Showing papers in "Current Organic Chemistry in 2022"

Recent Advances in Utilization of Deep Eutectic Solvents: An Environmentally Friendly Pathway for Multi-component Synthesis

Abstract: With the increasing analysis of saving environment, the researchers demonstrated much effort to replace toxic chemicals with environmentally benign ones. Eutectic mixtures are those solvents that fulfill the criteria of green solvents. The synthesis of organic compounds in the chemical and pharmaceutical industries makes it necessary to find unconventional solvents that cause no harmful impact on health parameters. This review showed that using deep eutectic mixture-based solvents to overcome the hazardous effects of harmful volatile organic solvents over the past few years has gained much more appeal. In most applications, deep eutectic mixtures aRecent Advances in Utilization of Deep Eutectic Solvents: An Environmentally Friendly Pathway for Multi-component Synthesisre used for a solvent or co- solvent role, as they are easy to use, easy dissolution of reactants, and non-evaporative nature. However, deep eutectic mixtures have also been investigated as catalysts, and this dual functionality has much scope in the future, as a significantly less range of deep eutectic mixtures is utilized for this.

Synthesis of Benzalacetophenone Based Isoxazoline and Isoxazole Derivatives

Abstract: The demand for natural product based drugs with less cost and efficient procedures has become a challenge to researchers. Benzalacetophenone is a natural product based species that is modified into numerous heterocyclic compounds including isoxazoline and isoxazole derivatives. The utility of isoxazoline and oxazole derivatives has been increased for the synthesis of the new and effective chemical entities to serve medicinal chemistry in the past few years. Isoxazoline and isoxazole are fascinating classes of heterocyclic compounds, which belong to N- and O-heterocycles, and are widely used as precursors for the development of drugs. This review highlights the recent work for the synthesis of mono and bis isoxazoline and isoxazole derivatives using stable benzalacetophenone and functionalization of isoxazoline and isoxazole, along with the prevailing biological properties.

Recent Advances in the Synthesis of Benzothiazole and its Derivatives

Abstract: Abstract: Benzothiazoles have recognized pharmacophores in the field of research, predominantly in synthetic and medicinal chemistry, on account of their significant pharmaceutical properties. This important class of derivatives endows an extensive range of biological activities like anti-inflammatory, antidiabetic, anticancer, anticonvulsant, antibacterial, antiviral, antioxidant, antituberculosis, enzyme inhibitors, etc. Hence, various methodologies have been accomplished to synthesize benzothiazole compounds considering the purity, yield, and selectivity of the products. This review provides different reaction methods that are involved in the synthesis of a variety of benzothiazole derivatives.

p-Coumaric acid: A naturally occurring chemical with potential therapeutic applications

Abstract: Coumaric acid is a hydroxy derivative of cinnamic acid with three different isomers (ortho, meta and para). Its most commonly available form is p-coumaric acid. p-Coumaric acid i.e., 4-hydroxycinnamic acid is a potent phenolic compound found to exist naturally in various plants, cereals, fruits and vegetables. It is one of the major constituent compounds of phenolic polymer lignin in lignocellulosic materials. Various natural and synthetic derivatives of p-coumaric acid have been reported in the literature. Different extraction methods including conventional methods such as solvent extraction, acidification, alkaline extraction etc. and recent approaches such as the clip-off method, sugaring out method, soft microwave extraction etc. for its qualitative and quantitative determination in various plant materials have been investigated by various researchers. This paper has discussed the synthesis of various derivatives of p-coumaric acid such as amides, esters, aldehydes, polymers, and copolymers. p-Coumaric acid and its derivatives have been found to possess different bioactive properties such as antioxidant, antimicrobial, anticancer, anti-arthritic, anti-inflammatory, gout prevention, anti-diabetic, anti-melanogenic, skin regeneration, gastroprotective, anti-ulcer, cardioprotective, hepatoprotective, reno-protective, bone formation, anti-angiogenic and anti-platelet etc. Owing to this huge bioactive potential, p-coumaric acid could be incorporated in edible food products, pharmaceutical products, cosmetics, etc. More studies are required to evaluate their compatability in these products. To the best of our knowledge, this is the first review discussing natural occurrence, extraction, natural derivatives, synthesis of various derivatives and therapeutic applications of p-coumaric acid

Recent Advances in Pinacol Rearrangement

Abstract: A pinacol rearrangement is a well-known reaction by which a 1,2-diol is converted to a carbonyl compound through an acid-catalyzed dehydration followed by a 1,2-migration of one of the neighboring substituents. Due to the particular abilities in installing polycyclic skeletons, quaternary carbon centers, and spirocyclic cores, the pinacol rearrangement reaction is a powerful and effective means of forming carbonyl functional groups in a variety of different molecules. Moreover, the substrates with an alkene group , a furan ring or alkyl chain tethered between the two diols have also been investigated as the expansion of pinacol rearrangement. Benefiting from the continuous development of the catalysis methodologies, pinacol rearrangements demonstrate synthetic utility in the preparation of natural products, bioactive molecules, and other functionally useful compounds. In this review, we discuss recent advances in the development of pinacol rearrangement and extended pinacol rearrangement reactions catalyzed by Brønsted acid, Lewis acid, and heterogeneous catalysts. In addition, we summarize several examples use pinacol rearrangements used in the synthesis of natural products and other valuable molecules.

Synthetic Utility of Aminomercapto[1,2,4]triazoles in the Preparation of Fused Triazoles

Abstract: Triazoles and their fused derivatives are regarded as one of the most pharmacologically significant pillars due to their potent, broad and numerous activities. This current review presents recent progress in the synthetic utility of 3-substituted-4-amino-5-mercapto[1,2,4]triazoles as building blocks for a diverse range of fused [1,2,4]triazoles with pharmacological interest eg. pyrazolo-triazoles, triazolo-thiadiazoles, triazolo-triazoles, triazolo-thiadiazines, triazolo-triazines, triazolo-tetrazines, triazolo-thiadiazepines, and others. The biological activity of some triazoles and their fused derivatives are also presented. This suggests that triazoles can be particularly promising synthons in synthesis of functionalized heterocyclic compounds used in the design of novel highly effective pharmaceuticals with a broad spectrum of bioresponses. All of these topics are drawn in this review during the period from 2000 to 2020.

New Trends in 1,4-Dipolar Cycloaddition Reactions. Thermodynamic Control Synthesis of Model 2'-(isoquinolin-1-yl)-spiro[oxindole-3,3'-pyrrolines]

Abstract: A direct synthesis of functionalized spiro[oxindole-3,3'-pyrrolines] is achieved via thermodynamic control (~60 oC), three-component 1,4-dipolar cycloaddition reaction involving 3-phenylimidazo[5,1-a]isoquinoline, dimethyl acetylenedicarboxylate and N-alkylisatins. Methods: Conversely, this one-pot reaction furnished, upon conduction at 25–38 oC, the expected 1,3-oxazepino[7,6-b]indoles as the main kinetic control products. The calculated energy of the optimized molecular structures of model spiro-oxindole and its isomeric oxazepino-indole indicate that spiro-oxindole is more stable by 76.1 kJ/mol. The structures of the synthesized spiro adducts were evidenced from NMR and MS spectral data and further confirmed by single-crystal X-ray diffraction. Characteristic features of the spiro-oxindoles are displaced in their 13C-spectra as diagnostic signals at ~53 and ~70 ppm assigned, respectively, to the spiro carbon-3 and sp3 CH-2' of the pyrroline ring. This unprecedented thermally induced pathway in 1,4-dipolar cycloaddition, utilizing imidazo[5,1-a]isoquinoline and related congeners would serve as a new route towards the synthesis of spiro[oxindole-3,3'-pyrrolines] that is a class of diverse biological activities. An insight into the thermodynamic control pathway is presented.

Application of Multi-component Reaction in the Synthesis of Heterocyclic [3.3.3] Propellane Derivatives

Abstract: Propellanes and derivatives have attractive properties due to their unique structure. Therefore, [3.3.3] propellanes, containing tricyclic structures with one of the carbon-carbon bonds common in three rings, were used in natural products, pharmaceutical compounds, and heterocyclic compounds, which were biologically important. The various multi-component reactions were applied in the synthesis of propellanes, which were highlighted throughout this review

Synthesis of spiropyrazoles under organic and nonorganic catalysis

Abstract: Spiropyrazoles display many biological biological activities such as antitumor, vasodilation, analgesic, phosphodiesterase inhibitors, aldosterone antagonistic, anabolic, androgenic, anti-inflammatory, progestational and salt-retaining activities and they also exert neuroprotection in dopaminergic cell death. Many efforts have been made to obtain these derivatives with high yield and excellent regio-, diastereo- and enantioselectivities. Most of the spiroprazole synthesis methods were proceeded in good to excellent yield in the presence of organic catalysts as for examples squaramide, NHC pre-catalyst, pyrrole derivatives, bis-oxazoline, DMAP, DABCO, thiourea derivatives, DBU, acetic acid and quinoline catalysts. In addition, the inorganic and organo-metallic catalysts have been proven their efficiency in synthesis of various types of spiro-pyrazoles in excellent yield. Thus, in this review we have compiled all citations for the synthesis of spiropyrazoles in the presence of various types of catalysts such as organic, inorganic, and metalorganic catalysts in the range 2020 to 2012. This review article is a useful compilation for researchers interested in the synthesis of spiropyrazole derivatives and will assist them in selecting appropriate catalysts for preparation of their spiropyrazoles.

An Expeditious Synthesis of Ethyl-2-(4-(arylmethylene)-5-oxo-4,5-dihydroisoxazol-3-yl)acetate Derivatives

Abstract: In this contribution, an operationally simple and efficient synthetic procedure for synthesizing derivatives of 4-(arylmethylene)-5-oxo-4,5-dihydroisoxazol-3-yl)acetate has been developed. This interesting synthetic protocol involves the one-pot cyclocondensation of diethyl 3-oxopentanedioate, aryl or heteroaryl aldehydes, and hydroxylamine hydrochloride catalyzed in an aqueous medium using an azolium salt as a robust organo-catalyst. In this work, for the first time, 1,3-dibenzyl-1H-benzo[d]imidazol-3-ium chloride was used as the catalyst for the synthesis of ethyl-2-(4-(arylmethylene)-5-oxo-4,5-dihydroisoxazol-3-yl)acetate derivatives from the commercially available starting materials. Notably, no by-products were observed during the multicomponent reaction. Optimization studies revealed that 5 mol% of 1,3-dibenzyl-1H-benzo[d]imidazol-3-ium chloride is sufficient to perform the experiment. Furthermore, examining the results of the temperature conditions showed that 70 ºC is the best temperature to carry out the reaction. In an optimization study, H2O was the most effective solvent to perform the three-component cyclization reaction. In this method, using H2O as the environmentally benign and inexpensive reaction medium, so from the point of view of the reaction medium, it can be said that this three-component heterocyclization obeys the principles of green chemistry. This procedure has several advantages, such as good to excellent yields, reasonable reaction times, isolation of heterocyclic products without column chromatography or other chromatographic methods, atom-economy, step-economy, and clean reaction profiles. Isoxazole-5(4H)-ones are the significant class of isoxazoles, which are used in nonlinear optical materials, filter dyes, molecular devices, and solar cells. Several structures of isoxazole-5(4H)-ones displayed eye-catching biological properties. On the other hand, azolium salts as important nitrogen-containing heterocycles are quaternary ammonium compounds with acidic hydrogen at 2-position, which are used as precursors for N-heterocyclic carbene (NHC) synthesis and also act as the catalyst in organic reactions. This procedure has several further advantages, such as good to excellent yields, reasonable reaction times, isolation of heterocyclic products without column chromatography or other chromatographic methods, atom-economy, step-economy, and clean reaction profiles. The heterocyclic products characterized using NMR and elemental analysis.

An overview of recent advances in isatin-based multicomponent reactions

Abstract: Isatin has been widely deployed in multicomponent reactions to prepare diverse heterocyclic compounds, which have garnered the attention of organic chemists considering their anti-inflammatory, anti-microbial, and antiviral activities, among others. This review discusses the applications of isatin in multicomponent reactions from 2019 to 2022. Isatin has been used as a raw material in multicomponent reactions due to its diverse biological and therapeutic activities. This overview may help stimulate the readers to exploit such convergent strategies in their synthetic endeavors.

Carboxylation of Alkenes and Alkynes Using CO2 as a Reagent: An Overview

Abstract: : CO 2 fixation reactions are of paramount interest both from economical and environmental perspectives. As an abundant, non-toxic, and renewable C1 feedstock, CO 2 can be utilized for the synthesis of fuels and commodity chemicals under elevated reaction conditions. The major challenge in the CO 2 utilization reactions is its chemical inertness due to high thermodynamic stability and kinetic barrier. The carboxylation of unsaturated hydrocarbons with CO 2 is an important transformation as it forms high-value reaction products having industrial as well as medicinal importance. This mini-review is mainly focused on the recent developments in the homogeneously and heterogeneously catalyzed carboxylation of alkenes and alkynes by using carbon dioxide as a reagent. We have highlighted various types of carboxylation reactions of alkenes and alkynes involving different catalytic systems, which comprise mainly C-H bond activation, hydrocarboxylation, carbocarboxylation, heterocarboxylation, and ring-closing carboxylation, including visible-light assisted synthesis processes. The mechanistic pathways of these carboxylation reactions have been described. Moreover, challenges and future perspectives of these carboxylation reactions are discussed.

Recent Advancements in Development of Radical Silylation Reactions.

Abstract: Transition metal-free radical hydrosilylation of alkynes and factionalized alkenes to vinylsilanes, organosilanes from alkenes, radical silylative cyclizations for sila heterocycles, aromatic dehydrogenative radical silylation, sila-amino acids, silyl hydroperoxides by using transition metal-free reaction conditions such as peroxides, photocatalyst, hydrogen atom transfer catalyst, radical initiators have become one of the most important and useful methodologies for the construction of C-Si bonds for their synthetic applications. In order to demonstrate the growth in this area, this review highlights the last twenty years of success in the fields of silylation of aromatics, silylative cyclizations of sila heterocycles, synthesis of vinylsilanes by hydrosilylation of alkynes, and functionalized alkenes, organosilanes from alkenes and dehydrogenative approaches for vinylsilanes involving radical mechanisms. We believe that summarizing these methods would be very useful for the chemists who are interested in the synthesis of organosilicon compounds for drug discovery or the development of silicon-based materials for industrial applications.

Super Base Derived Ionic Liquids: A Useful Tool in Organic Synthesis

Abstract: Over the last few decades, ionic liquids have been raised as a great appliance to pursue many organic transformations. In the present research, the synthetic application of ILs has emerged largely as solvents, additives, or catalysts. With the developing commercial methods, task-specific ionic liquids have been constructed by appointing guanidine, amidine and other superbasic cations. By the nature of the cation or the anion, the properties of the ionic liquids can be adjusted. In this regard, superbasic ionic liquids have been derived from both acyclic and cyclic guanidine or amidine derivatives. In particular, some common super bases such as 1,1,3,3-tetramethylguanidine (TMG), 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD), 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 1,5-diazabicyclo[4.3.0]non-5-ene (DBN), are used to design these special type of ionic liquids. These superbasic ionic liquids have shown a potential activity to accelerate many organic transformations including alcoholysis, esterification, multi-component reaction, Knoevenagel reaction, Michael addition, cyclization, etc. Additionally, because of their novel properties including high liquid range, nonvolatility, high thermal and chemical stability, these classic ionic liquids have a potential environmental impact and they are often found to play a promising role in the field of catalysis, electrochemistry, spectroscopy, and materials science. Not only that, the application of superionic liquids has been widely spread in the industrial and research area, especially, for the chemical transformation of CO2. This review aims to portray an outlook on the organic syntheses that have been promoted by superionic liquids in the last five years.

4-Aminocoumarin derivatives as multifaceted building blocks for the development of various bioactive fused coumarin heterocycles: a brief review

Abstract: Abstract: Aminocoumarins are found to be present in many natural products, pharmaceuticals, and organic materials. These derivatives demonstrate numerous biological activities including DNA gyrase, anti-proliferative and anti-breast cancer activities. Among the allaminocoumarin derivatives, 4-aminocoumarin derivatives have been reported to exhibit anticancer and anti-fungal properties. 4-Aminocoumarins and their derivatives are important precursors for the synthesis of coumarin fused N-heterocycles. Due to the presence of an amino group as well as enamine carbon, it is very reactive towards electrophiles and in most of the cases, it has a higher tendency to cyclize immediately by the various reaction path ways and provides the heterocyclic products. Unlike other aromatic amines, it did not give any Schiff base on reaction with aldehydes or ketones. Lamellarins, ningalin A, ningalin B, schumanniophytin, santiagonamine, goniothaline, and polyneomarline C are important natural coumarin fused N-heterocycles and show excellent biological activities, including antitumor, reversal of multidrug resistance, anti-HIV, wound healing, anti-malarial, anti-hepatitis, and anti-syphilis activities. The synthesized coumarin fused N-heterocycles have been reported to display Topoisomerases I inhibitory, DYRK1A inhibitory, and anti-cancer activities. Most of the syntheses of pyrrolo/imidazolo/indolo[3,2-c]coumarin, pyrido/quinolino[3,2-c]coumarins, pyrimidino[ c]coumarin and oxazino[c]coumarin have been synthesized easily from 4-aminocoumarin. This paper reviews the research data in the literature on the synthesis of bioactive coumarin fused heterocycles using 4-aminocoumarin derivatives over the period of 2-3 decades. It covers the synthetic applicability of 4-aminocoumarin for the development of coumarin fused 5-, 6-, and 8-membered ring derivatives via classical reaction protocols, microwavemediated reactions, organo-catalyzed reactions, transition metal-catalyzed reactions, and green reaction protocols.

Versatile approach for the synthesis of furo-coumarin derivatives

Abstract: Owing to useful physio-chemical properties of furo-coumarin derivatives, their synthetic and mechanistic investigation has been reported here. We have demonstrated a range of synthetic approach to access furan-fused coumarin derivatives. Many metal mediated, base and acid catalyzed approach have been revealed for the construction of thiscoumarin based fused heterocycles of biological importance. In addition to this, microwave assisted synthetic routes have been also revealed. The last and useful approach for the synthesis of these heterocycles includes use of purely solvent as a reaction media for synthesizing these interesting classes of heterocycles.

Mechanochemistry a Promising Tool on the Synthesis of Organometallic Pincer Compounds. Current State and Future Perspectives.

Abstract: Among the different synthethic proceedures available where the reactivity of substances is exploited using solid–state chemistry, such as microwave irradiation, ultrasound (sonochemistry), photochemistry, and mechanochemistry, the latter stands out as a synthetic tool on various areas of chemistry and materials sciences, acquiring great relevance in recent years. Thus, mechanochemistry has been applied in different areas such as organic synthesis, preparation of metal complexes, multicomponent pharmaceutical solid forms, catalysis, polymers, etc. However, despite the attractiveness of this sustainable technique, its application in the synthesis of coordination and organometallic compounds has been very incipient. On the other hand, pincer compounds have been a privileged ligand platform that has been profusely used for the synthesis of organometallic and coordination compounds for the last 20 years, finding applications on a large number of areas of chemistry, this being particularly true in the case of catalysis, being able to activate bonds difficult to activate such as C-H bonds, due in part to their characteristic thermal robustness. In this sense, on this perspective paper we present the current state of mechanochemistry in the preparation of organometallic pincer compounds and discuss future perspectives for the synthesis of these foremost interesting species via mechanochemistry.

Hedychium coronarium J. Koenig: Traditional Uses, Phytochemistry, Biological Activities and Future Aspects

Abstract: Hedychium coronarium J. Koenig belongs to the family Zingiberaceae, generally known as butterfly ginger, butterfly lily, cinnamon jasmine, garland flower and ginger lily. It is a medicinal plant grown throughout India, Southeast Asian countries, China, Japan, and Brazil. Traditionally, it is used as a febrifuge, tonic, anti-rheumatic, used to treat asthma, headache, arthritis, bronchitis, blood diseases, eye diseases, gastric diseases, and many other diseases. H. coronarium contains important secondary metabolites such as alcohols, aldehydes, ketones, esters, oxides, phenolics, flavonoids, saponins, glycosides, labdane diterpenes, and sesquiterpenes. Limonene, myrcene, p-cymene, camphene, γ-terpinene, β-pinene, 1,8-cineole, linalool, α-pinene, and 10-epi-γ-eudesmol have been identified as the main constituents of volatile oils of H. coronarium along with the key elements like trans-meta-mentha-2, 8-diene, linalool, α-terpineol, terpin-4-ol, α-pinene, γ-terpinene, and camphene. Phytochemical studies on various solvent extracts of H. coronarium revealed that the plant holds the diterpenes- coronarin-A-I, isocoronarin-D, pacovatin A; sesquiterpene- (+)-nerolidol, hedychiol A, hedychiol B 8,9-diacetate; sterols- daucosterol, stigmasterol, β-sitosterol and flavonoid- 5-hydroxy-3,7,4’-trimethoxyflavon, chrysin. Coronarin D, a bioactive compound, is reported for anti-cancer activities of H. coronarium. Diterpenes isolated from H. coronarium extracts and essential have been reported as antioxidant, antitumor, antidiabetic, antiproliferative, antihelmintic, mosquitocidal, larvicidal, antilithiatic, chemopreventive, antiophidian, insecticide, antifungal, allelopathic, and antimicrobial agent. Based on the literature, the essential oils, extracts and isolated active compounds of H. coronarium could be used to develop as flavor and fragrance agents, food preservatives, botanical pesticide, neutraceuticals and pharmaceuticals. This review paper aims to go over traditional uses, phytochemical analysis, pharmacological activities, scientific techniques for variety development, conservation, and proper utilization and identify future opportunities for H. coronarium.

Heterocyclic Moieties as Prospective Nematicides: An Overview

Abstract: Plant parasitic nematodes are destructive endoparasites having deleterious effect on about 5000 agricultural crops notably vegetables, fruits, field crops, ornamental plants, and even human health. The immense damage caused by nematodes has been estimated as US $150 billion per annum (21.3%) despite of the availability of commercialized nematicides. Nevertheless, crop protection is still dependent on the development of novel chemicals due to development of pesticide resistance line by diverse pathogens. The utilization of heterocyclic moieties in agricultural industry is considered as an effectual practice to manage plant diseases either as systemic or non-systemic. These scaffolds consist of heteroatoms in their ring structure such as N, S, O, which give a boost to their biological activity as reported. The principal heterocyclic scaffolds are the benzimidazole, pyridine, nicotinic acid, pyrrole, indole, isatin, triazine, triazole, pyrazole, amides, imidazole, cinnamic acid, oxadiazole, coumarin, thiadiazole, etc. derivatives which owing to their marvelous structural diversity are widely exploited. The prime purpose of the review is to provide information to researchers around the globe about varied heterocyclic scaffold decorations that have been employed for the synthesis of potential nematicidal candidates from 2000 onwards and their utilization to combat complex destructive biotic stress. Therefore, this review assembled the considerable synthetic chemistry and nematicidal investigation of moieties against various plant parasitic pathogens along with structure-activity relationship studies. The scientific details provided in the article will highlight the importance of heterocyclic compounds in the agricultural industry and may pave a pathway for the development of novel nematicides.

A Critical Review on Recent Advances in Base-Assisted Smiles Rearrangement

Abstract: Rearrangement reactions of organic substrates is a versatile and sustainable tool in the construction of complex and bioactive organics by virtue of their atom-economic, step-economic and waste-, time- as well as energy-minimizing attributes. The X → C (or Y) aryl rearrangement reaction through an intramolecular nucleophilic aromatic substitution is referred to as Smiles rearrangement. The Smiles rearrangement enables access to complex natural products and is a useful tool to obtain various types of compounds with diversified applications which have undergone a potent revival in recent years. In this review we summarize the recent reports on Smiles rearrangement and almost of them require a base. A few examples of the reported base-free Smiles rearrangements were also reviewed to provide comprehensive information on the selected topic. The literature review covers the published work on Smiles rearrangement reaction since 2017. The published work in these articles include simple Smiles, Truce-Smiles, radical Smiles, Ugi-Smiles, light-assisted Smiles, Dohmori-Smiles, electrochemical Smiles and phospha-Smiles rearrangement reactions for the construction of a variety of organic compounds including acyclic, heterocyclic, carbocyclic and polycyclic compounds. The formation of organic compounds with unusual ring sizes has also been discussed in the published work. Several domono/sequential reactions were also observed in these reports involving Smiles rearrangement as crucial step. The selected examples demonstrate the synthetic power of this approach and hence this review may be highly useful to the synthetic chemists aimed to use Smiles rearrangement in their plan.

Recent Advances in Base-Assisted Michael Addition Reactions.

Abstract: The Michael addition is an important, highly efficient, and atom-economical method for the diastereoselective and enantioselective C-C bond formation. MA used in the synthesis of natural products and drugs is tandem sequenced reactions. An important tandem sequence of Michael and Aldol additions is the Robinson annulation. MA is a versatile reaction employed for efficient bond formation between electron-poor olefins as Michael acceptors with varied nucleophiles as Michael donors. Apart from being involved in C-C bond formation, MA is also employed in the formation of C-X bond (X=O, N, S, P etc.) giving rise oxa-, aza-, thia-, phospha-Michael addition products. In recent years many articles have been published on MA. The mechanism of MA gives an insight into the reaction is initiated by the base. The present review provides comprehensive information on recent advancements in base-assisted Michael addition reactions including varied organic and inorganic bases, such as 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 1,4-Diazabicyclo[2.2.2]octane (DABCO), 4-dimethylaminopyridine (DMAP), triethylamine (Et3N), tributylamine (Bu3N), N,N-diisopropylethylamine (DIEPA), diethylamine (NHEt2), guanidine derivatives, and bifunctional thiourea. A variety of inorganic bases including metal alkoxides, metal acetates, metal hydroxides, metal hydrides, metal carbonates, metal halides, and triphenylphosphine (TPP) can also be successfully used in Michael reactions.

The Expedition of Azido-reductive Cyclization Approaches towards Various Heterocycles.

Abstract: Organic azides are in the interphase between chemistry, biology, medicine, and materials science. Their uses in peptide chemistry, combinatorial chemistry, and the synthesis of heterocycles are extensively explored. In this review, the focus is placed on the azido-reductive cyclization of azides and detailed its significant insights. The wide-ranging literature for synthesizing various heterocycles, employing chemoselective and straightforward protocols for azido-reduction with concomitant intramolecular cyclization, has been elaborated. In due course, the azido-reductive cyclization strategy witnessed the synthesis of essential heterocycles such as benzodiazepines, quinazolinones, piperidine, pyrrole and their derivatives. In addition, the review includes applications of azido-reductive cyclization strategies towards the synthesis of various iminosugars, drugs/APIs, and natural products embedding such heterocycles.

Transfer Hydrogenation Reactions by using Simple Biomass Alcohols as Hydrogen Sources

Abstract: Reduction of different unsaturated compounds by transfer hydrogenation (TH) has emerged as a more efficient methodology as compared to the classical method of using the molecular hydrogen both in industry and laboratory. Transfer hydrogenation is more advantageous in terms of safety and convenience. Alcohols, formic acid, esters, H2O, etc are the common molecules which are used as hydrogen donor in the transfer hydrogenation reaction. Primary alcohols namely methanol and ethanol were less explored as a hydrogen source in the TH reaction; probably due to the formation of aldehyde after dehydrogenation of these alcohols which are more reactive and may undergo side reactions. However, methanol and ethanol are cheap, easily available and easy to handle compounds. They can be easily obtained from biomass, coal, etc. Because of these advantages, chemists became more interested in the application of methanol and ethanol as hydrogen sources in the transfer hydrogenation reaction. In this review, we present an overview of the work reported by different groups on the transfer hydrogenation reactions with methanol and ethanol as the hydrogen sources.

New Developments in Chiral Phosphoric Acid Catalysis for Amine Synthesis.

Abstract: Asymmetric catalysis with chiral phosphoric acids (CPAs) has impacted a wide range of organic reactions, including those that generate chiral amines of interest in medicinal and natural products chemistry. Phosphodiester derivatives (RO)2PO2H offer linkages to various chiral alcohols and diols, permitting the CPA to transmit stereochemical information to reactants via ion-pairing and/or H-bonding interactions of the P=O and O–H bonds. This mini-review presents selected recent developments in CPA-catalyzed asymmetric synthesis of amines, emphasizing innovations from the literature of 2017–2021, with a few earlier examples to provide additional context. The coverage includes additions to imines, asymmetric protonation, induction of axial asymmetry, asymmetric Ugi and Passerini multicomponent coupling reactions, hydroaminations, and Minisci-type additions to heteroaromatic systems.

Triazole: A New Perspective in Medicinal Chemistry and Material Science

Abstract: Triazole, which can exist in two isomeric forms: 1,2,3- and 1,2,4-triazole, is considered to be a privileged scaffold with recognized biological and pharmaceutical potential. Furthermore, due to their physicochemical properties, the applications of triazoles have been explored in fields ranging from medicinal chemistry to materials science. Triazoles have not only drawn the attention of the scientific community for all the aforementioned properties but also due to their ability to be incorporated into other bioactive and functional molecules. The connection between two pharmacophores makes it possible to potentiate specific biological activities or add different properties. Interest in the compatibility of the triazole nucleus with peptide structures is highlighted in the development of new therapeutic targets. In epigenetics, triazole is linked to various compounds that are used in the creation of new drugs that could potentially inhibit histone-modifying enzymes. Other new and potentially more effective materials that can take advantage of a triazole moiety include light-emitting diodes and solar cells, among others. Hence, we propose a novel approach to the promising applications of triazolic ring, a compound that has been gaining prominence in organic chemistry due to its applicability to many different fields.

Iodine(III)-mediate Oxidative Cyanation, Azidation, Nitration, Sulfenylation and Slenization in Olefins and Aromatic Systems.

Abstract: Iodine(III) reagents represent nowadays a class of highly relevant oxidants in organic synthesis which possess important properties such as safer, non-toxic, green and easy to handle compounds. These characteristics in several cases, make them important alternatives to the procedures which use hazardous and strong reaction conditions. Based upon the ability as oxidants, they have been exploited in the functionalization of different aromatic nucleus, allowing the introduction of several groups: among them, inorganic functionalities. Herein, it is summarized the most relevant developed protocols for the functionalization of a broad amount of aryls, heteroaryls and olefins by introducing the inorganic groups cyano, azido, nitro, sulfur and selenium, using different iodine(III) reagents.

Applications of Choline Chlorine based Deep Eutectic Solvents as Sustainable Media and catalyst in the synthesis of Heterocyclic Scaffolds.

Abstract: Deep eutectic solvents (DESs), also referred to as low transition temperature mixtures (LTTMs), have emerged as sustainable and cheap alternatives to conventional organic solvents in organic synthesis. This is attributed to their exceptional characteristics viz. easy preparation with readily available cheap materials, water compatibility, non-flammability, non-toxicity, biocompatibility, biodegradability, etc. All these properties label them as versatile and cost-effective green solvents. The first reported DES, choline chloride urea mixture has appeared as an innocuous solvent and catalyst in many organic transformations. This prospective DES combination has been applied extensively to the synthesis of a wide range of heterocyclic compounds including quinolones, spirooxindoles, etc. The conditions employed are relatively mild and do not require additional acid catalysts or organic solvents. This eco-friendly blend for the synthesis of heterocycles reports excellent yields of products with shorter reaction times and a simple workup procedure. Evaluating these merits, this review focuses on the recent literature published on the use of choline chlorine-based DESs in the synthesis of a few important heterocyclic compounds.

A Review on the Catalytic Applications of Polyaniline Supported Palladium (Pd@PANI) in C–C Coupling Reactions

Abstract: The C ̶ C bond formation via the cross-coupling and homocoupling reactions of organic partners are central for the synthesis of many chemical probes and have valuable applications in the medicinal and pharmaceutical industries. Polyaniline (PANI) is the most useful performing polymer due to its non-toxicity, high stability, easy synthetic accessibility, and simplicity of doping/dedoping by treatment with aqueous acid and base. PANI plays a pivotal role as a polymer base for palladium (Pd) species and in most cases, the catalysts showed high yield, reaction transformation, and reusability. In this review, we discuss the application of Pd@PANI catalyst for cross-coupling/homocoupling reactions, analysis, characterization, and reusability. We covered all literature about Pd@PANI catalyst functions in Suzuki-Miyaura, Heck, Sonogashira, and Ullmann coupling reactions.

Supramolecular Chirality in Porphyrin Self-assembly Systems in Aqueous Solution

Abstract: The self-assembly process appears as a powerful and attractive strategy for constructing complex supramolecules by the spontaneous organization of appropriate building blocks. In this scenario, water-soluble porphyrinoids lend themselves as ideal paradigms to disclose the self-assembly phenomenon by exploiting their well-known tendency to build aggregates in aqueous media via weak non-covalent forces. Nevertheless, the spontaneous organization of achiral porphyrins can result in a final chiral superstructure moving away from single-molecule behaviour to supramolecular chirality. Therefore, over the years numerous attempts have been implemented to investigate how a porphyrin aggregate, made up of achiral monomers, becomes not-symmetric and which processes govern the bias for a certain enantiomeric assembly rather than another. Thus, in this mini-review, we exclusively discuss the main strategies for designing and building chiral aggregates in water from achiral porphyrin monomers, with particular regard to their chiroptical features.