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A series of task-specific ionic liquids (TSILs) based on glycerylimidazolium cations have been prepared by reaction of 1-chloropropanediol, a compound obtainable from glycerol (a widely available and in-expensive waste product), with the appropriate base (1-H-imidazole, 1,2-dimethylimidazole and 1-methyl-1-H-imidazole). The reaction of 3-(1H-imidazol-1-yl)propane-1,2-diol with chloroalkanes, bromoalkanes and alkyl mesylates gave the corresponding salts which were characterized. The possibility to use these ILs in palladium catalyzed reactions was evaluated, evidencing good catalyst stability and a high recyclability. [ABSTRACT FROM AUTHOR]

novel ionic liquid functionalized magnetic nanoparticle was prepared by anchoring an imidazolium ionic liquid bearing triethylene glycol moieties on the surface of silica-coated iron oxide nanoparticles. The material proved to be an effective host for the immobilization of a Pd catalyst through a subsequent simple ion-exchange process giving a highly water dispersible, active and yet magnetically recoverable Pd catalyst (Mag-IL-Pd) in the Suzuki-Miyaura coupling reaction in water. The as-prepared catalyst displayed remarkable activity toward challenging substrates such as heteroaryl halides and ortho-substituted aryl halides as well as aryl chlorides using very low Pd loading in excellent yields and demonstrating high TONs. Since the catalyst exhibited extremely low solubility in organic solvent, the recovered aqueous phase containing the catalyst can be simply and efficiently used in ten consecutive runs without significant decrease in activity and at the end of the process can be easily separated from the aqueous phase by applying an external magnetic field. This novel double-separation strategy with negligible leaching makes Mag-IL-Pd an eco-friendly and economical catalyst to perform this transformation. [ABSTRACT FROM AUTHOR]

A hydrophobic palladium complex of the chelating N-heterocyclic dicarbene (NHDC) (3) was synthesized through in situ deprotonation of a bisimidazolium salt (2) by Pd(OAc)2 in DMSO, subsequent basic hydrolysis and acidification resulted in the formation of four NHDC palladium complexes bearing carboxylic functional groups (4–7). Complexes 4–7 are air-stable, pH-responsive and water-soluble under basic conditions due to deprotonation of the carboxylic groups. The catalytic activities of the hydrophilic catalytic systems from 4–7 were preliminarily evaluated using the Suzuki–Miyaura cross-coupling reaction in pure water, high catalytic activity and chemical selectivity were observed in comparison with their hydrophobic analogue from 3. Either the catalytic aqueous solution or the pH-responsive catalysts were easily separated and could be recycled at least four times. TEM analysis revealed that Pd(0) nanoparticles were formed after the catalytic reaction. [ABSTRACT FROM AUTHOR]

A series of hydrophilic N,N-dimethylpyrrolidinium- and N,N-dimethylpiperidinium-based ionic liquids (ILs) have been prepared and applied as reaction media in the Wacker oxidation of styrene by hydrogen peroxide using PdCl2 as the catalyst. The efficiency of these ILs was compared with hydrophilic and hydrophobic imidazolium systems (including those with nitrile functionalities). The nature of the ionic liquid strongly influences the product distribution. In particular, in hydrophobic ILs, relevant amounts of 1,3-diphenyl-1-butene arising from styrene dimerization were detected, in addition to the expected phenylmethylketone. The formation of 1,3-diphenyl-1-butene may be attributed to the formation of Pd(0) species from “ClPdOH” (probably formed during the Wacker process) in a side-reaction. Consequently, the ability of the IL to favor or disfavor the reoxidation of “ClPdOH” to “ClPdOOH” by hydrogen peroxide, giving an homogeneous phase or a biphasic system, appears to be the main factor affecting selectivity. [ABSTRACT FROM AUTHOR]