The Baeyer-Villiger oxidation of ketones with Oxone in the presence of ionic liquids as solvents

Cyclic and linear ketones were readily oxidised with Oxone^® at 40 °C in ionic liquids as solvents and short times (2.5-20 h), affording their corresponding lactones and esters in high yields (65-95%). Both, aprotic and protic ionic liquids were used. The best conversion of ketones and the highest yields of products were obtained with 1-buty-3-methylimidazolium tetrafluoroborate and 1-methylimidazolium acetate as solvents. These ionic liquids were also efficiently recycled in the Baeyer-Villiger reaction without significant loss of activity. Several factors, such as the partial solubility of KHSO₅ in the ionic liquid, its viscosity and the presence of a proton in protic ionic liquids, have an influence on the course of the reaction.     

Useful Application of Acidic Ionic Liquids as Solvents in Baeyer–Villiger Oxidation with Hydrogen Peroxide for the Synthesis of Lactones

Cyclic ketones have been efficiently oxidized with hydrogen peroxide using acidic ionic liquids (ILs) as solvents. This is a new method for the synthesis of lactones with high yields that does not utilize any additional catalysts and enables ILs to be recycled.     

Oxidation of alcohols to aldehydes and ketones using selenium ionic liquid

A new type of ionic liquid supported selenium reagents were synthesized and found to be an excellent catalyst in the oxidation of alcohols to aldehydes and ketones in the presence of 30%H₂O₂.The predictable solubility of ionic liquids allows an easy separation of the oxidation products from the reaction mixture.Furthermore,the oxidation reaction can be carried out using an ionic liquid as the solvent,and the ionic liquid-supported selenium reagents can be recycled and used for four times with a little decrease in catalytic performance.     

Ionic liquid-supported TEMPO as catalyst in the oxidation of alcohols to aldehydes and ketones

We describe an efficient synthesis of an ionic liquid-supported TEMPO which was used for the oxidation of alcohols to aldehydes and ketones. The predictable solubility of ionic liquids allows an easy separation of the oxidation products from reagents. Furthermore, the oxidation can be carried out using an ionic liquid as the solvent instead of dichloromethane; and the IL-supported TEMPO can be recycled and used several times without the loss of efficiency.     

氨基醇杂多酸类离子液体催化环酮的Baeyer-Villiger氧化反应

合成了一系列氨基醇杂多酸类离子液体,并将其用于催化环酮的Baeyer-Villiger氧化反应.以2-庚基环戊酮为模板底物,H₂O₂为氧化剂,探究了此类氨基醇杂多酸类离子液体的催化活性,筛选出催化活性最高的催化剂为[Pro-ps]H₂PW₁₂O₄₀,最佳反应条件:n(2-庚基环戊酮)∶n(催化剂)∶n(H₂O₂)=1∶0. 03∶4,反应温度40℃,反应时间8 h,无溶剂.在最佳条件下,2-庚基环戊酮的转化率为98. 19%,产物δ-十二内酯的选择性可达82. 84%.水相中的离子液体[Pro-ps]H₂PW₁₂O₄₀经干燥后可以重复使用.经过5次循环使用后催化活性未见明显下降.[Pro-ps]H₂PW₁₂O₄₀还可用于催化其它多种环酮的Baeyer-Villiger氧化反应,结果表明,该催化剂具有良好的...     

Baeyer-Villiger Oxidation of Cyclic Ketones Catalyzed by Amino Acid Ionic Liquids

A series of amino-acid-based ionic liquids was synthesized via one-step protonation of the corresponding L-amino acid by utilizing an array of proton sources. The catalytic activity of the amino-acid-based ionic liquids for the Baeyer-Villiger oxidation of cyclic ketones was investigated using cyclopentanone as a model cycloketone. The proline-based ionic liquid [ProH]CF₃SO₃ was shown to exhibit the best catalytic activity. The reaction condition was optimized to give the following reagent ratio of n(cyclopentanone):n(catalyst):n(H₂O₂)=1:0.06:4, 60℃ and 6 h. Under the optimum conditions, the conversion of cyclopentanone was 96.57% and the selectivity for δ-valerolactone was 73.01%. The catalytic activity was shown to be constant after 4 cycles. A simple treatment was allowed for the recover and the reuse of [ProH]CF₃SO₃. The successful utilization of [ProH]CF₃SO₃ to catalyze a host of cyclic ketones via Baeyer-Villiger oxidation clearly demonstrated the capacity of [ProH]CF₃SO₃ to tolerate variation in the substrate.     

Generation and detection of the cyclohexadienyl radical in phosphonium ionic liquids

The formation of the cyclohexadienyl radical, C(6)H(6)Mu, in ionic and molecular solvents has been compared. This is the first time that a muoniated free radical is reported in an ionic liquid. In marked contrast to molecular liquids, free radical generation in ionic liquids is significantly enhanced. Comparison of the hyperfine interactions in the ionic liquid and in molecular solvents and with theoretical calculations, suggests significant and unforeseen solvent interaction with the cyclohexadienyl radical.     

Oxidation of Benzylic Alcohols to Carbonyl Compounds with Potassium Permanganate in Ionic Liquids

Abstract

The selective oxidation of primary and secondary benzylic alcohols with potassium permanganate in ionic liquids to give corresponding aldehydes and ketones in 83–97% yields has been described.     

S-Substituted-2-mercaptobenzthiazolium-based chiral ionic liquids: efficient organocatalysts for enantioselective sodium borohydride reductions of prochiral ketones

Novel chiral ionic liquids having chirality in their cationic part have been synthesized for evaluation of their catalytic potential as organocatalysts in sodium borohydride reduction of prochiral ketones to yield optically active secondary alcohols. The chiral ionic liquids have been synthesized from the reaction of (?)-menthol or (?)-borneol, chloroacetic acid and S-methyl/benzyl-2-mercaptobenzthiazole. The synthesized chiral ionic liquids have been characterized by ¹H, ¹³C NMR and Mass spectrometry. Moderate to excellent enantiomeric excess (ee > 99%) has been obtained in asymmetric sodium borohydride reduction of prochiral ketones using these salts as chiral catalysts.     

A Facile and Efficient Oxidation of α,β-Unsaturated Alcohols with Manganese Dioxide in Ionic Liquids under Mild Conditions

The oxidation of α,β-unsaturated primary and secondary alcohols to corresponding aldehydes and ketones by manganese dioxide in ionic liquids as a safe recyclable and accelerative reaction medium under mild conditions are described. The rate of the oxidation reaction is faster and the yield is higher than that with conventional procedures.     

Highly selective electrochemical fluorination of organic compounds in ionic liquids

Recent studies on electrochemical partial fluorination in ionic liquid fluoride salts are reviewed. At first, historical background and some problems of electrochemical fluorination in organic solvents are briefly mentioned. Solvent-free electrochemical fluorinations in ionic liquids are explained as follows. Ultrasonication was found to improve both the yield and current efficiency for electrochemical fluorination of α-phenylthioacetate, which is mainly attributable to marked mass transport promotion of the substrate and the suppression of anode passivation. Highly regioselective and efficient fluorination of cyclic ethers, lactones, and cyclic carbonate was achieved in Et₄NF·4HF and Et₃N·5HF. Selective fluorination of hardly oxidizable phthalide was realized using a combination of imidazolium and fluoride ionic liquids. The unique effect of imidazolium ionic liquids on electrochemical fluorodesulfurization of 3-phenylthiophthalide was explained. Reuse of ionic liquids for electrochemical fluorination is also possible.     

Palladium‐Catalyzed Cascade Annulation To Construct Functionalized β‐ and γ‐Lactones in Ionic Liquids

A highly efficient and mild palladium‐catalyzed, one‐pot, four‐step cascade annulation has been developed to afford functionalized β‐ and γ‐lactones in moderate to good yields with high regio‐ and diastereoselectivities in ionic liquids. The employment of ionic liquids under mild reaction conditions makes this transformation green and practical. Especially, this reaction provided a novel and convenient methodology for the construction of naturally occurring biologically active β‐ and γ‐lactones.     

室温离子液体在聚合反应中的应用

室温离子液体作为一种环境友好的“绿色溶剂”,具有很多独特的物理化学性能,可以应用于自由基聚合、阳离子聚合、配位聚合、电化学聚合等反应体系。本文介绍了室温离子液体在上述反应中的应用。     

Catalytic Oxidation of Alcohols to Corresponding Aldehydes or Ketones with TEMPO-Mediated Iodosobenzene in Water in the Presence of a Surfactant

An efficient, facile, and rapid oxidation of alcohols to the corresponding aldehydes or ketones with a stoichiometric amount of iodosobenzene (PhIO) in the presence of catalytic amounts of 2,2,6,6-tetramethyl-1-piperidinyloxyl free radical (TEMPO), KBr, and a surfactant, such as SDS (sodium dodecylsulfate), was reported. The oxidation proceeded in water at room temperature to afford aldehydes or ketones in excellent yields and high selectivity without overoxidation to carboxylic acids. Selective oxidation of primary alcohols in the presence of secondary alcohols was also achieved with the catalytic system of PhIO/TEMPO/KBr/SDS. A possible mechanism for the oxidation was supposed.     

Hydrogen-transfer reduction of aromatic ketones in basic ionic liquids

Abstract  

Several achiral and chiral basic ionic liquids (ILs) were prepared and tested as the medium for Ru-catalyzed hydrogen-transfer reduction of different aromatic ketones. Hydrogen-transfer reduction of ketones proceeded well in achiral basic ILs using chiral catalysts. The interesting observation was made that raising the reaction temperature did not have a negative effect on enantioselectivity of the reaction. On the other hand no reaction was observed in chiral ILs.     

Recombination of Lophyl Radicals in Pyrrolidinium‐Based Ionic Liquids

The recombination of photolytically generated lophyl radicals has been investigated by UV/Vis spectroscopy in 1‐alkyl‐1‐methylpyrrolidinium bis(trifluoromethylsulfonyl)imides (NTf₂) in comparison with 1‐butyl‐3‐methylimidazolium NTf₂, dimethyl sulfoxide, and triacetin. The 1‐alkyl‐1‐methylpyrrolidinium‐based ionic liquids contain an alkyl substituent varying between butyl and decyl groups. Optically pure ionic liquids are used in these studies. Temperature‐dependent investigation of lophyl radical recombination shows an increase in the radical recombination rate with increasing temperature in each solvent, which is caused by decreasing viscosity with increasing temperature. Furthermore, the viscosity of the 1‐alkyl‐1‐methylpyrrolidinium NTf₂ increases nearly linearly within the row of these ionic liquids. In contrast, the recombination of the photolytically generated lophyl radicals is significantly faster in the ionic liquids than in the traditional organic solvents under investigation. Moreover, the recombination rate increases with the length of the alkyl chain bound at the cation of the ionic liquid at a given temperature. This may be caused by an increase in the extent of lophyl radical recombination within the solvent cage. Solvent cage effects dominate in the case of lophyl radical recombination in ionic liquids bearing a long alkyl chain or if the temperature is near the melting temperature of the ionic liquid. The positive value of the activation entropy supports this hypothesis. The results obtained are important for discussion of bimolecular radical reactions in ionic liquids.     

Synthesis of chiral acetoxy lactones via the Baeyer-Villiger oxidation of cyclic aromatic acetoxy ketones

The α-acetoxylation of indanones and tetralones by using Mn(OAc)₃ followed by the enzyme catalyzed kinetic resolution of acetoxy ketones furnished both of the enantiomers of α-acetoxy ketones in good chemical and optical yields. The Baeyer-Villiger oxidation of α-acetoxy ketones with m-CPBA, CF₃SO₃H, and CH₂Cl₂, at rt gives the corresponding lactones without racemization. The acetoxy ketone moiety migrates selectively in order to form lactones. The mild hydrolysis of lactones affords phenolic α-hydroxycarboxylic acid derivatives.     

Acidic Ionic Liquids as Efficient and Environmentally Benign Medium for the Synthesis of 2-Phenylbenzimidazole

2‐Substituted benzimidazoles have been synthesized in excellent yields under solvent‐free conditions using a series of acidic ionic liquids as catalysts. The results indicate that SO₃H‐functionalized ionic liquids show higher catalytic activities than other acidic ionic liquids. The effects of reaction conditions such as the amounts of ionic liquids, the ratio of reactants were investigated. A Hammett method was used to determine the acidity order of these ionic liquids and the results were found to be relevant to the catalytic activities observed in the synthesis reaction. Besides, the reaction mechanism was stimulated using DFT method.     

Dy(OTf)3 in ionic liquid: an efficient catalytic system for reactions of indole with aldehydes/ketones or imines

Dy(OTf)₃ immobilized in ionic liquids was found to be an efficient catalytic system for the reactions of indole with aldehydes/ketones or imines. Enhanced activity was observed. The use of ionic liquids as the reaction media allows facile separation and recycling of the catalyst.     

Free Radical Polymerization of Acrylonitrile in Green Ionic Liquids

Free radical polymerization of acrylonitrile (AN) in ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF₄]), 2,2;m1-azobisisobutyronitrile (AIBN) as initiator was investigated. Early investigations on polymerizations using ionic liquids indicate that they serve as especially good solvents to achieve high molecular weight polymers. Free radical polymerizations result in higher molecular weight polymers, for ionic liquids have low chain transfer constants and act to stabilize the active radical during the process of polymerization. The thermal stability of polymers synthesized in ionic liquids have be improved obviously than that in traditional solvents.