[C12mim]Br: A Temperature‐dependent Phase Transfer Catalyst and Its Application for Aerobic Oxidative Synthesis of 2‐Aryl Benzimidazoles,Benzoxazoles or Benzothiozoles Catalyzed by TEMPO Based Ionic Liquid

The application of [C₁₂mim]Br ionic liquid/o‐xylene temperature‐dependent biphasic system into the [Imim‐TEMPO][Cl]/O₂‐promoted condensation between o‐phenylenediamines, o‐aminophenol or o‐aminothiophenol with aldehydes for preparing benzimidazoles, benzoxazoles or benzothiozoles is described. Several aldehydes and o‐phenylenediamines, o‐aminophenol or o‐aminothiophenol were reacted efficiently to form corresponding products in excellent yields. Both the [Imim‐TEMPO][Cl] and [C₁₂mim]Br could be reused at least eight times without significantly decreasing the catalytic activity.     

Magnetic Co‐doped NiFe2O4 Nanocomposite: A Heterogeneous and Recyclable Catalyst for the One‐Pot Synthesis of Benzimidazoles,Benzoxazoles and Benzothiazoles under Solvent‐Free Conditions

A simple and efficient procedure for the synthesis of benzimidazoles, benzoxazoles, and benzothiazoles via the condensation of o‐phenylenediamine, o‐aminophenol, and o‐aminothiophenol with various benzaldehydes by using magnetic Co‐doped NiFe₂O₄ nanoparticles has been developed. This nanocatalyst has advantages such as excellent product yields, solvent‐free conditions, and very short reaction times. After any experiment, the magnetic nanocatalyst could be easily separated with the aid of an external magnet and reused at least four times without any loss of its catalytic performance.     

Efficient and Reusable Sn(II)‐containing Imidazolium‐based Ionic Liquid as a Catalyst for the Oxidation of Benzyl Alcohol

A simple and efficient catalytic system [BBIM]Br–SnCl₂ for the oxidation of benzyl alcohol using hydrogen peroxide as the oxidant has been developed. Reaction conditions such as the catalyst dose, the solvents, reaction temperature, reaction time, and the amount of hydrogen peroxide were investigated. The optimum reaction conditions identified were 0.11 g of catalyst, no solvent, 65°C, 15 min, and 2 mmol of hydrogen peroxide. Oxidation of various alcohols was also investigated under the optimized conditions. The catalyst [BBIM]Br–SnCl₂ can be easily recovered and reused for six reaction runs without significant loss of catalytic activity, because the Sn species of the catalyst can be coordinated with the imidazole ring of the ionic liquid. The reused catalyst was further characterized by Fourier transform infrared spectroscopy to evaluate its chemical properties. The results proved that the [BBIM]Br–SnCl₂ catalyst was stable and reusable for the oxidation reactions. A possible mechanism for the oxidation of benzyl alcohol to benzaldehyde is proposed.     

Simple,Efficient, and Convenient One‐Pot Synthesis of Imidazole Derivatives in the Presence of Nanosilica‐supported Imidazolium Ionic Liquid as a Catalyst

An efficient and simple synthesis of 2,4,5‐trisubstituted imidazoles is achieved by three‐component cyclocondensation of benzil, aldehyde, and ammonium acetate by using nanosilica‐supported imidazolium ionic liquid as a catalyst under solvent‐free conditions. The key advantages of this process are high to excellent yields, short reaction time, easy work‐up, and the reusability of the catalyst.     

Efficient Aerobic Oxidative Synthesis of Benzimidazoles with Fe(III) based PEG1000 Dicationic Imidazolium Ionic Liquid/toluene Temperature‐dependent Biphasic System

A green protocol for the synthesis of benzimidazoles with Fe(III) based PEG1000 dicationic imidazolium ionic liquid ([PEG₁₀₀₀mim₂][FeCl₄]₂)/toluene temperature‐dependent biphasic system was described. Conformed by IR analysis, FeCl₄⁻ is the dominating anion species. It could be seen that aldehydes aryla mines and aromatic aldehydes bearing electron‐deficient group ( Cl,  Br,  NO₂) and electron‐rich groups ( OH,  N(CH₃)₂) on the aromatic rings gave good yields (78–96 %). Moreover, the Fe(III) based PEG1000 dicationic imidazolium ionic liquid could be recycled and reused without significant loss of catalytic activity after seven runs.     

A Mild and Simple One‐pot Synthesis of 2‐Substituted Benzimidazole Derivatives Using DDQ as an Efficient Oxidant at Room Temperature

A series of 2‐substituted benzimidazoles were prepared through one‐pot reaction of o‐phenylenediamine with various aryl aldehydes in the presence of 2,3‐dichloro‐5,6‐dicyano‐1,4‐benzoquinone (DDQ) in acetonitrile as solvent at room temperature. The reactions were smoothly preceded in excellent yields and short reaction times with an easy work‐up. The pure benzimidazoles as products were confirmed and characterized by physical and spectral data.     

An Efficient One‐pot Synthesis of Pyrazolone Derivatives Promoted by Acidic Ionic Liquid

A new class of pyrazolone derivatives has been isolated in good to excellent yields from the 2:1 condensation reaction between 3‐methyl‐1‐phenyl‐5‐pyrazolone and arylaldehydes in the presence of ionic liquid [HMIM]HSO₄. The compounds were characterised by their IR, NMR spectra, MS and elemental analyses. The important features of the methodology are a wide application range of substrates, higher yields and shorter reaction time.     

Amberlyst‐15‐Catalyzed Novel Synthesis of Quinoline Derivatives in Ionic Liquid

In recent years, ionic liquids have attracted much attention as useful synthetic solvents. Compared with classical molecular solvents, the ionic liquids are environmentally benign reaction media. A variety of quinoline derivatives have been synthesized under ionic liquid conditions using Amberlyst‐15 as catalyst.     

Hydroformylation of Oct‐1‐ene in Novel Ionic Liquid Crystals

Hydroformylation of oct‐1‐ene leading to nonanal (denoted by n) and 2‐methyloctanal (denoted by iso), in a novel series of caprolactam‐based and common imidazolium‐based ionic liquid crystals (ILCs; see Fig. 1) carried out for the first time (caprolactam=hexahydro‐2H‐azepin‐2‐one) (Scheme). Variation of the chain length (n) of the alkyl substituent (C_n) at the caprolactam cation (CP⁺) from n=12 to 18 caused the n/iso ratios to vary from 1.7 to 2.9. Meanwhile, the TOF (turnover frequency) decreased from 148 to 122 mol mol⁻¹ h⁻¹. Hydroformylation in the imidazolium‐based ILCs revealed that [C₁₆MIm]⋅BF₄ (n/iso 5.2, TOF 969 mol mol⁻¹ h⁻¹) was more favorable than [C₁₆MIm]⋅MsO (n/iso 3.7, TOF 969 mol mol⁻¹ h⁻¹) for the formation of the unbranched aldehyde. Although the n/iso ratio in caprolactam‐based ILCs was lower than that in imidazolium‐based ILCs, the conversions are higher in the former ILCs on the whole. It should be noted that the lamellar mesophase has a strong effect on the regioselectivity and TOF of the hydroformylation. Also, it is evident that the influences of different ILCs on the hydroformylation under the various reaction conditions are greatly different. The identification of the reaction products was established by GC and GC/MS analyses.     

A Simple,Mild and Efficient One‐Pot Synthesis of 2‐Substituted Benzimidazoles in the Presence of H2O2/HCl under Microwave Irradiation

A simple, fast and efficient method for the preparation of several 2‐substituted benzimidazole derivatives is reported. Compounds were synthesized through a rapid one‐pot synthesis via microwave irradiation, starting from aldehydes and o‐phenylenediamine, in the presence of H₂O₂/HCl system in acetonitrile. The significant features of this method are short reaction times, high yields, easy and quick isolation of the products.     

Novel Basic Ionic Liquid Based on Alkylammonium as Efficient Catalyst for Knoevenagel Reaction

The typical Knoevenagel condensation was carried out smoothly in the presence of a basic ionic liquid of N,N,N′,N′-tetramethyl-N′-hexyl-ethylenediammonium tetrafluoroborate ([TMHEDA]BF₄), and 99% of yield was obtained using ethyl cyanoacetate and benzaldehyde as substrates at 60 °C for 1 h. Four reuses of the ionic liquid without dramatic decrease in catalytic activity for Knoevenagel condensation demonstrated the good stability and operability of the ionic liquid. Moreover, the typical nucleophilic addition reactions were also accomplished by the same ionic liquid to check its feasibility. The dual function of the basic ionic liquid both as solvent and catalyst, combined with simple product separation and recycling, is expected to contribute to the development of a green and environmentally friendly strategy.     

Basic Ionic Liquid as Catalyst and Reaction Media for the One‐pot Three‐component Regioselective Synthesis of Various Thiazol‐2‐imine Derivatives

Thiazol‐2‐imine derivatives were synthesized in an easy and efficient route from the regioselective one‐pot three‐component reaction of aryl amine, alkylisothiocyanate, and various α‐haloketones in [omim][OH] basic ionic liquid. Recyclable reaction media, catalyst free, and short reaction times are the main advantages of this protocol. This method produces the products at room temperature in excellent yields (68–96%). Furthermore, the target compound 6b was determined by X‐ray crystallographic analysis.     

Zn3(BTC)2 as a Highly Efficient Reusable Catalyst for the Synthesis of 2‐Aryl‐1H‐Benzimidazole

Zn₃(BTC)₂ metal‐organic frameworks as recyclable and heterogeneous catalysts were effectively used to catalyze the synthesis of benzimidazole derivatives from o‐phenylendiamine and aldehydes in ethanol. This method provides 2‐aryl‐1H‐benzimidazoles in good to excellent yields with little catalyst loading. The catalyst was characterized using different techniques such as X‐ray diffraction (XRD), energy dispersive X‐ray (EDX) analysis, scanning electron microscopy (SEM), and Fourier transform infrared (FT‐IR) spectroscopy.     

A One‐pot Facile Synthesis of 2,3‐Dihydroxyquinoxaline and 2,3‐Dichloroquinoxaline Derivatives Using Silica Gel as an Efficient Catalyst

An efficient one‐pot reaction has been developed for the synthesis of 2,3‐dichloroquinoxaline derivatives 3a – n . The reaction was performed in two steps via a silica gel catalyzed tandem process from o‐phenylenediamine and oxalic acid, followed by addition of phosphorus oxychloride (POCl₃). A variety of 2,3‐dichloroquinoxalines have been obtained in good to excellent overall yields. Eight known compounds 3a – 3h were characterized by IR, ¹H‐NMR, and mass spectroscopies. Compounds 3i – 3n without spectroscopic data were characterized by IR, ¹H‐NMR, ¹³C‐NMR, and mass spectroscopies.     

Oxime‐derived palladacycle Immobilized in an Ionic Liquid Brush as an Efficient and Reusable Catalyst for Mozoroki‐Heck Reaction in Neat Water

An efficient and reusable heterogeneous catalyst with oxime‐derived palladacycle immobilized in an ionic liquid brush has been synthesized and an environmentally‐friendly procedure have been developed for coupling aryl iodides and bromides with acrylic acid. These reactions were conducted in neat water under aerobic conditions with water‐insoluble or even solid aryl halides and they proceeded smoothly and cleanly without any organic co‐solvent or other additives. The ionic liquid brush could be easily recovered and reused at least five times without significant loss of activity. The protocol has the advantages of excellent yields, environmental friendliness, and catalyst recyclability.     

Hypervalent Iodine(III) Sulfonate Reagent Mediated Synthesis of 4‐Aryl‐2‐Phenyloxazoles in Ionic Liquid

A new and efficient method for the synthesis of 4‐aryl‐2‐phenyloxazoles is described which is based upon the reaction of α‐[(2,4‐dinitrobenzene)sulfonyl]oxy ketone intermediates with benzamide in ionic liquid.     

Mesoporous Molecular Sieve MCM‐41 as a Novel and Efficient Catalyst to Synthesis of 2‐Substituted Benzimidazoles

o‐Phenylenediamine derivatives readily react with benzoyl chloride derivatives in the presence of MCM‐41 as catalyst to yield 2‐substituted benzimidazoles in very good yields.     

One‐pot Synthesis of Tetrahydrobenzo[b]pyrans Catalyzed by PEG‐1000 Bridged Primary Amine Functionalized Dicationic Ionic Liquid in Water

A novel poly (ethylene glycol) bridged primary amine functionalized dicationic ionic liquid ([PA‐PEG₁₀₀₀‐DIL][BF₄]) was synthesized and characterized by ¹H‐NMR, ¹³C‐NMR, FT‐IR and ESI‐MS. The thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) analysis indicated the high thermal stability of [PA‐PEG₁₀₀₀‐DIL][BF₄]. It was used as an efficient and recyclable catalyst for the synthesis of substituted tetrahydrobenzo[b]pyrans through a one‐pot three‐component condensation of aromatic aldehydes, malononitrile and dimedone in 86% ～ 96% yields within 10 ～ 30 min in water. This method offers several advantages such as mild reaction conditions, simple operation and environmental friendliness. Furthermore, the catalyst could be easily recovered and reused for at least five runs without obvious loss of catalytic activity.     

Palladium(II) Immobilized Onto the Glucose Functionalized Magnetic Nanoparticle as a New and Efficient Catalyst for the One‐pot Synthesis of Benzoxazoles

Palladium(II) have been immobilized into the nano magnetic Fe₃O₄ which was functionalized with glucose in order to achieve a one‐pot synthesis of 2‐substituted benzoxazole derivatives with high yields in the diverse range of organic solvents. The nano catalyst is highly dispersive in polar solvents and can be easily recovered and reused for 6 runs without significant loss of its activity. Finally, the catalyst was fully characterized by FT‐IR, TGA, CHN, SEM, EDX and atomic absorption spectroscopy.