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Developing more efficient and greener catalytic strategies for upgrading biomass to value-added chemicals and fuels is crucial for a more sustainable future. Recently, single-atom catalysts have played an important role in this mission.

The triazole heterocycle is a privileged scaffold in medicinal chemistry, since its structure is present in a large number of biologically active molecules, including several drugs currently in the market. Due to their vast applications, a wide variety of methods are described for their preparation, such as the 1,3-dipolar cycloaddition and processes involving diazo compounds and diazo transfer reactions. Considering the significant number of contributions from our research group to this chemistry in recent decades, in this account we discuss both the development of new methods for the synthesis of 1,2,3-triazoles and the preparation of new triazole-functionalized biologically active molecules using classical approaches.

Molecular rearrangements are important tools to increase the molecular diversity of new bioactive compounds, especially in the class of heterocycles. This review deals specifically with a very famous and widely applicable rearrangement known as the Dimroth Rearrangement. Although it has originally been observed for 1,2,3-triazoles, its amplitude was greatly expanded to other heterocycles, as well as from laboratory to large scale production of drugs and intermediates. The reactions that were discussed in this review were selected with the aim of demonstrating the windows that may be open by the Dimroth's rearrangement, especially in what regards the development of new synthetic approaches toward biologically active compounds.

In recent years, the development of new pharmaceutical formulations for the treatment of sporotrichosis has become a relevant research field. In this work, we aimed to develop an emulgel containing itraconazole and clotrimazole to ensure therapeutic effectiveness against Sporothrix brasiliensis. The topical use of a formulation that combines both drugs represents an interesting option for the complementary treatment of sporotrichosis. The emulgel formulation was prepared and evaluated for its zeta potential, viscosity, in vitro antifungal activity and stability at different storage conditions. The results showed that the newly developed emulgel displayed promising physicochemical characteristics, as well as a good in vitro inhibitory activity against S. brasiliensis yeasts. The results obtained in this work suggest that the emulgel containing itraconazole and clotrimazole might highly be efficient and a complementary therapy to oral administration in the treatment of sporotrichosis.

The P2X7 receptor (P2X7R) is an ion channel that promotes the passage of ions through the membrane through brief stimulation once activated by ATP, its endogenous opener. However, prolonged stimulation with ATP, which occurs in pathological processes, opens a nonselective pore in the plasma membrane, allowing the passage of large molecules and leading to cytokine release or even cell death. In this sense, the search for new inhibitors for this receptor has attracted a great deal of attention in recent years. Considering the booming of biomass upgrading reactions in recent years and the continued efforts to synthesize biologically active molecules containing the 1,2,3-triazole ring, in the present work, we aimed to investigate whether triazole-linked menadione-furan derivatives could present P2X7R inhibitory activity. The novel compounds were tested for their inhibitory activity on ATP-induced dye uptake in peritoneal macrophages. Some have shown promising results, having displayed IC

Herein, we describe the preparation and thorough characterization of a novel magnetically recoverable copper(I)-exchanged β-zeolite and its use as an efficient catalyst for the synthesis of 1,2,3-triazoles via the one-pot three-component reaction of organic halides, terminal acetylenes, and sodium azide in water. The magnetically recoverable β-zeolite could be easily separated from the reaction mixture with the aid of a magnet and reused in several consecutive reactions. Importantly, a series of characterizations studies allowed us to disclose the mechanism for the deactivation of the catalyst, and therefore to propose a method for its reactivation.

Lignocellulosic biomass is becoming a viable alternative or complementary source for obtaining petroleum-derived products such as fuels, polymers and fine chemicals, among others. Nevertheless, the successful upgrading of lignocellulosics requires the design of efficient and robust catalysts, where sulfonated mesoporous silica materials may be an ideal choice for exploration. Herein, we have conducted the upgrading of several mono-, di- and polysaccharides such as xylose, fructose, glucose, sucrose and cellulose to valuable platform chemicals using a novel catalyst comprising sulfonated dendritic mesoporous silica nanospheres. Additionally, a thorough comparative study was conducted encompassing arrays of sulfonated silicas as catalysts with the aim of relating their activities and appreciating the features which could be responsible for their activity.

Naphthoquinones are important molecules belonging to the general class of quinones, and many of these compounds have become drugs that are in the pharmaceutical market for the treatment of several diseases. A special subclass of compounds is that of the bis(naphthoquinones), which have two linked naphthoquinone units. In the last few years, several synthetic approaches toward such valuable compounds have been described, as well as their evaluation against numerous important biological targets. In this review, we provide a thorough discussion on the various synthetic methods reported for the synthesis of bis(naphthoquinone) analogues, also highlighting the biological activities of these substances.

The use of zeolite catalysts for biomass valorization has increasingly contributed to the development of more efficient and sustainable processes in recent times. ZSM-5 zeolites, in special, have displayed great potential as catalysts in such reactions owing to their promising features e.g. the tridimensional medium size pore system and the wide Si/Al ratio. Considering these facts, in this review we provide an outline of lignocellulosic biomass upgrading processes using ZSM-5 zeolites in their acidic form and exchanged with transition metals; we will cover not only the direct conversion of lignocellulosic biomass, but also the upgrading of its derivatives.

Multicomponent reactions are processes in which three or more reactants are introduced concurrently to deliver a single product that contains the essential parts of the starting materials, and those have emerged in the last few years as an important tool for the development of more sustainable processes in modern synthetic organic chemistry. Still, considering the pronounced attention devoted to zeolites as efficient and selective catalysts for organic transformations, in this work we have reviewed the recent applications of zeolites as catalysts in multicomponent reactions; initially, zeolites modified with transition metals were discussed, followed by zeolites with alkaline metals and in the final section, zeolites in the protonic form.

Background: Several quinones are on the pharmaceutical market as drugs for the treatment of several diseases. Objective: The aim of this review was to provide an overview on the quinones that have become drugs for several therapeutic applications. Method: We have comprehensively and critically discussed all the information available in the literature about quinonebased drugs. Results: In this review, the various aspects of the chemistry and biochemistry of these drugs are highlighted, including their repositioning, drug combination and their new uses. Conclusion: The number of studies related to quinone drugs for different pharmaceutical uses shows that the interest in new applications still increasing in recent years.

The use of graphitic carbon nitride (g-C3N4)-based catalysts in the upgrading of lignocellulosic biomass significantly contributes to the greener production of biofuels, polymer precursors, and building blocks. In recent years, several catalysts based on g-C3N4 have been developed and applied in both photocatalyzed and non-photocatalyzed (thermal) reactions. This Review provides an overview on the upgrading of lignocellulosic biomass deploying several compositions of g-C3N4-based catalysts.

The tumor suppressor protein p53 is often called “the genome guardian” and controls the cell cycle and the integrity of DNA, as well as other important cellular functions. Its main function is to trigger the process of apoptosis in tumor cells, and approximately 50% of all cancers are related to the inactivation of the p53 protein through mutations in the TP53 gene. Due to the association of mutant p53 with cancer therapy resistance, different forms of restoration of p53 have been subject of intense research in recent years. In this sense, this review focus on the main currently adopted approaches for activation and reactivation of p53 tumor suppressor function, focusing on the synthetic approaches that are involved in the development and preparation of such small molecules.

A magnetically recoverable catalyst [Fe 3 O 4 @SiO 2 -AEAPTMS-Pd(II)] was prepared, fully characterized and had its catalytic activity evaluated on the Suzuki cross-coupling reaction under microwave irradiation. The reaction conditions for the synthesis of biaryl compounds was optimized in two stages - an initial fractional design 2 4 , in which the parameters reaction time, temperature, solvent and catalyst loading were evaluated, followed by a Doehlert design. The factorial design proved to be a viable approach for obtaining the optimal reaction conditions based on a relatively small number of experiments. Additionally, the biaryl derivatives synthesized by this method were obtained with good to excellent yields (71–96%) and the recovery and reuse of the palladium catalyst was also evaluated.

Sporotrichosis occurs worldwide and is caused by the fungus Sporothrix brasiliensis. This agent has a high zoonotic potential and is transmitted mainly by bites and scratches from infected felines. A new association between the drugs clotrimazole and itraconazole is shown to be effective against S. brasiliensis yeasts. This association was formulated as a microemulsion containing benzyl alcohol as oil, Tween&reg, 60 and propylene glycol as surfactant and cosurfactant, respectively, and water. Initially, the compatibility between clotrimazole and itraconazole was studied using differential scanning calorimetry (DSC), thermogravimetric analysis (TG), Fourier transform infrared spectroscopy (FTIR), and X-ray powder diffraction (PXRD). Additionally, a simple and efficient analytical HPLC method was developed to simultaneously determine the concentration of clotrimazole and itraconazole in the novel microemulsion. The developed method proved to be efficient, robust, and reproducible for both components of the microemulsion. We also performed an accelerated stability study of this formulation, and the developed analytical method was applied to monitor the content of active ingredients. Interestingly, these investigations led to the detection of a known clotrimazole degradation product whose structure was confirmed using NMR and HRMS, as well as a possible interaction between itraconazole and benzyl alcohol.

An array of magnetically recoverable β-zeolites exchanged with late transition metals (Pd, Fe and Ir) have been synthesized and fully characterized and had their catalytic activity evaluated on the conversion of several bio-derived compounds to other value-added platform chemicals. The nature of the transition metals exchanged in the zeolite matrix and the significant effect of reaction conditions such as temperature, time and solvent usage on both the conversion and selectivity of the process are delineated.

Graphical abstract, Highlights • The repositioning of approved drugs is a promising approach for treating COVID-19. • Several approved drugs have shown anti-SARS-CoV-2 activity and are discussed herein. • In this review, the synthetic approaches toward such molecules was highlighted. • The mechanisms of action and pharmacological properties of such drugs is discussed., In December 2019, a new variant of SARS-CoV emerged, the so-called acute severe respiratory syndrome coronavirus 2 (SARS-CoV-2). This virus causes the new coronavirus disease (COVID-19) and has been plaguing the world owing to its unprecedented spread efficiency, which has resulted in a huge death toll. In this sense, the repositioning of approved drugs is the fastest way to an effective response to a pandemic outbreak of this scale. Considering these facts, in this review we provide a comprehensive and critical discussion on the chemical aspects surrounding the drugs currently being studied as candidates for COVID-19 therapy. We intend to provide the general chemical community with an overview on the synthetic/biosynthetic pathways related to such molecules, as well as their mechanisms of action against the evaluated viruses and some insights on the pharmacological interactions involved in each case. Overall, the review aims to present the chemical aspects of the main bioactive molecules being considered to be repositioned for effective treatment of COVID-19 in all phases, from the mildest to the most severe.

Ortho-naphthoquinone β-lapachone, a compound originally isolated from the Tabebuia sp tree, has showed pronounced activity against different parasites and cancer cells. However, its use presents limitations mostly related to its low bioavailability, solubility, thermal instability and photodecomposition. In order to overcome such disadvantages, this work aimed to evaluate different methodologies to promote the formation of inclusion complexes between β-lapachone and 2-hydroxypropyl-β-cyclodextrin. For this purpose, manual and automated mechanochemical processes as well as liquid phase methods were employed. The complexes were evaluated for entrapment efficiency (EE) and stability, that is, the maintenance of the entrapment over time. The samples which showed the best results were submitted to a thorough physicochemical and spectroscopic characterization, including 2D NMR techniques, and such analyses revealed that the mechanochemical process furnished the most stable inclusion complex.

In the past decades, the physicochemical properties of electron donor–acceptor, EDA, complexes (also called charge-transfer, CT, complexes) have been extensively studied, although their synthetic applications have been somewhat limited. However, in recent years, this scenario has started to change as an increasing number of examples have been reported. In this regard, this review aims to present and discuss the main aspects associated with the physicochemical properties of these complexes and a selection of synthetic photochemical applications in organic chemistry.

A magnetic ZSM-5 zeolite with a core–shell type structure was synthesized, fully characterized and had its catalytic activity evaluated on the valorization of bio-derived furfuryl alcohol. The catalytic system displayed a tuneable selectivity to γ-valerolactone, alkyl levulinates and even levulinic acid by simply changing the reaction conditions. Furthermore, the catalyst could be easily recovered and reused for several reaction cycles without significant losses in its catalytic activity.

The upgrading of biomass-derived compounds has arisen in recent years as a very promising research field in both academia and industry. In this sense, a lot of new processes and products have been developed, often involving levulinic acid as a starting material or intermediate. In the last few years, though, other scaffolds have been receiving growing attention, especially, angelica lactones. Considering these facts and the emergent applications of said molecules, in this review we will discuss their preparation and applications; the use of these frameworks as starting materials in organic synthesis to produce potential bioactive compounds will be covered, as will their use as a foundation to highly regarded compounds such as liquid alkanes with prospective use as fuels and polymers.

A new magnetically recoverable nanocatalyst was prepared by coating magnetite with niobium oxide (Fe3O4@Nb2O5) by using a simple wet impregnation method. The Fe3O4@Nb2O5 nanocatalyst was fully characterized, and its catalytic activity was evaluated by using the one-pot, three-component Biginelli reaction, with the aim to synthesize 1,4-dihydropyrimidinones, a class of compounds with diverse pharmacological properties. The developed protocol was applied to a wide range of aliphatic and aromatic substrates, and structurally diverse products were obtained in excellent yields. Compared with copper and nickel nanocatalysts, the Fe3O4@Nb2O5 nanocatalyst demonstrated superior catalytic activity at a remarkably low catalyst loading (0.1 mol %). This niobium nanocatalyst could be easily separated from the reaction mixture with an external magnet and was reused several times without any loss of its catalytic activity. Moreover, although the Biginelli reaction is a century-old reaction, its mechanism is still a controversial subject, and our investigation provided an insight into the reaction mechanism.

In the past decades, the physicochemical properties of electron donor–acceptor, EDA, complexes (also called charge-transfer, CT, complexes) have been extensively studied, although their synthetic applications have been somewhat limited. However, in recent years, this scenario has started to change as an increasing number of examples have been reported. In this regard, this review aims to present and discuss the main aspects associated with the physicochemical properties of these complexes and a selection of synthetic photochemical applications in organic chemistry.

Metal-free 1,3-dipolar cycloaddition reactions have proven to be a powerful tool for the assembly of key heterocycles, in particular diversely functionalized 1,2,3-triazoles. A number of metal-free (3+2)-cycloaddition approaches have been developed up to date with the aim to circumvent the use of metal catalysts allowing these reactions to take place in biological systems without perturbation of the naturally occurring processes. This feature article specifically provides an overview of emerging metal-free synthetic routes, and their mechanistic features, in the formation of functionalized 1,2,3-triazoles.

Metal-free 1,3-dipolar cycloaddition reactions have proven to be a powerful tool for the assembly of key heterocycles, in particular diversely functionalized 1,2,3-triazoles. A number of metal-free (3+2)-cycloaddition approaches have been developed up to date with the aim to circumvent the use of metal catalysts allowing these reactions to take place in biological systems without perturbation of the naturally occurring processes. This feature article specifically provides an overview of emerging metal-free synthetic routes, and their mechanistic features, in the formation of functionalized 1,2,3-triazoles.

A new magnetically recoverable nanocatalyst was prepared by coating magnetite with niobium oxide (Fe3O4@Nb2O5) by using a simple wet impregnation method. The Fe3O4@Nb2O5 nanocatalyst was fully characterized, and its catalytic activity was evaluated by using the one-pot, three-component Biginelli reaction, with the aim to synthesize 1,4-dihydropyrimidinones, a class of compounds with diverse pharmacological properties. The developed protocol was applied to a wide range of aliphatic and aromatic substrates, and structurally diverse products were obtained in excellent yields. Compared with copper and nickel nanocatalysts, the Fe3O4@Nb2O5 nanocatalyst demonstrated superior catalytic activity at a remarkably low catalyst loading (0.1 mol %). This niobium nanocatalyst could be easily separated from the reaction mixture with an external magnet and was reused several times without any loss of its catalytic activity. Moreover, although the Biginelli reaction is a century-old reaction, its mechanism is still a controversial subject, and our investigation provided an insight into the reaction mechanism.

Nanocatalysis has arisen in the last few years as a bridge between heterogeneous and homogenous catalysis.1 Metals deposited on the surface of magnetite nanomaterials have been used with the aim to increase the contact between the reagents and catalyst, mimicking homogeneous catalysts while presenting the advantages of heterogeneous catalysis such as easy separation from the reaction mixture, and recyclability.1 Lewis acid supported on magnetite, constitute a very important synthetic tool for the multi-component approaches, e.g. Biginelli reaction. This transformation still attracts researchers attention because 3,4-dihydropyrimidin2(1H)-ones obtained from this multicomponent reaction showed a wide range of biological activities.2 Attempting to disclose further developments on sustainable protocols, heterogeneous catalysis and nanomaterials,3 herein, we report the multicomponent synthesis of 3,4dihydropyrimidin-2(1H)-ones using a new, efficient, recyclable and reusable ferrite-Nb2O5 nanocatalyst.

Correction for 'Emerging approaches for the synthesis of triazoles: beyond metal-catalyzed and strain-promoted azide–alkyne cycloaddition' by Carolina G. S. Lima et al., Chem. Commun., 2015, 51, 10784–10796.