A 2,2',6,6'-tetraphosphinobiphenyl

The first example of a 2,2',6,6'-tetraphosphinobiphenyl was prepared and used as a ligand in a dinuclear palladium(II) complex. The close proximity of the two complex fragments induces a coupling pathway allowing the allosteric communication between the two palladium complex fragments.     

A remarkable effect of ionic liquids in transition-metal-free aerobic oxidation of benzylic alcohols

The transition-metal-free aerobic oxidation of benzylic alcohols is uniquely accelerated by a 1-butyl-3-methylimidazolium hexafluorophosphate (BMI-PF₆)/PhCF₃ biphasic system and Cs₂CO₃ to afford the corresponding ketones in good yields. The reaction system is also applicable to an oxidative cross-esterification of primary benzyl alcohols with a higher aliphatic alcohol.     

Selective aerobic oxidation of activated alcohols into acids or aldehydes in ionic liquids

Selective aerobic oxidation of activated primary alcohols into acids or aldehydes has been developed in ionic liquids. Under optimal conditions, various alcohols could be selectively converted into their corresponding acids or aldehydes in good to excellent yields. The newly developed catalytic systems could also be recycled and reused for three runs without any significant loss of catalytic activity.     

Aerobic oxidation of alcohols in carbon dioxide with silica-supported ionic liquids doped with perruthenate

The replacement of toxic Cr(VI) for O2 and of chlorinated solvents for supercritical carbon dioxide (or ionic liquids) in the oxidation of alcohols remains hindered by the low selectivity and activity of the current heterogeneous catalysts. Using an integrated approach that combines sol-gel entrapped perruthenate as aerobic catalyst, an encapsulated ionic liquid as solubility promoter, and scCO2 as the reaction solvent, we have developed a system capable of rapidly converting different alcohols into carbonyl compounds with complete selectivity, including substrates which are otherwise difficult to oxidise. The methodology is generally applicable and may easily be extended to other waste-free, catalytic syntheses of fine chemicals.     

咪唑类离子液体中的有机氧化反应

简要概括了离子液体的种类和特点,重点介绍了咪唑类离子液体中的Baeyer-Villiger、Corey-Chayk-ovsky、醇、芳香烃、烷烃及含硫化合物的氧化反应.指出作为新型绿色溶剂的离子液体具有许多独特的物理化学性质,在多个领域具有重要的应用价值.     

Palladium catalyzed cycloisomerization of 2,2-diallylmalonates in imidazolium ionic liquids

A series of palladium salts and complexes, including PdCl₂, PdCl₂/AgPF₆, PdCl₂(PhCN)₂, PdBr₂ and Pd₂(dba)₃ were used in imidazolium ionic liquids as catalysts for the cycloisomerization of diethyl 2,2-diallylmalonate. The order of reactivity follows the expected Pd atom hardness and, therefore, “naked” Pd²⁺ generated from PdCl₂ + AgPF₆ gives the highest turnover frequencies. The system comprising Pd species dissolved in ionic liquid can be reused with minor decrease in conversion, but with an apparent variation in the product distribution. The latter comes from a diminished catalytic activity and from formation of Brönsted acid sites. Finally, by using 1,10-undecadiene derivative we have observed that this Lewis acid induced cycloisomerization is specific for the formation of five-member rings.     

Electrochemical oxidation behavior of hydroxypivalaldehyde in the ionic liquids

The similar electrochemical oxidation behaviors of hydroxypivalaldehyde in ionic liquids （ILs） medium, C4MIMPF6, C4MIMBF4 and CsMIMPF6, are investigated using classic electrochemical methods, respectively. Only the product, hydroxypivalic acid is detected by high performance liquid chromatography （HPLC）. It can be conferred that the electrochemical oxidation of hydroxypivalaldehyde consists of two successive one-electron irreversible reactions at glass carbon （GC） electrode and the possible reaction mechanism in the ILs is proposed firstly. The diffusion coefficients of hydroxypivalaldehyde are obtained according to the electrochemical characteristics of hydroxypivalaldehyde in C4MIMPF6, C4MIMBF4 and CsMIMPF6.     

Recyclable 2nd generation ionic liquids as green solvents for the oxidation of alcohols with hypervalent iodine reagents

Alcohols undergo smooth oxidation with iodoxybenzoic acid (IBX) or with Dess-Martin-Periodinane (DMP) in hydrophilic [bmim]BF₄ and hydrophobic [bmim]PF₆ ionic liquids at room temperature under mild conditions to afford the corresponding carbonyl compounds in excellent yields with high selectivity. IBX and DMP promoted oxidations are faster in ionic liquids when compared to conventional solvents such as DMSO, DMF, EtOAc and H₂O. The recovery of the byproduct iodosobenzoic acid (IBA) is especially simple in ionic liquids. The recovered ionic liquids can be recycled in subsequent reactions with consistent activity.     

Chiral ionic liquids for catalytic enantioselective sulfide oxidation

A new class of catalytic ionic liquids, containing chiral tungstate(VI) anions, gives enantiomeric excesses up to 96% for sulfide oxidation to sulfoxides.     

Methyltrioxorhenium-catalysed oxidation of secondary amines to nitrones in ionic liquids

Nitrones serve as starting materials for the synthesis of many heterocycles. Oxidation of secondary amines using hydrogen peroxide and the catalytic amount of methyltrioxorhenium in ionic liquids is a useful method for the preparation of nitrones. Ultrasonic irradiation and ionic liquids have a positive influence on the reaction. The nitrones required were isolated in good yields. Corresponding hydroxylamines, which can be easily oxidised to nitrones, often accompanied the main products. Methyltrioxorhenium in ionic liquids was re-used in several reaction cycles without any deteriorating effect on the course of the reaction.     

Recent advances in oxidation catalysis using ionic liquids as solvents

Ionic liquids are an interesting alternative to classical solvents presenting several advantages. A variety of catalysts show good or even enhanced activities when applied in ionic liquids. Oxidation catalysis represents a large segment of industrial chemistry, providing both bulk chemicals and intermediates for high value added special products and pharmaceuticals. Particularly for the latter products organometallic and inorganic catalysts are being developed that can be applied in systems consisting of or containing ionic liquids. This work provides an overview on recent developments in this field.     

Task-oriented use of ionic liquids: efficient acetylation of alcohols and phenols

The ionic liquid 1-butyl-3-methylimidazolium acetate proves to be an excellent reaction medium for the acetylation of alcohols and phenols, providing better conditions than the acidic 1-butyl-3-methylimidazolium bisulfate. Reactions were carried at room temperature, with only a 10% excess of acylating agent and with no other solvent or catalyst added.     

Rhodium-catalyzed cross-coupling of allyl alcohols with aryl- and vinylboronic acids in ionic liquids

[reaction: see text] The direct coupling of aryl- and vinylboronic acids with allylic alcohols has been achieved in ionic liquids using a rhodium catalyst.     

Liquid phase behavior of ionic liquids with alcohols: experimental studies and modeling

Ionic liquids (ILs) have been suggested as potential "green" solvents to replace volatile organic solvents in reaction and separation processes due to their negligible vapor pressure. To develop ILs for these applications, it is important to gain a fundamental understanding of the factors that control the phase behavior of ionic liquids with other liquids. In this work, we continue our study of the effect of chemical and structural factors on the phase behavior of ionic liquids with alcohols, focusing on pyridinium ILs for comparison to imidazolium ILs from our previous studies. The impact of different alcohol and IL characteristics, including alcohol chain length, cation alkyl chain length, anion, different substituent groups on the pyridinium cation, and type of cation (pyridinium vs imidazolium) will be discussed. In general, the same type of behavior is observed for pyridinium and imidazolium ILs, with all systems studied exhibiting upper critical solution temperature behavior. The impacts of alcohol chain length, cation chain length, and anion, are the same for pyridinium ILs as those observed previously for imidazolium ILs. However, the effect of cation type on the phase behavior is dependent on the strength of the cation-anion interaction. Additionally, all systems from this study and our previous work for imidazolium ILs were modeled using the nonrandom two-liquid (NRTL) equation using two different approaches for determining the adjustable parameters. For all systems, the NRTL equation with binary interaction parameters with a linear temperature dependence provided a good fit of the experimental data.