Ruthenium catalysis in six-membered O-heterocycles synthesis

Due to significant biological activity associated with N-, O-, and S-heterocycles, several reports for their synthesis have appeared in recent decades. Traditional approaches require expensive or highly specialized equipment or would be of limited use to the synthetic organic chemist due to their highly inconvenient approaches. This review summarizes the applications of ruthenium metal with emphasis of their synthetic applications for oxygen-containing six-membered heterocylces. In summary, this review article describes the synthesis of heterocyclic rings containing different heteroatoms.     

Cobalt-catalyzed C–N,C–O,C–S bond formation: synthesis of heterocycles

In recent decades, a large number of reports related to the synthesis of N-, O- and S-containing heterocycles have appeared owing to a wide variety of their biological activity. Traditional approaches require expensive or highly specialized equipment or would be of limited use to the synthetic organic chemist due to their highly inconvenient approaches. New strategies have been developed for the preparation of heterocycles in the last decades. Metal and non-metal catalysts are used in organic reactions with high activity. These synthetic strategies are becoming important and highly rewarding protocols in organic synthesis. In this review article, the synthesis of heterocycles is presented with the application of cobalt metal as a catalyst. It describes the formation of different sized heterocyclic rings containing different heteroatoms.

     

Application of titanium catalysts for the syntheses of heterocycles

The metal catalyzed synthesis of heterocycles is becoming an important and highly rewarding protocol in organic synthesis. Traditional approaches require expensive or highly specialized equipment or would be of limited use to the synthetic organic chemist due to their highly inconvenient approaches. Titanium-mediated cyclization reactions have been recognized as some of the simplest and useful tools for regio- as well as stereoselective syntheses of five-membered N-heterocycles. This review summarizes the applications of titanium catalysts with emphasis of their synthetic applications for different heterocylces. This review covered interesting discoveries in the past few years.     

Synthesis and Biomedical Applications of Highly Porous Metal–Organic Frameworks

In this review, aspects of the synthesis, framework topologies, and biomedical applications of highly porous metal–organic frameworks are discussed. The term “highly porous metal–organic frameworks” (HPMOFs) is used to denote MOFs with a surface area larger than 4000 m² g⁻¹. Such compounds are suitable for the encapsulation of a variety of large guest molecules, ranging from organic dyes to drugs and proteins, and hence they can address major contemporary challenges in the environmental and biomedical field. Numerous synthetic approaches towards HPMOFs have been developed and discussed herein. Attempts are made to categorise the most successful synthetic strategies; however, these are often not independent from each other, and a combination of different parameters is required to be thoroughly considered for the synthesis of stable HPMOFs. The majority of the HPMOFs in this review are of special interest not only because of their high porosity and fascinating structures, but also due to their capability to encapsulate and deliver drugs, proteins, enzymes, genes, or cells; hence, they are excellent candidates in biomedical applications that involve drug delivery, enzyme immobilisation, gene targeting, etc. The encapsulation strategies are described, and the MOFs are categorised according to the type of biomolecule they are able to encapsulate. The research field of HPMOFs has witnessed tremendous development recently. Their intriguing features and potential applications attract researchers’ interest and promise an auspicious future for this class of highly porous materials.     

Synthetic Routes to Imidates and Their Applications in Organic Transformation: Recent Progress

Recent synthetic approaches and diverse applications of imidates are presented in this review. These motifs are successfully used as intermediates in organic transformations, such as the synthesis of N-heterocycles, natural products and metal complexes with a potential catalytic effect. Consequently, many attempts have been made for the development of efficient and facile synthetic methods of imidates in the past few years, as a continuum of previous paths. A wide range of organic compounds can be used as starting materials for these syntheses, including nitriles, isocyanides, amides etc. which through simple and flexible processes are converted to the desired imidates. Herein, an exploration of the recent synthetic routes of imidates and their diverse applications in organic transformations has been categorized and summarized.     

Recent Report on Thieno[2,3‐d]pyrimidines. Their Preparation Including Microwave and Their Utilities in Fused Heterocycles Synthesis

The review summarizes recent literatures dealing with the synthetic tools of thieno[2,3‐d]pyrimidine derivatives including their biological activities and their applications in the synthesis of heterocycles.     

Recent developments in the synthesis of nitrogen containing five-membered polyheterocycles using rhodium catalysts

The nitrogen-, oxygen- and sulfur-heterocycles possess a number of pharmacological activities and recently many reports appeared for the synthesis of these heterocycles. In few past years, metals are applied for the production of these heterocycles. These synthetic strategies involving metal catalysts became highly significant in the synthetic organic chemistry. This review article features the applications of rhodium metal catalysts for the preparation of five-membered N-polyheterocylces.     

Photochemical reactions as key steps in five-membered N-heterocycle synthesis

The chemists have been interested in light as an energy source to induce chemical reactions since the beginning of scientific chemistry. This review summarizes the chemistry of photochemical reactions with emphasis of their synthetic applications. The organic photochemical reactions avoid the polluting or toxic reagents and therefore offer perspectives for sustainable processes and green chemistry. In summary, this review article describes the synthesis of a number of five-membered N-heterocycles.     

Synthesis,Chemical–Physical Characterization,and Biomedical Applications of Functional Gold Nanoparticles: A Review

Relevant properties of gold nanoparticles, such as stability and biocompatibility, together with their peculiar optical and electronic behavior, make them excellent candidates for medical and biological applications. This review describes the different approaches to the synthesis, surface modification, and characterization of gold nanoparticles (AuNPs) related to increasing their stability and available features useful for employment as drug delivery systems or in hyperthermia and photothermal therapy. The synthetic methods reported span from the well-known Turkevich synthesis, reduction with NaBH₄ with or without citrate, seeding growth, ascorbic acid-based, green synthesis, and Brust–Schiffrin methods. Furthermore, the nanosized functionalization of the AuNP surface brought about the formation of self-assembled monolayers through the employment of polymer coatings as capping agents covalently bonded to the nanoparticles. The most common chemical–physical characterization techniques to determine the size, shape and surface coverage of AuNPs are described underlining the structure–activity correlation in the frame of their applications in the biomedical and biotechnology sectors.     

Metal and organo-complex promoted synthesis of fused five-membered O-heterocycles

Abstract

One of the highly emerging and an important aspect of organic chemistry is the metal and organo-complex promoted synthesis of the heterocycles. The methodologies used earlier for its synthesis were less approachable to the organic chemist due to their high cost, highly sophisticated instrumentation and problematic methods. For both stereoselective and regioselective synthesis of fused five-membered O-containing heterocycles, cyclic reactions that are metal and organo-complex promoted have been known to be very efficient. The present review article covers the different applications of metals and organo-complexes in the formation of fused five-membered oxygen containing fused heterocycles. The fascinating research that has been done in this area is enclosed in this review.     

Methods for the synthesis of 1H-pyrazolo[3,4-b]pyridine derivatives

This review covers and summarizes comprehensive data reported within the period from 2017 to 2021 on the synthetic strategies and approaches to 1H-pyrazolo[3,4-b]pyridine derivatives. Methods for the synthesis are systematized according to the method to assemble the pyrazolopyridine system, whereas their advantages and drawbacks are considered.

     

Enhancing Magnetic Communication between Metal Centres: The Role of s-Tetrazine Based Radicals as Ligands

Although 1,2,4,5-tetrazines or s-tetrazines have been known in the literature for more than a century, their coordination chemistry has become increasingly popular in recent years due to their unique redox activity, multiple binding sites and their various applications. The electron-poor character of the ring and stabilization of the radical anion through all four nitrogen atoms in their metal complexes provide new aspects in molecular magnetism towards the synthesis of new high performing Single Molecule Magnets (SMMs). The scope of this review is to examine the role of s-tetrazine radical ligands in transition metal and lanthanide based SMMs and provide a critical overview of the progress thus far in this field. As well, general synthetic routes and new insights for the preparation of s-tetrazines are discussed, along with their redox activity and applications in various fields. Concluding remarks along with the limitations and perspectives of these ligands are discussed.     

铜N-杂环卡宾化合物的合成及其在有机合成中的应用

N-杂环卡宾铜化合物具有简便易得,价廉低毒,性质稳定,结构类型多样并易于修饰等诸多优点,在很多领域具有重要的应用价值,因此铜的N-杂环卡宾化学在过去十几年中得到了快速发展。本文结合我们的工作,总结铜N-杂环卡宾化合物的合成方法、结构特点、转移卡宾配体用于合成其它金属卡宾化合物以及催化应用。     

Combined Dynamic Kinetic Resolution and C−H Functionalization for Facile Synthesis of Non-Biaryl-Atropisomer-Type Axially Chiral Organosilanes

Although asymmetric C−H functionalization has been available for the synthesis of structurally diverse molecules, catalytic dynamic kinetic resolution (DKR) approaches to change racemic stereogenic axes remain synthetic challenges in this field. Here, a concise palladium-catalyzed DKR was combined with C−H functionalization involving olefination and alkynylation for the highly efficient synthesis of non-biaryl-atropisomer-type (NBA) axially chiral oragnosilanes. The chemistry proceeded through two different and distinct DKR: first, an atroposelective C−H olefination or alkynylation produced axially chiral vinylsilanes or alkynylsilanes as a new family of non-biaryl atropisomers (NBA), and second, the extension of this DKR strategy to twofold o,o′-C−H functionalization led to the multifunctional axially chiral organosilicon compounds with up to >99 % ee.     

Recent synthetic methodologies for pyridopyrazines: An update

Abstract

Among heterocyclic compounds, pyridopyrazines are the scaffolds that have gained considerable attention on academic and industrial level due to their widespread applications as intermediates in the preparation of advanced and biologically potent pharmaceutical materials. Many pyridopyrazine derivatives are available in market to cure various pharmacological disorders. These candidates can be synthesized via a number of synthetic routes using various reagents like cyclocondensation of diaminopyridines with carbonyl compounds or their derivatives etc. In the present review, we have elaborated all these protocols along with different factors and reaction conditions such as use of metal catalyst, solvent-free and microwave irradiation, one-pot synthesis etc. that have resulted in high regioselectivity and yields. The review focuses on the synthetic methodologies developed in the last decade for different pyridopyrazine derivatives.     

Chemical Functionalization of Nanodiamonds: Opportunities and Challenges Ahead

Nanodiamond(ND)‐based technologies are flourishing in a wide variety of fields spanning from electronics and optics to biomedicine. NDs are considered a family of nanomaterials with an sp³ carbon core and a variety of sizes, shapes, and surfaces. They show interesting physicochemical properties such as hardness, stiffness, and chemical stability. Additionally, they can undergo ad‐hoc core and surface functionalization, which tailors them for the desired applications. Noteworthy, the properties of NDs and their surface chemistry are highly dependent on the synthetic method used to prepare them. In this Minireview, we describe the preparation of NDs from the materials‐chemistry viewpoint. The different methodologies of synthesis, purification, and surface functionalization as well as biomedical applications are critically discussed. New synthetic approaches as well as limits and obstacles of NDs are presented and analyzed.     

Synthetic routes for phenazines: an overview

Phenazines are known to exhibit a diverse range of biological properties, such as antimicrobial, antitumor, antioxidant, antimalarial, neuroprotectant, etc. Owing to their significant applications in both medicinal and industrial fields, the phenazine framework has emerged as a remarkable synthetic target. The most general approaches for synthesis of phenazines include the Wohl–Aue method, Beirut method, condensation of 1,2-diaminobenzenes with 2C-units, reductive cyclization of diphenylamines, oxidative cyclization of 1,2-diaminobenzene/diphenylamines, Pd-catalyzed N-arylation, multicomponent approaches, etc. Advances in the exploitation of synthetic routes for assembly of this scaffold are reported in this review.     

Chemical Protein Synthesis by Native Chemical Ligation and Variations Thereof

For a long time, the total synthesis of proteins was considered as a “mission impossible” because of the tedious and complex synthetic steps and demanding purification processes. However, with the development of modern synthetic methodologies, many protein syntheses have now been reported. More importantly, through chemical synthesis, desired modifications can be installed to target proteins precisely, which is a major advantage over traditional bio‐synthesis approaches. This review summarizes the techniques developed for protein assembly, including native chemical ligation, Se‐mediated ligation, and a range of other ligation methods. A few synthetic examples, whereby synthetic proteins with desired modifications have been utilized for related biological research, are also included. We believe that chemical synthesis can provide alternative pathways to solve problems that have hitherto proved insurmountable by traditional biological approaches.     

Strategies for the Synthesis of Chiral Carbon-Bridged Group IV ansa-Metallocenes

This minireview provides a survey of the various synthetic approaches to chiral ansa-metallocenes of Ti, Zr, and Hf containing a carbon-based bridge. The individual strategies to install substitution patterns at either the cyclopentadienyl framework or the bridging unit are highlighted with focus on the progress made towards a direct preparation of single complex stereoisomers. The review further includes the discussion of potential problems such as the formation of undesired diastereomers, the threat of racemization of enantiopure material, and synthetic challenges originating from the synthesis, purification, and isolation of the target complexes. The review has been written with the goal in mind to facilitate the design and synthesis of new chiral ansa-metallocene derivatives for emerging research areas in asymmetric catalysis and organometallic chemistry.     

Development of Single‐Molecule Magnets†

Single‐molecule magnets (SMMs) are paramagnetic molecules that can be magnetized below a certain temperature and have potential applications in high‐density information storage, magnetic qubits, spintronic devices, etc. The discovery of the first SMM, Mn₁₂, opened a new era of molecular magnetism and promoted collaborative researches between chemists and physicists for their exotic quantum as well as classical magnetic properties. In the recent past, great efforts have been made to develop strategies for constructing new SMMs with high energy barriers (U_eff) and blocking temperatures (T_B), resulting in great and fast development of SMMs. In this concise review, we highlight the main synthetic approaches and representative results in the design and synthesis of high performance SMMs. We hope to give the readers a basic understanding of SMMs and a snapshot of the representative researches on SMMs from a perspective of synthetic chemists.