Multicomponent reactions - opportunities for the pharmaceutical industry

Diastereoselective ZnCl2-Mediated Joullié-Ugi Three-Component Reaction for the Preparation of Phosphorylated N-Acylaziridines from 2H-Azirines

We disclose a direct approach to the diastereoselective synthesis of phosphorus substituted N-acylaziridines based on a one-pot ZnCl2-catalyzed Joullié-Ugi three-component reaction of phosphorylated 2H-azirines, carboxylic acids and isocyanides. Hence, this robust protocol offers rapid access to an array of N-acylaziridines in moderate-to-good yields and up to 98:2 dr for substrates over a wide scope. The relevance of this synthetic methodology was achieved via a gram-scale reaction and the further derivatization of the nitrogen-containing three-membered heterocycle. The diastereo- and regioselective ring expansion of the obtained N-acylaziridines to oxazole derivatives was accomplished in the presence of BF3·OEt2 as an efficient Lewid acid catalyst.

Ugi 5-center-4-component reaction of α-amino aldehydes and its application in synthesis of 2-oxopiperazines

A synthetic route leading to densely functionalized 2-oxopiperazines is presented. The strategy employs a 5-center-4-component variant of Ugi multicomponent reaction followed by a deprotection/cyclization sequence. N-Boc-α-amino aldehydes were used for the first time as carbonyl components in a key Ugi 5-center-4-component reaction (U-5C-4CR). It is shown that the presented synthetic route can lead to rigid, heterocyclic scaffolds, as demonstrated by the synthesis of tetrahydro-2H-pyrazino[1,2-a]pyrazine-3,6,9(4H)-trione β-turn mimetic and derivatives of 1,6-dioxooctahydropyrrolo[1,2-a]pyrazine and 3,8-dioxohexahydro-3H-oxazolo[3,4-a]pyrazine.

Novel terpyridines as Staphylococcus aureus gyrase inhibitors: efficient synthesis and antibacterial assessment via solvent-drop grinding

Aim: This study was designed to synthesize a novel series of terpyridines with potential antibacterial properties, targeting multidrug resistance. Materials & methods: Terpyridines (4a-h and 6a-c) were synthesized via a one-pot multicomponent reaction using 2,6-diacetylpyridines, benzaldehyde derivatives and malononitrile or ethyl 2-cyanoacetate. The reactions, conducted under grinding conditions with glacial acetic acid, produced high-yield compounds, confirmed by spectroscopic data. Results: The synthesized terpyridines exhibited potent antibacterial activity. Notably, compounds 4d and 4h demonstrated significant inhibition zones against Staphylococcus aureus and Bacillus subtilis, outperforming ciprofloxacin. Conclusion: Molecular docking studies highlighted compounds 4d, 4h and 6c as having strong binding affinity to DNA gyrase B, correlating with their robust antibacterial activity, suggesting their potential as effective agents against multidrug-resistant bacterial strains.

Recent advances in the application of alkynes in multicomponent reactions

Alkynes have two active positions to carry out chemical reactions: C[triple bond, length as m-dash]C and C-H. These two positions are involved and activated in different reactions using different reagents. In this study, we investigated the reactions of alkynes that are involved in multi-component reactions through the C-C and C-H positions and examined the progress and gaps of each reaction by carefully studying the mechanism of the reactions. Firstly, we investigated and analyzed the reactions involving the C[triple bond, length as m-dash]C position of alkynes, including the reactions between derivatives of alkynes with RN3, sulfur compounds (RSO2R', DMSO, S8, DABCO(SO2)2 and DABSO), barbituric acids, aldehydes and amines, COOH, α-diazoesters or ketones, and isocyanides. Then, we examined and analyzed the important reactions involving the C-H position of alkynes and the progress and gaps in these reactions, including the reaction between alkyne derivatives with amines and aldehydes for the synthesis of propargylamines, the reaction between alkynes with CO2 and the reaction between alkynes with CO.

Domino Three-Component N-Acylation/[4 + 2] Cycloaddition/Alder-ene Synthesis of Polysubstituted Benzo[f]isoindole-4-carboxylic Acids

Diversely substituted, partially saturated benzo[f]isoindole-4-carboxylic acids were synthesized by a new three-component reaction (3CR) starting from cinnamic amines (3-arylallylamines), maleimides, and maleic anhydride. The process consists of N-acylation of the amines by maleic anhydride, intramolecular [4 + 2] cycloaddition in vinylarenes (the IMDAV reaction), and the concluding Alder-ene reaction between Diels-Alder intermediates and maleimides. All of the reaction steps proceed in a highly regio- and stereoselective manner, furnishing five adjacent chiral centers and leading to a single diastereoisomer of the title compound. The efficiency of the transformation is secured by thermal conditions or utilization of soft Lewis acids (Yb(OTf)3) as catalysts. The kinetics and mechanism of the 3CR were studied by using dynamic 19F NMR. Based on the NMR data and density functional theory (DFT) calculations, the IMDAV, not the Alder-ene, reaction is the rate-limiting step of the entire process.

Indole-pyridine carbonitriles: multicomponent reaction synthesis and bio-evaluation as potential hits against diabetes mellitus

Background: Diabetes mellitus is a significant health disorder; therefore, researchers should focus on discovering new drug candidates. Methods: A series of indole-pyridine carbonitrile derivatives, 1-34, were synthesized through a one-pot multicomponent reaction and evaluated for antidiabetic and antioxidant potential. Results: In this library, 12 derivatives - 1, 2, 4, 5, 7, 8, 10-12, 14, 15 and 31 - exhibited potent inhibitory activities against α-glucosidase and α-amylase enzymes, in comparison to acarbose (IC50 = 14.50 ± 0.11 μM). Furthermore, kinetics, absorption, distribution, metabolism, excretion and toxicity and molecular docking studies were used to interpret the type of inhibition, binding energies and interactions of ligands with target enzymes. Conclusion: These results indicate that the compounds may be promising hits for controlling diabetes mellitus and its related complications.

Three-Component Photochemical 1,2,5-Trifunctionalizations of Alkenes toward Densely Functionalized Lynchpins

Radical remote 1,n-difunctionalization reactions (n > 2) of alkenes are powerful tools to efficiently introduce functional groups with selected distances into target molecules. Among these reactions, 1,5-difunctionalizations are an important subclass, leading to sought-after scaffolds, but typically suffer from tailored starting materials and strict limitations for the formed functional group in 2-position. Seeking to address these issues and to make radical 1,5-difunctionalizations of alkenes more applicable, we report a novel three-component 1,2,5-trifunctionalization reaction between imine-based bifunctional reagents and two distinct alkenes, driven by visible light energy transfer-catalysis. Key to achieving this selective one-step installation of three different functional groups via the choreographed formation of four bonds was the utilization of a 1,2-boron shift and the rigorous capitalization of radical polarities and stabilities. Thorough mechanistic studies were carried out, and the synthetic utility of the obtained products was demonstrated by various downstream modifications. Notably, in addition to the functionalization of individual functional groups, their interplay gave rise to a unique array of cyclic products.

An organo-photocatalyzed visible-light-driven multi-component approach for carbothioaryl/alkylation of activated alkenes via C(sp3)-H bond functionalization

A visible-light-driven organophotocatalyzed multi-component approach for carbothiolation of activated alkenes is demonstrated under environmentally benign and redox-neutral conditions, involving direct C(sp3)-H functionalization followed by electrophilic alkyl/arylthiolation. The three-component difunctionalization reaction is a complete transition-metal and peroxide-free process conducted under milder conditions. In this composite reaction, by employing bench-stable reagents, the formation of two new C(sp3)-C(sp3) and C(sp3)-S bonds is achieved for a wide variety of substrates, showcasing the excellent functional group tolerance and chemoselectivity of the methodology. Furthermore, the scalability and utilization of natural sunlight instead of artificial blue LEDs, along with the use of an inexpensive and easy-to-prepare pyrylium salt as an organo-photocatalyst, make this protocol greener and more energy efficient.

Immobilized nickel boride nanoparticles on magnetic functionalized multi-walled carbon nanotubes: a new nanocomposite for the efficient one-pot synthesis of 1,4-benzodiazepines

In this study, a new magnetic nanocomposite consisting of Ni2B nanoparticles anchored on magnetic functionalized multi-walled carbon nanotubes (Fe3O4/f-MWCNT/Ni2B) was synthesized and characterized using various techniques such as FT-IR, XRD, FESEM, SEM-based EDX, SEM-based elemental mapping, HRTEM, DLS, SAED, XPS, BET, TGA, and VSM. The as-prepared magnetic nanocomposite was successfully employed for the preparation of bioactive 1,4-benzodiazepines from the three-component reaction of o-phenylenediamine (1), dimedone (2), and different aldehydes (3), in polyethylene glycol 400 (PEG-400) as a solvent at 60 °C. The obtained results demonstrated that the current one-pot three-component protocol offers many advantages, such as good-to-excellent yields within acceptable reaction times, favorable TONs and TOFs, eco-friendliness of the procedure, easy preparation of the nanocomposite, mild reaction conditions, a broad range of products, excellent catalytic activity, green solvent, and reusability of the nanocomposite.

Multicomponent Reactions Using C,N-Binucleophilic Nature of Aminopyrazoles: Construction of Pyrazole-Fused Heterocycles

Synthesis of pyrazole-fused heterocycles has gained considerable attention in recent years due to their wide applications in medicinal chemistry. Aminopyrazoles are versatile building blocks for the synthesis of pyrazole-fused heterocycles by multicomponent reactions. Due to the presence of multiple reaction sites, they have fascinating chemical reactivity. Thus, they have been extensively used in multicomponent reactions for the construction of pyrazole-fused heterocycles. Although few review articles on the preparation and applications of aminopyrazoles are known in the literature, to date there is no dedicated review article on the construction of pyrazole-fused heterocycles exploring the reactivity of amino pyrazoles as C,N-binucleophiles in multicomponent reactions. Considering this, herein the multicomponent reactions for the construction of pyrazole-fused heterocycles exploring C,N-binucleophilic nature of amino pyrazoles have been reported.

Structure assignment, conformational properties and discovery of potential targets of the Ugi cinnamic adduct NGI25

The structure assignment and conformational analysis of cinnamic derivative N-benzyl-N-(2-(cyclohexylamino)-2-oxoethyl) cinnamamide (NGI25) was carried out through Nuclear Magnetic Resonance (NMR) spectroscopy, Molecular Dynamics (MD) and Quantum Mechanics (QM), i.e. semiempirical and Density Functional Theory (DFT) calculations. Moreover, Homonuclear (COSY, NOESY) and heteronuclear (HSQC, HMBC) experiments were applied to assign its protons and carbons. After structure identification, NGI25 was subjected to computational calculations to reveal its most favorable conformations. In particular, MD studies were performed in two different solvents, DMSO of intermediate polarity and hydrophobic CHCl₃. The obtained results suggest that NGI25 adopts similar conformations in both environments. In particular, the two aromatic rings of the molecule reside in spatial vicinity, while they remain quite distant from the cyclohexane. 2D NOESY experiments confirmed the in silico MD and QM calculations. Finally, molecular docking calculations were performed in order to reveal possible enzyme-targets for NGI25. Swiss target module was used to guide the discovery of new targets based on the structure of NGI. Indeed, it was predicted that NGI25 inhibited butyrylcholinesterase (BCHE) and lipoxygenase (LOX). Molecular docking experiments, followed by Molecular Dynamics studies, confirmed the favorable binding of NGI25 to both enzymes.Communicated by Ramaswamy H. Sarma.

Ugi Four-Component Reactions Using Alternative Reactants

The Ugi four-component reaction (Ugi-4CR) undoubtedly is the most prominent multicomponent reaction (MCRs) that has sparked organic chemists' interest in the field. It has been widely used in the synthesis of diverse heterocycle molecules such as potential drugs, natural product analogs, pseudo peptides, macrocycles, and functional materials. The Ugi-4CRs involve the use of an amine, an aldehyde or ketone, an isocyanide, and a carboxylic acid to produce an α-acetamido carboxamide derivative, which has significantly advanced the field of isocyanide-based MCRs. The so-called intermediate nitrilium ion could be trapped by a nucleophile such as azide, N-hydroxyphthalimide, thiol, saccharin, phenol, water, and hydrogen sulfide instead of the original carboxylic acid to allow for a wide variety of Ugi-type reactions to occur.β In addition to isocyanide, there are alternative reagents for the other three components: amine, isocyanide, and aldehyde or ketone. All these alternative components render the Ugi reaction an aptly diversity-oriented synthesis of a myriad of biologically active molecules and complex scaffolds. Consequently, this review will delve deeper into alternative components used in the Ugi MCRs, particularly over the past ten years.

2-Benzyl-3-morpholino-7-(thiophen-2-yl)-6-(thiophen-2-ylmethyl)-6,7-dihydro-5H-pyrrolo[3,4-b]pyridin-5-one

The new polyheterocyclic compound 2-benzyl-3-morpholino-7-(thiophen-2-yl)-6-(thiophen-2-ylmethyl)-6,7-dihydro-5H-pyrrolo[3,4-b]pyridin-5-one (1) was synthesized via a one-pot process involving an Ugi-Zhu three-component reaction coupled to a cascade aza-Diels-Alder cycloaddition/N-acylation/decarboxylation/dehydration process, using toluene as the solvent, ytterbium (III) triflate as the Lewis acid catalyst, and microwave-dielectric heating to increase the overall yield by up to 73%, while decreasing the reaction time to less than one hour. Product 1 was fully characterized by its physicochemical properties and using spectroscopic techniques (IR, HRMS and NMR).

Multicomponent Reactions for the Synthesis of Active Pharmaceutical Ingredients

Multicomponent reactions 9i.e., those that engage three or more starting materials to form a product that contains significant fragments of all of them), have been widely employed in the construction of compound libraries, especially in the context of diversity-oriented synthesis. While relatively less exploited, their use in target-oriented synthesis offers significant advantages in terms of synthetic efficiency. This review provides a critical summary of the use of multicomponent reactions for the preparation of active pharmaceutical principles.

Nanostructured silicate catalysts for environmentally benign Strecker-type reactions: status quo and quo vadis

Chemical processes are usually catalytic transformations. The use of catalytic reagents can reduce the reaction temperature, decrease reagent-based waste, and enhance the selectivity of a reaction potentially avoiding unwanted side reactions leading to green technology. Chemical processes are also frequently based on multicomponent reactions (MCRs) that possess evident improvements over multistep processes. Both MCRs and catalysis tools are the most valuable principles of green chemistry. Among diverse MCRs, the three-component Strecker reaction (S-3-CR) is a particular transformation conducive to the formation of valuable bifunctional building blocks (α-amino nitriles) in organic synthesis, medicinal chemistry, drug research, and organic materials science. To be a practical synthetic tool, the S-3-CR must be achieved using alternative energy input systems, safe reaction media, and effective catalysts. These latter reagents are now deeply associated with nanoscience and nanocatalysis. Continuously developed, nanostructured silicate catalysts symbolize green pathways in our quest to attain sustainability. Studying and developing nanocatalyzed S-3-CR condensations as an important model will be suitable for achieving the current green mission. This critical review aims to highlight the advances in the development of nanostructured catalysts for technologically important Strecker-type reactions and to analyze this progress from the viewpoint of green and sustainable chemistry.

Fluorescent annulated imidazo[4,5-c]isoquinolines via a GBB-3CR/imidoylation sequence - DNA-interactions in pUC-19 gel electrophoresis mobility shift assay

Herein we report the development of a sequential synthesis route towards annulated imidazo[4,5-c]isoquinolines comprising a GBB-3CR, followed by an intramolecular imidoylative cyclisation. X-Ray crystallography revealed a flat 3D structure of the obtained polyheterocycles. Thus, we evaluated their interactions with double-stranded DNA by establishing a pUC-19 plasmid-based gel electrophoresis mobility shift assay, revealing a stabilising effect on ds-DNA against strand-break inducing conditions.

Multicomponent reactions and photo/electrochemistry join forces: atom economy meets energy efficiency

Visible-light photoredox catalysis has been regarded as an extremely powerful tool in organic chemistry, bringing the spotlight back to radical processes. The versatility of photocatalyzed reactions has already been demonstrated to be effective in providing alternative routes for cross-coupling as well as multicomponent reactions. The photocatalyst allows the generation of high-energy intermediates through light irradiation rather than using highly reactive reagents or harsh reaction conditions. In a similar vein, organic electrochemistry has experienced a fruitful renaissance as a tool for generating reactive intermediates without the need for any catalyst. Such milder approaches pose the basis toward higher selectivity and broader applicability. In photocatalyzed and electrochemical multicomponent reactions, the generation of the radical species acts as a starter of the cascade of events. This allows for diverse reactivity and the use of reagents is usually not covered by classical methods. Owing to the availability of cheaper and more standardized photo- and electrochemical reactors, as well as easily scalable flow-setups, it is not surprising that these two fields have become areas of increased research interest. Keeping these in view, this review is aimed at providing an overview of the synthetic approaches in the design of MCRs involving photoredox catalysis and/or electrochemical activation as a crucial step with particular focus on the choice of the difunctionalized reagent.

Novel cellulose supported 1,2-bis(4-aminophenylthio)ethane Ni(ii) complex (NiII(BAPTE)(NO3)2-Cell) as an efficient nanocatalyst for the synthesis of spirooxindole derivatives

Cellulose was used as a support for immobilizing a Ni(ii) complex of 1,2-bis(4-aminophenylthio)ethane to prepare NiII(BAPTE)(NO3)2-Cell as a new organo-inorganic hybrid nanocatalyst. The properties of the prepared catalyst were studied using various analyses such as FT-IR, XRD, SEM, TGA and EDX. NiII(BAPTE)(NO3)2-Cell was employed as a reusable catalyst for the synthesis of spirooxindole derivatives via a three-component condensation of isatin, malononitrile and reactive methylene compounds. The nanocatalyst can be readily and quickly separated from the reaction mixture and can be reused for at least eight successive reaction cycles without a significant reduction in efficiency. The facile accessibility to the starting materials, use of green solvents and conducting the reactions in eco-friendly and cost-effective conditions have made this protocol a suitable method for preparing spirooxindole derivatives.

Supported l-tryptophan on Fe3O4@SiO2 as an efficient and magnetically separable catalyst for one-pot construction of spiro[indene-2,2'-naphthalene]-4'-carbonitrile derivatives

In this work, l-tryptophan functionalized silica-coated magnetic nanoparticles were readily prepared and evaluated as a recyclable magnetic nanocatalyst for the synthesis of spiro[indene-2,2'-naphthalene]-4'-carbonitrile derivatives through the one-pot four-component reaction of malononitrile, cyclohexanone, aromatic aldehydes, and 1,3-indandione. This novel magnetic nanocatalyst was confirmed to be effective and provide products in moderate to excellent yields under reflux conditions. The structure of obtained nanoparticles was characterized using FT-IR, XRD, VSM, EDX, elemental mapping, FE-SEM, and TGA. This synthetic protocol provides several benefits such as excellent yields in short reaction times (64-91%), saving costs, reusability of the catalyst using an external magnet (seven runs), and low catalyst loading.

Green Chemistry in the Synthesis of Pharmaceuticals

The principles of green chemistry (GC) can be comprehensively implemented in green synthesis of pharmaceuticals by choosing no solvents or green solvents (preferably water), alternative reaction media, and consideration of one-pot synthesis, multicomponent reactions (MCRs), continuous processing, and process intensification approaches for atom economy and final waste reduction. The GC's execution in green synthesis can be performed using a holistic design of the active pharmaceutical ingredient's (API) life cycle, minimizing hazards and pollution, and capitalizing the resource efficiency in the synthesis technique. Thus, the presented review accounts for the comprehensive exploration of GC's principles and metrics, an appropriate implication of those ideas in each step of the reaction schemes, from raw material to an intermediate to the final product's synthesis, and the final execution of the synthesis into scalable industry-based production. For real-life examples, we have discussed the synthesis of a series of established generic pharmaceuticals, starting with the raw materials, and the intermediates of the corresponding pharmaceuticals. Researchers and industries have thoughtfully instigated a green synthesis process to control the atom economy and waste reduction to protect the environment. We have extensively discussed significant reactions relevant for green synthesis, one-pot cascade synthesis, MCRs, continuous processing, and process intensification, which may contribute to the future of green and sustainable synthesis of APIs.

Synthesis of styryl-linked fused dihydropyridines by catalyst-free multicomponent reactions

Herein, we report a rapid catalyst-free three-component reaction of 2-hydroxy-1,4-naphthoquinone, cinnamaldehydes and 3-aminopyrazoles in ethanol medium under reflux conditions for the easy access of styryl-linked dihydropyridines fused with naphthoquinone and pyrazole moiety. A wide variety of cinnamaldehyde derivatives and 3-aminopyrazoles were found suitable for this three-component reaction. All the products were fully characterized by spectroscopic tools and by recording single crystal XRD of one of the product. Catalyst-free reaction conditions, short reaction time, good yields of the products, easy purification process, formation of three new bonds (Two C-C and one C-N) in one-pot and products having four different bioactive moieties are the notable features of this methodology.

Uniting Amide Synthesis and Activation by PIII/PV-Catalyzed Serial Condensation: Three-Component Assembly of 2-Amidopyridines

An organophosphorus (P^III/P^V redox) catalyzed method for the three-component condensation of amines, carboxylic acids, and pyridine N-oxides to generate 2-amidopyridines via serial dehydration is reported. Whereas amide synthesis and functionalization usually occur under divergent reaction conditions, here a phosphetane catalyst (together with a mild bromenium oxidant and terminal hydrosilane reductant) is shown to drive both steps chemoselectively in an auto-tandem catalytic cascade. The ability to both prepare and functionalize amides under the action of a single organocatalytic reactive intermediate enables new possibilities for the efficient and modular preparation of medicinal targets.

High-component reactions (HCRs): An overview of MCRs containing seven or more components as versatile tools in organic synthesis

Recently, multi-component reactions (MCRs) have gained special attention due to their versatility for the synthesis of polycyclic heterocycles. Moreover, their applicability can become more widespread as they can be combined together as a union of MCRs. In this overview, the authors have tried to collect the MCRs containing more than seven components that can lead to effectual heterocycles in organic and/or pharmaceutical chemistry. The review contains papers published up to the end of 2020. The subject is classified based on the number of substrates, such as seven-, eight-, nine-, ten-, and more components. The authors expect their report to be helpful for researchers to clarify their route to significant MCRs.

3-Substituted 2-isocyanopyridines as versatile convertible isocyanides for peptidomimetic design

We report the use of 3-substituted 2-isocyanopyridines as convertible isocyanides in Ugi four-component reactions. The N-(3-substituted pyridin-2-yl)amide Ugi products can be cleaved by amines, alcohols, and water with Zn(OAc)2 as a catalyst. In addition, the applicability of the method was demonstrated in constrained di-/tripeptides bearing acid and base sensitive protective groups obtained via Ugi-4CR post-condensation modifications.

Dimensional Reduction of Lewis Acidic Metal-Organic Frameworks for Multicomponent Reactions

Owing to hindered diffusions, the application of porous catalytic materials has been limited to relatively simple organic transformations with small substrates. Herein we report a dimensional reduction strategy to construct a two-dimensional metal-organic framework (MOF), Zr₆OTf-BTB, with 96% accessible Lewis acidic sites as probed by the bulky Lewis base pivalonitrile. With nearly free substrate accessibility, Zr₆OTf-BTB outperformed two three-dimensional MOF counterparts of similar Lewis acidity (Zr₆OTf-BPDC and Zr₆OTf-BTC) in catalyzing sterically hindered multicomponent reactions (MCRs) for the construction of tetrahydroquinoline and aziridine carboxylate derivatives with high turnover numbers (TONs). Zr₆OTf-BTB was also superior to the homogeneous benchmark Sc(OTf)₃ with nearly 14 times higher TON and 9 times longer catalyst lifetime. Furthermore, the topology-activity relationships in these Zr-based Lewis acidic MOFs were rationalized by comparing their Lewis acidity, numbers of Lewis acidic sites, and sterically accessible Lewis acidic sites. Zr₆OTf-BTB was successfully used to construct several bioactive molecules via MCRs with excellent efficiency. This dimensional reduction strategy should allow the development of other MOF catalysts for synthetically useful and complicated organic transformations.

Supported Cu(II)-Schiff base: novel heterogeneous catalyst with extremely high activity for eco-friendly, one-pot and multi-component C-S bond-forming reaction toward a wide range of thioethers as biologically active cores

An effective and proficient process for the synthesis of a variety of thioethers via the one-step reaction of benzyl halides, aryl halides, and thiourea is presented. This strategy is a one-pot procedure to achieve a variety of thioethers without the requirement to thiols as starting compounds. A range of thioethers containing electron donating/electron-withdrawing functional groups were obtained with good to excellent yields under mild conditions. Moreover, the nanocatalyst exhibited excellent recyclability for the reaction, making it more sustainable. One-pot and multi-component synthesis, high yields of final products, green reaction media, high activity of nanocatalyst, simple separation of the products and catalyst, and high regioselectivity are several highlights of this method.

Electrochemical TEMPO-Catalyzed Oxidative Ugi-Type Reaction

Oxidative isocyanide-based multicomponent reactions (oxidative IMCRs) are very useful tools for the rapid construction of molecular diversity starting from readily available and stable substrates. Despite all their benefits, such multicomponent reactions are underdeveloped and strictly limited to 3-component processes. Indeed, in the presence of several reaction partners, the oxidation event needs to be rigorously chemoselective, which becomes incredibly more intricate as the number of reactive components increases. Nonetheless, we could overcome this significant pitfall and reach the first oxidative Ugi-type 4-IMCR by capitalizing on a very mild and green TEMPO-catalyzed electro-oxidation process. Employing alcohols as aldehyde surrogates and in the notable absence of any supporting electrolyte, this transformation proved to be extremely chemoselective in the presence of an amine and was compatible with a wide range of alcohols, amines, isocyanides, and carboxylic acids.

Synthesis of (E)-5-Arylvinyl-7-methyltetrazolo[1,5-a]pyrimidines

Abstract

A three-component reaction of 5-aminotetrazole with aromatic aldehydes and acetylacetone under solvent- and catalyst-free conditions at a temperature of 150–160°С proceeds with the formation of (E)-5-arylvinyl-7-methyltetrazolo[1,5-a]pyrimidines. 5,7-Dimethyltetrazolo[1,5-a]pyrimidine is formed as a side-product of the reaction.

A review on multicomponent reactions catalysed by zero-dimensional/one-dimensional titanium dioxide (TiO2) nanomaterials: Promising green methodologies in organic chemistry

Heterogeneous catalysis has currently become an emerging tool for the design and development of sustainable manufacturing processes in order to obtain advanced intermediates, fine chemicals, and bioactive molecules. This field has been considered efficient and eco-friendly, as it investigates the utilization of non-hazardous metals for atom-economical reactions. Nanomaterials have created a significant impact on scientific and engineering advancements due to their tunable properties with superior performance over their massive counterparts. Due to the increased demand for heterogeneous catalysts in industries and academia, different transition metal oxides have been made into substantial nanostructures. Among them, titanium dioxide (TiO₂) nanomaterials have received more attention on account of their chemical stability, low cost, dual acid-base properties, good oxidation rate and refractive index. Different modifications of TiO₂ extend their applications as active catalysts or catalyst supports in diverse catalytic processes, such as photovoltaics, lithium batteries, pigments and others. One-dimensional (1-D) TiO₂ nanostructures such as nanotubes, nanowires and nanorods have achieved greater importance owing to the unique properties of improved porosity, decreased inter-crystalline contacts, large surface-to-volume ratio, superior dispersibility, amplified accessibility of hydroxyl (-OH) groups and presence of good concentrations of Brønsted/Lewis acid sites. Since the discovery, 1-D TiO₂ nanostructures have served good photocatalytic applications, but were less explored in organic transformations. While many articles and reviews have covered the applications of 0-D and 1-D TiO₂ nanostructured materials (NSMs) in photoelectrochemical reactions and solar cells, there are other interesting applications of these as well. In contrast to the conventional multi-step processes that utilise the stepwise formation of individual bonds, one-pot conversions based on multicomponent reactions (MCRs) have acquired much significance in contemporary organic synthesis. This paper presents a critical review on history, classification, design and synthetic utility of titania-based nanostructures, which could be used as robust solid-acid catalysts and catalyst supports for MCRs. Further, to put ideas into perspective, the introduction and applications of MCRs for various organic transformations have been discussed.

Multicomponent reactions (MCR) in medicinal chemistry: a patent review (2010-2020)

Introduction: Multicomponent reactions (MCR) has been utilized to synthesize a vast range of analogs belonging to diverse classes of heterocyclic compounds offering multidimensional pharmaceutical applications. The unique feature of MCR includes the synthesis of highly functionalized molecules in a single pot to build quick libraries of compounds of biological interest to identify new leads as potential therapeutic agents.Area covered: The current review article covers the patents published in the last decade in order to highlight the importance of multicomponent reactions for synthesizing complex-functionalized molecules of high biological significance.Expert opinion: Easily automated one-pot multicomponent reactions (MCRs) has demonstrated successful impact at different stages of the lead discovery, lead optimization, and pre-clinical process development arenas. Application of MCRs is the recent advancement in the field of drug design and discovery which will expectedly lead to the development of medicinally important heterocyclic compounds with a vast range of biological activities.

Dual active 1, 4-dihydropyridine derivatives: Design, green synthesis and in vitro anti-cancer and anti-oxidant studies

The present work describes the design of 1,4-dihydropyridines (1,4-DHPs) with diverse variations in structural and functional groups. The physico-chemical properties and drug-like molecule nature evaluations were carried out using SWISSADME. A simple, economical, eco-friendly, water-mediated and Para-Toluene sulfonic acid catalysed multicomponent and one-pot synthetic method from nitroketene N, S- acetals (NMSM) and corresponding aldehydes has been developed. All compounds (6a-u and 13a-h) were subjected to in vitro assays against two important human cancer cell lines Viz. are Laryngeal carcinoma (Hep2) and Lung adenocarcinoma (A549) cells. The reduction level of DPPH (%) used to evaluate the anti-oxidant properties. The 1,4-DHP derivatives, 6o, 6u and 6l displayed the potent anti-cancer activity with IC₅₀ value of 10 µM, 14 µM and 10 µM against the Hep2 and 8 µM, 9 µM and 50 µM against the A549 cells. Similarly, the anti-oxidant properties of 6o, 6l and 6u at a standard concentration of 50 µg, are found to be 70.12%, 63.90% and 59.57% respectively favours the 1,4-DHP derivatives dual activity potentials. The compounds, 6o and 6l found to be equivalent with standard drug, Doxorubicin.

Introduction of Succinimide as A Green and Sustainable Organo-Catalyst for the Synthesis of Arylidene Malononitrile and Tetrahydrobenzo[b] pyran Derivatives

AIM AND OBJECTIVE

In this work, we tried to introduce a non-toxic and stable organic compound named succinimide as a green and efficient organo-catalyst for the promotion of the synthesis of arylidene malononitrile and tetrahydrobenzo[b]pyran derivatives. Using this method led to a clean procedure to achieve these types of bioactive compounds without a specific purification step. The rate and yield of the reactions were excellent, and also succinimide showed acceptable reusability as the catalyst.

MATERIALS AND METHODS

In a 25 mL round-bottom flask, [A: a mixture of aromatic aldehyde (1 mmol), malononitrile (1.1 mmol) and B: a mixture of aromatic aldehyde (1.0 mmol), malononitrile (1.1 mmol)] and succinimide (0.2 mmol) in H2O/ EtOH [5 mL (1:1)] was stirred at 80 °C for an appropriate time. After completion of the reaction, which was monitored by TLC [n-hexane-EtOAc (7:3)], the mixture was cooled to room temperature, and the solid product was filtered, washed several times with cold distilled water to obtain the corresponding pure product.

RESULTS

After the optimization of the conditions and amount of the catalyst, a series of aromatic aldehydes containing either-electron-donating or electron-withdrawing substituents were successfully used for both of the reactions. The reactions rates and yields under the selected conditions were excellent. The nature and electronic properties of the substituents had no obvious effect on the rate and yield of the reaction. Meanwhile, the catalyst showed acceptable reusability for these two reactions.

CONCLUSION

In this work, we have introduced Succinimide as a green and safe organo-catalyst for the efficient synthesis arylidene malononitrile and tetrahydrobenzo[b]pyran derivatives. The results showed that the catalyst had excellent efficiency in green aqueous media and also the reusability of the catalyst was good.