Academic literature on the topic 'Heterocyclic Aromatic Systems'

Recently, we discovered that the delocalization of nitrogen lone-pair electrons (NLPEs) in five-membered nitrogen heterocycles created a second σ-aromaticity in addition to the prototypical π-aromaticity. Such dual-aromatic compounds, such as the pentazole anion, were proved to have distinct chemistry in comparison to traditional π-aromatics, such as benzene, and were surprisingly unstable, susceptible to electrophilic attack, and relatively difficult to obtain. The dual-aromatics are basic in nature, but prefer not to be protonated when confronting more than three hydronium/ammonium ions, which violates common sense understanding of acid−base neutralization for a reason that is unclear. Here, we carried out 63 test simulations to explore the stability and reactivity of three basic heterocycle anions (pentazole anion N5¯, tetrazole anion N4C1H1¯, and 1,2,4-triazole anion N3C2H2¯) in four types of solvents (acidic ions, H3O+ and NH4+, polar organics, THF, and neutral organics, benzene) with different acidities and concentrations. By quantum mechanical calculations of the electron density, atomistic structure, interatomic interactions, molecular orbital, magnetic shielding, and energetics, we confirmed the presence of dual aromaticity in the heterocyclic anions, and discovered their reactivity to be a competition between their basicity and dual aromaticity. Interestingly, when the acidic ions H3O+/NH4+ are three times more in number than the basic heterocyclic anions, the anions turn to violate acid−base neutralization and remain unprotonated, and the surrounding acidic ions start to show a significant stabilization effect on the studied heterocyclic anions. This work brings new knowledge to nitrogen aromatics and the finding is expected to be adaptable for other pnictogen five-membered ring systems.

The substitution of isoelectronic B–N units for C–C units in aromatic hydrocarbons produces novel heterocycles with structural similarities to the all-carbon frameworks, but with fundamentally altered electronic properties and chemistry. Since the pioneering work of Dewar some 50 years ago, the relationship between B–N and C–C and the wealth of parent all-carbon aromatics has captured the imagination of organic, inorganic, materials, and computational chemists alike, particularly in recent years. New applications in biological chemistry, new materials, and novel ligands for transition-metal complexes have emerged from these studies. This review is aimed at surveying activity in the area in the past couple of decades. Its organization is based on ring size and type of the all-carbon or heterocyclic subunit that the B–N analog is derived from. Structural aspects pertaining to the retention of aromaticity are emphasized, along with delineation of significant differences in physical properties of the B–N compound as compared to the C–C parent.Key words: boron-nitrogen heterocycles, aromaticity, organic materials, main-group chemistry.

The conjugated circuits model is applied to heterocycles containing divalent sulfur. A novel parametrization is introduced for 4n + 2 and 4n conjugated circuits containing a single sulfur atom. The relative aromatic stabilities of a number of heterocyclic systems containing divalent sulfur are studied. Comparison is made whenever possible with earlier reported resonance energies of these compounds, obtained by using Huckel MO and SCF π-MO models, and appropriate reference structures. Special attention is given to positional isomers. An explanation of the differences amongst such isomers is given.

The review surveys the reactions of electron-deficient azaaromatic compounds with mono- and bifunctional nucleophilies in which a nucleophilic attack at the unsubstituted CH carbon of an aromatic ring is one of the key steps. Use of the SNH methodology for the synthesis of fused heterocyclic systems by means of nucleophilic addition –addition AN–AN, addition –substitution of hydrogen AN–SNH, tandem substitution of hydrogen SNH–SNH, and other strategies will be discussed. Intramolecular SNH reactions will also be considered as effective synthetic tools to obtain condensed heterocyclic systems.

Two consecutive N-heterocyclic carbene (NHC) catalytic systems were combined in a one-pot cascade reaction for the assembly of aromatic aldehydes and 2-haloenals into a structurally complex γ-lactone backbone.

The halogenated derivatives of heterocyclic compounds (haloarenes) are highly utilized in many fields of chemistry, including drug discovery, medicinal, and material chemistry. There are a variety of ways to functionalize an aromatic system and introduce halogen substituent into the ring. However, electrophilic aromatic substitution (EAS) has been the focus of growing attention, particularly for electronrich substrates. Electrophilic aromatic bromination protocols are one of the most important electrophilic aromatic substitution reactions. However, preparation of bromoarenes classically recommends the use of highly oxidative agents along with utilizing various metal catalysts in a halogenated solvent. The corrosive and toxic nature of these reagents and need of harsh conditions for these protocols make their utility less desirable in current practice. Furthermore, lack of regioselectivity for most substituted aromatics is the other distinguished drawback, since most products contain ortho/para directors which afford a mixture of isomers. The innovation of our procedure for the bromination of various substituted aromatic compounds is twofold in that highly regiospecific para-bromination of activated aryls by treatment with NBS has been accomplished. Although various reaction mediums, such as cyclohexane, acetone, and acetonitrile has been used in this procedure, the significant high yields of the product formation along with the very short reaction times using acetonitrile make this approach more attractive. That this regiospecific p-substitution takes place under such mild conditions leads us to question whether it is EAS.

Heterocyclic synthesis via processes involving single electron transfer, namely aromatic SRN1 ,reactions and copper metal- and cuprous halide-promoted substitutions have been investigated. The cyclisation step in all the 'syntheses is effected by an intramolecular aromatic nucelophilic substitution on a halogen atom which is ortho to the side chain bearing the nucleophilic species (generally an amide or thioamide moiety). The process of entrainment has been shown to be a valuable technique for effecting reactions performed' under SRN1 conditions. The mechanisms of, and the mechanistic relationships between the substitution processes, were investigated using well documented diagnostic probes for the SRN1 reaction and by conducting series of experiments on simple reaction systems whose behaviour under SRN1 conditions was already known. Ring systems prepared by the methods noted above include benzoxazoles, benzothiazoles, 1 ,3-benzothiazines, indoles and a tricyclic system. Attempts to prepare seven-membered heterocycles by increasing the length of the side chain proved unsuccessful. When the side chain bears a carbonyl function adjacent to the aromatic ring, an intramolecular SNAr reaction takes place and cyclisation of N-(2-haloaroyl)-N'-phenylthioureas occurred under mild conditions. Quinazolinones and a 1 ,3-benzothiazinone have been synthesised in this manner which appears to have little precedent in the chemical literature. The preparation of seven-membered heterocycles by an SNAr cyclisation proved fruitless extension of the side chain length by one carbon atom (effected by the preparation of an N-cinnamoyl-N-phenylthiourea) resulted in the cyclisation of the side chain. Reaction of certain of the N,N-disubstituted thioureas with copper (1) iodide results in the formation of 2-halobenzanilides by a novel rearrangement.

Cette etude a ete faite pour demontrer l'efficacite des methodes d'optimisation et d'automatisation; elle a permis un gain de rendement de 36 points (de 41 a 77%) associe a une forte diminution de la duree globale de la reaction (76h a 2h30)

Benzophenone (BP) and substituted BPs constitute a major class of aromatic ketones and are of potential interest in various areas of excited state solution phase photochemistry and photobiology. High triplet state energy, faster rate of intersystem crossing (ISC) and higher triplet state quantum yield enables BP systems as potential photosensitizers via triplet energy transfer mechanism. The short lived triplet state of BP systems are highly reactive and acts as potential electron acceptor and interesting photochemical behavior have been observed for photoinduced electron transfer reactions in various solvent media, in particular for donor-bridgeacceptor (D-B-A) family. Though detailed spectroscopic studies of BP and substituted BP are documented, not much attention are given to its heterocyclic analogue. Substitution of aromatic ring carbon with one or more heteroatom (N and S) results in drastical change in photochemical properties and excited state reactivity. In solution phase and in nanosecond time domain heteroaromatic ketones form the triplet excited state that upon subsequent photoreactions, leads to formation of short lived species viz. radicals, ions and radical ions. Therefore exploring the trends in excited state reactivity with the variation with functional group and ring substitution and solvent medium is of considerable interest. The complete reaction mechanism of a photoreaction can be understood by studying reactivity of various short lived intermediates formed. In solution phase, the reactivity of a certain species or rate of a chemical reaction can be well understood by correlating to its structure. This approach requires accurate reproducible techniques for the excited state structural determination. Wide range of time resolved (TR) spectroscopies spanning over whole electromagnetic spectrum have been developed over decades and successfully applied to study excited state phenomena. In a typical two beam experiment, the pump pulse excites the molecular system to higher electronic state and the probe pulse records the spectrum of intermediate species at variable delay time with respect to the pump. The data from different TR techniques used to be complementary in nature and the combination helps in a deeper understanding of excited state reaction mechanism. Though time resolved absorption (TRA) is the most popular and oldest technique to study the excited state photoreactions, no structural information and the poor spectral resolution of the broad and overlapping absorption bands are the limitations towards predicting the reactive intermediates with accuracy. However time resolved resonance Raman (TR3) spectroscopy is a very sensitive technique to obtain vibrational structural information of short lived intermediates. The position and intensity of highly resolved Raman bands provide information about the structural and kinetics parameters respectively. From a set of Raman spectra along various delay time, structure of multiple intermediates evolved for parallel photoreactions can be predicted accurately. We have employed TRA, TR3 and density functional theoretical (DFT) calculation to address few fundamental questions about effect of solvent and ring substitution on the excited state structure and energetics of heterocyclic ketones, hence the reactivity. Comparing the experimental findings with the theoretical output not only makes the data more accurate but also several additional conclusions can be drawn that could not be performed only with the experimental modality. In chapter 1 of the thesis, we have presented a general summary of photophysical phenomena and measured properties and parameters of heterocyclic ketones. Typical photoreactions involving various related aromatic ketones obtained from literature are discussed. This is followed by a brief account of theory of resonance Raman spectroscopy and density functional theoretical calculation. The objectives of the present investigation are highlighted. The detailed assembly of experimental techniques employed for present investigation is discussed in chapter 2. The lasers, spectrometers, collection optics, detection systems and data collection and analysis procedures are briefly illustrated for individual set up. The theory of methods of DFT calculations is also discussed. The effect of substitution of N atom in the aromatic rings on excited state structure and reactivity (hydrogen abstraction reaction) for isomeric (2, 3, 4) benzoylpyridines (BzPy) in various solvents is studied using the above experimental and theoretical methodologies and is presented in Chapter 3. In neutral solvents viz. acetonitrile and carbon tetrachloride the photogenerated lowest triplet state (T1) is observed to be formed that follow monoexponetial decay. In the presence of hydrogen donating solvents like methanol and isopropanol the triplet state is found to undergo hydrogen abstraction reaction to form a ketyl radical and solvent radical. The lifetime and absorption and Raman features of triplet state and ketyl radicals are entirely different from each other and lack any overlapping characteristics. The observed enhanced reactivity of BzPy in comparison to BP is believed to be because of the introduction of the N hetero atom in one of the phenyl ring. From the theoretical data, it was clear that more planarity is attained in case of BzPy as compared to BP and contributes to the enhanced reactivity. The spin density calculation shows that one third of the spin is localized in the phenyl ring in case of BP. The total spin density on Phenyl ring is 0.62 and on carbonyl group is 1.45. In case of BzPy the spin density on phenyl ring is 0.45 and on carbonyl group is 1.59. This indicates that in the excited state the spin is localized more on the carbonyl group. Also from charge density calculation using DFT it is clear that in the triplet state of BzPy the oxygen atom of C=O group is more positive than in case of BP which makes it more electrophilic. Among the three isomeric BzPy the trend in charge density is dependent on the position of nitrogen and found to be in the order of 2-BzPy>3-BzPy>4-BzPy. This can be explained on the basis of -I and –M effect of N atom and the extent depends on its position. So the trend for case of photoreduction follows the order 2-BzPy>3-BzPy>4-BzPy. The hydrogen abstraction reaction used to be considerably fast that produces a substrate ketyl radical and solvent radical (donor radical). These radicals further can dimerise to form various photoproducts viz. Pinacols or can form a stable complex between them. The fate of the radicals formed as a result of hydrogen abstraction of 4-BzPy and the accurate characterization of the adduct is explained in Chapter 4. In the present case the cross coupling reaction of the radicals is observed at longer delay time to form a light absorbing transient (LAT) which is the dominant pathway over other parallel reactions. The exact position of the donor radical in the complex is predicted by correlating the experimental Raman bands and theoretically obtained structural parameters and vibrational frequency. The adduct formed as a result of cross coupling reaction was identified as p-LAT, 2-[4-(hydroxylpyridylmethylene)cyclohexa-2,5dienyl]propan-2-ol. In case of benzoylthiophenes (BzTh), the effect of substitution of S atom on the excited state structure and reactivity towards various hydrogen donors viz. phenol and indole in different solvents are presented in Chapter 5. The difference in rate and mechanism of photoreaction for both the hydrogen donors are compared. For TPK the T1 state is of ππ* character and the T2 state is of nπ* character as is confirmed by flash photolysis and low temperature phosphorescence spectra in EPA matrix. The CO bond length for the triplet state species is more than that of ground state. In case of the ππ* triplet prominent structural changes in thienyl ring are observed and the phenyl ring remains much unaltered. The reaction of the triplet state species with phenol in two different solvents shows a relatively faster rate of reaction. If only ππ* triplet has been taking part in reaction, it might have resulted in slow reaction rate. Because the reaction rate is fairly high, It is concluded that not only ππ* triplet is involved in reaction but there is a contribution from the little higher energy T2 state having nπ* character. The reactivity trends towards hydrogen transfer reaction for three isomeric dithienyl ketones with respect to the position of heteroatoms in the ring are presented in Chapter 6. Energetically close lying (ππ* and nπ*) triplet states are observed to undergo state switching with the change in position of heteroatom in the ring and thus define the characteristics of the triplet state and plays important role in predicting the reactivity trend. Brief summary of the present investigation along with important possible extensions of the present work in described in Chapter 7.

Benzophenone (BP) and substituted BPs constitute a major class of aromatic ketones and are of potential interest in various areas of excited state solution phase photochemistry and photobiology. High triplet state energy, faster rate of intersystem crossing (ISC) and higher triplet state quantum yield enables BP systems as potential photosensitizers via triplet energy transfer mechanism. The short lived triplet state of BP systems are highly reactive and acts as potential electron acceptor and interesting photochemical behavior have been observed for photoinduced electron transfer reactions in various solvent media, in particular for donor-bridgeacceptor (D-B-A) family. Though detailed spectroscopic studies of BP and substituted BP are documented, not much attention are given to its heterocyclic analogue. Substitution of aromatic ring carbon with one or more heteroatom (N and S) results in drastical change in photochemical properties and excited state reactivity. In solution phase and in nanosecond time domain heteroaromatic ketones form the triplet excited state that upon subsequent photoreactions, leads to formation of short lived species viz. radicals, ions and radical ions. Therefore exploring the trends in excited state reactivity with the variation with functional group and ring substitution and solvent medium is of considerable interest. The complete reaction mechanism of a photoreaction can be understood by studying reactivity of various short lived intermediates formed. In solution phase, the reactivity of a certain species or rate of a chemical reaction can be well understood by correlating to its structure. This approach requires accurate reproducible techniques for the excited state structural determination. Wide range of time resolved (TR) spectroscopies spanning over whole electromagnetic spectrum have been developed over decades and successfully applied to study excited state phenomena. In a typical two beam experiment, the pump pulse excites the molecular system to higher electronic state and the probe pulse records the spectrum of intermediate species at variable delay time with respect to the pump. The data from different TR techniques used to be complementary in nature and the combination helps in a deeper understanding of excited state reaction mechanism. Though time resolved absorption (TRA) is the most popular and oldest technique to study the excited state photoreactions, no structural information and the poor spectral resolution of the broad and overlapping absorption bands are the limitations towards predicting the reactive intermediates with accuracy. However time resolved resonance Raman (TR3) spectroscopy is a very sensitive technique to obtain vibrational structural information of short lived intermediates. The position and intensity of highly resolved Raman bands provide information about the structural and kinetics parameters respectively. From a set of Raman spectra along various delay time, structure of multiple intermediates evolved for parallel photoreactions can be predicted accurately. We have employed TRA, TR3 and density functional theoretical (DFT) calculation to address few fundamental questions about effect of solvent and ring substitution on the excited state structure and energetics of heterocyclic ketones, hence the reactivity. Comparing the experimental findings with the theoretical output not only makes the data more accurate but also several additional conclusions can be drawn that could not be performed only with the experimental modality. In chapter 1 of the thesis, we have presented a general summary of photophysical phenomena and measured properties and parameters of heterocyclic ketones. Typical photoreactions involving various related aromatic ketones obtained from literature are discussed. This is followed by a brief account of theory of resonance Raman spectroscopy and density functional theoretical calculation. The objectives of the present investigation are highlighted. The detailed assembly of experimental techniques employed for present investigation is discussed in chapter 2. The lasers, spectrometers, collection optics, detection systems and data collection and analysis procedures are briefly illustrated for individual set up. The theory of methods of DFT calculations is also discussed. The effect of substitution of N atom in the aromatic rings on excited state structure and reactivity (hydrogen abstraction reaction) for isomeric (2, 3, 4) benzoylpyridines (BzPy) in various solvents is studied using the above experimental and theoretical methodologies and is presented in Chapter 3. In neutral solvents viz. acetonitrile and carbon tetrachloride the photogenerated lowest triplet state (T1) is observed to be formed that follow monoexponetial decay. In the presence of hydrogen donating solvents like methanol and isopropanol the triplet state is found to undergo hydrogen abstraction reaction to form a ketyl radical and solvent radical. The lifetime and absorption and Raman features of triplet state and ketyl radicals are entirely different from each other and lack any overlapping characteristics. The observed enhanced reactivity of BzPy in comparison to BP is believed to be because of the introduction of the N hetero atom in one of the phenyl ring. From the theoretical data, it was clear that more planarity is attained in case of BzPy as compared to BP and contributes to the enhanced reactivity. The spin density calculation shows that one third of the spin is localized in the phenyl ring in case of BP. The total spin density on Phenyl ring is 0.62 and on carbonyl group is 1.45. In case of BzPy the spin density on phenyl ring is 0.45 and on carbonyl group is 1.59. This indicates that in the excited state the spin is localized more on the carbonyl group. Also from charge density calculation using DFT it is clear that in the triplet state of BzPy the oxygen atom of C=O group is more positive than in case of BP which makes it more electrophilic. Among the three isomeric BzPy the trend in charge density is dependent on the position of nitrogen and found to be in the order of 2-BzPy>3-BzPy>4-BzPy. This can be explained on the basis of -I and –M effect of N atom and the extent depends on its position. So the trend for case of photoreduction follows the order 2-BzPy>3-BzPy>4-BzPy. The hydrogen abstraction reaction used to be considerably fast that produces a substrate ketyl radical and solvent radical (donor radical). These radicals further can dimerise to form various photoproducts viz. Pinacols or can form a stable complex between them. The fate of the radicals formed as a result of hydrogen abstraction of 4-BzPy and the accurate characterization of the adduct is explained in Chapter 4. In the present case the cross coupling reaction of the radicals is observed at longer delay time to form a light absorbing transient (LAT) which is the dominant pathway over other parallel reactions. The exact position of the donor radical in the complex is predicted by correlating the experimental Raman bands and theoretically obtained structural parameters and vibrational frequency. The adduct formed as a result of cross coupling reaction was identified as p-LAT, 2-[4-(hydroxylpyridylmethylene)cyclohexa-2,5dienyl]propan-2-ol. In case of benzoylthiophenes (BzTh), the effect of substitution of S atom on the excited state structure and reactivity towards various hydrogen donors viz. phenol and indole in different solvents are presented in Chapter 5. The difference in rate and mechanism of photoreaction for both the hydrogen donors are compared. For TPK the T1 state is of ππ* character and the T2 state is of nπ* character as is confirmed by flash photolysis and low temperature phosphorescence spectra in EPA matrix. The CO bond length for the triplet state species is more than that of ground state. In case of the ππ* triplet prominent structural changes in thienyl ring are observed and the phenyl ring remains much unaltered. The reaction of the triplet state species with phenol in two different solvents shows a relatively faster rate of reaction. If only ππ* triplet has been taking part in reaction, it might have resulted in slow reaction rate. Because the reaction rate is fairly high, It is concluded that not only ππ* triplet is involved in reaction but there is a contribution from the little higher energy T2 state having nπ* character. The reactivity trends towards hydrogen transfer reaction for three isomeric dithienyl ketones with respect to the position of heteroatoms in the ring are presented in Chapter 6. Energetically close lying (ππ* and nπ*) triplet states are observed to undergo state switching with the change in position of heteroatom in the ring and thus define the characteristics of the triplet state and plays important role in predicting the reactivity trend. Brief summary of the present investigation along with important possible extensions of the present work in described in Chapter 7.

<p>Neurological disorders are a major public health concern due to prevalence, severity of symptoms, and impact on caregivers and economic losses. While genetic susceptibility likely has a role in most cases, exposure to toxicants can lead to neurotoxicity, including potentially developmental origins of adult disease or increased risk of disease onset. These exposures are not necessarily large, acute exposures, but could accumulate, with a chronic low-dose exposure, causing toxicity. This research focuses on the potential neurotoxicity of two classes of dietary toxins/toxicants, heterocyclic aromatic amines (HAAs) and per- and polyfluoroalkyl substances (PFAS). HAAs, such as PhIP, harmane, and harmine, are formed in charred or overcooked meat, coffee, tobacco, and other foods. PFAS are largely used in making household materials, but are found in small amounts in eggs and dairy products and largely in contaminated water. While these two classes are diverse in terms of structure, common neurotoxic targets and mechanisms often exist. Therefore, we tested the effects of these chemicals on cell viability and neurotoxicity. In the first aim, we aimed to elucidate the mechanism of toxicity of harmane and harmine, focusing on their ability to cause mitochondrial dysfunction. The second aim was to determine the effects of either harmane or PhIP on the nigrostriatal motor systems and motor function of rats and mice, respectively. The third aim determined the effects of PFAS on neurodevelopment of Northern leopard frogs, focusing on changes in neurotransmitter levels and accumulation in the brain. Harmane did not cause motor dysfunction, but potentially affected the nigro-striatal motor system in an age- or sex-dependent manner. PhIP had differential effects on dopamine levels over time and caused motor dysfunction after subchronic exposure in mice. Perfluorooctane sulfonate (PFOS) accumulated in the brains of frogs and PFAS caused changes in neurotransmitter levels that were dose- and time-dependent. Overall, this research shows that toxins/toxicants humans are exposed to over their whole lives through their diet and contaminated water can cause neurotoxicity, potentially leading to or increasing risk of disease states. </p>

AbstractAzaborines (or borazines) represent an interesting class of heterocycles incorporating a boron–nitrogen structural motif within an aromatic ring system. This creates a system that is isosteric to traditional all-carbon ring systems, as the lone pair on nitrogen can donate into the empty orbital at boron to afford aromatic properties. Reviewed herein are synthetic strategies to access mono- and bicyclic azaborine cores, along with subsequent functionalization strategies, some of which are uniquely applicable due to the inherent dipole imparted on these ring systems.

Diazine alkaloid (pyridazine, pyrimidine and pyrazine) scaffold, a widespread two-nitrogen containing compounds in nature (DNA, RNA, flavors, and fragrances), constitutes a central building block for wide range of pharmacological applications. Diazines are reported to exhibit antimetabolite (antifolate and), anticancer, antibacterial, antiallergic, tyrosine kinase, antimicrobial, calcium channel antagonistic, anti-inflammatory, analgesic, antihypertensive, antileishmanial, antituberculostatic, anticonvulsant, diuretic and potassium-sparing, to antiaggressive activities. Pyridazine (1,2-diazine), pyrimidine (1,3-diazine) and pyrazine (1,4-diazine) are found as mono-systems, fused or annulated in pharmaceutical, agrochemical or materials. These six-membered heterocyclic aromatic moieties defined as privileged scaffolds constitute diverse chemical structures and as such hold substantial interest for organic, medicinal and biological chemists. This chapter will focus on elaboration of the different synthetic approaches applied in preparing pharmacologically active decorated diazines with special care on pyrimidines (non-fused substituted forms) that are endowed with clinical applications. Synthetic approaches applied in preparing selected FDA approved drugs with pyrimidine as a central unit bearing different substituents will be intensively explored. Special attention will be given to novel synthetic methodologies that served molecules with improved druglikeness and ADME-Tox properties.

This paper aims to analyze and systematize aspects of coordination chemistry of nitrones and the field of application of coordination compounds based of nitrones. Nitrones as a class of organic compounds have been known for a long time. They are used in organic synthesis as starting materials for acyclic compounds and as «spin trapping agents» for studying various processes in biological systems. A significant amount of nitrone derivatives has pharmacological activity and is a part of some drugs. The high electron density on the oxygen atom of the nitronе group promotes the formation of coordination compounds. This property of nitrones is widely used to influence their reactivity. Nitrones can also be potential corrosion inhibitors due to their ability to form stable complexes. But the coordination chemistry of this class of compounds remains poorly studied. The literature describes coordination compounds of metals with aliphatic, six-membered aromatic and some heterocyclic compounds. Analysis of the literature showed that nitronе-based coordination compounds attract considerable attention with their useful properties, in particular: they can affect the passage of 1,3-dipolar cycloaddition reactions, act as catalysts in Heck, Kumada and ketone hydrogenation reactions, show antitumor activity against HepG2 cells. The wide range of applications of coordination compounds of nitrones and their small number indicate the ability to generate a significant number of new compounds with new properties.

Pyrazoles have a wide range of applications in medicinal chemistry, drug discovery, agrochemistry, coordination chemistry, and organometallic chemistry. Their popularity has skyrocketed since the early 1990s. Basically, Pyrazole (C3H3N2H) is a simple doubly unsaturated five membered heterocyclic aromatic ring molecule comprising two nitrogen (N) atoms at positions 1- and 2- and three carbon (C) atoms. Pyrazole nucleus is synthesized with various strategies such as multicomponent approach, dipolar cycloadditions, cyclocondensation of hydrazine with carbonyl system, using heterocyclic system and multicomponent approach. A special emphasis is placed on a thorough examination of response processes. Furthermore, the reasons for the increasing popularity of pyrazoles in several fields of science are examined. Pyrazoles have recently been the focus of many techniques, mostly because of how frequently they are used as scaffolds in the synthesis of bioactive chemicals and reactions in various media. The goal of this chapter is to discuss the current developments in synthetic techniques and biological activity related to pyrazole derivatives. The many pharmacological functions of the pyrazole moiety and different synthesis techniques were discussed. This chapter has summarized novel strategies and wide applications of pyrazole scaffold.