Remarkable Effect of PEG-1000-based Dicationic Ionic Liquid for N-hydroxyphthalimide-catalyzed Aerobic Selective Oxidation of Alkylaromatics

Abstract

Abstract. PEG 1000-based functional dicationic acidic ionic liquid (PEG 1000 -DAIL) was used for the first time as the reaction solvent for the N-Hydroxyphthalimide (NHPI)-cobalt acetate(Co(OAc) 2 ) catalyzed aerobic oxidations of alkylaromatics to the corresponding acids. It enhanced the efficient catalytic ability of NHPI: 99.9 % conversion of toluene with 99.5 % selectivity for benzoic acid could be obtained at 80 °C in 10 h and ethylbenzene was selectively oxidized to benzoic acid. Several alkylaromatics were efficiently oxidized to their corresponding acids under mild conditions. For substituted toluene, the conversions of substrates and the selectivity of products was affected by the position and kind of substituted groups, respectively. Both the catalyst and PEG 1000 -DAIL could be reused at least eight times without significantly decreasing the catalytic activity.(doi: 10.5562/cca2051)

Efficient metal-free oxidation of ethylbenzene with molecular oxygen utilizing the synergistic combination of NHPI analogues

“…Our results showed that the pyridinium salt group played a crucial role for the observed high performance in this catalytic system. Recently, oximes, structurally similar to NHPI, has been found to facilitate the oxidation of hydrocarbons catalyzed by NHPI and its derivatives [35][36][37]. Mechanistic study revealed that the corresponding N-oxyl radicals of oximes were produced easily due to its lower >NO H bond dissociation enthalpy (BDE) than that of NHPI.…”

N-Hydroxyphthalimide Supported on Silica Coated with Ionic Liquids Containing CoCl2 (SCILLs) as New Catalytic System for Solvent-Free Ethylbenzene Oxidation

“…Because of its poor solubility in hydrocarbons, the processes are usually carried out in polar solvents, e.g., in acetic acid [7], acetonitrile [8], or benzonitrile [9]. The use of compressed CO 2 [10][11][12] and ionic liquids [11,[13][14][15][16][17][18] has also been reported. In order to use NHPI in industrial processes, it is necessary to develop efficient methods of its recovery and reuse.…”

Solvent‐Free Aerobic Oxidation of Ethylbenzene Promoted by NHPI/Co(II) Catalytic System: The Key Role of Ionic Liquids

“…[18] Several examples have been reported on the use of ILs as solvents for NHPImediated oxidations of a wide range of substrates, [19,20] including the conversion of alkyl aromatic hydrocarbons, such as pxylene, toluene, EB, cumene and their derivatives, to the corresponding carboxylic acids. [21][22][23] Among the wide range of ILs commercially available, it was demonstrated that the imidazolium-based ones are particularly suitable for promoting aerobic oxidations, as they can accelerate the electron transfer from metal ions to O 2 by stabilization of the resulting superoxyl radical. [24][25][26][27] Recently, some of us reported the oxidation of cumene and other alkylaromatic hydrocarbons to hydroperoxides in the presence of various N-hydroxyimides, including NHPI, in a broad range of ILs composed of 1-alkyl-3-methylimidazolium cations and bis(trifluoromethylsulfonyl)imide ( OSO 3 ] anions.…”