1-(1-Alkylsulfonic)-3-methylimidazolium chloride as a reusable Brønsted acid catalyst for the regioselective azidolysis of epoxides under solvent-free conditions

In this study, 1-(1-alkylsulfonic)-3-methylimidazolium chloride as a new, green, and reusable Brønsted acid catalyst was prepared. In this protocol, we used for the regioselective ring-opening reactions of various epoxiodes with sodium azide to afford the corresponding β-azido alcohols in excellent yields and short reaction time under mild and neutral reaction conditions. This method offers several advantages including excellent regioselectivity, clean reactions, simple work-up procedure, a recyclable catalyst, and use of an eco-friendly catalyst.     

Enantioselective Radical‐Polar Crossover Reactions of Indanonecarboxamides with Alkenes

Highly efficient asymmetric intermolecular radical‐polar crossover reactions were realized by combining a chiral N,N′‐dioxide/Ni^II complex catalyst with Ag₂O under mild reaction conditions. Various terminal alkenes and indanonecarboxamides/esters underwent radical addition/cyclization reactions to afford spiro‐iminolactones and spirolactones with good to excellent yields (up to 99 %) and enantioselectivities (up to 97 % ee). Furthermore, a range of different radical‐mediated oxidation/elimination or epoxide ring‐opening products were obtained under mild reaction conditions. The Lewis acid catalysts exhibited excellent performance and precluded the strong background reaction.     

Efficient synthesis of 3,4-dihydropyrano[3,2-c]chromenes catalyzed by Ni(II)-functionalized Li<Superscript>+</Superscript>-Montmorillonite in a one-pot fashion under solvent-free conditions

A family of 3,4-dihydropyrano[3,2-c]chromenes were synthesized from 4-hydroxycoumarin and malononitrile via a one-pot reaction under solvent-free conditions at 100 °C catalyzed by Ni@Imine-Li⁺-MMT. This methodology tolerates most of the substrates and has the merits of lower loading of the catalyst, absence of solvents, excellent yields and reusability of the catalyst. A reasonable mechanism is also proposed. This catalytic system can be reused for at least five times with a negligible loss of activity. The prepared catalyst was characterized by using FTIR, TGA, SEM, TEM, uv-DRS, EDX and XRD.     

A green one-pot three-component synthesis of α-aminophosphonates under solvent-free conditions and ultrasonic irradiation using Fe3O4@SiO2-imid-PMAn as magnetic catalyst

An efficient and environment friendly process for the synthesis of α-aminophosphonates has been devised. Through a one-pot three-component condensation of various aldehydes, amines, and triethyl phosphite in the presence of Fe₃O₄@SiO₂-imid-PMAⁿ nanoparticles as magnetic catalysts under solvent-free conditions and ultrasonic irradiation, α-aminophosphonates were obtained with excellent yields. The reactions under solvent-free conditions at room temperature are compared with the ultrasonic-assisted reactions. This new procedure has notable advantages such as short reaction time, excellent yields, easy purification, and the absence of any tedious workup or purification. The aforementioned catalyst could be easily recovered by an external magnetic field and can be reused for six consecutive reaction cycles without significant loss of activity. In addition, SEM and DLS of the catalyst after the reaction cycle were investigated.     

Preparation,characterization and use of sulfonylbis(1,4-phenylene)<Emphasis Type="Italic">bis</Emphasis>(sulfamic acid) as an eco-benign,efficient, reusable and heterogeneous catalyst for the synthesis of mono- and <Emphasis Type="Italic">bis</Emphasis>-chromenes

Sulfonylbis(1,4-phenylene)bis(sulfamic acid) (SPSA) is easily prepared and recognized as a new heterogeneous catalyst by the reaction of 4,4′-sulfonyldianiline with chlorosulfonic acid. This reagent was used for the synthesis of the mono- and bis-chromene derivatives. All reactions were performed under mild reaction conditions in high to excellent yields. The advantages of using the SPSA as a heterogeneous catalyst in these reactions are: being environmentally friendly, low cost, commercially availability and easy to separate from the mixture of the reaction and high reusable catalyst. Using this catalyst, results in acceptable reaction time and high yields with high purity of the obtained products without utilizing any organic solvents. The catalyst was characterized by FT-IR, ¹H NMR, ¹³C NMR, mass and TGA studies. All the products were characterized by FT-IR, ¹H, ¹³C NMR, HRMS, melting point and elemental analyses.     

A comparative screening of the catalytic activity of nanocrystalline M<Superscript>II</Superscript>Zr<Subscript>4</Subscript>(PO<Subscript>4</Subscript>)<Subscript>6</Subscript> ceramics in the one-pot synthesis of 1,6-diamino-4-aryl-2-oxo-1,2-dihydropyridine-3,5-dicarbonitrile derivatives

A four-component reaction of hydrazine hydrate, ethyl cyanoacetate, malononitrile, and aromatic aldehydes was achieved in the presence of nanocrystalline M^IIZr₄(PO₄)₆ ceramics (M^II: Mn, Fe, Co, Ni, Cu, Zn, Cd) as heterogeneous catalysts to produce N-amino-2-pyridones. The reactions were performed in the presence of different catalysts, and it is observed that CdZr₄(PO₄)₆ nanocrystallines are the best catalysts among those examined. Atom economy, excellent yields in short times, high catalytic activity, recycling of catalyst, and environmental benignity are some of the important features of this protocol.     

Enantioselective Radical-Polar Crossover Reactions of Indanonecarboxamides with Alkenes

Highly efficient asymmetric intermolecular radical-polar crossover reactions were realized by combining a chiral N,N′-dioxide/Ni^II complex catalyst with Ag₂O under mild reaction conditions. Various terminal alkenes and indanonecarboxamides/esters underwent radical addition/cyclization reactions to afford spiro-iminolactones and spirolactones with good to excellent yields (up to 99 %) and enantioselectivities (up to 97 % ee). Furthermore, a range of different radical-mediated oxidation/elimination or epoxide ring-opening products were obtained under mild reaction conditions. The Lewis acid catalysts exhibited excellent performance and precluded the strong background reaction.     

Cobalt mediated by desulfurization toward the synthesis of isothiocyanates

A highly efficient and simple protocol for the construction of aromatic and aliphatic isothiocyanates from their respective amines in the presence of cheap, readily available, and air-stable cobalt catalyst is described. All reactions were carried out under optimized reaction conditions and gave target products in good to excellent yields within shorter reaction time.     

Synthesis of trans‐dihydrofurans using bis (1(3‐trimethoxysilylpropyl)‐3‐methyl‐imidazolium) nickel tetrachloride tethered to colloidal silica nanoparticles

An efficient multicomponent synthesis of dihydrofurans is described by a one‐pot condensation reaction of 4‐bromophenacyl bromide, aromatic aldehydes, and dimedone using an ionic liquid tethered to colloidal silica nanoparticles under reflux conditions in acetonitrile. The ionic liquid tethered to colloidal silica nanoparticles is characterized by ¹H NMR spectroscopy, scanning electron microscopy, energy‐dispersive spectroscopy, thermogravimetric analysis, and dynamic light scattering. Atom economy, a wide range of products, high catalytic activity, excellent yields in short reaction times, diastereoselective synthesis, reusability of the catalyst, and low catalyst loading are some of the important features of this protocol.     

An Improved Protocol for the Synthesis of Quinoline‐2,3‐dicarboxylates under Neutral Conditions via Biomimetic Approach

A mild and efficient protocol for synthesis of quinoline derivatives in aqueous medium under neutral conditions is described. The reaction proceeded smoothly in H₂O catalyzed by supramolecular catalyst β‐CD. By this protocol, various quinoline derivatives were synthesized in excellent yields.     

<Superscript>18</Superscript>F- and <Superscript>11</Superscript>C-labelling of quantum dots with n.c.a. [<Superscript>18</Superscript>F]fluoroethyltosylate and [<Superscript>11</Superscript>C]methyliodide: a feasibility study

Quantum dots functionalized on the outer surface with either amino- or carboxyl functions were labelled with [¹⁸F]fluoroethyltosylate and [¹¹C]methyliodide in order to use the positron emitter-labelled fluorescence agents for multimodality imaging techniques, i.e. fluorescence imaging and positron emission tomography. ¹⁸F-Labelling of both compounds was realized with yields up to 5% as determined by size exclusion chromatography, which is twice as much as reported in literature before [1]. ¹¹C-Labelling of amino- and carboxyl-QDs proceeded with good yields (up to 45 and 35%, respectively) under optimized reaction conditions. In general for both QD-types and both labelling agents the labelling yield increased with the amount of QDs used in the reaction as well as with reaction time and reaction temperature.     

Water as a solvent for Ru‐catalyzed click reaction: Highly efficient recyclable catalytic system for triazolocoumarins synthesis

A new family of Ru (III) complexes has been synthesized, characterized and their catalytic performance has been tested for alkyne–azide cycloaddition (AAC) in water under ultrasonic irradiation conditions. These complexes are found to be effective heterogeneous catalysts for the regioselective synthesis of 1,4‐disubstituted‐1,2,3‐triazoles giving access to these products in excellent yields. The catalyst system is equally active for one‐pot multi‐component protocol of the AAC reactions. Also, successive sequencing of Huisgen reaction with Knoevenagel condensation reaction results in the effective assembly of a diversified hitherto unreported 1,2,3‐triazolyl coumarin frameworks. In present strategy, the catalyst could be easily isolated by simple filtration and reused up to eight consecutive cycles without significant drop in the reaction yields. During the leaching experiment, there is no leaching amount of the catalyst was detected, suggesting true heterogeneity in the catalytic system. The results of gram‐scale reaction and green metrics calculations also confirmed the sustainability and industrial applicability of the current catalytic protocol.     

Iodine Catalyzed One‐pot Synthesis of 3,4‐Dihydroquinazolin‐4‐ones from Anthranilic Acids,Ortho Esters and Amines under Solvent‐free Conditions

A simple and efficient procedure has been developed for the one‐pot synthesis of 3,4‐dihydroquinazolin‐4‐ones from anthranilic acids, ortho esters and amines using a catalytic amount of iodine under solvent‐free conditions to afford the corresponding products in excellent yields. The direct use of commercially available catalyst, mild and solvent‐free reaction conditions, short reaction time, easy workup and excellent yields are the advantages of the present protocol.     

A convenient one-pot three component synthesis of 3-aminoalkylated indoles catalyzed by 3-chlorophenylboronic acid

An efficient protocol was developed for the synthesis of 3-aminoalkylated indoles using 3-chlorophenylboronic acid as a catalyst under ambient temperature conditions. The three-component reaction of indoles, aromatic aldehydes and N-methyl aniline offered corresponding 3-aminoalkylated indoles in excellent yields. This protocol presents some remarkable features such as mild reaction conditions, simple workup procedure and excellent yields.     

Acidic ionic liquid immobilized on nanoporous Na<Superscript>+</Superscript>-montmorillonite as an efficient and reusable catalyst for the formylation of amines and alcohols

In this work, nanoporous sodium montmorillonite clay (Na⁺-MMT) was used as a support for the immobilization of 1-methyl-3-(trimethoxysilylpropyl)-imidazolium hydrogen sulfate. The Na⁺-MMT chemical modification ([Na⁺-MMT-[pmim]HSO₄) was confirmed by a variety of techniques including Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy and potentiometric titration. The catalytic performance of this immobilized acidic ionic liquid was probed for the N-formylation of a variety of amines using formic acid under solvent-free conditions. This reagent is also useful for the formylation of benzylic alcohols. The procedure gave the products in excellent yields in very short reaction times. Also, this catalyst can be reused ten times without loss of its catalytic activity.     

Solvent-free,microwave-assisted highly efficient,rapid and simple synthesis of biphenyl compounds by using silica based Pd(II) catalyst

To maintain catalytic performance of any catalyst for a long time, the selection of support material is a very important parameter for heterogeneous catalytic systems, and this performance makes the catalyst valuable. In view of its low cost and availability, silica can be considered as a good support material for transition metal ions in the cross coupling reactions. Therefore, this study describes i) silica-gel based palladium catalyst with a long-term catalytic performance, ii) rapid, simple, economic, and green procedure which was developed for Suzuki reactions. The catalyst showed superior reusability (ten runs) and catalytic efficiency against coupling reactions under mild conditions (50°C, 5 min and air atmosphere). Moreover, the catalyst gave partially good reaction yields with aril chlorides which have poor activity in coupling reactions. In addition, an excellent turnover number (TON: 66000) and frequency (TOF: 825000) were obtained using very small catalyst loading (1.5 × 10^?3 mol %). This paper concludes that silica-gel based Pd(II) catalyst and the protocol of synthesis of biaryls were suitable for coupling reactions.     

Water opportunities: catalyst and solvent in Mukaiyama aldol addition of Rawal’s diene to carbonyl derivatives

Addition reactions between Rawal’s diene and different carbonyl compounds are rapidly and efficiently promoted by water. No catalyst or any other additive, water as an eco-friendly medium, clean reaction conditions, a simple work-up, and short reaction times are the salient features in this procedure. The protocol is general, proceeding well with moderate to good yields for various aldehydes and activated ketones. Based on the experimental ¹H NMR results, a Mukaiyama aldol mechanism was proposed as the reaction pathway, affording open chain products.     

Claycop/hydrazine: A new and highly efficient recyclable/reusable catalytic system for 1,4‐disubstituted‐1,2,3‐triazole synthesis under solvent‐free conditions

Clay‐supported copper(II) nitrate (claycop) has been used as an efficient catalyst for azide–alkyne cycloaddition reactions leading to 1,4‐disubstituted 1,2,3‐triazoles. The highly efficient claycop/hydrazine hydrate catalytic system affords triazoles in a few minutes (1–20 min) at room temperature, under mild and solvent‐free conditions. High regioselectivity, excellent yields, ease of claycop synthesis and recyclability/reusability of the catalyst are considered as practical merits of the protocol.     

Efficient and economic halogenation of aryl amines via arenediazonium tosylate salts

Arenediazonium tosylate salts have been successfully employed as a new and efficient reagent in halogenation reactions. A novel and economic protocol has been developed for the bromination and chlorination of various anilines using arenediazonium tosylate salts. A wide variety of reaction conditions were studied in acetonitrile at either room temperature or 60 °C in the presence or absence of catalyst with good to excellent yields. A surprising result showed the formation of acetanilides as a major product of aniline and methyl-substituted aniline halogenations in high yields.     

Solvent- and metal-free selective oxidation of thiols to disulfides using I2/DMSO catalytic system

We describe herein a simple, fast and inexpensive protocol for the oxidative coupling of thiols employing a stoichiometric amount of DMSO and iodine as the catalyst. Various aromatic disulfides were obtained in good to excellent yields in short reaction times at room temperature, while aliphatic disulfides were achieved in good yields when the reactions were conducted under microwave irradiation.