Synthesis of symmetrical and unsymmetrical 3,3-di(indolyl)indolin-2-ones under controlled catalysis of ionic liquids

Three ionic liquids, [BMIM][BF₄] doped with 60 mol % of LiCl ([BMIM][BF₄]-LiCl), N,N,N,N-tetramethylguanidinium trifluoroacetate (TMGT), and N,N,N,N-tetramethylguanidinium triflate (TMGT_f) were found useful as catalyst solvents for controlled 3-indolylation of isatins. Our investigation revealed that the reaction between isatin and indoles in [BMIM][BF₄]-LiCl or TMGT_f media stops at the step of addition of the two components providing 3-indolyl-3-hydroxyindolin-2-ones while the ionic liquid TMGT runs the reaction further through accompanying Friedel-Crafts substitution to afford symmetrical 3,3-di(indol-3-yl)indolin-2-ones. To take advantage of the difference between the effects of these ionic liquids on the reaction progress, we planned a two-step protocol for the efficient synthesis of unsymmetrical 3,3-di(indol-3-yl)indolin-2-ones.     

Synthesis of Dehydroabietic Acid (2-Acryloyloxy) Ethyl Ester in Ionic Liquids

A simple ionic liquid methodology for the synthesis of a novel derivative of dehydroabietic acid is described. 1-Butyl-3-methylimidazolium tetrafluoroborate [bmim]BF₄, a typical ionic liquid, was used as an efficient and environmentally benign solvent in the synthesis of dehydroabietic acid (2-acryloloxy) ethyl ester by O-acylation reaction of dehydroabietic acid chloride with 2-hydroxyethyl acrylate. This new method showed the advantages of mild reaction conditions, short reaction times, good yields, and recyclable solvent.     

An Efficient and Green One‐pot Synthesis of 12‐Aryl‐8,9,10,12‐tetrahydrobenzo[a]xanthen‐11‐one Derivatives Promoted by Sulfamic Acid in [BMIM]BF4 Ionic Liquid

An efficient and green procedure for the synthesis of novel 12‐aryl‐8,9,10,12‐tetrahydrobenzo[a]xanthen‐11‐one derivatives has been described through one‐pot condensation of 2‐naphthol, arylaldehyde and 5,5‐dimethyl‐cyclohexane‐1,3‐dione in the presence of sulfamic acid (NH₂SO₃H) in ionic liquid 1‐n‐butyl‐3‐methylimidazolium tetrafluoroborate ([BMIM]BF₄). These reactions proceed with good yields under short reaction time. Furthermore, the green catalytic system can be recycled specific times with no decreases in yields and reaction rates.     

An Efficient and Facile Synthesis of tert‐Butyl 2‐(Methylamino)‐3‐nitro‐5‐oxo‐4‐aryl‐7,8‐dihydro‐4H‐pyrano[3,2‐c]pyridine‐6(5H)‐carboxylate derivatives in [BMIM]BF4

In this research, we have developed an efficient three‐component reaction for the synthesis of pyrano[3,2‐c]pyridine derivatives from the reaction of aromatic aldehydes, tert‐butyl 2,4‐dioxopiperidine‐1‐carboxylate, and N‐methyl‐1‐(methylthio)‐2‐nitroethylen‐1‐amine in [BMIM]BF₄ medium. The advantages of this method were readily available starting materials, simple reaction conditions, and satisfactory yields.     

Synthesis and Luminescence of 14-Aryl- or Alkyl-14H-dibenzo[a,j]xanthenes Catalyzed by 2-1′-Methylimidazolium-3-yl-1-ethyl Sulfate

A facile and efficient synthesis of 14-aryl or alkyl-14H-dibenzo[a,j]xanthenes has been accomplished by treatment of β-naphthol with aryl or alkyl aldehydes catalyzed by 2-1′-methylimidazolium-3-yl-1-ethyl sulfate in ionic liquid [BMIM][BF₄] at 80°C. The luminescence of products was studied in detail.     

Direct Electrochemistry and Electrocatalysis Behaviors of Glucose Oxidase Based on Hyaluronic Acid-Carbon Nanotubes-Ionic Liquid Composite Film

Multi‐walled carbon nanotubes (MWNTs) were dispersed in the ionic liquid [BMIM][BF₄] to form a uniform black suspension. Based on it, a novel glucose oxidase (GOx)‐hyaluronic (HA)‐[BMIM][BF₄]‐MWNTs/GCE modified electrode was fabricated. UV‐vis spectroscopy confirmed that GOx immobilized in the composite film retained its native structure. The experimental results of EIS indicated MWNTs, [BMIM][BF₄] and HA were successfully immobilized on the surface of GCE and [BMIM][BF₄]‐MWNTs could obviously improve the diffusion of ferricyanide toward the electrode surface. The experimental results of CV showed that a pair of well‐defined and quasi‐reversible peaks of GOx at the modified electrode was exhibited, and the redox reaction of GOx at the modified electrode was surface‐confined and quasi‐reversible electrochemical process. The average surface coverage of GOx and the apparent Michaelis‐Menten constant were 8.5×10⁻⁹ mol/cm² and 9.8 mmol/L, respectively. The cathodic peak current of GOx and the glucose concentration showed linear relationship in the range from 0.1 to 2.0 mmol/L with a detection limit of 0.03 mmol/L (S/N=3). As a result, the method presented here could be easily extended to immobilize and obtain the direct electrochemistry of other redox enzymes or proteins.     

离子液体[BMIM]Br与[BMIM][BF4]配比浓度对Br-离子电荷转移的调节

利用X射线吸收精细结构光谱(XAFS)及紫外吸收光谱两种方法, 分析了离子液体1-丁基-3-甲基咪唑溴盐([BMIM]Br)中逐渐掺入1-丁基-3-甲基咪唑四氟硼酸盐([BMIM][BF₄])时, Br^-阴离子与咪唑阳离子之间氢键作用及电荷偏移量的改变. 随着[BMIM][BF₄]加入量增多, Br 元素XAFS近边(XANES)显示吸收峰降低, 吸收边位置向低能端位移0.9 eV; 扩展边(EXAFS)算出径向结构显示Br 与近邻原子间平均配位数降低、平均键长增长; 紫外光谱也有明显蓝移减色效应. 这些结果都表明Br₄^-的掺入改变了Br^-与阳离子间的电荷偏移量, 负电荷更多地转移到Br^-上, 量化计算的数据同样支持该结论.     

Synthesis of Unsymmetrical Ureas and S‐Thiocarbamates under Catalyst‐free Conditions in a [BMIM]BF4 Ionic Liquid

Unsymmetrical ureas and S‐thiocarbamates were prepared in good to excellent yields by direct condensation of phenylurea with amines and thiols in 1‐butyl‐3‐methylimidazolium tetrafluoroborate ([BMIM]BF₄) without the addition of any additives. The [BMIM]BF₄ ionic liquid is a mild medium and can be recycled and reused several times.     

Effect of ionic liquid organizing ability and amine structure on the rate and mechanism of base induced elimination of 1,1,1-tribromo-2,2-bis(phenyl-substituted)ethanes

The kinetics of the elimination reaction of 1,1,1-tribromo-2,2-bis(phenyl-substituted)ethanes into the corresponding 1,1-dibromo-2,2-bis(phenyl-substituted)ethenes induced by amines were studied in three room temperature ionic liquids ([BMIM][BF₄], [BMIM][PF₆], [BdMIM][BF₄]). In order to have information about reagent-ionic liquid interactions, the reaction was carried out over the temperature range (293.1-313.1 K). To study the effect of the amine on the rate and occurrence of the elimination reaction, several primary, secondary and tertiary amines with different structure (cyclic and acyclic), basicity and steric requirements were used. The data collected show that the reaction occurs faster in ionic liquids than in other conventional solvents. Furthermore, ionic liquids seem to be able to induce, for the studied reaction, a shift of mechanism from E1_cb (in MeOH) versus E2 (in ionic liquid).     

The Synthesis of Anatase TiO2 Nanoparticles by Solvothermal Method using Ionic Liquid as Additive

The solvothermal reactions of Ti(OiPr)₄ in alcohol using ionic liquid as additive were investigated. In the presence of [BMIM][Cl], [BMIM][Br], [BMIM][NTf₂], [BMIM][SO₃Me], [BMIM][SO₄Me], or [BMIM][OTf] (BMIM = 1‐Butyl‐3‐methylimidazolium), pure anatase nanoparticles were obtained. The controlled hydrolysis of Ti(OiPr)₄ in the presence of ionic liquids to form titanium oxo clusters plays a key role in the formation of anatase nanostructures, and ionic liquids can be repeatedly used to synthesise anatase nanoparticles. However, in the presence of [BMIM][PF₆], [BMIM]₂[Ti(OH)₆] was obtained by an anion exchange reaction.     

Ionic Liquid [bmim]BF4 as an Efficient and Recyclable Reaction Medium for the Synthesis of O-Acetyl Cyanohydrin via One-Pot Condensation of Aldehyde,TMSCN, and Ac2O

Ionic liquid [bmim]BF₄ has been demonstrated to be an efficient and environmentally friendly reaction medium as well as reaction promoter for the synthesis of O-acetyl cyanohydrin via one-pot condensation of aldehyde, TMSCN, and Ac₂O without Lewis acid or any special activation. In addition, the recovered ionic liquid could be reused for subsequent runs without the loss of activity.     

Catalytic olefin epoxidation with cyclopentadienyl-molybdenum complexes in room temperature ionic liquids

Complexes of the type (η⁵-C₅R₅)Mo(CO)₃X (X = Me, Cl; R = H, Me), being efficient homogeneous catalysts for the epoxidation of olefins, have been examined for their catalytic performance at 55 °C in systems containing room temperature ionic liquids (RTILs) of composition [BMIM]NTf₂, [BMIM]PF₆, [C₈MIM]PF₆ and [BMIM]BF₄. The catalytic performance for cyclooctene epoxidation depends strongly on the water content of the system, the catalyst solubility in the RTIL, and the reaction behaviour of the RTIL under the applied reaction conditions. The catalysts can be recycled without significant loss of activity when a reaction system containing [BMIM]NTf₂ and [BMIM]PF₆ in a 4:1 relationship is used. High proportions of [BMIM]PF₆ lead to a ring opening reaction (diol formation), due to HF formation and the presence of residual water.     

Ionic Liquid-Based Ultrasound-Assisted Extraction of Chlorogenic Acid from Lonicera japonica Thunb

Hydrophilic ionic liquid of [BMIM][BF₄] was successfully applied for the ultrasound-assisted extraction (UAE) of hydrophilic chlorogenic acid from Lonicera japonica Thunb. To explore this extraction procedure, the corresponding extraction parameters including the sample size, [BMIM][BF₄] concentration, pH, extraction temperature, ultrasonic power and extraction time were investigated. The results revealed that the [BMIM][BF₄]-based UAE efficiency of chlorogenic acid was higher than that of the ethanol-based UAE and the traditional refluent ethanol extraction. And the study on the method reliability further confirmed that the [BMIM][BF₄]-based UAE is suitable for the effective extraction of chlorogenic acid from honeysuckle.     

Microwave‐Assisted Synthesis and Characterization of CuO Nanocrystals

CuO feather‐like and flower‐like crystals have been synthesized by a fast microwave‐assisted solution approach using Cu(NO₃)₂ and NaOH. The morphology transformation of CuO could be achieved by ionic liquid 1‐n‐butyl‐3‐methyl imidazolium tetrafluoroborate ([BMIM]BF₄). With [BMIM]BF₄, flower‐like CuO were obtained, whereas without [BMIM]BF₄, feather‐like CuO were obtained. The possible formation mechanism of flower‐like CuO was discussed on the basis of experimental results. The products were characterized by XRD, FESEM/EDS, and TEM/SAED. In addition, the adsorption of [BMIM]BF₄ on flower‐like CuO was confirmed by FTIR and TG/DSC, and the band gap energies of the flower‐like CuO was estimated by UV‐vis spectra.     

Aerobic and Electrochemical Oxidative Cross‐Dehydrogenative‐Coupling (CDC) Reaction in an Imidazolium‐Based Ionic Liquid

The ionic liquid 1‐butyl‐3‐methylimidazolium tetrafluoroborate [BMIm][BF₄] has demonstrated high efficiency when applied as a solvent in the oxidative nitro‐Mannich carbon? carbon bond formation. The copper‐catalyzed cross‐dehydrogenative coupling (CDC) between N‐phenyltetrahydroisoquinoline and nitromethane in [BMIm][BF₄] occurred with high yield under the described reaction conditions. Both the ionic liquid and copper catalyst were recycled nine times with almost no lost of activity. The electrochemical behavior of the tertiary amine substrate and β‐nitroamine product was investigated employing [BMIm][BF₄] as electrolyte solvent. The potentiostatic electrolysis in ionic liquid afforded the desired product with a high yield. This result and the cyclic voltammetric investigation provide a better understanding of the reaction mechanism, which involves radical and iminium cation intermediates.     

Chelation-controlled asymmetric aminohalogenation reaction

The chelation-controlled asymmetric aminohalogenation of α,β-unsaturated 3-aryl-N-acyl-N-4-phenyl-2-oxazolidinones have been established by using palladium(II) acetate as the catalyst and as the chelation metal. The reaction is very convenient to perform by simply mixing the three reactants, cinnamates, N,N-dichloro-p-toluenesulfonamide and catalyst together with 4 Å molecular sieves at rt in any convenient vial of appropriate size without special protection from inert gases. Unlike the previous asymmetric aminohalogenation, the ionic liquid, [BMIM][NTf₂], was found to be superior to [BMIM][BF₄] as the reaction media. It was also found that palladium(II) acetate has to be used together with 1 equiv of MeCN to achieve the opposite chelation control. The resulting absolute stereochemistry of the product was unambiguously determined by X-ray structural analysis.     

Highly efficient synthesis of amides via Ritter chemistry with ionic liquids

The utility of Brønsted-acidic imidazolium ionic liquid [BMIM(SO₃H)][OTf] as catalyst for the high yield synthesis of a wide variety of amides under mild conditions via the Ritter reaction of alcohols with nitriles has been demonstrated. As alternative methods for the carbocation generation step, NOPF₆ immobilized in [BMIM][PF₆] ionic liquid was used in the Ritter reaction of bromides with nitriles and for the synthesis of adamantyl amides from adamantane and nitriles.     

功能化离子液体为载体液相合成二氢吡啶酮衍生物

在微波辐照条件下, 以甲基咪唑、氯乙醇和四氟硼酸钠为原料制备了含羟基功能化离子液体1-(2-羟乙基)-3-甲基咪唑四氟硼酸盐([2-hydemim][BF₄]), 并以其为液态载体, 首先与乙酰乙酸乙酯反应, 得到的中间体再分别和Meldrum酸、醋酸铵以及各种芳香醛反应, 最后在温和的条件下用甲醇钠进行切割反应, 得到了一系列产率和纯度较高的3,4-二氢吡啶酮衍生物, 目标化合物不需要进一步的色谱纯化处理, 纯度为95%～98%, 产率为83%～93%. 回收得到的功能化离子液体可以重复套用至少6次也不影响其活性. 表明该方法是一种高效的3,4-二氢吡啶酮衍生物的组合化学合成方法.     

[Omim][BF4], a green and recyclable ionic liquid medium for the one-pot chemoselective synthesis of benzoxazinones

An efficient procedure for the one-pot chemoselective synthesis of 2H-benzo[b][1,4]oxazin-3(4H)-one derivatives from their corresponding o-aminophenols is developed using DBU in the ionic liquid [omim][BF₄]. Upon completion of the reaction and separation of the product, the ionic liquid is recovered and successfully reused over nine recycles without any noticeable loss of performance.     

A Green and Novel Method of Synthesizing 2,2'-Arylmethylene Bis(3-hydroxy-5,5-dimethylcyclohex-2-enone) Catalyzed by L-Histidine in Ionic Liquid

An efficient and green approach to the synthesis of 2,2′‐arylmethylene bis(3‐hydroxy‐5,5‐dimethylcyclohex‐2‐enone) using L‐histidine as the catalyst is described. In addition, room temperature ionic liquid 1‐butyl‐3‐methylimidazonium tetrafluoroborate [bmim]BF₄ was used as green recyclable alternatives to volatile organic solvents for this condensation reaction. This green catalytic system can be recycled several times with no decreases in yields and reaction rates.