Structural Chemistry of C-N Axially Chiral Compounds.

Stereoisomers arising from the rotational restriction about a CN single bond, namely CN atropisomers, have recently attracted considerable attention in the field of synthetic organic chemistry. Diverse CN atropisomeric compounds have been prepared with high optical purity through catalytic enantioselective reactions, and they have been used in various asymmetric reactions as chiral building blocks and chiral ligands. CN atropisomers are attractive compounds from the viewpoint of not only synthetic organic chemistry but also medicinal chemistry. Recently, various CN atropisomeric bioactive compounds have been found, and their biological activity, the target selectivity, and the pharmacokinetics have been revealed to differ significantly between atropisomers. On the other hand, we feel that the chemistry community is still not fully aware of the fascinating biological properties of CN atropisomers. This review article comprehensively describes CN atropisomeric compounds exhibiting diverse biological activities as well as the synthesis or separation of atropisomers and their rotational stability.

Heterocyclic compounds are an important class of compounds in the field of pharmaceutical and synthetic organic chemistry. The Schiff bases contain azomethine linkages which are obtained by the condensation of aldehyde/ketone with amines. Among the various types of Schiff bases, the chalcone-based Schiff bases play a vital role in the treatment of various ailments and various applications, which can be synthesized by using different types of chalcones as the starting materials. These types of compounds were synthesized by using various techniques like conventional means of synthesis, microwave-assisted reaction, heterocyclic catalyst-mediated synthesis and also by means of trituration. The chalcone or bis-chalcone-based Schiff bases and their derivatives contain -C=N linkage which exhibits various activities including antimicrobial, anticancer, antioxidant, antidiabetic and immunosuppressant activities. Beyond these activities, these types of Schiff bases are also used in various chemical industries and fluorescent sensors, which also play a major role in the field of synthetic organic chemistry and coordination chemistry as intermediates. This review discusses the numerous synthetic strategies along with their applications in the field of medicine. Thus, this review will be helpful in developing more effective drug-like scaffolds for use in future drug design. Keywords: Schiff bases, Chalcone-based Schiff bases, Antimicrobial, Anticancer, Antioxidant, Biological Applications

In the periodic table of elements, indium is located within group 13, and has the atomic number 49. Indium is classified as one of the chemical elements of post-transition metals. Indium is silvery-white in color, soft, and possesses a high level of malleability. Although indium is a relatively rare element, it is indispensable in industry applications worldwide. German metallurgists discovered indium in 1863. It was not until the early 1990s, however, that scientists in the field of synthetic organic chemistry attempted genuine studies to explore the roles of indium or indium-related reagents. Focusing on indium or indium-related reagents, many recent investigations have led to significant advances in synthetic organic chemistry. Various applications have been examined and a growing number of useful chemical transformations using indium or indium-related reagents are being revealed and reported. Chemical transformations of the reactive functional groups are an essential point, particularly for the successful implementation of a sequence of multiple-step chemical schemes. For this purpose, a variety of strategic reaction methodologies have been developed, including those utilizing indium or indium-related reagents. Indium metal was discovered to be useful for the protection and deprotection of functional groups, while trivalent indium Lewis acids have been effective in a wide variety of chemical transformations. This chapter describes an efficient oxone-mediated esterification of aldehydes using indium(III) triflate, which is also one of the trivalent indium Lewis acids. Esterification is performed primarily on aromatic and heterocyclic aldehydes. The results show the effectiveness of this esterification methodology and suggest the potential in the further development of these reagents, which could enhance the field of synthetic organic chemistry.

Conjugated dienes have occupied a pivotal position in the field of synthetic organic chemistry and medicinal chemistry. They act as important synthons for the synthesis of various biologically important molecules and therefore, gain tremendous attention worldwide. A wide range of synthetic routes to access these versatile molecules have been developed in the past decades. Transition metal-catalyzed cross-dehydrogenative coupling (CDC) has emerged as one of the utmost front-line research areas in current synthetic organic chemistry due to its high atom economy, efficiency, and viability. In this review, an up-to-date summary including scope, limitations, mechanistic studies, stereoselectivities, and synthetic applications of transition metal-catalyzed double Cvinyl-H bond activation for the synthesis of conjugated dienes has been reported since 2013. The literature reports mentioned in this review have been classified into three different categories, i.e. (a) Cvinyl-Cvinyl bond formation via oxidative homo-coupling of terminal alkenes; (b) Cvinyl-Cvinyl bond formation via non-directed oxidative cross-coupling of linear/cyclic alkenes and terminal/internal alkenes, and (c) Cvinyl-Cvinyl bond formation via oxidative cross-coupling of directing group bearing alkenes and terminal/internal alkenes. Overall, this review aims to provide a concise overview of the current status of the considerable development in this field and is expected to stimulate further innovation and research in the future.

In the field of synthetic organic chemistry, photochemical and electrochemical approaches are often considered to be competing technologies that induce single electron transfer (SET). Recently, their fusion, i. e., the "photoelectrochemical" approach, has become the focus of attention. In this approach, both solar and electrical energy are used in creative combinations. Historically, the term "photoelectrochemistry" has been used in more inorganic fields, where a photovoltaic effect exhibited by semiconducting materials is employed. Semiconductors have also been studied intensively as photocatalysts; however, they recently have taken a back seat to molecular photocatalysts. In this account, we would like to revisit semiconductor photocatalysts in the field of synthetic organic chemistry to demonstrate that semiconductor "photoelectrochemical" approaches are more than mere alternatives to molecular photochemical and/or electrochemical approaches.

Recently, electron has been recognized as the simplest catalyst in the field of synthetic organic chemistry. Addition or removal of electron can activate small molecules for further chemical transformations, which is referred to as redox catalysis. Reductive and/or oxidative single electron transfer (SET) can be induced by means of electro- and photochemistry, where an electron can play a role of catalysts. Radical ions are primarily generated via SET, offering unique reactive intermediates.Distonic radical ions are transient species with formally separated radical and charge cites. They potentially exhibit radical and ion reactivities independently, which may differ from usual radical ions. However, distonic radical ions are not commonly used as reactive intermediates in the field of synthetic organic chemistry, probably because of lack of their simple generation methods.We have been developing oxidative SET-triggered cycloadditions in a lithium perchlorate/nitromethane solution. Radical cations are involved in the reactions as distinctive reactive intermediates, facilitating intermolecular carbon-carbon bond formations. We questioned whether the distonic radical cation can also be generated by oxidative SET, leading to novel chemical transformations. In this presentation, oxidative SET-catalyzed vinylcyclopopane rearrangements will be described. Figure 1

17 - Applications of the Olefin Metathesis Reaction

Explosive growth in the use of open shell reactivity, including neutral radicals and radical ions, in the field of synthetic organic chemistry has been observed in the past decade, particularly since the advent of ruthenium complexes in 2008. These complexes generally induce single-electron transfer (SET) processes via visible-light absorption. Additionally, recent significant advancements in organic electrochemistry involving SET processes to provide open shell reactivity offer a complementary method to traditional polarity-driven reactions described by two-electron transfer processes. In this Review, we highlight the importance of intramolecular SET processes in the field of synthetic organic chemistry, which seem to be more elusive than the intermolecular versions, since they are net redox-neutral and thus cannot simply be regarded as oxidations or reductions. Such intramolecular SET processes can rationally be understood in combination with concomitant bond formations and/or cleavages, and are regulated by a structural motif that we call a "redox tag." In order to describe modern radical-driven reactions involving SET processes, we focus on a classical formalism in which electrons are treated as particles rather than waves, which offers a practical yet powerful approach to explain and/or predict synthetic outcomes.

Heterogeneity of meroterpenoids arising from their dual biosynthetic origins is constantly provoking synthetic chemists to utilize their ingenuity and revise their retrosynthetic logic. By studying recent publications on meroterpenoid synthesis, tremendous advances in the field of synthetic organic chemistry can be witnessed. This minireview covers some of the most intriguing total syntheses and synthetic studies towards the meroterpenoid class of natural products from the last five years.

Biogenic amine organocatalysts have transformed the field of synthetic organic chemistry. Yet despite their use in synthesis and to label biomolecules in vitro, amine organocatalysis in vivo has received comparatively little attention – despite the potential of such reactions to be interfaced with living cells and to modify cellular metabolites. Herein we report that biogenic amines derived from L‐tyrosine catalyze the self‐aldol condensation of butanal to 2‐ethylhexenal – a key intermediate in the production of the bulk chemical 2‐ethylhexanol – in the presence of living Escherichia coli and outperform many amine organocatalysts currently used in synthetic organic chemistry. Furthermore, we demonstrate that cell lysate from E. coli and the prolific amine overproducer Corynebacterium glutamicum ATCC 13032 catalyze this reaction in vitro, demonstrating the potential for microbial metabolism to be used as a source of organocatalysts for biocompatible reactions in cells.

Due to the increasing relevance of fluorine-containing organic molecules in drug design, the synthesis of organofluorine compounds has gained high significance in synthetic organic chemistry. Trifluoromethylative difunctionalizations of carbon-carbon multiple bonds, with the simultaneous incorporation of a CF3 group and another functional element, have considerable potential. Because of the high importance of carbon-carbon bond-forming reactions in organic synthesis, carbotrifluoromethylations and, in particular, aryltrifluoromethylations or heteroaryltrifluoromethylations are considered to be increasing fields of synthetic organic chemistry. The aim of the current review is to summarize recent developments of aryltrifluoromethylation or heteroaryltrifluoromethylation reactions.

In recent years, the most significant development in the field of synthetic organic chemistry has been the application of biological systems to chemical reactions. Reactions catalyzed by enzymes and enzyme systems display far greater specificities than more conventional organic reactions. Biological and/or enzymatic syntheses and transformations, that is, “microbial transformations,” have great potential. Some of these reactions have already been shown to have useful applications in the fields of synthetic organic chemistry and biotechnology. This article reviews the current status of the rapidly developing field of microbial transformation, the methodology, available technological procedures, and fields of application being described especially in relation to conventional organic synthesis methods.

Heterocyclic nitrogen compounds, including fused 1,5-naphthyridines, have versatile applications in the fields of synthetic organic chemistry and play an important role in the field of medicinal chemistry, as many of them have a wide range of biological activities. In this review, a wide range of synthetic protocols for the construction of this scaffold are presented. For example, Friedländer, Skraup, Semmlere-Wolff, and hetero-Diels-Alder, among others, are well known classical synthetic protocols used for the construction of the main 1,5-naphthyridine scaffold. These syntheses are classified according to the nature of the cycle fused to the 1,5-naphthyridine ring: carbocycles, nitrogen heterocycles, oxygen heterocycles, and sulphur heterocycles. In addition, taking into account the aforementioned versatility of these heterocycles, their reactivity is presented as well as their use as a ligand for metal complexes formation. Finally, those fused 1,5-naphthyridines that present biological activity and optical applications, among others, are indicated.

Microwave-assisted organic reactions have been applied as an effective technique in organic synthesis. Microwave irradiation often leads to shorter reaction times, increased yields, easier workup, matches with green chemistry protocols, and can enhance the region and stereo selectivity of reactions. In fact, the high usefulness of microwave-assisted synthesis encouraged us to increase the efficiency of several organic transformations and synthesis. High-speed microwave-assisted chemistry has attracted a considerable amount of attention in recent years and has been applied successfully in various fields of synthetic organic chemistry, proteins, peptides, drug discovery, and green chemistry. The various roles of microwave-assisted organic chemistry in green and sustainable chemistry are discussed, beginning with the strategies, technologies, and methods that were employed routinely at the time of the first reports of microwave applications. Microwave processing has several advantages over conventional sintering/heating, such as the reduction in cycle time, energy efficiency, eco-friendliness, and providing finer microstructures, leading to improved mechanical properties. Herein, we also describe the evolution of the microwave and some early applications of microwave assistance in the biomolecular sciences and treatment of solid malignant tumors.

Manganese-catalyzed C–H activation has become an emerging area in organic chemistry. These efficient and eco-friendly manganese catalysed reactions provides new opportunities in the field of synthetic organic chemistry.