Insight into the hydrophobic functionalization of cellulose microfibrils using the Passerini three-component reaction

The aqueous catalyst-free one-pot Passerini 3-component reaction (P-3CR) was employed for the functionalization of dialdehyde cellulose (DAC) derived from the periodate oxidation of microfibrillated cellulose (MFC) with insights provided by 13C and 15N CP-MAS NMR and FTIR analyses. The kinetics of the P-3CR revealed rapid progress within the initial 2 h, reaching a plateau between 6 and 18 h. The reaction achieved a maximum degree of substitution (DS) with only 1 equivalent of carboxylic acid and isocyanide with respect to the number of aldehydes, therefore demonstrating the atom economy character of the P-3CR performed on MFC. Variable DS values (0.08 to 0.37) were achieved by altering the degree of oxidation of DAC (ranging from 0.48 to 1.1) when reacted with heptanoic acid and tert-butyl isocyanide. Additionally, aliphatic chain lengths of carboxylic acids from C4 to C11 were successfully used for the functionalization of DAC with distinct hydrophobic chains. Furthermore, while cosolvents negatively affected the DS when using heptanoic acid, a significant increase was observed in the case of undecanoic acid due to an improved solubility of the reagent. The aqueous medium P-3CR can thus be considered a versatile tool to tailor the functionalization of MFC and provide it with hydrophobicity.

Benzenesulfonamide decorated dihydropyrimidin(thi)ones: carbonic anhydrase profiling and antiproliferative activity

In the last decades, carbonic anhydrases (CAs) have become the top investigated innovative pharmacological targets and, in particular, isoforms IX and XII have been widely studied due to the evidence of their overexpression in hypoxic tumors. The frantic race to find new anticancer agents places the quick preparation of large libraries of putative bioactive compounds as the basis of a successful drug discovery and development programme. In this context, multi-component and, in general, one-step reactions are becoming very popular and, among them, Biginelli's reaction gave clean and easy-to-isolate products. Thus, we synthesized a series of Biginelli's products (10-17a-b) and similar derivatives (20-21) bearing the benzenesulfonamide moiety, which is known to inhibit CA enzymes. Through the stopped-flow technique, we were able to assess their ability to inhibit the targeted CAs IX and XII in the nanomolar range with promising selectivity over the physiologically relevant isoforms I and II. Crystallography studies and docking simulations helped us to gain insight into the interaction patterns established in the enzyme-inhibitor complex. From a chemical similarity-based screening of in-house libraries of compounds, a diphenylpyrimidine (23) emerged. The surprisingly potent inhibitory activity of 23 for CAs IX and XII along with its strong antiproliferative effect on two (triple-negative breast cancer MDA-MB-231 and glioblastoma U87MG) cell lines laid the foundation for further investigation, again confirming the key role of CAs in cancer.

Recent developments in the total synthesis of natural products using the Ugi multicomponent reactions as the key strategy

The total syntheses of selected natural products using different versions of the Ugi multicomponent reaction is reviewed on a case-by-case basis. The revision covers the period 2008-2023 and includes detailed descriptions of the synthetic sequences, the use of state-of-the-art chemical reagents and strategies, as well as the advantages and limitations of the transformation and some remedial solutions. Relevant data on the isolation and bioactivity of the different natural targets are also briefly provided. The examples clearly evidence the strategic importance of this transformation and its key role in the modern natural products synthetic chemistry toolbox. This methodology proved to be a valuable means for easily building molecular complexity and efficiently delivering step-economic syntheses even of intricate structures, with a promising future.

First-row transition metal for isocyanide-involving multicomponent reactions (IMCR)

First-row transition metal catalyzed transformations that are able to construct complex molecules from simple, readily obtainable feedstocks have become a keystone of modern synthetic organic chemistry. Particularly, the multicomponent reaction (MCR) involving carbon-carbon (C-C) as well as carbon-heteroatom (C-X) bond formation plays an essential role in many chemical conversions, and insurgencies in these reactions powerfully improve the overall synthetic efficiency. Recently, MCRs emerges rapidly because of its greener sides like eco-friendly nature, swift and straightforward execution, high atom/step economy, and construction of aimed product with lowest or no by-product, usually in quantitative yield. Curiously, the exceptional divalent carbon atoms of isocyanides make them predominantly useful components in multicomponent reactions. As a result of widespread research over the past few decades, numerous well-designed and effective procedures for the first-row TM-catalyzed MCR to afford the various entities have been reported. These aspects are summarized in this review article. A particular focus on comparative discussion of various first-row transition-metal catalyzed isocyanide-based multicomponent reactions through mechanistic details included in the review article.

α-Substituted ketones as reagent for Passerini modification of carboxymethyl cellulose: Toward dually functionalized derivatives and thermo-sensitive chemical hydrogels

The present works describes the Passerini modification of carboxymethyl cellulose (CMC) by using a library of nine α-substituted ketones derivatives, differing in their hydrophobicity and reactivity, conjointly with cyclohexyl isocyanide. The Passerini ligation, achieved in aqueous and mild conditions, was shown to be successful, leading to a large panel of dually functionalized CMC derivatives, in an eco-friendly manner. A particular attention was dedicated to the influence of the experimental parameters such as the stoichiometry, the nature of a co-solvent or the temperature, which allowed to tune the extent of modification. The reactivity of the ketone was proven to be governed by its i) compatibility with water, ii) sterical accessibility, and by iii) the presence of neighboring electron-withdrawing group. The resulting Passerini CMC products modified by methacrylate moieties (CMC-MA) were used as reactive macromonomer under a "grafting through" approach. The copolymerization of CMC-MA with oligoethylene glycol methacrylate (OEGMA) and diethylene glycol methacrylate (DEGMA) upon thermal radical reaction conditions enabled to generate tightly cross-linked chemical hydrogels, with a thermo-sensitive and thermo-reversible behavior, reflected by a macroscopical shrinkage/swelling response, and confirmed by SAXS analysis. Such chemical strategy paves the way toward multifunctional polysaccharide-based networks with potential utilizations as drug delivery devices, dye removals or actuators.

Efficient synthesis of new indenopyridotriazine [4.3.3]propellanes and spiroindenopyridotriazine-4H-pyran derivatives

The pyrido[1,2,4]triazines as substrates, generated from 1,6-diaminopyridinone derivatives and ninhydrin, were reacted with malononitrile and CH-acids to afford a new library spiro[indeno[1,2-e]pyrido[1,2-b][1,2,4]triazine-7,5'-pyran]-1,3,6'-tricarbonitrile in ethanol at reflux condition in excellent yield. Also, novel indenopyridotriazine [4.3.3]propellanes were synthesized via the reaction of pyrido[1,2,4]triazine and N-methyl-1-(methylthio)-2-nitroethenamine (NMSM) by using of HOAc in ethanol. The important aspects of this protocol are the abundance of starting materials, mild conditions, structural diversity of products, excellent yields and easy isolation of products with no chromatographic technique.

DFT stimulation and experimental insights of chiral Cu(II)-salen scaffold within the pocket of MWW-zeolite and its catalytic study

A Cu(II)-salen complex encapsulated in MWW-framework as an efficient chiral organocatalyst was developed for the synthesis of 3,4-dihydropyrimidin-2-(1H)-one (DHPMs) derivatives via an asymmetric pathway. In order to confirm its structural properties, single-crystal X-ray diffraction, powder XRD, BET, XPS, FE-SEM, EDX, UV-Vis, and FTIR spectra were used. Using computer-assisted DFT calculations, the Cu(II)-salen complex has been fine-tuned to fit into the pocket of the porous MWW support while keeping its chirality. This organocatalyst was shown to be a potent catalyst for the formation of the desired DHPMs product under short reaction times. Furthermore, this green protocol allows rapid and simple isolation of active MWW-trapped Cu(II)-salen scaffolds and its reusability in at least five consecutive runs without losing much of its activity.

Fe3O4@nano-almond shell@OSi(CH2)3/DABCO: a novel magnetic nanocatalyst for the synthesis of chromenes

In this work, we report the synthesis and characterization of Fe₃O₄@nano-almond shell@OSi(CH₂)₃/DABCO as a novel magnetic natural-based basic nanocatalyst. The characterization of this catalyst was achieved using different spectroscopy and microscopy techniques, such as Fourier-transform infrared spectroscopy, X-ray diffractometry, field-emission scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy and mapping, vibrating-sample magnetometry, Brunauer-Emmett-Teller measurements, and thermogravimetric analysis. This catalyst was used for the one-pot synthesis of 2-amino-4H-benzo[f]chromenes-3-carbonitrile from the multicomponent reaction of aldehyde and malononitrile with α-naphthol or β-naphthol under solvent-free conditions at 90 °C. The yields of the obtained chromenes are 80-98%. The attractive features of this process are its easy work-up, mild reaction conditions, reusability of the catalyst, short reaction times and excellent yields.

Multicomponent Reaction-Assisted Drug Discovery: A Time- and Cost-Effective Green Approach Speeding Up Identification and Optimization of Anticancer Drugs

Multicomponent reactions (MCRs) have emerged as a powerful strategy in synthetic organic chemistry due to their widespread applications in drug discovery and development. MCRs are flexible transformations in which three or more substrates react to form structurally complex products with high atomic efficiency. They are being increasingly appreciated as a highly exploratory and evolutionary tool by the medicinal chemistry community, opening the door to more sustainable, cost-effective and rapid synthesis of biologically active molecules. In recent years, MCR-based synthetic strategies have found extensive application in the field of drug discovery, and several anticancer drugs have been synthesized through MCRs. In this review, we present an overview of representative and recent literature examples documenting different approaches and applications of MCRs in the development of new anticancer drugs.

The vital use of isocyanide-based multicomponent reactions (MCR) in chemical synthesis

Multicomponent (MCRs) reactions are classified as one-pot reaction where more than two starting materials are employed to form a single product that contains the building blocks of the starting components. MCRs are considered a convenient approach in synthetic chemistry and have many advantages over the traditional one or two-component reaction, by reducing the number of sequential multiple steps required and often producing better yields. This chapter dissects the use of isocyanide-based MCRs and the elegant chemistry that they offer to build useful scaffolds in the chemical synthetic field. In addition MCRs are considered as one of the recognisable options for increasing “greenness” during the synthesis of pharmaceutical and industrial products.

Multicomponent Synthesis of Unsymmetrical Derivatives of 4-Methyl-Substituted 5-Nitropyridines

The multicomponent reaction of 2-nitroacetophenone (or nitroacetone), acetaldehyde diethyl acetal, β-dicarbonyl compound, and ammonium acetate in an acetic acid solution allowed the acquisition of previously undescribed 4-methyl-substituted derivatives of 5-nitro-1,4-dihydropyridine in satisfactory yields. The oxidation of the obtained 5-nitro-1,4-dihydropyridine derivatives resulted in the corresponding 2,4-dimethyl-5-nitropyridines. In addition, for the first time in the synthesis of unsymmetrical 1,4-dihydropyridines by the Hantzsch reaction acetaldehyde, diethyl acetal was used as a source of acetaldehyde. The use of more volatile and sufficiently reactive acetaldehyde in this reaction did not lead to a controlled synthesis of unsymmetrical 5-nitro-1,4-dihydropyridines. The proposed multicomponent approach to the synthesis of 4-methyl-substituted 5-nitro-1,4-dihydropyridines and their subsequent aromatization into pyridines made it possible to obtain previously undescribed and hardly accessible substituted 5(3)-nitropyridines.

Catalyst-free synthesis of diverse fluorescent polyoxadiazoles for the facile formation and morphology visualization of microporous films and cell imaging

The development of facile polymerizations toward functional heterocyclic polymers is of great significance for chemistry and materials science. As an important class of heterocyclic polymers, polyoxadiazoles (PODs) have found applications in various fields. However, the synthetic difficulties of PODs greatly restrict their structural diversity and property investigation. Herein, we report a series of catalyst-free multicomponent polymerizations (MCPs) that can facilely synthesize functional PODs with well-defined and diversified topological structures from commercially available or readily accessible aldehydes, carboxylic acids, secondary amines, and (N-isocyanimino)triphenylphosphorane at room temperature. Unlike conventional Ugi polycondensations, the present Ugi-type MCPs can in situ generate oxadiazole moieties in polymer backbones. The obtained PODs possess good solubility, high thermal and morphological stability, and excellent film-forming ability. The introduction of aggregation-induced emission (AIE) moieties together with the inherent structural features of PODs endow these polymers with multiple functionalities. The AIE-active linear PODs can form fluorescent microporous films with stable and ordered structures based on the simple breath figure patterning method, and the self-assembly morphologies can be directly visualized by fluorescence microscopy in a high-contrast and sensitive manner. Moreover, both the linear and hyperbranched AIE-active PODs possess excellent biocompatibility, good lysosome specificity, and excellent photobleaching resistance, which enable them to serve as promising lysosome-specific fluorescent probes in biological imaging.

Catalyzed Methods to Synthesize Pyrimidine and Related Heterocyclic Compounds

This review covers articles published in the period from 2010 to mid-2022 on synthetic advances in the formation of pyrimidine and related heterocyclic compounds. Special emphasis has been given to the different types of cycloadditions, taking into account the number of their components and leading to the formation of the pyrimidine ring. Due to the large number of publications on the Biginelli reaction and related reactions, this will be dealt with in a separate review in the near future.

Enantioselective Ugi and Ugi-azide reactions catalyzed by anionic stereogenic-at-cobalt(III) complexes

Ugi reactions and related variations are proven to be atom and step-economic strategies for construction of highly valuable peptide-like skeletons and nitrogenous heterocycles. The development of structurally diverse range of novel catalytic systems and the discovery of new approaches to accommodate a broader scope of terminating reagents for asymmetric Ugi four-component reaction is still in high demand. Here, we report a strategy that enables enantioselective Ugi four-component and Ugi-azide reactions employing anionic stereogenic-at-cobalt(III) complexes as catalysts. The key nitrilium intermediates, generated through the nucleophilic addition of isocyanides to the chiral ion-pair which consists of stereogenic-at-cobalt(III) complexes counteranion and a protonated iminium, are trapped by either carboxylic acids or in situ-generated hydrazoic acid, delivering α-acylamino amides and α-aminotetrazoles in good to excellent enantioselectivities (up to 99:1 e.r.).

In Melting Points We Trust: A Review on the Misguiding Characterization of Multicomponent Reactions Adducts and Intermediates

We discuss herein the problems associated with using melting points to characterize multicomponent reactions’ (MCRs) products and intermediates. Although surprising, it is not rare to find articles in which these MCRs final adducts (or their intermediates) are characterized solely by comparing melting points with those available from other reports. A brief survey among specialized articles highlights serious and obvious problems with this practice since, for instance, cases are found in which as many as 25 quite contrasting melting points have been attributed to the very same MCR adduct. Indeed, it seems logical to assume that the inherent non-confirmatory nature of melting points could be vastly misleading as a protocol for structural confirmation, but still many publications (also in the Q1 and Q2 quartiles) insist on using it. This procedure contradicts best practices in organic synthesis, and articles fraught with limitations and misleading conclusions have been published in the MCRs field. The drawbacks inherent to this practice are indeed serious and have misguided MCRs advances. We therefore suggest some precautions aimed at avoiding future confusions.

Multicomponent reactions as a privileged tool for multitarget-directed ligand strategies in Alzheimer's disease therapy

Among neurodegenerative pathologies affecting the older population, Alzheimer's disease is the most common type of dementia and leads to neurocognitive and behavioral disorders. It is a complex and progressive age-related multifactorial disease characterized by a series of highly interconnected pathophysiological processes. Within the last decade, the multitarget-directed ligand strategy has emerged as a viable approach to developing complex molecules that exhibit several pharmacophores which can target the different enzymes and receptors involved in the pathogenesis of the disease. Herein, we focus on using multicomponent reactions such as Hantzsch, Biginelli and Ugi to develop these biologically active multitopic ligands.

Synthesis of (E)-2-(1H-tetrazole-5-yl)-3-phenylacrylenenitrile derivatives catalyzed by new ZnO nanoparticles embedded in a thermally stable magnetic periodic mesoporous organosilica under green conditions

ZnO nanoparticles embedded in a magnetic isocyanurate-based periodic mesoporous organosilica (Fe₃O₄@PMO–ICS–ZnO) were prepared through a modified environmentally-benign procedure for the first time and properly characterized by appropriate spectroscopic and analytical methods or techniques used for mesoporous materials. The new thermally stable Fe₃O₄@PMO–ICS–ZnO nanomaterial with proper active sites and surface area as well as uniform particle size was investigated for the synthesis of medicinally important tetrazole derivatives through cascade condensation and concerted 1,3-cycloaddition reactions as a representative of the Click Chemistry concept. The desired 5-substituted-1H-tetrazole derivatives were smoothly prepared in high to quantitative yields and good purity in EtOH under reflux conditions. Low catalyst loading, short reaction time and the use of green solvents such as EtOH and water instead of carcinogenic DMF as well as easy separation and recyclability of the catalyst for at least five consecutive runs without significant loss of its activity are notable advantages of this new protocol compared to other recent introduced procedures.

NiII NPs entrapped within a matrix of l-glutamic acid cross-linked chitosan supported on magnetic carboxylic acid-functionalized multi-walled carbon nanotube: a new and efficient multi-task catalytic system for the green one-pot synthesis of diverse heterocyclic frameworks

In the present study, a new l-glutamic acid cross-linked chitosan supported on magnetic carboxylic acid-functionalized multi-walled carbon nanotube (Fe₃O₄/f-MWCNT-CS-Glu) nanocomposite was prepared through a convenient one-pot multi-component sequential strategy. Then, nickel^II nanoparticles (Ni^II NPs) were entrapped within a matrix of the mentioned nanocomposite. Afterward, the structure of the as-prepared Fe₃O₄/f-MWCNT-CS-Glu/Ni^II nanosystem was elucidated by various techniques, including FT-IR, PXRD, SEM, TEM, SEM-based EDX and elemental mapping, ICP-OES, TGA/DTA, and VSM. In the next part of this research, the catalytic applications of the mentioned nickel^II-containing magnetic nanocomposite were assessed upon green one-pot synthesis of diverse heterocyclic frameworks, including bis-coumarins (3a–n), 2-aryl(or heteroaryl)-2,3-dihydroquinazolin-4(1H)-ones (5a–r), 9-aryl-3,3,6,6-tetramethyl-3,4,5,6,7,9-hexahydro-1H-xanthene-1,8(2H)-diones (7a–n), and 2-amino-4-aryl-7,7-dimethyl-5-oxo-5,6,7,8-tetrahydro-4H-chromene-3-carbonitriles (9a–n). The good-to-excellent yields of the desired products, satisfactory reaction rates, use of water solvent or solvent-free reaction medium, acceptable turnover numbers (TONs) and turnover frequencies (TOFs), along with comfortable recoverability and satisfying reusability of the as-prepared nanocatalyst for at least eight successive runs, and also easy work-up and purification procedures are some of the advantages of the current synthetic protocols.

In this research work, an Fe₃O₄/f-MWCNT-CS-Glu/Ni^II hybrid nanocomposite was synthesized, characterized, and used as a new and efficient multi-task catalytic system for the green one-pot synthesis of diverse heterocyclic frameworks.

Diverse and efficient catalytic applications of new cockscomb flower-like Fe3O4@SiO2@KCC-1@MPTMS@CuII mesoporous nanocomposite in the environmentally benign reduction and reductive acetylation of nitroarenes and one-pot synthesis of some coumarin compounds

In this research, Fe₃O₄@SiO₂@KCC-1@MPTMS@Cu^II as a new cockscomb flower-like mesoporous nanocomposite was prepared and characterized by various techniques including Fourier transform infrared (FT-IR) spectroscopy, powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), SEM-based energy-dispersive X-ray (EDX) spectroscopy, inductively coupled plasma-optical emission spectrometry (ICP-OES), thermogravimetric analysis/differential thermal analysis (TGA/DTA), vibrating sample magnetometry (VSM), UV-Vis spectroscopy, and Brunauer-Emmett-Teller (BET) and Barrett-Joyner-Halenda (BJH) analyses. The as-prepared Fe₃O₄@SiO₂@KCC-1@MPTMS@Cu^II mesoporous nanocomposite exhibited satisfactory catalytic activity in the reduction and reductive acetylation of nitroarenes in a water medium and solvent-free one-pot synthesis of some coumarin compounds including 3,3'-(arylmethylene)bis(4-hydroxy-2H-chromen-2-ones) (namely, bis-coumarins) (3a-n) and 2-amino-4-aryl-7,7-dimethyl-5-oxo-5,6,7,8-tetrahydro-4H-chromene-3-carbonitriles (6a-n) along with acceptable turnover numbers (TONs) and turnover frequencies (TOFs). Furthermore, the mentioned Cu^II-containing mesoporous nanocatalyst was conveniently recovered by a magnet from reaction environments and reused for at least seven cycles without any significant loss in activity, which confirms its good stability.

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.

Catalytic Approaches to Multicomponent Reactions: A Critical Review and Perspectives on the Roles of Catalysis

In this review, we comprehensively describe catalyzed multicomponent reactions (MCRs) and the multiple roles of catalysis combined with key parameters to perform these transformations. Besides improving yields and shortening reaction times, catalysis is vital to achieving greener protocols and to furthering the MCR field of research. Considering that MCRs typically have two or more possible reaction pathways to explain the transformation, catalysis is essential for selecting a reaction route and avoiding byproduct formation. Key parameters, such as temperature, catalyst amounts and reagent quantities, were analyzed. Solvent effects, which are likely the most neglected topic in MCRs, as well as their combined roles with catalysis, are critically discussed. Stereocontrolled MCRs, rarely observed without the presence of a catalytic system, are also presented and discussed in this review. Perspectives on the use of catalytic systems for improved and greener MCRs are finally presented.

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.

Stereoselective Synthesis of δ- and ε-Amino Ketone Derivatives from N-tert-Butanesulfinyl Aldimines and Functionalized Organolithium Compounds

The addition of functionalized organolithium compounds derived from 5-chloro-2-methoxy-1-pentene and 6-chloro-2-methoxy-1-hexene to N-tert-butanesulfinyl aldimines imines, and a subsequent hydrolysis of the enol ether moiety, yielded different δ- and ε-amino ketone derivatives, respectively, in moderate yields and diastereoselectivities. The application of these compounds in organic synthesis was demonstrated by the preparation of 2-substituted 6-methylpiperidines in a stereoselective manner, among them natural alkaloids (+)- and (−)-isosolenopsin A.

Passerini Multicomponent Reactions Enabling Self-Reporting Photosensitive Tetrazole Polymers

We introduce the synthesis of photosensitive tetrazole monomers via Passerini multicomponent reactions (MCRs). We exploit the MCR's tolerance toward various functional groups under mild, catalyst-free conditions in a one-pot reaction setup to generate tetrazole-containing monomers featuring a methacrylic moiety, which enables their subsequent reversible addition-fragmentation chain transfer (RAFT) polymerization. By employing tetrazoles with either a 4-methoxy phenyl or a pyrene substituent, further modifications of the polymers in a wavelength-orthogonal, self-reporting fashion upon irradiation with either UV or visible light become possible.

Tetramethylguanidine-functionalized melamine as a multifunctional organocatalyst for the expeditious synthesis of 1,2,4-triazoloquinazolinones

Novel nano-ordered 1,1,3,3-tetramethylguanidine-functionalized melamine (Melamine@TMG) organocatalyst was prepared and adequately identified by various techniques including FTIR, EDX, XRD and SEM spectroscopic or microscopic methods as well as TGA and DTG analytical methods. The Melamine@TMG, as an effective multifunctional organocatalyst, was found to promote smoothly the three-component synthesis of 1,2,4-triazoloquinazolinone derivatives using cyclic dimedone, 3-amino-1,2,4-triazole and different benzaldehyde derivatives in EtOH at 40 °C. This practical method afforded the desired products in high to excellent yields (86-99%) and short reaction times (10-25 min). The main advantages of this new method are the use of heterogeneous multifunctional nanocatalyst, simple work-up procedure with no need for chromatographic purification, highly selective conversion of substrates and recyclability of the catalyst, which could be used in five consecutive runs with only a small decrease in its activity.

A comprehensive survey upon diverse and prolific applications of chitosan-based catalytic systems in one-pot multi-component synthesis of heterocyclic rings

Heterocyclic compounds are among the most prestigious and valuable chemical molecules with diverse and magnificent applications in various sciences. Due to the remarkable and numerous properties of the heterocyclic frameworks, the development of efficient and convenient synthetic methods for the preparation of such outstanding compounds is of great importance. Undoubtedly, catalysis has a conspicuous role in modern chemical synthesis and green chemistry. Therefore, when designing a chemical reaction, choosing and or preparing powerful and environmentally benign simple catalysts or complicated catalytic systems for an acceleration of the chemical reaction is a pivotal part of work for synthetic chemists. Chitosan, as a biocompatible and biodegradable pseudo-natural polysaccharide is one of the excellent choices for the preparation of suitable catalytic systems due to its unique properties. In this review paper, every effort has been made to cover all research articles in the field of one-pot synthesis of heterocyclic frameworks in the presence of chitosan-based catalytic systems, which were published roughly by the first quarter of 2020. It is hoped that this review paper can be a little help to synthetic scientists, methodologists, and catalyst designers, both on the laboratory and industrial scales.

Efficient One-Pot Synthesis of 3,4-Dihydropyrimidin-2(1H)-ones via a Three-Component Biginelli Reaction

Multicomponent reactions are considered to be of increasing importance as time progresses due to the economic and environmental advantages such strategies entail. The three-component Biginelli reaction involves the combination of an aldehyde, a β-ketoester and urea to produce 3,4-dihydropyrimidin-2(1H)-ones, also known as DHPMs. The synthesis of these products is highly important due to their myriad of medicinal properties, amongst them acting as calcium channel blockers and antihypertensive and anti-inflammatory agents. In this study, silicotungstic acid supported on Ambelyst-15 was used as a heterogeneous catalyst for the Biginelli reaction under solventless conditions. Electron-poor aromatic aldehydes gave the best results. Sterically hindered β-ketoesters resulted in lower reaction yields. The reaction was carried out under heterogeneous catalysis to allow easy recovery of the product from the reaction mixture and recycling of the catalyst. The heterogeneity of the reaction was confirmed by carrying out a hot filtration test.

Green chemistry and coronavirus

The novel coronavirus pandemic has rapidly spread around the world since December 2019. Various techniques have been applied in identification of SARS-CoV-2 or COVID-19 infection including computed tomography imaging, whole genome sequencing, and molecular methods such as reverse transcription polymerase chain reaction (RT-PCR). This review article discusses the diagnostic methods currently being deployed for the SARS-CoV-2 identification including optical biosensors and point-of-care diagnostics that are on the horizon. These innovative technologies may provide a more accurate, sensitive and rapid diagnosis of SARS-CoV-2 to manage the present novel coronavirus outbreak, and could be beneficial in preventing any future epidemics. Furthermore, the use of green synthesized nanomaterials in the optical biosensor devices could leads to sustainable and environmentally-friendly approaches for addressing this crisis.

A straightforward, environmentally beneficial synthesis of spiro[diindeno[1,2-b:2',1'-e]pyridine-11,3'-indoline]-2',10,12-triones mediated by a nano-ordered reusable catalyst

A library of new spiro[diindeno[1,2-b:2',1'-e]pyridine-11,3'-indoline]-2',10,12-trione derivatives has been prepared in an efficient, one-pot pseudo four-component method mediated by a reusable heterogeneous nano-ordered mesoporous SO3H functionalized-silica (MCM-41-SO3H) catalyst. Excellent yields, short reaction times, as well as convenient non-chromatographic purification of the products and environmental benefits such as green and metal-free conditions constitute the main advantages of the developed synthetic methodology. The obtained fused indole-indenone dyes would be of interest to pharmaceutical and medicinal chemistry. Furthermore, due to their sensitivity to pH changes, they could be used as novel pH indicators.

Synthesis of Nβ-Protected Amino Sulfenyl Methyl Formamides and Sulfonyl Methyl Formamides: A Simple Protocol

Chiral amino acid-derived formamides represent one of the most versatile components in multicomponent reactions. Herein, we describe a facile synthesis of N^β-protected amino sulfenyl methyl formamides and sulfonyl methyl formamides via the Mannich reaction of N^α-protected amino alkyl thiols followed by oxidation using 3-chloroperbenzoic acid (m-CPBA). This protocol is applicable to a wide range of Fmoc- and Cbz-protected amino acids. Notably, the reaction provides high yield and retains the stereochemistry of the chiral center of the starting component.

Self-Reporting of Folding and Aggregation by Orthogonal Hantzsch Luminophores Within a Single Polymer Chain

Self-reporting fluorescence methods for monitoring folding and aggregation of proteins have a long history in biochemistry. Placing orthogonal luminophores within individual synthetic polymer chains for self-reporting both folding (i.e., its intramolecular compaction to isolated single-chain nanoparticles, SCNPs) and unbidden aggregation (i.e., the intermolecular association of SCNPs) remains a great challenge. Herein, a simple and efficient platform to identify both single-chain compaction and intermolecular aggregation phenomena via photoluminescence is presented based on simultaneous synthesis through Hantzsch ester formation of orthogonal luminophores within the same polymer chain. Starting from non-luminescent β-ketoester-decorated chains, intramolecular compaction is visually detected through fluorescence arising from Hantzsch fluorophores generated as intra-chain connectors during folding. Complementary, intermolecular association is identified via aggregation-induced emission (AIE) from orthogonal luminophores displaying intense photoluminescence at redshifted wavelengths after formation of multi-SCNPs assemblies.

How and Why to Investigate Multicomponent Reactions Mechanisms? A Critical Review

We review the most innovative efforts and greatest challenges faced when elucidating multicomponent reactions (MCRs) mechanisms. When compared to traditional reactions, the often two or more concurrent reactions pathways and the greater number of possible intermediates in MCRs turn their mechanistic investigation both a harder and trickier task. The common approaches used to investigate reaction mechanisms are often unable to clarify MCRs mechanisms; hence few but clever approaches are currently used to determine these mechanisms and to depict their key transformations. Their complexity has required most innovative approaches and the use of a number of unique techniques that have shed light over the favored pathway selected from the myriad of alternatives theoretically available for MCRs. This review focuses on the most successful efforts applied by a few leading groups to perform these puzzlingly investigations.

The Ugi three-component reaction and its variants

A broad variety of α-aminoamide-based compounds have been synthesized via the three-component version of the Ugi reaction (U-3CR) or by any of its variants (Ugi-Zhu-3CR, Orru-3CR, Ugi-4C-3CR, Ugi-Joullié-3CR, GBB-3CR, Ugi-Reissert-3CR, and so on).