Efficient synthesis of benzophenone derivatives in Lewis acid ionic liquids

Ru(II)-Catalyzed regioselective carbene insertion into β-carbolines and isoquinolines

A protocol for carbene insertion into the inert C(sp²)-H bond has been established wherein β-carbolines and isoquinolines are explored as intrinsic directing groups. The Ru(II)-catalyzed strategy employing sulfoxonium ylides as the carbene precursor offers an effective and atom-economical functionalization of substrates of biological interest with only DMSO as the sole by-product. The strategy is scalable to gram scale, and it also showcases a wide range of functional group tolerance. ESI-MS studies assisted in the identification of intermediates and consolidation of a probable mechanistic pathway. Furthermore, investigations revealed that the functionalized molecules not only displayed selective inhibition against cancer cell lines, but also demonstrated promising photophysical properties.

Iridium-catalyzed arylation of sulfoxonium ylides and arylboronic acids: a straightforward preparation of α-aryl ketones

A highly efficient iridium(iii)-catalyzed arylation coupling of sulfoxonium ylides with arylboronic acids to generate α-aryl ketones has been established for the first time.

Novel Aryl-Imidazolium Ionic Liquids with Dual Brønsted/Lewis Acidity as Both Solvents and Catalysts for Friedel–Crafts Alkylation

Unique tunable aryl-imidazolium magnetic ionic liquids with dual functions as a solvent–catalyst and dual Brønsted–Lewis acidity (B-L MILs) are applied for Friedel–Crafts alkylation without additional solvents. The catalytic properties of these B-L MILs in the Friedel–Crafts alkylation of p-xylene with benzyl chloride are investigated. The various reaction parameters, including the catalyst dosage, reaction time, reaction temperature, molar ratio of reactants, and reusability, are discussed. The results show that the B-L MIL 5c has more excellent product selectivity (>99%) and reactant conversion (>99%) under the following optimum conditions (reaction temperature = 80 °C, reaction time = 0.5 h, molar ratio of p-xylene to benzyl chloride = 6:1, and catalyst 5c dosage = 1.0 mole %) than traditional catalysts reported in the previous literature. Specifically, due to the mesomeric effect between the FeCl4 anion and hydrogen atom at cationic moiety, the catalyst B-L MILs with the molar fraction of FeCl3 equal to 0.5 can be easily recovered and provide satisfactory catalytic activity after being re-used six times.

An efficient and green method for regio- and chemo-selective Friedel–Crafts acylations using a deep eutectic solvent ([CholineCl][ZnCl2]3)

An efficient and environmentally benign method for regio- and chemo-selective Friedel–Crafts acylation using deep eutectic solvent ([CholineCl][ZnCl₂]₃) under solvent-free microwave irradiation.

Efficient Synthesis of 1-Acetylpyrene Using [Bmim]Cl–FeCl3 Ionic Liquid as Dual Catalyst and Solvent

Friedel–Crafts acylation of pyrene with acetic anhydride to 1-acetylpyrene catalyzed by three metal chloride and three Lewis acidic ionic liquids (ILs) containing 1-butyl-3-methylimidazolium chloride ([Bmim]Cl) and different metal chloride was investigated. ILs were prepared and tested for the acylation to explore the effects of Lewis acidity of ILs on the synthesis of 1-acetylpyrene. [Bmim]Cl–FeCl3 was found to be the most suitable catalyst, and the possible pathway for the acylation of pyrene with acetic anhydride catalyzed by [Bmim]Cl–FeCl3-IL was discussed. Pure 1-acetylpyrene was obtained and its structure was identified by gas chromatography–mass spectrometer, Fourier transform infrared and 1H NMR spectra.

Determination of hydrogen-bond-accepting and -donating abilities of ionic liquids with halogeno complex anions by means of 1H NMR spectroscopy

Hydrogen-bond-accepting (HBA) and -donating (HBD) parameters of ionic liquids (ILs) with halogeno complex anions are determined by means of (1)H NMR spectroscopy. Thereby, the imidazolium cation serves both as part of the IL and as (1)H NMR probe. The HBA and HBD strength are calculated in terms of the empirical polarity parameters β and α according to the Kamlet-Taft equation. The study includes 1-butyl-3-methylimidazolium ILs with chloroaluminates of various mole fractions from 0 to 0.67 of AlCl(3), anions of the general chemical formula MtX(n)(-) (Mt=metal, X=halide) as well as tri- and pentaiodide. The (1)H NMR chemical shift of the hydrogen atom in the two position of the imidazolium cation is a function of the HBA ability of the corresponding anion. For the chloroaluminates the HBA ability decreases and the HBD ability increases with increasing mole fraction of the Lewis acid. In general, the HBA strength of the studied ILs increases in the following order: MoCl(6)(-) < Al(2)Cl(7)(-) < AlCl(4)(-) < WCl(7)(-) < I(5)(-) < SnCl(5)(-) < I(3)(-) < SbCl(6)(-) < TiCl(5)(-) < BBr(4)(-) < SnCl(3)(-). The corresponding HBD ability shows a reverse trend.

Friedel-Crafts acylation of arenes with carboxylic acids using polystyrene-supported aluminum triflate

Cross-linked polystyrene-supported aluminum triflate (Ps- Al(OTf)3) has been shown to be a mild, efficient, and chemoselective heterogeneous Lewis acid catalyst for the acylation of aromatic compounds. The catalyst can be easily prepared from cheap starting materials, is stable (as a bench top catalyst) and is reusable.

Efficient Lewis acid ionic liquid-catalyzed synthesis of the key intermediate of coenzyme Q10 under microwave irradiation

An efficient synthesis of a valuable intermediate of coenzyme Q₁₀ by microwave-assisted Lewis acidic ionic liquid (IL)-catalyzed Friedel-Crafts alkylation is reported. The acidity of six [Etpy]BF₄-based ionic liquids was characterized by means of the FT-IR technique using acetonitrile as a molecular probe. The catalytic activities of these ionic liquids were correlated with their Lewis acidity. With increasing Lewis acid strength of the ionic liquids, their catalytic activity in the Friedel-Crafts reaction increased, except for [Etpy]BF₄-AlCl₃. The effects of the reaction system, the molar fraction of Lewis acid in the Lewis acid ILs and heating techniques were also investigated. Among the six Lewis acid ionic liquids tested [Etpy]BF₄-ZnCl₂ showed the best catalytic activity, with a yield of 89% after a very short reaction time (150 seconds). This procedure has the advantages of higher efficiency, better reusability of ILs, energy conservation and eco-friendliness. The method has practical value for preparation of CoQ₁₀ on an industrial scale.