Selective α-bromination of aryl carbonyl compounds: prospects and challenges

The α-bromination of carbonyl compounds is one of the most important transformations and also important precursors in synthetic organic chemistry. Particularly, the side chain monobromination of carbonyl compounds has been a challenging task, because during the reaction a small amount of disubstituted or ring brominated products as an impurity is always accompanied with monosubstituted product in the reaction mixture. In recent years substantial advances have been made for the synthesis of brominated aromatic carbonyl compounds with high selectivity. In this review, we have summarized various methods for the synthesis of α-bromo aromatic carbonyl compounds.     

Synthesis and characterization of ethidium analogs: Emphasis on amino and azido substituents

A series of eight ethidium derivatives has been synthesized in which the substituents at R₃ and R₈ have been varied with hydrogen, azido and amino functions. Three of these compounds are new and their synthesis and characterization by uv-visible, ir and ¹H nmr spectroscopy are presented. The synthesis and characterization of the other compounds are also given for comparison, because the compounds served as precursors, or the synthetic route undertaken for these compounds differed from that reported previously.     

Reduction of Aromatic Nitro Compounds under Solvent-free Condition Using Almnina-suppored Hydrazine/Fe2 (NO3)3· 9H2O

The application of microwave techniques for chemical synthesis has attracted considerable interest in recent years because of their enhanced selectivity, reduced reaction time, easier work-up procedure. Aromatic amines are widely used as intermediate for dyes, photographic materials, pharmaceutical and agricultural chemicals and as antioxidants. So, particularly intense interest has been directed toward the synthesis of these compounds. Reduction of aromatic nitro compounds is one of the important routes to prepare them. Generally, the processes have been carried out in solvent. [ 1 ～ 6] The drawback of these methods is long reaction time.     

Enantioselective Strategies for The Synthesis of N−N Atropisomers

Axially chiral compounds have been always considered a laboratory curiosity with rare prospects of being applied in asymmetric synthesis. Things have changed very quickly in the last twenty years when it was understood the important role and the enormous impact that these compounds have in medicinal, biological and material chemistry. The asymmetric synthesis of atropisomers became a rapidly expanding field and recent reports on the development of N−N atropisomers strongly prove how this research field is a hot topic open to new challenges and frontiers of asymmetric synthesis. This review focuses on the recent advances in the enantioselective synthesis of N−N atropisomers highlighting the strategies and breakthroughs to obtain this novel and stimulating atropisomeric framework.     

Cyclic Hypervalent Iodine Reagents for Atom‐Transfer Reactions: Beyond Trifluoromethylation

Hypervalent iodine compounds are privileged reagents in organic synthesis because of their exceptional reactivity. Among these compounds, cyclic derivatives stand apart because of their enhanced stability. They have been widely used as oxidants, but their potential for functional‐group transfer has only begun to be investigated recently. The use of benziodoxol(on)es for trifluoromethylation (Togni's reagents) is already widely recognized, but other transformations have also attracted strong interest recently. In this Review, the development in the area since 2011 will be presented. After a short summary of synthetic methods to prepare benziodoxol(on)e reagents, their use to construct carbon–heteroatom and carbon–carbon bonds will be presented. In particular, the introduction of alkynes by using ethynylbenziodoxol(on)e (EBX) reagents has been highly successful. Breakthroughs in the introduction of alkoxy, azido, difluoromethyl, and cyano groups will also be described.     

Bioinspired and green synthesis of nanoparticles from plant extracts with antiviral and antimicrobial properties: A critical review

Currently green synthesis of nanoparticles has attained much interest because of their safe nature, environmentally benign, ease in manufacturing, and low production cost. It is a reliable process for developing a wide array of nanostructures such as metal salts from plants/fungal/bacterial extract and hybrid materials. Green synthesis of nanoparticles provided promising and sustainable alternative approach to conventional synthesis approaches. Recent studies demonstrated that nanoparticles are highly promising for antiviral and antimicrobial properties. Here in, the advancement in green synthesis of nanoparticles using natural compounds such as plant extracts, fruit juices and other relevant sources have been highlighted. A deep insight into antiviral and antimicrobial activities of these nanoparticles provided. These nanoparticles offer diverse opportunity to counter life threating viral and other antimicrobial infections. This review offers understanding of the recent data that provide the readers various strategies to design and develop advance nanomaterials via greener approach. Current challenges, critical overview and future outlook of the green synthesis of nanoparticles and possibilities of their effective and exotic exploration for antimicrobial and antiviral applications are summarized.     

Advances in polymer based Friedlander quinoline synthesis

Nitrogen containing heterocyclic compounds has acquired their remarkable and distinct place in the wide area of organic synthesis due to the broad range of applications. Among them, quinoline motifs have attracted researchers in the synthetic chemistry because of its presence in the large number of pharmacologically active compounds. Different methods for synthesis of quinoline derivatives are reported, among them the Friedlander synthesis have provided comparatively more efficient approach. Many of the reported conventional Friedlander methodologies have some problems such as difficult product isolation procedures, poor yields and use of expensive catalysts, etc. Recently, polymer or solid supported synthetic approaches have attracted the attention of researchers because of their easy execution, greater selectivity, increased product yields, simple work-up procedures, recoverability and reusability of the catalysts. In consideration with the advantages of polymer supported synthetic strategies, the proposed review covers the role of polymers in the Friedlander synthesis; which may use polymers of organic, inorganic or hybrid in nature and of nanolevel as well.     

Synthesis of symmetrical biaryl compounds by homocoupling reaction

Since the development of the Ullmann coupling in the early 20th Century, there has been intense and continuous research on the syntheses of biaryl compounds, which appears as an interesting branch of organic chemistry.A myriad of methodologies for the synthesis of biaryl compounds have been studied and well established, including homocoupling methodologies, which in general are robust as well as consolidated strategies. Biaryl systems are quite relevant building blocks for the synthesis of more complex chemical structures. Besides the diversity of functional groups that can be used to promote a new aryl-aryl bond, there is a wide variety of transition metals that can act as catalyst in these processes.In this review, we summarized numerous methodologies of homocoupling reactions for the synthesis of symmetrical biaryl compounds.     

Fermentative production of chemicals that can be used for polymer synthesis

The fermentative production of chemicals that can be used as monomers for the synthesis of polymers has become an important topic in biotechnology research because of the limited nature of petroleum and environmental issues. In particular, the fermentative production of metabolites such as dicarboxylic acids, amino acids, and diols, which are suitable as building blocks for subsequent polymerization, has attracted much attention. Various wild-type and metabolically engineered microorganisms have been developed for the efficient production of these chemicals from renewable resources. In addition, the development of fermentation strategies to achieve the highest possible productivities has been another focus of research, considering that these monomers should be produced at costs low enough to compete with petroleum-derived ones. In this paper, the metabolic pathways leading to the synthesis of such important monomers including succinic acid, lactic acid, fumaric acid, propan-1,2-diol, and propan-1,3-diol are reviewed. In addition, the metabolic engineering and fermentation strategies for their production are reviewed.     

Review of Synthesis of Spiro Heterocyclic Compounds from Isatin

Isatin is an essential building block in organic synthesis and shows various biological activities. The most attractive application of isatin in organic synthesis is undoubtedly in the highly reactive C-3 carbonyl group, which is a prochiral center as well. The construction of a spiroheterocyclic framework has always been a challenging endeavor for synthetic organic chemists as it frequently requires synthetic design based on specific strategies. This review gives a short summary of the advances in the use of isatin in the synthesis of various spiroheterocyclic compounds through multicomponent reactions and 1,3-dipolar cycloaddition reactions.     

Recent advances in the synthesis of N-containing heteroaromatics via heterogeneously transition metal catalysed cross-coupling reactions

N-containing heteroaromatics are important substructures found in numerous natural or synthetic alkaloids. The diversity of the structures encountered, as well as their biological and pharmaceutical relevance, have motivated research aimed at the development of new economical, efficient and selective synthetic strategies to access these compounds. Over more than 100 years of research, this hot topic has resulted in numerous so-called "classical synthetic methods" that have really contributed to this important area. However, when the selective synthesis of highly functional heteroaromatics like indoles, quinolones, indoxyls, etc. is considered these methods remain limited. Recently transition metal-catalysed (TM-catalysed) procedures for the synthesis of such compounds and further transformations, have been developed providing increased tolerance toward functional groups and leading generally to higher reaction yields. Many of these methods have proven to be the most powerful and are currently applied in target- or diversity-oriented syntheses. This review article aims at reporting the recent developments devoted to this important area, focusing on the use of heterogeneous catalysed procedures that include either the formation of the heterocyclic ring towards the nuclei or their transformations to highly substituted compounds.     

Regio- and stereoselective functionalization of alkenes with emphasis on mechanistic insight and sustainability concerns

Alkene is an attractive substrate for chemists due to its easy availability and reactivity towards large number of reactants affording diverse range of organic compounds. It reacts under ionic and free radical mechanisms including single electron transfer (SET). In this review, strategies used for C–C and C-heteroatom functionalization of alkene has been discussed with emphasis on the regio, stereoselectivity, mechanistic detail and sustainability aspects. These strategies mainly follow the free radical mechanism, and the highly reactive carbon radicals show uncontrollable regio- and stereoselectivities. Thus these strategies still need to be focused; especially in the asymmetric versions. The regio- and stereoselectivities of functionalization of alkenes have been highlighted and debated. In addition, the hazardous reagents such as Cl₂, Br₂ I₂, CO, peroxides, and benzene have also been discussed with the emphasis on their impact on the environment. Their plausible green alternatives have also been suggested, such as MX as halogen replacement; CO surrogates (formaldehyde etc.); sustainable aromatic solvents as benzene replacement. The non-green strategies relying on pre-formed silyl hydride and their green alternative strategies such as transfer hydrogenations have also been indicated. The applications of the functionalization of alkenes for the total synthesis of bioactive compounds have also been discussed in detail. In addition, future perspectives are also highlighted for further developments in the functionalization of alkenes.     

Synthesis and applications of thiosulfonates and selenosulfonates as free-radical reagents

Chalcogenative sulfones (thiosulfonates and selenosulfonates), as reactants for organic transformations, are widely used and interesting because of their potential to react with nucleophiles, electrophiles, and free radicals. As stable radical reagents, the synthesis and applications of chalcogenative sulfones have opened up a novel pathway to synthesize many kinds of compounds containing sulfur or selenium motifs. However, despite the numerous recent works on the synthesis and applications of thiosulfonates and selenosulfonates as radical reagents, no review has yet provided a summary of the literature. In this paper, we aim to review the synthesis and applications strategies of chalcogenative sulfones as radical reagents reported over the past several decades. Different types of catalysis are discussed in this review: (i) metal catalysis; (ii) visible-light catalysis; (iii) synergistic catalysis; and (iiii) other types. Concurrently, in visible-light catalysis and metallaphotoredox catalysis sections, we highlight that developing relatively environmentally friendly synthetic methods in this area is always a great challenge, but also a persistent pursuit. Finally, the scopes, limitations, mechanisms, and existing problems of some reactions are described briefly.     

Glycosamino acids: building blocks for combinatorial synthesis-implications for drug discovery

The unique functions of carbohydrates, including energy storage, transport, modulation of protein function, intercellular adhesion, signal transduction, malignant transformation, and viral and bacterial cell-surface recognition, underlie a significant pharmaceutical potential. The development of combinatorial carbohydrate libraries in this important arena has been slow, in contrast to the rapid development of combinatorial synthesis in the area of small-molecule libraries and biopolymers. This is largely as a result of the inherent difficulties presented by this class of polyfunctional compounds. Nevertheless, strategies to cope with these problems have been devised over the past seven years, and combinatorial carbohydrate libraries have appeared. The incorporation of an amino acid moiety into the carbohydrate scaffold generates glycosamino acids, which are attractive building blocks for the preparation of carbohydrate-based libraries because of the well-established automated peptide synthesis. Derivatization as well as homo- and heterooligomerization of glycosamino acids can be used to create novel structures with unique properties. Glycosamino acids are hybrid structures of carbohydrates and amino acids which can be utilized to generate potential glycomimetics and peptidomimetics. The incorporation of glycosamino acids into peptides allows the engineering of carbohydrate-binding sites into synthetic polypeptides, which may also influence the pharmacokinetic and dynamic properties of the peptides. Furthermore, sugar-amino acid hybrids offer a tremendous structural and functional diversity, which is largely unexplored and requires combinatorial strategies for efficient exploitation. This article provides an overview of previous work on glycosamino acids and discusses their use in combinatorial synthesis and drug discovery. Supporting information for this article is available on the WWW under http://www.angewandte.com or from the author.     

New Forms and Functions of Tellurium: From Polycations to Metal Halide Tellurides

Metal chalcogenides and metal chalcogenide halides are distinguished by their structural diversity and by their very different physical properties. Therefore, the synthesis of novel compounds from this class is always a rewarding goal for the preparatively oriented solid-state chemist. Over the past few years, many syntheses and structural investigations have stimulated the field. The emphasis of the research has been placed on selenium-rich and tellurium-rich compounds, which are characterized by directed covalent bonds between the chalcogen atoms. Compounds with novel chalcogen polycations have also become accessible during the past few years by reacting the chalcogen elements with transition metal halides, or from chemical vapor deposition in the sense of chemical transport reactions. In these compounds, tellurium differs from its lighter homologues by a pronounced tendency towards greater covalence. This article attmepts to provide an overview of new developments in the field of compounds with chalcogen polycations and of metal chalcogenide halides, with an emphasis on compounds containing molybdenum and tungsten as the transition metals and tellurium as the chalcogen.     

The synthesis of 7-deazaguanines as potential inhibitors of guanosine triphosphate cyclohydrolase I

Variously substituted 7-deazaguanines are of interest as inhibitors of GTP cyclohydrolase I, the first enzyme in the biosynthetic pathway leading to dihydrofolate and tetrahydrobiopterin. Methods are described for the synthesis of 7-deazaguanines substituted at positions 2, 6 and 9 (purine numbering) such that a wide diversity of compounds can be prepared. These methods supplement our previous work that established routes for the synthesis of 7- and 8-substituted 7-deazaguanines. Emphasis is placed on the properties of 2-thioalkyl pyrimidines as intermediates because they provide the basis for a traceless solid-state synthesis of purines, pteridines, and their analogues. Compounds prepared have been assessed in a primary screen for their ability to inhibit GTPCH I and 8-methyldeazaguanine has been shown to be significantly more potent than any inhibitor yet described. Several compounds appeared to undergo transformation by GTPCH I; with the aid of a model reaction, their behaviour can be interpreted in the context of the mechanism of the hydrolytic phase of GTPCH I.     

多孔有机骨架材料对顺式二醇化合物富集分离的研究进展

基于在碱性环境下硼酸能与顺式二醇化合物可逆共价结合形成稳定的五元或六元环酯,而在酸性环境下环酯开环释放顺式二醇化合物这一特性,设计合成高效、高选择性、高富集性能的硼亲和材料的研究备受关注。近年来,许多研究工作者合成了各种类型的硼亲和材料,应用于高选择性富集顺式二醇化合物。金属有机骨架(MOFs)和共价有机骨架(COFs)由于具有孔径可调、高孔隙率、高比表面积、骨架结构可调和化学及热稳定性良好等特点,被广泛应用于色谱分离和样品前处理领域。为赋予MOFs和COFs材料对顺式二醇化合物的富集选择性,各种不同结构和不同种类的硼酸修饰的MOFs和COFs被合成出来。该综述主要是对近几年来80余篇源于科学引文索引关于硼酸功能化MOFs和COFs的种类、合成方法及其应用文章的总结,包括“金属配体-片段共组装”“合成后修饰”和“自下而上”的硼酸功能化多孔材料的修饰策略,以及硼酸功能化MOFs和COFs的种类,介绍了其在化学分析和生物分析领域的发展概况和应用前景,客观评价了硼酸功能化MOFs和COFs的区别和优缺点。该文旨在让研究人员能够充分了解近几年硼酸功能化多孔有机骨架材料的研究现状、掌握合成思路和方法,为其应用提供一定的理论指导和技术支撑,为加快硼酸功能化多孔有机骨架材料的商业化脚步贡献绵薄之力。     

Gold-catalyzed cyclizations of alkynol-based compounds: synthesis of natural products and derivatives

The last decade has witnessed dramatic growth in the number of reactions catalyzed by gold complexes because of their powerful soft Lewis acid nature. In particular, the gold-catalyzed activation of propargylic compounds has progressively emerged in recent years. Some of these gold-catalyzed reactions in alkynes have been optimized and show significant utility in organic synthesis. Thus, apart from significant methodology work, in the meantime gold-catalyzed cyclizations in alkynol derivatives have become an efficient tool in total synthesis. However, there is a lack of specific review articles covering the joined importance of both gold salts and alkynol-based compounds for the synthesis of natural products and derivatives. The aim of this Review is to survey the chemistry of alkynol derivatives under gold-catalyzed cyclization conditions and its utility in total synthesis, concentrating on the advances that have been made in the last decade, and in particular in the last quinquennium.     

Progress in the chemistry of 5-acetylthiazoles

This review deals with the synthesis and reactions of 5-acetylthiazoles. Some of these reactions have been used successfully for the production of biologically important compounds. The main purpose of this review is to present a survey of the literature on the chemistry of 5-acetylthiazoles and to provide useful and up-to-date information on their applications because these compounds have not been previously reviewed.     

SAR studies of quinoline and derivatives as potential treatments for Alzheimer’s disease

Quinoline analogs are an important class of N-based heterocyclic compounds, which have received extensive attention because of their use in medicinal chemistry and organic synthesis. Over the past few decades, several new scaffold-based functionalization synthesis strategies have been reported for quinolines. Quinoline derivatives have a wide range of biological activities, including anti-Alzheimer’s disease activity. Herein, we review research on quinoline and related analogs as anti-Alzheimer’s disease agents from 2001 to 2022 and particularly highlight the structure–activity relationships and molecular binding modes. This review provides information for the rational design of more effective and target-specific drugs for Alzheimer's disease.