Contemporary Organic Chemistry Research Articles

1,2,3-Triazole Containing Hybrids as Potential Pharmacological Agents: A Review

1,2,3-Triazoles constitute a versatile class of nitrogen containing five-membered heterocycles, exhibiting wide range of pharmacological properties which include antibacterial, antifungal, anticancer, antimalarial, antidiabetic, anti-inflammatory, antihypertensive and antioxidant, among various others. Medicinal chemists have been interested in this aromatic ring as a framework since the inception of click chemistry as considered as the building block of contemporary organic chemistry. Extensive research into this framework’s linker characteristic has led to the synthesis and evaluation of numerous 1,2,3-triazole hybrids bearing a wide range of heterocyclic moieties as potential leads for various biological targets. This molecular hybridization has also added advantage of the improved pharmacological activity overcoming the problem of multiple drug resistance and reduced toxicity. This review summarizes the pharmacological activities of various 1,2,3-triazole containing hybrids and conjugates, covering articles published in past decade (2013 till date) and will be of great assistance to medicinal chemistry researchers in providing a useful direction for the future drug discovery.

The introduction of the disconnection approach into polymer synthesis

AbstractThe disconnection approach, a widely utilized method of design synthesis route, has played crucial roles in contemporary organic chemistry for decades. Here, we provide an introduction to the construction of polymer main chains. The implementation of the strategy hinges on determining where to disconnect based on the successful polymerization reaction in order to infer a suitable monomer. By investigating specific covalent bonds and structures in polymers, several specific linkers are highlighted to demonstrate how to design and synthesize polymer main chains using reverse thinking, thus inspiring those in polymer synthesis.

Copper-catalyzed carbonylative catenation of olefins: Direct synthesis of γ-boryl esters

<h2>Summary</h2> Carbonylation reactions have become an important part of contemporary organic chemistry, as they represent powerful methodologies for typically facilitating access to the core (CO)_n or (CH₂)_m building blocks with carbon monoxide as the C1 source. Here, we report a copper-catalyzed carbonylative catenation and borylation of olefins under mild conditions showing for the first time. In this procedure, two molecules of CO were regarded as the –CH₂CO– structure source. Direct carbonylative borofunctionalization of various β-substituted styrenes and alcohols leads to γ-boryl esters in high diastereomeric selectivity. Further synthetic transformations of the obtained γ-boryl esters have been developed as well. Mechanistic studies revealed that the –CH₂CO– block was derived from two molecules of CO, and a possible reaction pathway was proposed.

Updates on hypervalent-iodine reagents: metal-free functionalisation of alkenes, alkynes and heterocycles.

Hypervalent iodine (HVI) chemistry is a rapidly growing subdomain of contemporary organic chemistry because of its enormous synthetic applications. The high nucleofugality of the phenyliodonio group (-I+Ph) and its radical nature, serving as a single-electron oxidant makes HVI compounds highly valuable in organic synthesis. Due to the feasibility and benignity, reactions that rely solely on HVI reagents as promoters have received particular interest. Considering their great influence and synthetic potential, we contribute a brief synopsis on this field with a specific emphasis on metal-free functionalisations of alkenes, alkynes and heterocycles. The discussion is divided according to the type of substrate and reaction type and elaborated with mechanism and representative examples.

Impact of the boron substituent on the molecular structures and electronic properties of N-heterocycle-substituted indolylboranes

π-conjugated systems containing boron have emerged as exciting subjects in contemporary organic materials chemistry. A number of fascinating organoboron materials have been reported, however, knowledge of how the substituents on the boron affect electronic properties is inadequate. Herein, three new C, N chelates were designed, changing the substituent at boron led to the formation of tetra- and tri-coordinated systems that have distinct electronic structures and photophysical properties. The fluorophores containing different coordinate boron atom always exhibited distinctive optical properties, however, the exploration of the influence of the boron substituent on the molecular structures and electronic properties is inadequate. Herein, three new C, N chelates were designed, changing the substituent at boron led to the formation of tetra- and tri-coordinated systems that have distinct electronic structures and photophysical properties.

Synthesis of Pyrrolo[2,1‐a]isoquinoline Class of Natural Product Crispine A

AbstractAs a naturally occurring small‐molecule, various optical isomers of chiral pyrrolo[2,1‐a]isoquinoline alkaloid crispine A represent a potential class of chiral molecules in contemporary organic chemistry, and possess diverse biological activities. The range of pharmacological activities include antidepressant, antiplatelet, antileukemic, and anticancer activities. This review provides an overview of the literature on the strategies, employed in the synthesis of crispine A in their racemic and enantiopure forms via Bischler‐Napieralski cyclization, Pictet‐Spengler cyclization, N‐Alkylation/Acylation‐cyclization, Oxidative cyclization, and Asymmetric hydrogenation in the period of 1931–2021. This study accentuates the need for the developing more effective synthesis, and search for involved biological applications for the pyrroloisoquinoline class of natural product. Attention has been drawn towards the use of relatively less documented but easily accessible naturally occurring diastereomeric scaffolds namely, garcinia and hibiscus acids. These lactones obtained from (+)‐ and (−)‐2‐hydroxycitric acids bearing chemically amenable functional groups are investigated as an ideal choice for the enantiopure synthesis of the (−)‐(R)‐ and (+)‐(S)‐Crispine A structural frame work.

On-Surface Strain-Driven Synthesis of Nonalternant Non-Benzenoid Aromatic Compounds Containing Four- to Eight-Membered Rings.

The synthesis of polycyclic aromatic hydrocarbons containing various non-benzenoid rings remains a big challenge facing contemporary organic chemistry despite a considerable effort made over the last decades. Herein, we present a novel route, employing on-surface chemistry, to synthesize nonalternant polycyclic aromatic hydrocarbons containing up to four distinct kinds of non-benzenoid rings. We show that the surface-induced mechanical constraints imposed on strained helical reactants play a decisive role leading to the formation of products, energetically unfavorable in solution, with a peculiar ring current stabilizing the aromatic character of the π-conjugated system. Determination of the chemical and electronic structures of the most frequent product reveals its closed-shell character and low band gap. The present study renders a new route for the synthesis of novel nonalternant polycyclic aromatic hydrocarbons or other hydrocarbons driven by internal stress imposed by the surface not available by traditional approaches of organic chemistry in solution.

Reproducibility in Electroorganic Synthesis-Myths and Misunderstandings.

The use of electric current as a traceless activator and reagent is experiencing a renaissance. This sustainable synthetic method is evolving into a hot topic in contemporary organic chemistry. Since researchers with various scientific backgrounds are entering this interdisciplinary field, different parameters and methods are reported to describe the experiments. The variation in the reported parameters can lead to problems with the reproducibility of the reported electroorganic syntheses. As an example, parameters such as current density or electrode distance are in some cases more significant than often anticipated. This Minireview provides guidelines on reporting electrosynthetic data and dispels myths about this technique, thereby streamlining the experimental parameters to facilitate reproducibility.

Synthesis and structure of sodium 1-alkoxy-1,4-dioxo-2-alkenolates and bis-(4-alkyl(aryl)- 1-oxo-1-alkoxyalkane-2,4-dionato) metals (II) based on them

A priority task in contemporary organic chemistry consists in the synthesis of practically useful metal complexes having carbonyl-containing ligands. The present article details the isolation of several new bis-(4-alkyl(aryl)-1-oxo-1-alkoxyalkane-2,4-dionato) metals (II) via complex formation of metal salts of (zinc (II), copper (II) and nickel (II)) with sodium 1-alkoxy-1,4-dioxo-2-alkenolates obtained by condensation of alkyl (aryl) methyl ketones with dialkyl oxalates in the presence of sodium or sodium hydride as a condensing reagent. The structure of the synthesised sodium oxoenolates and metal complexes was confirmed by spectral analysis methods (IR, NMR 1 H-, NMR 13 C-spectroscopy and mass spectrometry). In the IR spectra of the solid samples of the isolated compounds, stretching vibrations bands of ester carbonyl groups were identified, as well as high-intensity ether bands due to the vibrations of С-О-С bonds. For compounds containing aromatic fragments, bands corresponding to vibrations of monosubstituted benzene rings were found in the IR spectra. The NMR spectra of 1 H of sodium oxoenolates and metal complexes recorded in DMSO-d 6 demonstrated characteristic signals of ethoxy and n - butoxy fragments, methine protons, as well as protons of aromatic rings. Chemical shifts of carbon atoms in the NMR spectra 13 C of sodium oxoenolates correspond well to the reference values. In the mass spectra of synthesised compounds recorded in electrospray mode, signals of protonated and cationised molecules were observed [M+H] + , [M+NH 4 ] + , [M+Na] + , [M+K] + . Using quantum chemical methods, the models of the obtained compounds were constructed along with a calculation of the formation energies and dissociation constants. Optimisation of the geometric parameters of the equilibrium states of sodium oxoenolate and metal complexes was carried out using the following two methods: density functional theory (DFT) and self-consistent field (SCF). The relative formation energies indicate high stability of the synthesised substances, while, according to the data obtained, copper complexes are characterised by greater stability in the gas phase as compared to zinc and nickel.

Tert-Butyl Nitrite (TBN), a Multitasking Reagent in Organic Synthesis.

The upsurge interest in the development of efficient methodologies for the construction of nitrogen-containing frameworks via the use of expedient reagents have been creating a renaissance in contemporary organic chemistry. In this perspective, tertbutyl nitrite (TBN) is an emerging building block. Due to its unique structural features, it shows differential reactivity under different reaction conditions. These diverse reactivities have resulted in the construction of a diverse array of complex N-containing molecules. The primary objective of the present review is to bring the latest findings of TBN in terms of its applications in reactions (oxidation, diazotization, nitrosation, nitration, oximation, N-synthon, and miscellaneous reactions) into the limelight. For simplicity and brevity, reactions in each section are explained with the mechanism of formation and selected examples are given.

A Study of Catalytic Oxidation of a Library of C₂ to C₄ Alcohols in the Presence of Nanogold.

The classical stoichiometric oxidation of alcohols is an important tool in contemporary organic chemistry. However, it still requires huge modifications in order to comply with the principles of green chemistry. The use of toxic chemicals, hazardous organic solvents, and the large amounts of toxic wastes that result from the reactions are a few examples of the problems that must be solved. Nanogold alone or conjugated with palladium were supported on different carriers (SiO2, C) and investigated in order to evaluate their catalytic potential for environmentally friendly alcohol oxidation under solvent-free and base-free conditions in the presence H2O2 as a clean oxidant. We tested different levels of Au loading (0.1–1.2% wt.) and different active catalytic site forms (monometallic Au or bimetallic Au–Pd sites). This provided new insights on how the structure of the Au-dispersions affected their catalytic performance. Importantly, the examination of the catalytic performance of the resulting catalysts was oriented toward a broad scope of alcohols, including those that are the most resistant to oxidation—the primary aliphatic alcohols. Surprisingly, the studies proved that Au/SiO2 at a level of Au loading as low as 0.1% wt. appeared to be efficient and prospective catalytic system for the green oxidation of alcohol. Most importantly, the results revealed that 0.1% Au/SiO2 might be the catalyst of choice with a wide scope of utility in the green oxidation of various structurally different alcohols as well as the non-activated aliphatic ones.

Luxury of N‐Tosylhydrazones in Transition‐Metal‐Free Transformations

AbstractThis review is focused on the recent developments in transition‐metal‐free transformations using N‐tosylhydrazones, emerging building blocks in contemporary organic chemistry. Emphasis is given to their synthetic potential, scope, mechanism and limitations. N‐Tosylhydrazones, derivatives of carbonyl compounds, can undergo a wide range of reactions under transition‐metal‐free reaction conditions. The chemical behaviour of tosylhydrazones is unique under different reaction conditions as they can act as diazo precursors, carbene sources, 1,3‐dipoles, ambiphilic reagents, one‐carbon synthons, and an alternative to the parent carbonyl compounds. These diverse reactivities have resulted in the development of novel C−C and C−heteroatom bond‐forming reactions. The potential of N‐tosylhydrazones in transition‐metal‐free reactions is evident from the synthesis of a handful of molecules such as cyclopropanes, di‐ and triarylmethanes, pyrazoles, triazoles, pyridazines, ethers, carbamates, thioacetals, thiadiazoles and many others.magnified image

Cyclopentyl Methyl Ether: An Elective Ecofriendly Ethereal Solvent in Classical and Modern Organic Chemistry.

Solvents represent one of the major contributions to the environmental impact of fine‐chemical synthesis. As a result, the use of environmentally friendly solvents in widely employed reactions is a challenge of vast real interest in contemporary organic chemistry. Within this Review, a great variety of examples showing how cyclopentyl methyl ether has been established as particularly useful for this purpose are reported. Indeed, its low toxicity, high boiling point, low melting point, hydrophobicity, chemical stability towards a wide range of conditions, exceptional stability towards the abstraction of hydrogen atoms, relatively low latent heat of vaporization, and the ease with which it can be recovered and recycled enable its successful employment as a solvent in a wide range of synthetic applications, including organometallic chemistry, catalysis, biphasic reactions, oxidations, and radical reactions.

Heterogeneous acidic catalysts for the tetrahydropyranylation of alcohols and phenols in green ethereal solvents

The application of heterogeneous catalysis and green solvents to the set up of widely employed reactions is a challenge in contemporary organic chemistry. We applied such an approach to the synthesis and further conversion of tetrahydropyranyl ethers, an important class of compounds widely employed in multistep syntheses. Several alcohols and phenols were almost quantitatively converted into the corresponding tetrahydropyranyl ethers in cyclopentyl methyl ether or 2-methyltetrahydrofuran employing NH4HSO4 supported on SiO2 as a recyclable acidic catalyst. Easy work up of the reaction mixtures and the versatility of the solvents allowed further conversion of the reaction products under one-pot reaction conditions.

Cu-Catalyzed Cascade Annulation of Diaryliodonium Salts and Nitriles: Synthesis of Nitrogen-Containing Heterocycles

Developing versatile methodologies to construct various nitrogen­-containing heterocycles is a crucially significant part of contemporary organic chemistry. This review summarizes recent developments on the formation of nitrogen-containing heterocycles triggered by diaryliodonium salts. Diaryliodonium salts, as electrophilic arylating agents in the presence of catalytic copper salts, can react with nitriles to give N-arylnitrilium cations, which are highly reactive species. These species can efficiently react with nucleophiles, including C-, N- and O-nucleophiles, to give the corresponding products. This strategy is not only efficient and convenient, but also enables the synthesis of diverse nitrogen-containing heterocycles such as quinolines, quinazolines, and phenanthridines.1 Introduction2 Strategies and Mechanisms3 Cascade Annulations3.1 Cascade Annulation of Diaryliodoniums, Nitriles and C-Nucleo­philes3.2 Cascade Annulation of Diaryliodoniums, Nitriles and N-Nucleo­philes3.3 Cascade Annulation of Diaryliodoniums, Nitriles and O-Nucleo­philes4 Summary and Outlook

George A. Olah (1927-2017).

George A. Olah (1927-2017).

ChemInform Abstract: Dimerization of Donor—Acceptor Cyclopropanes

AbstractReview: [20 refs.

Novel crown ether functionalized imidazolium-based acidic ionic liquid catalyzed synthesis of pyrazole derivatives under solvent-free conditions

An innovatively designed novel crown ether functionalized imidazolium-based reusable acidic ionic liquid [crown ether MIm] [HSO4] has been efficiently implemented for the synthesis of pyrazole derivatives using various substituted enaminones, hydrazine hydrate and phenyl hydrazine under solvent-free conditions. Structural novelty and task efficiency of the catalyst, high yields of desired products, greener approach attributing high atom economy and solvent-free conditions render this protocol suitable to cope with the current demand in contemporary organic chemistry. The inventive idea of utilizing crown ether functionalized ionic liquid as a catalyst was for the first time demonstrated in this protocol.

A bright outlook for carbon coupling

Dual Catalysis In contemporary organic chemistry, it is straightforward to forge bonds between unsaturated carbons (i.e., carbons already engaged in double bonds) using cross-coupling catalysis. The protocol runs into some trouble, however, if one or both starting carbon centers are saturated (purely single-bonded). Tellis et al. and Zuo et al. independently found that combining a second, light-activated catalyst with a nickel cross-coupling catalyst could achieve selective coupling of saturated and unsaturated reagents (see the Perspective by Lloyd-Jones and Ball). Their methods rely on single-electron transfer from the light-activated catalyst to the saturated carbon, thereby enhancing its reactivity more effectively than the two-electron mechanisms prevailing in traditional protocols. Science , this issue p. [433][1], p. [437][2]; see also p. [381][3] [1]: /lookup/volpage/345/433?iss=6195 [2]: /lookup/volpage/345/437?iss=6195 [3]: /lookup/volpage/345/381?iss=6195

Dual catalysis. Single-electron transmetalation in organoboron cross-coupling by photoredox/nickel dual catalysis.

The routine application of C(sp3)-hybridized nucleophiles in cross-coupling reactions remains an unsolved challenge in organic chemistry. The sluggish transmetalation rates observed for the preferred organoboron reagents in such transformations are a consequence of the two-electron mechanism underlying the standard catalytic approach. We describe a mechanistically distinct single-electron transfer-based strategy for the activation of organoboron reagents toward transmetalation that exhibits complementary reactivity patterns. Application of an iridium photoredox catalyst in tandem with a nickel catalyst effects the cross-coupling of potassium alkoxyalkyl- and benzyltrifluoroborates with an array of aryl bromides under exceptionally mild conditions (visible light, ambient temperature, no strong base). The transformation has been extended to the asymmetric and stereoconvergent cross-coupling of a secondary benzyltrifluoroborate.