Access to Substituted 1,1-Diarylalkanes by Friedel-Crafts Benzylations Mediated by FeCl3-based Deep Eutectic Solvents

The development of new, more efficient Friedel-Crafts benzylation methodologies that provide access to 1,1-diarylalkanes is an important objective of interest for the production of pharmaceuticals and fine chemical products. In this regard, this study introduces a novel synthetic route to 1,1-diarylalkanes conducted in the Deep Eutectic Solvent (DES) 3 FeCl3 ⋅ 6 H2O/Gly, which serves as both a reaction medium and promoter. Under these conditions, Friedel-Crafts benzylations of various arenes bearing activating and deactivating ortho-/para-directing groups, can be performed using diverse benzylating reagents such as styrenes, alcohols, acetates, ethers, and chlorides. Importantly, highly electronically deactivated electrophiles, including those with CF3 and NO2 groups, are suitable substrates. This methodology provides a wide range of asymmetric 1,1-diarylalkanes (up to 132 examples) with generally good yields and high regioselectivities. The efficiency of this approach was demonstrated with the multigram-scale synthesis (10 mmol) of 1-phenyl-1-xylyl ethane (PXE), a liquid with great industrial applicability. Moreover, the Fe(III)-based DES could be reused for 20 consecutive cycles with no appreciable erosion of the yields.

Efficient synthesis of novel thiadiazolo[2,3-b]quinazolin-6-ones catalyzed by diphenhydramine hydrochloride-CoCl⋅6H2O deep eutectic solvent

In this research, a new Lewis acid-based deep eutectic solvent (LA-DES) was synthesized using diphenhydramine hydrochloride and CoCl2·6H2O, (2[HDPH]:CoCl42-), and identified by FT-IR and 1HNMR techniques. The physicochemical properties of this LA-DES, such as thermal behavior, thermal stability, and solubility in common solvents were also investigated. The catalytic ability of 2[HDPH]:CoCl42- was ascertained in the efficient synthesis of a novel array of thiadiazolo[2,3-b]quinazolin-6-one scaffolds via a one-pot three-component reaction of dimedone/1,3-cyclohexanedione, aldehydes, and 5-aryl-1,3,4-thiadiazol-2-amines/3-(5-amino-1,3,4-thiadiazol-2-yl)-2H-chromen-2-one under solvent-free conditions. This catalyst was also successfully utilized for the synthesis of mono- and bis-thiadiazolo[2,3-b]quinazolin-6-ones from dialdehydes or bis-1,3,4-thiadiazol-2-amine. The simplicity of enforcement, short reaction time, avoidance of toxic organic solvents, scalability of the synthesis procedure, excellent atom economy, high reaction mass efficiency, and low E-factor are other outstanding advantages of this newly developed method. Furthermore, due to the convenient recovery and reuse of LA-DES, this protocol is economically justified and environmentally friendly.

FeIII -Based Eutectic Mixtures as Multi-task and Reusable Reaction Media for Efficient and Selective Conversion of Alkynes into Carbonyl Compounds

An efficient, simple and general protocol for the selective hydration of terminal alkynes into the corresponding methyl ketones has been developed by using a cheap, easy-to-synthesise and sustainable FeIII -based eutectic mixture [FeCl3  ⋅ 6H2 O/Gly (3 : 1)] as both promoter and solvent for the hydration reaction, working: i) under mild (45 °C) and bench-type reaction conditions (air); and ii) in the absence of ligands, co-catalysts, co-solvents or toxic, non-abundant and expensive noble transition metals (Au, Ru, Pd). When the final methyl ketones are solid/insoluble in the eutectic mixture, the hydration reaction takes place in 30 min, and the obtained methyl ketones can be isolated by simply decanting the liquid FeIII -DES, allowing the direct isolation of the desired ketones without VOC solvents. By using this straightforward and simple isolation protocol, we have been able to recycle the FeIII -based eutectic mixture system up to eight consecutive times. Furthermore, the FeIII -eutectic mixture is able to promote the selective and efficient formal oxidation of internal alkynes into 1,2-diketones, with the possibility of recycling this system up to three consecutive times. Preliminary investigations into a possible mechanism for the oxidation of the internal alkynes seem to indicate that it proceeds through the formation of the corresponding methyl ketones and α-chloroketones.

Preparation of polysubstituted imidazoles using AC-SO3H/[Urea]7[ZnCl2]2 as an efficient catalyst system: a novel method, and α-glucosidase inhibitor activity

Deep eutectic solvents (DESs) act as both an organic solvent and a useful catalyst for organic synthesis reactions, especially the synthesis of heterocyclic compounds containing the element nitrogen. DESs exhibit many important properties namely large liquid fields, biodegradability, outstanding thermal stability, and moderate vapor pressure. Amorphous carbon-bearing sulfonic acid groups (AC-SO3H) are one of the new-generation solid acids showing strong acid activity. Based on the simultaneous presence of acidic functional groups such as carboxylic acid, phenolic, and sulfonic acid groups, they exhibit many important activities namely strong Brønsted acid, high surface area, high stability, reusability, and recyclability. In this study, AC-SO3H was made from rice husk via the carbonization and sulfonation processes, and the surface properties and structure were examined using contemporary methods such as FT-IR, P-XRD, TGA, SEM, and EDS. And, [Urea]7[ZnCl2]2 was synthesized from urea and ZnCl2 with a mole ratio of 7 : 2; the structure is defined using FT-IR and TGA. By combining AC-SO3H and [Urea]7[ZnCl2]2 we aim to form an effective catalyst/solvent system for the preparation of polysubstituted imidazole derivatives through the multi-component cyclization reaction from nitrobenzenes, benzil, aldehydes, and ammonium acetate. The major products are obtained with high isolation yields above 60%. To assess the catalyst system's activity, the recovery and reusability of the AC-SO3H/[Urea]7[ZnCl2]2 system were examined with hardly any performance modification. In an effort to create potential enzyme α-glucosidase inhibitors, several novel polysubstituted imidazoles were created. Five of these compounds showed good enzyme α-glucosidase inhibitor activity. The most effective substances were IMI-13, IMI-15, and IMI-20, with IC50 values that were greater than the acarbose at 16.5, 15.8, and 11.6 μM, respectively - the acarbose (IC50, 214.5 μM) as the positive control.

Selective synthesis of 3-formylbenzofuran and 3-acylbenzofuran using a chalcone rearrangement strategy

We developed a method for highly selective synthesis of two benzofuran isomers, by rearranging and subsequently transforming 2-hydroxychalcones. Depending on the reaction conditions, synthesis of 3-formylbenzofurans, unconventional products, and 3-acylbenzofurans was achieved through cyclized 2,3-dihydrobenzofurans obtained from the rearranged products. The facile synthesis of 3-formylbenzofurans facilitated synthesis of the natural product, puerariafuran, from the corresponding chalcone.

A New Pathway for the Preparation of Pyrano[2,3-c]pyrazoles and molecular Docking as Inhibitors of p38 MAP Kinase

We report a new pathway to synthesize pyrano[2,3-c]pyrazoles and their binding mode to p38 MAP kinase. Pyrano[2,3-c]pyrazole derivatives have been prepared through a four-component reaction of benzyl alcohols, ethyl acetoacetate, phenylhydrazine, and malononitrile in the presence of sulfonated amorphous carbon and eosin Y as catalysts. All products were characterized by melting point, ¹H and ¹³C NMR, and HRMS (ESI). The products were screened in silico for their binding activities to both the ATP-binding pocket and the lipid-binding pocket of p38 MAP kinase, using a structure-based flexible docking provided by the engine ADFR. The results showed that eight synthesized compounds had a higher affinity to the lipid pocket than to the other target site, which implied potential applications as allosteric inhibitors. Finally, the most biologically active compound, 5, had a binding affinity comparable to those of other proven lipid pocket inhibitors, with affinity to the target pocket reaching -10.9932 kcal/mol, and also had the best binding affinity to the ATP-binding pockets in all of our products. Thus, our research provides a novel pathway for synthesizing pyrano[2,3-c]pyrazoles and bioinformatic evidence for their biological capability to block p38 MAP kinase pockets, which could be useful for developing cancer or immune drugs.

One-pot three-component synthesis of 1-amidoalkyl naphthols and polyhydroquinolines using a deep eutectic solvent: a green method and mechanistic insight

The multicomponent synthesis of 1-amidoalkyl naphthols and polyhydroquinolines has been developed as an atom-economic procedure catalyzed by a deep eutectic solvent ([CholineCl][ZnCl₂]₃).

Synthesis of a new series of 2-hydroxy-5-iodo-N'-(1-arylethylidene)benzohydrazides using a deep eutectic solvent as solvent/catalyst under sonication

We report here the preparation of 2-hydroxy-5-iodo-N'-(1-arylethylidene)benzohydrazide compounds in good to excellent yields (83-98%) within a short reaction time (10-15 min), through a clean and efficient procedure. Seventeen new compounds were synthesized and fully characterized by FT-IR, NMR, and HRMS. The deep eutectic solvent can be recovered easily by phase extraction and can be reused up to several times without any significant loss of catalytic activity. Additionally, the method has a wide substrate scope and provides an accessible route for the large-scale direct synthesis of 2-hydroxy-5-iodo-N'-(1-arylethylidene)benzohydrazides.

An efficient multicomponent synthesis of 2,4,5-trisubstituted and 1,2,4,5-tetrasubstituted imidazoles catalyzed by a magnetic nanoparticle supported Lewis acidic deep eutectic solvent

A mild and highly efficient reaction for the synthesis of 2,4,5-trisubstituted and 1,2,4,5-tetrasubstituted imidazoles catalyzed by a magnetically supported Lewis acidic deep eutectic solvent on magnetic nanoparticles (LADES@MNP) has been developed via one-pot multicomponent processes under solvent-free sonication. These reactions have good to excellent yields, mild conditions, and work-up simplicity. This method represents a new method for the preparation of 2,4,5-trisubstituted and 1,2,4,5-tetrasubstituted imidazoles. More importantly, LADES@MNP can be easily recovered by magnetic separation and reused five times without significant loss of catalytic activity.

A mild and highly efficient method for the synthesis of 2,4,5-trisubstituted and 1,2,4,5-tetrasubstituted imidazoles catalyzed by a Lewis acidic deep eutectic solvent on magnetic nanoparticles (LADES@MNP).

Synthesis and Properties of Magnetic Aryl-Imidazolium Ionic Liquids with Dual Brønsted/Lewis Acidity

A series of unique tunable aryl-imidazolium magnetic ionic liquids (MILs) with dual acidity that contain both Brønsted and Lewis acidic sites (abbreviated as B-L MILs) were synthesized and characterized using nuclear magnetic resonance and mass spectrometry. Physical properties, such as thermal properties, magnetic susceptibility, and Brønsted and Lewis acidity, were measured. These properties were found to depend on the cation structure. These B-L MILs had good solubility in many organic solvents, good thermal stability, and low melting points, and exhibited magnet-like behavior. For these B-L MILs, the Brønsted acidity was measured using ultraviolet-visible (UV-Vis), and the Lewis acidity was measured using Fourier transform infrared spectroscopy (FTIR). The results showed that B-L MILs with an electron-withdrawing group in the aryl-imidazolium moiety had higher Brønsted acidity, whereas those with an electron-donating group had higher Lewis acidity. This type of ionic liquid, with both Brønsted and Lewis acidic sites, is expected to be a useful solvent and catalyst for organic reactions.

Magnetic solid-phase extraction for the removal of mercury from water with ternary hydrosulphonyl-based deep eutectic solvent modified magnetic graphene oxide

A novel ternary hydrosulphonyl-based deep eutectic solvent (THS-DES) comprised of choline chloride/itaconic acid/3-mercaptopropionic acid (molar ratio 2:1:1) was firstly synthesized. The composition, property and microscopic structure of the new magnetic adsorbent (THS-DES@M-GO) based on the THS-DES modified the magnetic graphene oxide (M-GO) was characterized by the system. Magnetic solid-phase extraction (MSPE) based THS-DES@M-GO was firstly researched for the removal of mercury (Hg²⁺) from water. Various influencing factors such as the mass of adsorbent, solution pH, initial Hg²⁺ concentration, the removal time and temperature had been systematically tested. Under optimized conditions the removal efficiency (R%) could achieved 99.91%. The precision, repeatability and stability experiments were investigated in detail to evaluate the presented method. The relative standard deviations (RSD) of the removal efficiency were 0.053%, 1.49% and 1.55%, respectively. The maximum adsorption capacity (Q_max) was 215.1 mg g^-1 and the data of the experiment fitted well with Langmuir model. Elution experimental studies shown that 94.94% of Hg²⁺ could be eluted by ethylenediaminetetraacetic acid (EDTA). After seven cycles of adsorption-desorption processes, the THS-DES@M-GO still retained a high removal efficiency of 90.23%. Compared with other adsorbents prepared in this work, THS-DES@M-GO displayed higher removal efficiency for Hg²⁺. Interference study proved the composites was tolerated and stabled under the complex matrix. What's more, the analysis of mercury contaminated water (from Guizhou, P.R., China) proved that the proposed method could be used to remove Hg²⁺ in practical application.

Deep eutectic solvent-catalyzed arylation of benzoxazoles with aromatic aldehydes

A green and efficient synthesis of 2-arylbenzoxazoles using deep eutectic solvent as a homogeneous catalyst has been developed for the first time.

Highly Efficient Enzymatic Acylation of Dihydromyricetin by the Immobilized Lipase with Deep Eutectic Solvents as Cosolvent

A novel deep eutectic solvent (DES)-DMSO cosolvent system has been, for the first time, successfully used as the reaction medium for the enzymatic acylation of dihydromyricetin (DMY) catalyzed by the immobilized lipase from Aspergillus niger (ANL). The cosolvent mixture, ChCl:Glycerol-DMSO (1:3, v/v) proved to be the optimal medium. With the newly developed cosolvent, the initial reaction rate of enzymatic acylation of DMY achieved 11.1 mM/h and the conversion of DMY was 91.6%. ANL@PD-MNPs is stable and recyclable in this cosolvent, offering 90% conversion rate after repeated use of 5 times. The lipid-solubility of DMY-16-acetate was 10 times higher than that of its raw materials DMY. The results showed that the DMY-16-acetate product exhibits good antioxidative activity. The present research illustrated that the use of DES-DMSO cosolvent may become a feasible alternative for the synthesis of DMY ester.

A green and efficient method for the synthesis of pyrroles using a deep eutectic solvent ([CholineCl][ZnCl2]3) under solvent-free sonication

A green and efficient method for Paal–Knorr pyrrole synthesis has been developed under mild conditions.

Crystal structure of Zn(ZnCl4)2(Cho)2: the transformation of ions to neutral species in a deep eutectic system

The ions of the ZnCl₂/choline chloride deep eutectic system form a neutral complex by coordination to a central metal ion.

Brønsted acidic ionic liquid-promoted direct C3-acylation of N-unsubstituted indoles with acid anhydrides under microwave irradiation

A green and efficient method for the synthesis of 3-acylindoles using a Brønsted acidic ionic liquid under microwave irradiation has been developed.

Zinc-based deep eutectic solvent-mediated hydroxylation and demethoxylation of lignin for the production of wood adhesive

Choline chloride–ZnCl₂ deep-eutectic solvent (ChCl–ZnCl₂ DES), mole ratio 1 : 2, was used to improve the chemical reactivity of wheat straw alkali lignin under different temperatures and times of pretreatment.

An extremely efficient and green method for the acylation of secondary alcohols, phenols and naphthols with a deep eutectic solvent as the catalyst

An efficient and green method was developed for the acylation of secondary alcohols, phenols and naphthols using deep eutectic solvent [CholineCl][ZnCl₂]₃ as a catalyst at room temperature under solvent-free conditions.