Sonochemical Synthesis and Characterization of Some Alkoxyl-Functionalized Ionic Liquids Derived from 1-Butoxyl-3-butyl Imidazolium Bromide

Non-conventional techniques, such as power ultrasound (US) has been used to promote one-pot synthesis of second generation ionic liquids (ILs), reducing reaction times and improving yields. Because of the emerging importance of the ILs as green materials with wide ranging applications and our general interests in green processes such as sonication, 1-butoxyl-3-butyl imidazolium bromide (alkoxyl-functionalized) and their derivatives were synthesized using a facile and green US assisted procedure. Their structures were characterized by FT–IR, ¹H-NMR, ¹³C-NMR and mass spectroscopy.     

Use of 1-alkyl-3-methylimidazolium-based ionic liquids as background electrolytes in capillary electrophoresis for the analysis of inorganic anions

Separation of inorganic anions in CE is often a challenging task because the electrophoretic mobilities of inorganic anions are comparable to or even greater than the EOF mobility. In this study, we present the use of ionic liquids (ILs) as background electrolytes (BGEs) in CE of inorganic anions. The 1-alkyl-3-methylimidazolium-based ILs as BGEs dynamically coated the capillary wall and induced a reversed EOF. This allowed the anions to comigrate with the EOF and yielded a rapid separation. Increasing the alkyl chain length of the ILs and BGE concentration can significantly improve the separation resolution. With 40 mM 1-butyl-3-methylimidazolium tetrafluoroborate as BGE, good separations of five model anions (Br-, I-, NO2(-), NO3(-), and SCN-) were achieved in a range of buffer pH values. The separation efficiency was as high as 34 600-155 000, and the RSDs of the migration times were less than 0.8% (n = 5).     

High-intensity ultrasound and microwave, alone or combined, promote Pd/C-catalyzed aryl-aryl couplings

Pd-catalyzed homo- and cross-couplings of boronic acids and aryl halides were successfully carried out both in aqueous media under high-intensity ultrasound (US) and in DME under microwave (MW). Heterogeneous catalysis with Pd/C was employed, avoiding phosphine ligands and phase-transfer catalysts. In a trial series involving 15 different iodo- and bromoaryls and 7 boronic acids, both energy sources drastically reduced reaction times affording biaryls in acceptable to good yields. With palladium(II) acetate as catalyst, electron-deficient aryl chlorides also reacted, affording a few biaryls in acceptable yields. Ullmann-type zinc-mediated homocoupling of iodo- and bromoaryls in the presence of Pd/C under CO₂ atmosphere was achieved in aqueous media under US, though not under MW. Suzuki homo- and cross-couplings were also carried out in a new reactor developed in our laboratory, featuring combined US and MW irradiation, further improving a green synthetic method.     

Solvent Role of Ionic Liquids in Fundamental Chemical Reaction Dynamics Analyzed by Time-Resolved Spectroscopy

Ionic liquids (ILs), which are used as solvents for chemical reactions, are different from conventional organic solvents owing to their designability. Physicochemical parameters of the ILs, such as polarity and viscosity, that affect chemical equilibria and reaction kinetics can be tuned by changing the combination of anions and cations or by varying the lengths of the alkyl chains present in the cations. We were interested in knowing how these physicochemical parameters affect fundamental chemical reactions in ILs. Therefore, in this personal account, we investigate our recent work on two different photochemical reactions in ILs, namely excited-state intramolecular proton transfer of hydroxyflavone and photodissociation of aminodisulfide, using time-resolved spectroscopic techniques. Interestingly, the roles of the ILs in these chemical reactions are quite different. The effect of the cationic species of the ILs (i. e., the head groups and number of alkyl carbons) on the solvation environment upon photoexcitation and reaction rate are discussed.     

离子液体与微波协同促进有机合成反应

介绍了离子液体作溶剂、助溶剂、催化剂和反应试剂与微波协同促进有机合成的研究进展。离子液体与微波协同促进有机合成反应,缩短了反应时间,提高了反应的选择性和产率,对环境更加友好。     

Ligand‐free,copper‐catalyzed,one‐pot,three‐component synthesis of novel 1,2,3‐triazole‐linked indoles in magnetized water

Magnetized water (MW) is used as a green and new solvent‐promoting medium for the one‐pot, three‐component synthesis of novel 1,2,3‐triazole‐linked indoles catalyzed by copper iodide. A broad range of 2‐aryl‐1‐(prop‐2‐ynyl)‐1H‐indole‐3‐carbaldehydes were reacted with alkyl halides and sodium azide via copper‐catalyzed azide–alkyne cycloaddition reactions in MW in the absence of any ligand. This method offers the advantages of short reaction times, green procedure, low cost, simple work‐up, quantitative reaction yields, and no need for any organic solvent.     

Fast catalytic epoxidation with H(2)O(2) and [gamma-SiW(10)O(36)(PhPO)(2)](4-) in ionic liquids under microwave irradiation

Olefin epoxidation by [gamma-SiW10O36(PhPO)2]4- and H2O2 occurs in hydrophobic ionic liquids (ILs), with yields and selectivity up to >99%. The catalytic IL phase is recyclable. Under MW irradiation the reaction occurs with up to 200 turnovers per minute. Simultaneous cooling is instrumental for quantitative H2O2 conversion.     

N,N’-dimethyl formamide (DMF) mediated Vilsmeier–Haack adducts with 1,3,5-triazine compounds as efficient catalysts for the transesterification of β-ketoesters

Abstract

N, N’-dimethyl formamide (DMF) mediated Vilsmeier–Haack (VH) adducts with 1,3,5-triazine compunds such as trichloroisocyanuric acid (TCCA) and trichlorotriazine (TCTA) were prepared by replacing classical oxy chlorides POCl₃, and SOCl₂, which were explored as efficient catalysts for the transesterification of β-ketoesters. The prepared (TCCA/DMF) and (TCTA/DMF) adducts improved greenery of the classical Vilsmeier–Haack reagents (POCl₃/DMF), and (SOCl₂/DMF), and demonstrated their better efficient catalytic ativity. Reaction times were in the range: 3.5 to 6.5?hr (SOCl₂/DMF); 2.8–5.2?hr (POCl₃/DMF); 2.5–5.2?hr (TCCA/DMF) and 2.5–5.0?hr (TCTA/DMF) catalytic systems. Ultrasonically (US) assisted protocols with these reagents further reduced the reaction times (two to three times), while microwave assisted (MW) protocols with these reagents were much more effective. The reactions could be completed in only few seconds (less than a minute) in MWassisted protocols as compared to US assited reactions, followed by good product yields.     

Synthesis of Ti(OH)OF ⋅ 0.66 H2O in Imidazolium-based Ionic Liquids

The influence of the cation of imidazolium-derived ionic liquids (ILs) on a low-temperature solution-based synthesis of hexagonal tungsten bronze (HTB) type Ti(OH)OF ⋅ 0.66 H₂O and bronze-type TiO₂(B) is investigated. The IL (C_xmim BF₄) acts as solvent and also as reaction partner with respect to the decomposition of [BF₄]⁻, releasing F⁻. In the present study, the chain length of the alkyl chain side groups attached to the imidazolium ring was varied (C₂mim BF₄ to C₁₀mim BF₄), and the obtained solids were analyzed by Powder X-Ray diffraction (PXRD) followed by Rietveld refinement. As a main finding these analyses indicate a transformation of Ti(OH)OF ⋅ 0.66 H₂O into TiO₂(B), and upon prolonged reaction time finally also into anatase TiO₂. Rietveld analysis suggests that when using ILs with longer alkyl chains, the conversion of Ti(OH)OF ⋅ 0.66 H₂O is slower compared to syntheses performed with smaller alkyl chains. Hence, Ti(OH)OF ⋅ 0.66 H₂O appears to be metastable and is stabilized by long-chain ILs serving as surfactant attached to the crystallites’ surface. In this view, the ILs shield the nanoparticles and thus slow down the conversion into the more stable compounds. This confirms previous findings that ILs act as both, solvent and reaction medium in this reaction, thus enabling the synthesis of peculiar Ti-oxides.     

An efficient preparation and characterization of 1-(2-ethoxy-2-oxoethyl)imidazolium based ionic liquids derivatives as potential bioactive agents

A set of new 1-(2-ethoxy-2-oxoethyl)imidazolium-based ionic liquids (1–16) have been prepared via the alkylation reaction of ethyl 2-(1H-imidazol-1-yl)acetate with various type of substituted alkyl halides using a microwave irradiation reaction in yields above 90%. The chemical structures of the manufactured ILs (1–16) were analyzed by mass and NMR spectroscopy. The newly prepared ILs were examined for their in vitro anti-microbial activities towards different types of Gram (+) and Gram (−) bacteria, and also for their antifungal activities. The preliminary tests showed that most of the resultant ILs presented modest activities towards S. aureus and B. subtilis with IZ values ranging between 10 and 14 mm, while the E. coli activities was in the range of 16 and 20 mm. However, ILs (1–16) displayed poor activities against the C. albicans.     

Selective Synthesis of 2,6-Dimethylnaphthalene by Transalkylation in the Presence of Acid Ionic Liquids[Cnmim]Cl-AlCl3

A highly selective synthesis of 2,6-dimethylnaphthanlene(2,6-DMN) by transalkylation between 2-methylnaphthanlene(2-MN) and 1,2,4,5-tetramethylbenzene(TeMB) was performed with 1-alkyl-3-methylimidazo- lium aluminum chloride([Cnmim]Cl-AlCl3) ionic liquids(ILs) as catalysts. The influences of the alkyl group as the organic cation, the acidic strength of [C4mim]Cl-AlCl3 ILs as well as the reaction conditions on the catalytic performance were investigated. [C4mim]Cl-AlCl3 ILs[x(AlCl3)=71%] exhibited high activity and selectivity toward 2,6-DMN. The selectivity to 2,6-DMN and the 2,6-DMN/2,7-DMN ratio reached up to 68.2% and 3.7:1, respectively. The UV-Vis spectrum of TeMB treated by different ILs shows that the protonated degree of TeMB dependeds on the acidity strength of ILs, which has a significant impact on the reaction results. The high protonated degree of TeMB is advantageous to enhancing the conversion of transalkylation and the large stereo-hindrance effect of TeMB is favorable to improving the selecivity to 2,6-DMN.     

Pd(II) immobilized on mesoporous silica by N-heterocyclic carbene ionic liquids and catalysis for hydrogenation

In this work we synthesized Pd(II) immobilized on mesoporous silica by N-heterocyclic carbene (NHC) ionic liquids (ILs) with different alkyl chain lengths. The catalysts were characterized by Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), low-angle X-ray powder diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and nitrogen sorption. The catalysts were used for the hydrogenation of alkenes and allyl alcohol. The results indicated that the catalysts were very active, selective, and stable. The selectivity for the hydrogenation of allyl alcohol to 1-propanol increased with the increase of the alkyl chain length of the ILs. The effect of supercritical CO(2) (scCO(2)) on the hydrogenation of allyl alcohol was also studied, and it was demonstrated that scCO(2) could enhance the selectivity of the reaction considerably. The XPS study showed that the valence of Pd(II) remained unchanged under hydrogenation conditions.     

离子液体对β-糖苷酶催化合成红景天苷的影响(英文)

研究了混合溶剂体系中阴离子分别为BF4-,PF6-,Cl-,Br-和I的14种离子液体对来源于黑布林糖苷酶催化合成红景天苷反应的影响.结果表明,在最佳反应条件下,β-糖苷酶的反应初速度和红景天苷的产率分别为3.3mmol/(L·h)和24.5%.离子液体咪唑阳离子的烷基链长(C2~C10)对β-糖苷酶的活性影响较大,当烷基链长为C6时,糖苷酶表现出较高的催化活性.     

Effect of the structure of imidazolium cations in [BF4](-)-type ionic liquids on direct electrochemistry and electrocatalysis of horseradish peroxidase in Nafion films

The direct electrochemistry and bioelectrocatalysis of horseradish peroxidase (HRP) in Nafion films at glassy carbon electrode (GCE) was investigated in three [BF(4)](-)-type room-temperature ionic liquids (ILs) to understand the structural effect of imidazolium cations. The three ILs are 1-ethyl-3-methylimidazolium tetrafluoroborate ([Emim][BF(4)]), 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF(4)]) and 1-hexyl-3-methylimidazolium tetrafluoroborate ([Hmim][BF(4)]). A small amount of water in the three ILs is indispensable for maintaining the electrochemical activity of HRP in Nafion films, and the optimum water contents decrease with the increase of alkyl chain length on imidazole ring. Analysis shows that the optimum water contents are primarily determined by the hydrophilicity of ILs used. In contrast to aqueous medium, ILs media facilitate the direct electron transfer of HRP, and the electrochemical parameters obtained in different ILs are obviously related to the nature of ILs. The direct electron transfer between HRP and GCE is a surface-confined quasi-reversible single electron transfer process. The apparent heterogeneous electron transfer rate constant decreases gradually with the increase of alkyl chain length on imidazole ring, but the changing extent is relatively small. The electrocatalytic reduction current of H(2)O(2) at the present electrode decreases obviously with the increase of alkyl chain length, and the mass transfer of H(2)O(2) via diffusion in ILs should be responsible for the change. In addition, the modified electrode has good stability and reproducibility; the ability to tolerate high levels of F(-) has been greatly enhanced due to the use of Nafion film. When an appropriate mediator is included in the sensing layer, a sensitive nonaqueous biosensor could be fabricated.     

Transformation of Iodosulfuron-Methyl into Ionic Liquids Enables Elimination of Additional Surfactants in Commercial Formulations of Sulfonylureas

Efficient use of herbicides for plant protection requires the application of auxiliary substances such as surfactants, stabilizers, wetting or anti-foaming agents, and absorption enhancers, which can be more problematic for environment than the herbicides themselves. We hypothesized that the combination of sulfonylurea (iodosulfuron-methyl) anion with inexpensive, commercially available quaternary tetraalkylammonium cations could lead to biologically active ionic liquids (ILs) that could become a convenient and environment-friendly alternative to adjuvants. A simple one-step synthesis allowed for synthesizing iodosulfuron-methyl based ILs with high yields ranging from 88 to 96% as confirmed by UV, FTIR, and NMR. The obtained ILs were found to possess several favorable properties compared to the currently used sodium salt iodosulfuron-methyl, such as adjustable hydrophobicity (octanol-water partition coefficient) and enhanced stability in aqueous solutions, which was supported by molecular calculations showing cation–anion interaction energies. In addition, soil mobility and volatility of ILs were more beneficial compared to the parental herbicide. Herbicidal activity tests toward oil-seed rape and cornflower revealed that ILs comprising at least one alkyl chain in the decyl to octadecyl range had similar or better efficacy compared to the commercial preparation without addition of any adjuvant. Furthermore, results of antimicrobial activity indicated that they were practically harmless or slightly toxic toward model soil microorganisms such as Pseudomonas putida and Bacillus cereus.     

Stability and growth behavior of transition metal nanoparticles in ionic liquids prepared by thermal evaporation: how stable are they really?

Recently we developed an access to metal- and metal-oxide colloids based on thermal evaporation of metals into ionic liquids (ILs). Here we present systematic studies on the long-time stability of gold and copper nanoparticles (NPs) in different ILs. The influence of metal concentration and temperature on the ripening of the as-prepared gold NPs in different ILs was investigated by transmission electron microscopy (TEM) and UV-vis absorption measurements. Short alkyl chain-length-methyl-imidazolium salts with weakly coordinating perfluorinated counter anions (PF(6), BF(4) or Tf(2)N, bis(trifluoromethanesulfonyl)amide) were found to be better stabilizers compared to ILs with cations bearing long alkyl chains (trihexyltetradecylphosphonium, 1-octyl-3-methylimidazolium) and anions of higher coordination strength (DCA, dicyanamide). In the latter ILs fast particle growth and agglomeration was observed. In the well-stabilizing ILs initially very small NPs form which undergo a similar ripening process at room temperature as at higher temperatures. The final particle size depends largely on the used IL and the metal and to a minor extent on the temperature. The metal concentration seems to be an unimportant factor.     

Highly efficient one-pot synthesis of primary amides catalyzed by scandium(III) triflate under controlled MW

The present Letter highlights a versatile synthetic protocol for the one-pot synthesis of primary amides employing scandium(III) triflate as a catalyst in water under controlled MW. This methodology offers excellent yields in shorter reaction times with enhanced selectivity.     

A convenient method to access long-chain and functionalised mixed methylphosphonate esters and their application in the synthesis of ionic liquids

A new method to synthesise long-chain and functionalised methylphosphonate esters and the corresponding ionic liquids is reported. The synthesis comprises the formation of dialkyl methylphosphonate esters in a S(N)2 reaction followed by the use of these esters as alkylating agents to form the corresponding, new alkyl methylphosphonate ILs.     

Titanocene-catalyzed carbosilylation of alkenes and dienes using alkyl halides and chlorosilanes

A new method for regioselective carbosilylation of alkenes and dienes has been developed by the use of a titanocene catalyst. This reaction proceeds efficiently at 0 degrees C in THF in the presence of Grignard reagents by the combined use of alkyl halides (R'-X, X = Br or Cl) and chlorotrialkylsilanes (R3'Si-Cl) as the alkylating and silylating reagents, respectively. Terminal alkenes having aryl or silyl substituents (YRC=CH2, Y = Ar or Me3Si, R = H or Me) afford addition products YRC-(SiR'3)-CH2R' in good yields, whereas 1-octene and internal alkenes were sluggish. When 2,3-disubstituted 1,3-butadienes were used instead of alkenes, alkyl and silyl units are introduced at the 1- and 4-positions giving rise to allylsilanes in high yields under similar conditions. The present reaction involves (i) addition of alkyl radicals toward alkenes or dienes, and (ii) electrophilic trapping of benzyl- or allylmagnesium halides with chlorosilanes. The titanocene catalyst plays important roles in generation of these active species, i.e., alkyl radicals and benzyl- or allylmagnesium halides.     

Activity and stability of α-chymotrypsin in biocompatible ionic liquids: enzyme refolding by triethyl ammonium acetate

In view the of wide scope of structural information of biomolecules in biocompatible ionic liquids (ILs) in various applications including chemical and biochemical, it is essential to study the productive preferential interactions between biological macromolecules and biocompatible ILs. We have therefore explored the stability and activity of α-chymotrypsin (CT) in the presence of five ILs from different families, such as triethyl ammonium acetate (TEAA), triethyl ammonium phosphate (TEAP) from ammonium salts, 1-benzyl-3-methylimidazolium chloride ([Bzmim][Cl]), 1-benzyl-3-methylimidazolium tetrafluoroborate ([Bzmim][BF(4)]) from imidazolium salts and tetra-butyl phosphonium bromide (TBPBr) from phosphonium families. Circular dichroism (CD) and UV-vis spectrophotometer experiments were used to study CT stabilization by ILs, related to the associated structural changes and enzyme activity studies, respectively. We observed that all ILs have a dominant contribution to the stabilization of CT. The stability and activity of CT depends on the structural arrangement of the ions of ILs. Our experimental results explicitly elucidate that more hydrophobic imidazolium and phosphonium cations carrying longer alkyl chains of ILs ([Bzmim][Cl], [Bzmim][BF(4)] and TBPBr) were weak stabilizers for CT, while small alkyl chain molecules of triethyl ammonium salts (TEAA and TEAP) are strong stabilizers and therefore more biocompatible for CT stability. Our CD and NMR measurements reveal that TEAA is a refolding additive for CT from a quenched thermal unfolded enzyme structure.