Highly efficient and versatile chemoselective addition of amines to epoxides in water catalyzed by erbium(III) triflate

Eco-Friendly Synthesis of PEtOz-PA: A Promising Polymer for the Formulation of Curcumin-Loaded Micelles

The need to develop alternative methods or to use "green" solvents constitutes an essential strategy under the emerging field of green chemistry, particularly in the development of new synthetic strategies in the field of pharmaceutic industry. We report an eco-friendly method of synthesis of poly(2-ethyl-2-oxazoline)-palmitoylate (PEtOz-PA) using Er(OTf)₃ as Lewis's acid catalyst in 2-MeTHF. The novel biomolecule derivative was characterized to confirm palmitoyl group substitution and employed for the formulation, characterization, and antioxidant activity evaluation of curcumin-loaded polymeric micelles.

The Highly Efficient Synthesis of 1,2-Disubstituted Benzimidazoles Using Microwave Irradiation

The benzimidazole ring of the heterocyclic pharmacophores is one of the most widespread and studied systems in nature. The benzimidazole derivative synthesis study is a crucial point for the development of a clinically available benzimidazole-based drug. Here, we report a simple microwave assisted method for the synthesis of 1,2-disubstituted benzimidazoles. The combination of the molar ratio of N-phenyl-o-phenylenediamine:benzaldehyde (1:1) using microwave irradiation and only 1% mol of Er(OTf)₃ provides an efficient and environmental mild access to a diversity of benzimidazoles under solvent-free conditions. The proposed method allows for the obtainment of the desired products in a short time and with very high selectivity.

Gram-Scale Domino Synthesis in Batch and Flow Mode of Azetidinium Salts

Azetidinium salts are important motifs in organic synthesis but are difficult to obtain due to extremely long synthetic protocols. Herein, a rapid continuous-flow process for the on-demand synthesis of azetidinium salts is described. In particular, the nucleophilic addition of secondary amines and the subsequent intramolecular N-cyclization have been investigated in batch and continuous-flow modes, exploring the effects of solvent type, temperature, reaction time, and amine substituent on the synthesis of azetidinium salts. This has enabled us to quickly identify optimal reaction conditions and obtain microkinetic parameters, verifying that the use of a flow reactor leads to a reduction of the activation energy for the epichlorohydrin aminolysis due to the better control of mass and heat transfer during reaction. This confirms the key role of continuous-flow technologies to affect the kinetics of a reaction and make synthetic protocols ultrarapid and more efficient.

Montmorillonite K10: An Efficient Organo-Heterogeneous Catalyst for Synthesis of Benzimidazole Derivatives

The use of toxic solvents, high energy consumption, the production of waste and the application of traditional processes that do not follow the principles of green chemistry are problems for the pharmaceutical industry. The organic synthesis of chemical structures that represent the starting point for obtaining active pharmacological compounds, such as benzimidazole derivatives, has become a focal point in chemistry. Benzimidazole derivatives have found very strong applications in medicine. Their synthesis is often based on methods that are not convenient and not very respectful of the environment. A simple montmorillonite K10 (MK10) catalyzed method for the synthesis of benzimidazole derivatives has been developed. The use of MK10 for heterogeneous catalysis provides various advantages: the reaction yields are decidedly high, the work-up procedures of the reaction are easy and suitable, there is an increase in selectivity and the possibility of recycling the catalyst without waste formation is demonstrated. The reactions were carried out in solvent-free conditions and in a short reaction time using inexpensive and environmentally friendly heterogeneous catalysis. It has been shown that the reaction process is applicable in the industrial field.

M-Type SrFe12O19 Ferrite: An Efficient Catalyst for the Synthesis of Amino Alcohols under Solvent-Free Conditions

Magnetically separable strontium hexaferrite SrFe12O19 was prepared using the chemical coprecipitation method, and the nanostructured material was characterized by X-ray diffraction, scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS), and BET analysis. The SEM images showed the homogeneity of the chemical composition of SrFe12O19 and uniform distribution of size and morphology. The pore size of the nanomaterial and its specific area were determined by BET measurements. Strontium hexaferrite SrFe12O19 exhibited a strong magnetic field, which is highly suitable in the heterogeneous catalysis as it can be efficiently separated from the reaction. The magnetic nanocatalyst showed high activity and environmentally benign heterogeneous catalysts for the epoxide ring-opening with amines affording β-amino alcohols under solvent-free conditions. When unsymmetrical epoxides were treated in the presence of aromatics amines, the regioselectivity was influenced by the electronic and steric factors. Total regioselectivity was observed for the reactions performed with aliphatic amines. The magnetically SrFe12O19 nanocatalyst showed excellent recyclability with continuously good catalytic activities after four cycles.

Highly regioselective ring-opening of epoxides with amines: a metal- and solvent-free protocol for the synthesis of β-amino alcohols

We herein report a metal- and solvent-free acetic acid-mediated ring-opening reaction of epoxides with amines. This process provides β-amino alcohols in high yields with excellent regioselectivity. Importantly, this epoxide ring-opening protocol can be used for the introduction of amines in natural products during late-stage transformations.

Eco-Friendly Extraction and Characterisation of Nutraceuticals from Olive Leaves

Olive tree (Olea europaea L.) leaf, a waste by-product of the olive oil industry, is an inexpensive and abundant source of biophenols of great interest for various industrial applications in the food supplement, cosmetic, and pharmaceutical industries. In this work, the aqueous extraction of high-added value compounds from olive leaves by using microfiltered (MF), ultrapure (U), and osmosis-treated (O) water was investigated. The extraction of target compounds, including oleuropein (Olp), hydroxytyrosol (HyTyr), tyrosol (Tyr), verbascoside (Ver), lutein (Lut), and rutin (Rut), was significantly affected by the characteristics of the water used. Indeed, according to the results of liquid chromatography tandem mass spectrometry, the extracting power of microfiltered water towards rutin resulted very poor, while a moderate extraction was observed for oleuropein, verbascoside, and lutein. On the other hand, high concentrations of hydroxytyrosol were detected in the aqueous extracts produced with microfiltered water. The extraction power of ultrapure and osmosis-treated water proved to be very similar for the bio-active compounds oleuropein, verbascoside, lutein, and rutin. The results clearly provide evidence of the possibility of devising new eco-friendly strategies based on the use of green solvents which can be applied to recover bioactive compounds from olive leaves.

Green Synthesis of Privileged Benzimidazole Scaffolds Using Active Deep Eutectic Solvent

The exploitation and use of alternative synthetic methods, in the face of classical procedures that do not conform to the ethics of green chemistry, represent an ever-present problem in the pharmaceutical industry. The procedures for the synthesis of benzimidazoles have become a focus in synthetic organic chemistry, as they are building blocks of strong interest for the development of compounds with pharmacological activity. Various benzimidazole derivatives exhibit important activities such as antimicrobial, antiviral, anti-inflammatory, and analgesic activities, and some of the already synthesized compounds have found very strong applications in medicine praxis. Here we report a selective and sustainable method for the synthesis of 1,2-disubstituted or 2-substituted benzimidazoles, starting from o-phenylenediamine in the presence of different aldehydes. The use of deep eutectic solvent (DES), both as reaction medium and reagent without any external solvent, provides advantages in terms of yields as well as in the work up procedure of the reaction.

Montmorillonite K10-Catalyzed Solvent-Free Conversion of Furfural into Cyclopentenones

A simple and eco-friendly montmorillonite K10 (MK10)-catalyzed method for the synthesis of cyclopentenone derivatives from biomass-produced furfural has been developed. The versatility of this protocol is that the reactions were performed under solvent-free conditions and in a short reaction time under heterogeneous catalysis. Montmorillonite K10 is mostly explored as a heterogeneous catalyst since it is inexpensive and environmentally friendly.

Efficient synthesis of organic thioacetates in water

Thioacetates as precursors of thiols are interesting starting points for synthesizing other organosulfur compounds. Herein, we propose a simple, efficient and fast method to obtain organic thioacetates using water as a solvent. Taking into account the great attention that has been paid toward environmentally friendly synthetic procedures in the past decades, we prove the role and the strength of the thioacetate anion as a nucleophile for nucleophilic displacement reactions in an aqueous medium. The reactions were carried out under pH control, to prevent the decomposition of the mesylate starting materials, using potassium carbonate as a safe and mild base. A simple work up allows products to be obtained with excellent yield and acceptable purity.

Biorenewable Deep Eutectic Solvent for Selective and Scalable Conversion of Furfural into Cyclopentenone Derivatives

The development of novel synthetic routes to produce bioactive compounds starting from renewable sources has become an important research area in organic and medicinal chemistry. Here, we present a low-cost procedure for the tunable and selective conversion of biomass-produced furfural to cyclopentenone derivatives using a mixture of choline chloride and urea as a biorenewable deep eutectic solvent (DES). The proposed medium is a nontoxic, biodegradable, and could be reused up to four times without any unfavorable effect on the reaction yield. The process is tunable, clean, cheap, simple and scalable and meets most of the criteria; therefore, it can be considered as an environmental sustainable process in a natural reaction medium.

Post-synthesis of Zr-MOR as a robust solid acid catalyst for the ring-opening aminolysis of epoxides

Zirconosilicate with the MOR topology (Zr-MOR) was successfully prepared using a two-step post-synthesis strategy from pre-dealumination of a H-MOR zeolite and subsequent dry impregnation of Cp₂ZrCl₂.

Catalytic Organic Reactions in Water toward Sustainable Society

Traditional organic synthesis relies heavily on organic solvents for a multitude of tasks, including dissolving the components and facilitating chemical reactions, because many reagents and reactive species are incompatible or immiscible with water. Given that they are used in vast quantities as compared to reactants, solvents have been the focus of environmental concerns. Along with reducing the environmental impact of organic synthesis, the use of water as a reaction medium also benefits chemical processes by simplifying operations, allowing mild reaction conditions, and sometimes delivering unforeseen reactivities and selectivities. After the "watershed" in organic synthesis revealed the importance of water, the development of water-compatible catalysts has flourished, triggering a quantum leap in water-centered organic synthesis. Given that organic compounds are typically practically insoluble in water, simple extractive workup can readily separate a water-soluble homogeneous catalyst as an aqueous solution from a product that is soluble in organic solvents. In contrast, the use of heterogeneous catalysts facilitates catalyst recycling by allowing simple centrifugation and filtration methods to be used. This Review addresses advances over the past decade in catalytic reactions using water as a reaction medium.

Concise, Protecting-Group-Free Synthesis of (+)-Nemonapride via Eu(OTf)3-Catalyzed Aminolysis of 3,4-Epoxy Alcohol

A concise, protecting-group-free synthesis of the antipsychotic agent (+)-nemonapride has been achieved featuring a europium(III) trifluoromethanesulfonate (Eu(OTf)₃)-catalyzed C4 selective aminolysis of a 3,4-epoxy alcohol by benzylamine and an expedient use of the resulting 4-benzylamino-1,3-diol product for constructing the pyrrolidine skeleton.

Nucleophilic addition of amines, alcohols, and thiophenol with epoxide/olefin using highly efficient zirconium metal organic framework heterogeneous catalyst

Zr based MOF exhibited excellent activity in the ring opening of epoxides/nucleophilic addition of activated olefins with wide range of nucleophiles.

Aqueous MW eco-friendly protocol for amino group protection

In this paper a new catalyst-free and on-water method for protection of amines and amino acids with di-tert-butyl dicarbonate, 9-fluorenylmethoxycarbonyl chloride, acetyl chloride and tosyl chloride is presented.

Tungsten-catalyzed regioselective and stereospecific ring opening of 2,3-epoxy alcohols and 2,3-epoxy sulfonamides

The first catalytic, highly C3-selective, stereosepecific ring-opening reaction of 2,3-epoxy alcohols and 2,3-epoxy sulfonamides has been accomplished. This process was efficiently promoted by W-salts, and the developed method was applicable to various epoxides with diverse N- and O-nucleophiles affording the products in good to excellent yields (up to 95%) and generally with high regioselectivities (C3:C2 up to >99:1).

Rapid catalyst screening by a continuous-flow microreactor interfaced with ultra-high-pressure liquid chromatography

A high-throughput screening system for homogeneous catalyst discovery has been developed by integrating a continuous-flow capillary-based microreactor with ultra-high-pressure liquid chromatography (UHPLC) for fast online analysis. Reactions are conducted in distinct and stable zones in a flow stream that allows for time and temperature regulation. UHPLC detection at high temperature allows high throughput online determination of substrate, product, and byproduct concentrations. We evaluated the efficacies of a series of soluble acid catalysts for an intramolecular Friedel-Crafts addition into an acyliminium ion intermediate within 1 day and with minimal material investment. The effects of catalyst loading, reaction time, and reaction temperature were also screened. This system exhibited high reproducibility for high-throughput catalyst screening and allowed several acid catalysts for the reaction to be identified. Major side products from the reactions were determined through off-line mass spectrometric detection. Er(OTf)(3), the catalyst that showed optimal efficiency in the screening, was shown to be effective at promoting the cyclization reaction on a preparative scale.

Ruthenium-catalyzed selective monoamination of vicinal diols

The monoamination of vicinal diols in the presence of in situ generated ruthenium catalysts has been investigated. Among the various phosphines tested in combination with [Ru(3)(CO)(12)], N-phenyl-2-(dicyclohexyl-phosphanyl)pyrrole showed the best performance. After optimization of the reaction conditions this system was applied to different secondary amines and anilines as well as a number of vicinal diols. With the exception of ethylene glycol, monoamination of the vicinal diols occurred selectively and the corresponding amino alcohols were obtained in good yields, producing water as the only side product.