TiO2 as a Reusable Catalyst for the One‐Pot Synthesis of 3,4‐Dihydropyrimidin‐2(1H)‐ones under Solvent‐Free Conditions

An efficient solvent‐free method for the synthesis of various 3,4‐dihydropyrimidin‐2(1H)‐ones using TiO₂ as a recyclable heterogeneous catalyst is described. Compared to known methods, satisfactory results are obtained with excellent yields, short reaction times, and simplicity in the experimental procedure.     

ZnCl2 supported on Fe3O4@SiO2 core–shell nanocatalyst for the synthesis of quinolines via Friedländer synthesis under solvent‐free condition

A magnetic nanocatalyst of Fe₃O₄@SiO₂/ZnCl₂ was prepared by supporting ZnCl₂ on silica‐coated magnetic nanoparticles of Fe₃O₄. This recoverable catalyst was used for the synthesis of quinolines via Friedländer synthesis from 2‐aminoaryl ketones and α‐methylene ketones under solvent‐free condition. The prepared catalyst was characterized by FT‐IR, TEM, SEM, XRD, EDX, ICP‐OES, VSM and BET. It was found that Fe₃O₄@SiO₂/ZnCl₂ showed higher catalytic activity than homogenous ZnCl₂, and could be reused several times without significant loss of activity.     

One‐pot Synthesis of 3,4‐Dihydropyrimidin‐2(1H)‐ones Catalysed by Cupric Acetate under Solvent‐free Conditions

A solvent‐free synthesis of 3,4‐dihydropyrimidin‐2(1H)‐ones from aromatic aldehydes, β‐keto ester/acetyl acetone and urea catalysed by cupric acetate under thermal condition is reported as a simple and an efficient protocol. Compared with classical Biginelli reaction reported in 1893, this new method provides much improved modification in terms of yield and reaction time. The usage of milder catalyst, environmental friendly procedures and excellent yields within a very short time (5–15 min) are the advantages of the method in which the involvement of solvent‐free condition adds an edge to the method. Thus, the efficiency of the protocol enabled the rapid synthesis of 3,4‐dihydropyrimidin‐2(1H)‐one derivatives in a short duration.     

A Modified Synthesis of Some Novel Polycyclic Aromatic Phenazines and Quinoxalines by Using the Tungstate Sulfuric Acid (TSA) as a Reusable Catalyst under Solvent‐free Conditions

Considering the synthesis of new compounds, we developed heterocyclic chemistry. We also helped to improve the classical synthetic route for the synthesis of quinoxalines and phenazines through implement in terms of solvent‐free reaction. For the condensation of 1,2‐dicarbonyls and o‐phenylenediamines under solvent‐free conditions at room temperature, tungstate sulfuric acid (TSA) was found to be an efficient and reusable reagent. The high yield of the pure products and simple preparation of the catalyst have allowed the synthesis of several phenazines and quinoxalines using this methodology.     

Application of Nanosized Cu0.5Co0.5Fe2O4 Spinel Ferrite as a Nanocatalyst in the Synthesis of 14‐Aryl‐14H‐dibenzo[a,j]xanthene Derivatives under Solvent‐free Conditions

Copper and cobalt substituted spinel ferrites Cu_1‐xCo_xFe₂O₄ (0≤X≤1) have been synthesized by using hydrothermal method. The resultant spinel ferrites were systematically characterized by different techniques such as X‐ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X‐ray spectroscopy (EDX), and Fourier transform infrared spectroscopy (FT‐IR). It was indicated that all the resultant spinel ferrites obtained by the hydrothermal method had the single‐phase crystalline. The resultant spinel ferrites were employed in the synthesis of 14‐aryl‐14‐H‐dibenzo[a,j]xanthene derivatives. It was found that the nanocatalyst Cu_0.5Co_0.5Fe₂O₄ displays the best performance in the synthesis of 14‐aryl‐14H‐dibenzo[a,j]xanthenes. The catalyst was reused several times without significant loss of its activity for the preparation of desired product. In addition high yields of the products, solvent‐free conditions and reusability of the catalyst are other worthwhile advantages of the present study.     

An Eco‐friendly Three Component Manifold for the Synthesis of α‐Aminophosphonates under Catalyst and Solvent‐free Conditions,X‐ray Characterization and Their Evaluation as Anticancer Agents

A series of α‐aminophosphonates were synthesized through one‐pot condensation of aryl aldehydes, aryl amines and diethyl phosphite in the absence of any catalyst and organic solvents. All the synthesized α‐aminophosphonates were characterized by spectral and elemental analysis and in the case of compound 4j by X‐ray crystallography. Some of these new α‐aminophosphonate derivatives were found to have cytotoxic activity on the cancer cell line DU145 in vitro by the MTT method.     

A Simple and Efficient One‐pot Synthesis of 1,4‐dihydropyridines Using Nano‐WO3‐ supported Sulfonic Acid as an Heterogeneous Catalyst under Solvent‐free Conditions

Nano‐tungsten trioxide‐supported sulfonic acid (n‐WSA) was found to be an effective heterogeneous cat‐ alyst for the one‐pot reaction of aromatic aldehydes, β‐dicarbonyl compounds and ammonium acetate to afford 1,4‐dihydropyridine derivatives in good to excellent yields. The other main advantages of the pres‐ ent method are short reaction times, simple workup, ease in purification and environmentally benign methodology. The reaction conditions were optimized employing Response Surface Method technique (Central Composite Design (CCD)) which is economically considerable because of the minimum number of experiments required to evaluate the effects of multiple parameters on the response.     

Synthesis of Polysubstituted Quinolines Using Cyanuric Chloride as a Catalyst Under Aqueous Conditions

A mild, eco‐friendly and efficient route for the synthesis of quinolines and polycyclic quinolines via Friedländer annulation using cyanuric chloride as a catalyst under aqueous conditions is described.     

Alumina as a Support and Catalyst for the Synthesis of Benzothiazoles in Solvent‐free Condition

Arylbenzothiazole ( 4 ) and benzothiazolylcoumarins ( 5 ) were prepared by the condensation of 2‐aminothiophenol ( 1 ) and hydroxybenzaldehydes ( 2 ) and 3‐ethoxycarbonylcoumarinnin ( 3 ), respectively, in solvent‐free condition. Of the solid support used, γ‐Al₂O₃ demonstrated the best activity. A linear regression line obtained from correlation between relative formation rate and Hammett constants with slope of 0.653 suggested that this condensation process is less sensitive to the substituents on the phenyl ring due to low efficacy of polarization in the solid state. In general, good yields (>80% yield) were obtained for the formation of 4 . Conversely, yields of 5 were poor, because of γ‐Al₂O₃ catalytic decomposition of 3 to form 2 (without P₂O₅) and coumarin (with P₂O₅).     

Iodine‐Catalyzed Friedlander Quinoline Synthesis under Solvent‐Free Conditions

Polyfunctional quinolines were synthesized using Friedlander method catalyzed by molecular iodine in high yields at 60 °C under solvent‐free conditions.     

Fe3O4@SiO2@Im‐bisethylFc [HC2O4] as a novel recyclable heterogeneous nanocatalyst for synthesis of bis‐coumarin derivatives

Nanomagnetic bisethylferrocene‐containing ionic liquid supported on silica‐coated iron oxide (Fe₃O₄@SiO₂@Im‐bisethylFc [HC₂O₄]) as a novel catalyst was designed and synthesized. The described catalyst was recycled and used without change in the time and efficiency of the condensation reaction. The Fourier transform‐infrared spectroscopy (FT‐IR), scanning electron microscopy images, X‐ray diffraction patterns, energy‐dispersive X‐ray spectroscopy, transmission electron microscope and vibrating‐sample magnetometer results confirmed the formation of Fe₃O₄@SiO₂@Im‐bisethylFc [HC₂O₄] magnetic nanoparticle. The novel bis‐coumarin derivatives were identified by ¹H‐NMR, ¹³C‐NMR, FT‐IR and CHNS analysis.     

L-Proline Catalyzed Enamination of β-Dicarbonyl Compounds under Solvent-free Conditions

A simple, general and efficient method has been developed for synthesis of various β-enamino ketones and esters by reacting β-dicarbonyl compounds with amines using a catalytic amount of L-proline at room temperature under solvent-free conditions in excellent yields.     

An Efficient Synthesis of 14‐Aryl or Alkyl‐14H‐Dibenzo[a. j]Xanthenes Using Reusable HBF4‐SiO2 Catalyst Under Thermal and Solvent‐Free Conditions

A simple and convenient procedure for the synthesis of 14‐aryl or alkyl‐14H‐dibenzo[a. j]xanthene derivatives is described through a one‐pot condensation of β‐naphthol with various aryl or alkyl aldehydes in the presence of HBF₄‐SiO₂ as the catalyst under thermal and solvent‐free conditions.     

A Facile Synthesis of 2,2,4‐Trisubstituted‐1,2‐Dihydroquinolines Catalyzed by Zinc Triflate under Solvent‐Free Conditions

An efficient process has been developed for the synthesis of 2,2,4‐trisubstituted‐1,2‐dihydroquinolines in good yields through a simple one‐pot condensation between anilines and ketones in the presence of zinc triflate as a catalyst at room temperature under solvent‐free conditions.     

Dowex as Reusable Acidic Polymeric Catalyst in the Efficient and Regioselective Conversion of Epoxides into β‐Hydroxy Thiocyanates under Solvent Free Conditions

A convenient and efficient procedure for the regioselective ring opening of epoxides in the presence of Dowex (strongly acidic cationic exchange resin), as reusable eco‐friendly catalyst under solvent free conditions is described. Thus, several β‐hydroxy thiocyanates, useful intermediates toward pharmaceutical and biologically active molecules, are easily obtained in high isolated yields.     

Green Synthesis of Imidazole Derivatives via Fe3O4‐MNPs as Reusable Catalyst

In this research, a one‐pot, efficient, and high yielding procedure for the synthesis of imidazole derivatives is investigated. The procedure was carried out via multicomponent reaction of isothiocyanate, alkyl bromides, N‐methylimidazole, and triphenylphosphine in the presence of magnetic iron oxide nanoparticles (Fe₃O₄‐MNPs) as reusable catalyst under solvent‐free conditions at 50°C. Also, Fe₃O₄‐MNPs were produced using green synthetic method by reduction of ferric chloride solution with Clover Leaf water extract. The nanoparticles generated using this procedure can potentially be important in different purposes such as organic synthesis. Easy, simple, rapid, and clean procedures for the synthesis of imidazole derivatives are the advantages of this study.     

Microwave‐assisted Friedländer Synthesis of Polysubstituted Quinolines Based on Poly(ethylene glycol) Bound Acetoacetate

Polysubstituted quinolines were efficiently prepared on the soluble polyethylene glycol (PEG) by microwave irradiation Friedländer condensation of PEG bound acetoacetate with 2‐aminoarylketones promoted by catalytic amount of polyphosphoric acid, and subsequently cleavage from the PEG with MeONa in MeOH. The polymer‐supported synthesis provided the target compounds in excellent yield and purity with a facile work‐up procedure.     

Solvent‐free Chemoselective Synthesis of 1,1‐diacetates Catalyzed by Iron Zirconium Phosphate

In the present study, a mild, rapid, and efficient method for the protection of aldehydes with acetic anhydride (AA) in the presence of iron zirconium phosphate (ZPFe), at room temperature is reported. Selective conversion of aldehydes was observed in the presence of ketones. Under these conditions, different aldehydes bearing electron‐withdrawing and electron‐donating substituents were reacted with AA and the corresponding 1,1‐diacetates (acylals) were obtained in high to excellent yields. The steric and electronic properties of the different substrates had a significant influence on the reaction conditions. Also, the deprotection of 1,1‐diacetates has been achieved using this catalyst in water. The catalyst was characterized by several physico‐chemical techniques. It was recovered easily from the reaction mixture, regenerated, and reused at least 7 times without significant loss in catalytic activity. This protocol has the advantages of easy availability, stability, reusability of the eco‐friendly catalyst, chemoselectivity, simple experimental and work‐up procedure, solvent‐free conditions and only a stoichiometric amount of AA is needed.     

γ‐Fe2O3@Cu3Al‐LDH‐TUD as a new Amphoteric,Highly Efficient and Recyclable Heterogeneous Catalyst for the Solvent‐free Synthesis of Dihydropyrano[3,2‐c]pyrazoles and dihydropyrano[3,2‐c]chromens

Thiourea dioxide was immobilized on γ‐Fe₂O₃@Cu₃Al‐LDH magnetic nanoparticles to prepare the γ‐Fe₂O₃@Cu₃Al‐LDH‐TUD MNPs. The structure and properties of these magnetic nanoparticles were established by FT‐IR, EDX, SEM, XRD, and hystogram of particle size analytical methods. The results obtained from these analytical methods confirmed the successful immobilization of the thiourea dioxide onto the magnetic support. The synthesized magnetic nanoparticles (MNPs) exhibited high catalytic activity in one‐pot three‐component reactions under mild and solvent‐free conditions for the synthesis of diverse ranges of dihydropyrano[3,2‐c]pyrazoles and dihydropyrano[3,2‐c]chromens. All the reactions proceeded smoothly to furnish the respective products in excellent yields. Simple isolation of the products, avoidance of harmful organic solvents, versatility of the catalyst and its easy magnetic separation and reusability with no significant loss of activity are the main advantages of the present method.     

Green Biginelli‐type Reaction: Solvent‐free Synthesis of 5‐unsubstituted 3,4‐dihydropyrimdin‐2(1H)‐ones

The Biginelli‐type compounds, 5‐unsubstituted 3,4‐dihydropyrimdin‐2(1H)‐ones were synthesized by a one‐pot three‐component condensation of aromatic aldehydes, aromatic ketones and urea in the presence of SnCl₄ · 5H₂O under solvent‐free conditions. The advantages of this method are short reaction time (4–10 min), excellent yields (74–97%), inexpensive catalyst and solvent‐free conditions. A plausible mechanism was proposed.