyclization, organo-catalyzed cyclization, and thermal-induced topochemical reaction. Thus, we report herein the recent approaches on intramolecular azide-alkyne cycloaddition ‘Click Chemistry‘ with their wide-spread emerging applications in the developement of a diverse range of molecules including fused-heterocycles, well-defined peptidomemics, and macrocyclic architectures of various notable features.     

芳基钌抗癌化合物的研究进展

无机药物化学领域正在快速发展,尤其是有机金属配合物作为癌症的治疗和诊断试剂有很大的潜力.芳基钌配合物中芳基对抗癌活性有重要影响,并能调控配合物金属中心的热力学和动力学性能.配合物的构效关系研究,对进一步合理设计/合成具有潜在药用价值的有机金属配合物至关重要.本文选取钌芳基配合物作为抗癌药物的具体实例进行讨论,重点介绍了多种芳基钌配合物的构效关系及抗癌机理.     

Synthesis of three-dimensional fused and spirocyclic oxygen-containing cyclobutanone derivatives

An approach to fused and spirocyclic oxygen-containing cyclobutanone derivatives based on ketene [2+2] cycloaddition with vinyl ethers is described. Using alicyclic chloroanhydrides as ketene sources as well as cyclic vinyl ethers in the reaction resulted in the formation of three-dimensional conformationally restricted building blocks of interest to medicinal chemistry and organic synthesis. In particular, 2-oxaspiro(bicyclo[3.2.0]heptane-7,1′-cycloalkane)-6-ones and 2-oxaspiro(bicyclo[4.2.0]octane-8,1′-cycloalkane)-6-ones were obtained. The procedure involves readily available and inexpensive starting materials and allows construction of complex molecular architectures on a large scale in a single run.     

Intramolecular 1,3-dipolar cycloaddition as a route to triazolobenzodiazepines and pyrrolobenzodiazepines

Intramolecular 1,3-dipolar cycloaddition between an alkyne and an azide leads to a series of 1,2,3-triazolo-fused 1,4-benzodiazepines, 1,2,5-benzothiadiazepines, pyrrolobenzodiazepines and pyrrolobenzothiadiazepines (eight examples). The products are privileged structures in medicinal chemistry. The precursor azido alkynes are obtained, usually as transient intermediates, by treatment of the corresponding aldehydes (derived from α-amino acids) with the Bestmann-Ohira reagent.     

[4 + 2]-Cycloadditionen mit inversem Elektronenbedarf,XVII. Oxepin und 2,7-Dimethyloxepin als Dienophile bei Diels-Alder-Cycloadditionen mit inversem Elektronenbedarf

[4 + 2] Cycloadditions with Inverse Electron Demand, XVII. Oxepin and 2,7-Dimethyloxepin as Dienophiles in Diels-Alder Cycloadditions with Inverse Electron Demand The cycloaddition reactions of oxepin ( 1 ) with the tetrazine 3 and the triazine 12 yield the dihydrooxepino[4,5-d]pyridazine 5 and the oxepino[4,5-c]pyridine 13 , resp., via [2 + 4] cycloaddition as well as the phthalazine 9 and the isoquinoline 14 , resp., most probably via [6 + 4] cycloaddition. On the contrary, 2,7-dimethyloxepin ( 15 ) only gives the products 16 and 20 , which result from [2 + 4] cycloaddition. Oxidation of 16 by silver(I) oxide leads to the oxepino[4,5-d]pyridazine 17 , which as well as 20 in hydrochloric acid rearranges to the pseudoazulenes 19 and 21 , resp.     

Metal-organic frameworks exhibiting strong anion-pi interactions

Coordination polymers offer a significant potential for applications in adsorption, guest and anion recognition and sensing. Their structure commonly provides binding sites for such specific interactions as pi-pi stacking and XH...pi hydrogen bonding. The latter reflects the ability of the pi-cloud to interact with positively polarized atoms. An electrostatic interaction between anionic species and electron deficient heterocycles, which parallels the above binding scheme, is also possible and very recently the existence of anion-pi interactions was proved in the solid state and in solution. This effect may be significant also for biomolecule/solution interfaces, as it occurs in protein structures. In fact, such interactions could be especially relevant for host-guest chemistry of coordination polymers, particularly for functionalization of hydrophobic crystal cavities and for the design of geometrically rigid anion receptors. However, typical electron deficient heterocycles such as 1,3,5-triazines and 1,2,4,5-tetrazines are very weak donors and they are hardly suitable for bridging metal ions and the generation of coordination frameworks. As a system that combines efficient donor properties towards transition metal ions and a pronounced ability for anion-pi interactions we have developed unsubstituted pyridazino[4,5-d]pyridazine, which was readily accessible by a novel one-pot synthesis involving inverse electron demand Diels-Alder cycloaddition (Scheme 1). Unusual anion binding properties of the ligand may be clearly related to its electron-deficiency (LUMO energy -1.591 vs. -0.288 eV for the parent pyridazine), influenced also by N-coordination to such Lewis acids as metal ions.     

Catalyst-Free Regio- and Diastereoselective Synthesis of Heterocyclic Nucleosides in the Eco-friendly Solvent 2-Methyltetrahydrofuran†

An efficient and practical synthesis of heterocyclic nucleosides is developed by a catalyst-free highly regioselective and diastereoselective [3+2] annulation of α-purine-substituted acrylates with nitrones. The reaction operates with excellent functional group tolerance, very mild reaction conditions, and with the green, sustainable, and eco-friendly 2-methyltetrahydrofuran (2-MeTHF) as solvent. Compared with other reactions of electron-deficient olefin dipolarophiles with nitrones, different regioselective cycloaddition products were observed in this work. This 1,3-dipolar cycloaddition reaction gives a series of isoxazolidinyl nucleosides in good to excellent yields with promising applications in biochemistry and medicinal chemistry.      

Catalytic Asymmetric [8+2] Annulation Reactions Promoted by a Recyclable Immobilized Isothiourea

Higher‐order cycloaddition reactions constitute an efficient approach towards the construction of medium to large ring systems. However, enantioselective versions of these transformations remain scarce, which hampers their deployment in medicinal chemistry, or any other discipline in which homochirality is deemed crucial. Herein, we report a novel method for the production of enantiomerically enriched cycloheptatrienes fused to a pyrrolidone ring on the basis of an isothiourea‐catalyzed periselective [8+2] cycloaddition reaction between chiral ammonium enolates (generated in situ from carboxylic acids) and azaheptafulvenes. The resulting bicyclic compounds can be hydrogenated, but, most remarkably, they can also undergo completely regioselective [4+2] cycloaddition with active dienophiles to give architecturally complex polycyclic compounds in a straightforward manner.     

Graphdiyne:Structure of Fluorescent Quantum Dots

Graphdiyne (GDY) as an emerging two‐dimensional carbon allotrope exhibits excellent performance in energy chemistry, catalytic chemistry, optoelectronics, electronics, etc. because of the unique structure combining an sp‐ and sp²‐hybrid carbon network. However, the poor solubility of pristine GDY is a major obstacle to its applications in many fields. Proposed here is a facile strategy to control the preparation of GDY quantum dots (GDY‐Py QDs), in which pyrene groups are covalently linked to GDY by using a Sonogashira cross‐coupling reaction. The as‐prepared GDY‐Py QDs, with an average diameter of about 3±0.1 nm, show superior dispersibility in many organic solvents and water. The GDY‐Py QDs display not only bright fluorescent with a high relative quantum yield (QY) of 42.82 %, but they are also well‐behaved as contrast agents in cell imaging. The GDY‐Py QDs are bestowed with high stability and non‐cytotoxicity, and exhibit long fluorescent times, and have potential for optical imaging and biomedical applications.     

On the medicinal chemistry of ferrocene

Organometallic chemistry and biochemistry have been merged in the last two decades into a new field: bioorganometallic chemistry. This new research area was devoted to the synthesis of new organometallic compounds and their biological and medical effects against some types of diseases, such as cancer and malaria. For several years, the use of ferrocene in bioorganometallic chemistry has been growing rapidly, and several promising applications have been developed since ferrocene is a stable, nontoxic compound and has good redox properties. This review will focus on ferrocenyl compounds which have been biologically evaluated against certain diseases. This area has attracted many researchers due to the promising results of some ferrocene compounds in the medicinal applications. Copyright © 2007 John Wiley & Sons, Ltd.     

Inverse‐Electron‐Demand Diels–Alder Reactions: Principles and Applications

Inverse‐electron‐demand Diels–Alder (iEDDA) reactions are an intriguing class of cycloaddition reactions that have attracted increasing attention for their application in bioorthogonal chemistry, the total synthesis of natural products, and materials science. In many cases, the application of the iEDDA reaction has been demonstrated as an innovative approach to achieve target structures. The theoretical aspects of this class of reactions are of particular interest for scientists as a means to understand the various factors, such as steric strain and electron density of the attached groups, that govern the reaction and thus to elucidate the reaction mechanism. This review aims to summarize both theoretical investigations and application‐driven research work on the iEDDA reaction. First, the historical aspects and the theoretical basis of the reaction, especially recent advances in time‐dependent density functional theory (TD‐DFT) calculations, as well as catalysis strategies will be highlighted and discussed. Second, the applications of this novel reaction in the context of materials science, bioorthogonal chemistry, and total synthesis of natural products will be elaborated with selected recent examples. The challenges and opportunities of the iEDDA reaction will be highlighted to give more insight into its potential applications in many other research areas.     

Transformations based on ring-opening of gem-difluorocyclopropanes

gem-Difluorocyclopropanes are an important fluorinated class of compounds with applications in medicinal chemistry, material sciences and organic synthesis. The transformations based on their ring-opening reactions have been recognized to be useful methods for rapidly synthesizing various fluorinated organic molecules. In this digest paper, we describe these efforts and highlight their powerfully potential and applications as fluorine-containing synthons in organic chemistry.