Mercury-catalyzed synthesis of heterocycles

Due to significant biological activity associated with N-, O- and S-heterocycles, a number of 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 mercury metal with emphasis of their synthetic applications for heterocylces. In summary, this review article describes the synthesis of different sized heterocyclic rings containing different heteroatoms.     

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.

     

Transition metal-mediated routes to cyclopentenones

Cyclopentenones are not only key building blocks for organic synthesis, but many possess interesting biological properties in their own right. This review begins with an overview of the biological importance of cyclopentenones and a summary of the main classical routes to cyclopentenones. A detailed account of recent advances in transition metal-mediated approaches to cyclopentenones follows. The aim of the review is to draw attention to transition metal-mediated approaches to cyclopentenones that are starting to be applied in organic synthesis, and to highlight promising cyclopentenone-forming reactions that have not yet realised their full potential in a synthetic context.     

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.     

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 fluoroalkylated compounds using fluoroalkyl anhydrides

Fluoroalkyl-containing organic compounds have exhibited wide applications in the field of pharmaceuticals, agrochemicals and materials science due to their outstanding properties such as biological activity, metabolic stability, lipophilicity, excellent chemical and thermal stability. Therefore, various synthetic strategies have been developed for the construction of fluoroalkyl-containing compounds, using highly active fluorinating reagents and fluorinated building blocks. Recently, the use of easily available and inexpensive trifluoroacetic anhydride (TFAA) and its anhydride analogues has attracted great attention to access numerous fluoroalkyl-containing compounds through cyclization and coupling reactions. In this review, we summarized the recent advances in the synthesis of fluoroalkylated compounds using fluoroalkyl anhydrides as reagents. This review aims to provide a reference for researchers on how to develop new synthetic straregies of fluorine-containing organic compounds and achieve kilograms or even tons preparation of fluorine-containing organic compounds using fluoroalkyl anhydrides.     

Use of monoterpenes, 3-carene and 2-carene, as synthons in the stereoselective synthesis of 2,2-dimethyl-1,3-disubstituted cyclopropanes

The current review represents a systematic survey of the use of 2- and 3-carenes in the synthesis of chiral non-racemic organic compounds containing a 2,2-dimethyl-1,3-disubstituted cyclopropane fragment. The synthetic approaches to the cyclopropane derivatives are classified on the basis of the retention of their parent carane bicyclic skeleton in the final product or cleavage of the six-membered ring along the synthetic route.     

Total Syntheses of Pladienolide-Derived Spliceosome Modulators

Pladienolides, an emerging class of naturally occurring spliceosome modulators, exhibit interesting structural features, such as highly substituted 12-membered macrocycles and epoxide-containing diene side chains. The potential of pladienolides as anti-cancer agents is confirmed by H3B-8800, a synthetic analog of this natural product class, which is currently under Phase I clinical trials. Since its isolation in 2004 and the first total synthesis in 2007, a dozen total syntheses and synthetic approaches toward the pladienolide class have been reported to date. This review focuses on the eight completed total syntheses of naturally occurring pladienolides or their synthetic analogs, in addition to a synthetic approach to the main framework of the natural product.     

Transition Metals in the Synthesis and Functionalization of Indoles [New Synthesis Methods (72)]

The use of transition-metal complexes as reagents for the synthesis of complex organic compounds has been under development for at least several decades, and many extraordinary organic transformations of profound potential have been realized. However, adoption of this chemistry by the practicing synthetic organic chemist has been inordinately slow, and only now are transition-metal reagents beginning to achieve their rightful place in the arsenal of organic synthesis. Several factors contributed to the initial reluctance of synthetic organic chemists to use organometallic reagents. Lacking education and experience in the ways of elements having d electrons, synthetic chemists viewed organometallic processes as something mysterious and unpredictable, and not to be discussed in polite society. Organometallic chemists did not help matters by advertising their latest advances as useful synthetic methodology, but restricting their studies to very simple organic systems lacking any serious functionality (e.g., the “methyl, ethyl, butyl, futile” syndrome). Happily, things have changed. Organometallic chemists have turned their attention to more complex systems, and more recently trained organic chemists have benefited from exposure to the application of transition metals. This combination has set the stage for major advances in the use of transition metals in the synthesis of complex organic compounds. This review deals with one aspect of this area, the use of transition metals in the synthesis of indoles.     

Modern Approaches to the Synthesis and Transformations of Practically Valuable Benzothiazole Derivatives

The review is devoted to modern trends in the chemistry of 2-amino and 2-mercapto substituted benzothiazoles covering the literature since 2015. The reviewed heterocycles belong to biologically active and industrially demanded compounds. Newly developed synthesis methods can be divided into conventional multistep processes and one-pot, atom economy procedures, realized using green chemistry principles and simple reagents. The easy functionalization of the 2-NH₂ and 2-SH groups and the benzene ring of the benzothiazole moiety allows considering them as highly reactive building blocks for organic and organoelement synthesis, including the synthesis of pharmacologically active heterocycles. The review provides a summary of findings, which may be useful for developing new drugs and materials and new synthetic approaches and patterns of reactivity.     

Recent developments in synthesis of embelin heterocyclic derivatives and their biological applications

Embelin (2,5-dihydroxy-3-undecyl-1,4-benzoquinone) has attracted a great deal of synthetic attention as a biologically active heterocyclic compound in the last decades. The high reactivity of its carbonyl groups, active methylene group, and hydroxyl groups represents challenges to many organic reactions for the synthesis of various embelin derivatives. This review summarizes for the first time the most recent and relevant approaches towards the synthesis of embelin-linked heterocyclic derivatives.     

可见光促进的偕二氟烯烃制备与应用研究进展

偕二氟烯烃化合物在医药、材料、精细化工等领域具有广泛的应用,同时也是一类非常重要的用于制备各类复杂的有机氟化合物的有机合成中间体.可见光催化反应具有条件温和、绿色清洁等特点,已经成为有机化学中非常重要的合成手段之一.本文综述了近年来可见光促进的偕二氟烯烃化合物的制备及其在有机合成化学中的应用.     

Selected strategies for the synthesis of triphenylenes

This tutorial review surveys the most useful strategies for the synthesis of triphenylenes. It is aimed at organic chemists in general and, in particular, synthetic chemists interested in the development of advanced materials for organic electronic devices. The synthetic strategies considered are classified according to the structures of their key intermediates. Selected examples illustrate the variety of target structures and the method(s) of choice for their synthesis.     

Growing Utilization of Radical Chemistry in the Synthesis of Pharmaceuticals

Our current unhealthy lifestyle and the exponential surge in the population getting affected by a variety of diseases have made pharmaceuticals or drugs an imperative part of life, making the development of innovative strategies for drug discovery or the introduction of refined, cost-effective and modern technologies for the synthesis of clinically used drugs, a need of the hour. Ever since their discovery, free radicals and radical cations or anions as reactive intermediates have captivated the chemists, resulting in an exceptional utilization of these moieties throughout the field of chemical synthesis, owing to their unprecedented and widespread reactivity. Sticking with the idea of not judging the book by its cover, despite the conventional thought process of radicals being unstable and difficult to control entities, scientists and academicians around the globe have done an appreciable amount of work utilizing both persistent as well as transient radicals for a variety of organic transformations, exemplifying them with the synthesis of significant biologically active pharmaceutical ingredients. This review truly accounts for the organic radical transformations including radical addition, radical cascade cyclization, radical/radical cross-coupling, coupling with metal-complexes and radical cations coupling with nucleophiles, that offers fascinating and unconventional approaches towards the construction of intricate structural frameworks of marketed APIs with high atom- and step-economy; complementing the otherwise employed traditional methods. This tutorial review presents a comprehensive package of diverse methods utilized for radical generation, featuring their reactivity to form critical bonds in pharmaceutical total synthesis or in building key starting materials or intermediates of their synthetic journey, acknowledging their excellence, downsides and underlying mechanisms, which are otherwise poorly highlighted in the literature. Despite great achievements over the past few decades in this area, many challenges and obstacles are yet to be unraveled to shorten the distance between the academics and the industry, which are all discussed in summary and outlook.     

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.     

Simplifying the synthesis of dendrimers: accelerated approaches

Dendrimers are highly branched and monodisperse macromolecules that display an exact and large number of functional groups distributed with unprecedented control on the dendritic framework. Based on their globular structure, compared to linear polymers of the same molecular weight, dendrimers are foreseen to deliver extraordinary features for applications in areas such as cancer therapy, biosensors for diagnostics and light harvesting scaffolds. Of the large number of reports on dendrimer synthesis only a few have reached commercial availability. This limitation can be traced back to challenges in the synthetic paths including a large number of reaction steps required to obtain dendritic structures with desired features. Along with an increased number of reaction steps come not only increased waste of chemical and valuable starting materials but also an increased probability to introduce structural defects in the dendritic framework. This tutorial review briefly covers traditional growth approaches to dendrimers and mainly highlights accelerated approaches to dendrimers. A special focus capitalizes on the impact of the click chemistry concept on dendrimer synthesis and the promise it has to successfully accomplish highly sophisticated dendrimers, both traditional as well as heterofunctional, in a minimum number of chemical steps. It is clear that accelerated synthetic approaches are of greatest importance as these will encourage the scientific community to synthesize and access dendrimers for specific applications. The final goal of accelerated synthesis is to deliver economically justified dendritic materials for future applications without compromising the environmental perspective.     

Halogen-Induced Controllable Cyclizations as Diverse Heterocycle Synthetic Strategy

In organic synthesis, due to their high electrophilicity and leaving group properties, halogens play pivotal roles in the activation and structural derivations of organic compounds. Recently, cyclizations induced by halogen groups that allow the production of diverse targets and the structural reorganization of organic molecules have attracted significant attention from synthetic chemists. Electrophilic halogen atoms activate unsaturated and saturated hydrocarbon moieties by generating halonium intermediates, followed by the attack of carbon-containing, nitrogen-containing, oxygen-containing, and sulfur-containing nucleophiles to give highly functionalized carbocycles and heterocycles. New transformations of halogenated organic molecules that can control the formation and stereoselectivity of the products, according to the difference in the size and number of halogen atoms, have recently been discovered. These unique cyclizations may possibly be used as efficient synthetic strategies with future advances. In this review, innovative reactions controlled by halogen groups are discussed as a new concept in the field of organic synthesis.     

Solid-phase synthesis of heterocyclic aromates: applicability towards combinatorial chemistry; a review

Because of their biological activity, stability in vivo, the rigid spatial positioning of their substituents, and their synthetic challenges, heterocyclic aromates continue to be of interest to both academic and industrial medicinal chemists. Currently, many drug-like heterocyclic aromates are prepared via solid-phase organic chemistry methods. This review examines the applicability of those methods towards combinatorial chemistry with respect to the basic demands of such an approach: 1) synthesis, work-up and subsequent purification should be easily automated enabling the efficient simultaneous synthesis of large numbers of highly pure compounds in a minimum amount of time, 2) large diversity among the ligands to be synthesized, 3) high conversion rates of the individual reaction steps, and 4) the use of commercially available starting materials. Although many methods have been developed for the synthesis of heterocyclic aromates, very few of the available methods enable the synthesis of highly diverse heteroaromatic libraries.     

Design and synthesis of porous non-noble metal oxides for catalytic removal of VOCs

The design and synthesis of highly active non-noble metal oxide catalysts, such as transition- and rare-earth-metal oxides, have attracted significant attention because of their high efficiency and low cost and the resultant potential applications for the degradation of volatile organic compounds(VOCs). The structure-activity relationships have been well-studied and used to facilitate design of the structure and composition of highly active catalysts. Recently, non-noble metal oxides with porous structures have been used as catalysts for deep oxidation of VOCs, such as aromatic hydrocarbons, aliphatic compounds, aldehydes, and alcohols, with comparable activities to their noble metal counterparts. This review summarizes the growing literature regarding the use of porous metal oxides for the catalytic removal of VOCs, with emphasis on design of the composition and structure and typical synthetic technologies.