OsO(4) in ionic liquid [Bmim]PF(6): a recyclable and reusable catalyst system for olefin dihydroxylation. remarkable effect of DMAP

Ionic Liquids in Metal, Photo-, Electro-, and (Bio) Catalysis

Ionic liquids (ILs) have unique physicochemical properties that make them advantageous for catalysis, such as low vapor pressure, non-flammability, high thermal and chemical stabilities, and the ability to enhance the activity and stability of (bio)catalysts. ILs can improve the efficiency, selectivity, and sustainability of bio(transformations) by acting as activators of enzymes, selectively dissolving substrates and products, and reducing toxicity. They can also be recycled and reused multiple times without losing their effectiveness. ILs based on imidazolium cation are preferred for structural organization aspects, with a semiorganized layer surrounding the catalyst. ILs act as a container, providing a confined space that allows modulation of electronic and geometric effects, miscibility of reactants and products, and residence time of species. ILs can stabilize ionic and radical species and control the catalytic activity of dynamic processes. Supported IL phase (SILP) derivatives and polymeric ILs (PILs) are good options for molecular engineering of greener catalytic processes. The major factors governing metal, photo-, electro-, and biocatalysts in ILs are discussed in detail based on the vast literature available over the past two and a half decades. Catalytic reactions, ranging from hydrogenation and cross-coupling to oxidations, promoted by homogeneous and heterogeneous catalysts in both single and multiphase conditions, are extensively reviewed and discussed considering the knowledge accumulated until now.

Boosting Thermal Stability of Volatile Os Catalysts by Downsizing to Atomically Dispersed Species

Os-based catalysts present remarkable catalytic activity; however, their use has been limited by the undesirable side reactions that generate highly toxic and volatile OsO₄ even at room temperature. Herein, we demonstrate that the thermal stability of Os-based catalysts can be dramatically improved by downsizing Os nanoparticles (NPs) into atomically dispersed species. We observed that Os NPs were converted into OsO₄ after calcination at 250 °C followed by sublimation, whereas single Os sites retained their structure after calcination. Temperature-programmed oxidation analysis confirmed that Os NPs started to undergo oxidation at 130 °C, whereas atomically dispersed Os preserved its state up to 300 °C. The CO oxidation activity of the atomically dispersed Os catalyst at 400 °C (100% conversion) was stably preserved over 30 h. By contrast, the activity of Os NP catalyst declined drastically. This study highlights the unique catalytic behavior of atomically dispersed catalysts, which is distinct from that of NP-based catalysts.

The oxidation of 4-alkyl and 4-aryl-1,4-dihydropyridines to pyridines with hydrogen peroxide in an ionic liquid

An efficient oxidation of 4-alkyl and 4-aryl-1,4-dihydropyridines to the corresponding pyridines with hydrogen peroxide in ionic liquids at room temperature in excellent yields is described.

A facile ionic liquid promoted synthesis, cholinesterase inhibitory activity and molecular modeling study of novel highly functionalized spiropyrrolidines

A series of novel dimethoxyindanone embedded spiropyrrolidines were synthesized in ionic liquid, [bmim]Br and were evaluated for their inhibitory activities towards cholinesterases. Among the spiropyrrolidines, compound 4f exhibited the most potent activity with an IC50 value of 1.57 µM against acethylcholinesterase (AChE). Molecular docking simulation for the most active compound was employed with the aim of disclosing its binding mechanism to the active site of AChE receptor.

A novel one-pot green synthesis of dispirooxindolo-pyrrolidines via 1,3-dipolar cycloaddition reactions of azomethine ylides

A facile synthesis of dispirooxindolopyrrolidines has been accomplished via a one-pot three component 1,3-dipolar cycloaddition reaction. The reaction of azomethine ylides generated in situ from L-phenylalanine and substituted isatins with a series of unusual (E)-2-oxoindolino-3-ylidene acetophenone dipolarophiles in the ionic liquid 1-butyl-3-methylimidazolium bromide [bmim]BF4, furnished the cycloadducts in good yields, with the regioisomers 5a-f being obtained with high selectivity. Furthermore, the recyclability of [bmim]BF4, up to five times, was also investigated.

Solvent-free, [Et3NH][HSO4] catalyzed facile synthesis of hydrazone derivatives

Eco-friendly and efficient synthesis of hydrazone derivatives.

[Et3NH][HSO4]-catalyzed eco-friendly and expeditious synthesis of thiazolidine and oxazolidine derivatives

Facile, sustainable and efficient synthesis of thiazolidine/oxazolidine derivatives.

[Et3NH][HSO4]-mediated functionalization of hippuric acid: an unprecedented approach to 4-arylidene-2-phenyl-5(4H)-oxazolones

Facile, sustainable and economical synthesis of Erlenmeyer azlactones.

Efficient catalyst reuse by simple dissolution in non-conventional media

This feature article is a description of the achievements made on the development of attractive sustainable approaches to synthetic organic chemistry, namely, catalyst reuse by simple dissolution in water and ionic liquids and asymmetric transformations induced by readily available chiral ionic liquids.

Dynamic Solvation in Imidazolium-Based Ionic Liquids on Short Time Scales

Steady-state and time-resolved Stokes shift data for the probe coumarin 153 in two imidazoles, six imidazolium-based ionic liquids, and several other solvents are presented. These results are consistent with our original suggestion (J. Phys. Chem. B 2004, 108, 10245-10255) that initial solvation is dominated by the organic moiety of the ionic liquid, and they show that for the imidazole-based liquids initial solvation is in all cases very rapid. Solvation by methylimidazole and butylimidazole is complete in 100 ps, and all of the imidazolium ionic liquids demonstrate similarly rapid initial solvation. Owing to the importance of determining the amount of initial solvation that is missed in a given experiment with finite time resolution, we discuss a method of estimating the intramolecular contribution to the reorganization energy. This method yields 2068 cm(-1) and is compared with an alternative method.

Poly(ethylene Glycol) (400) as Superior Solvent Medium against Ionic Liquids for Catalytic Hydrogenations with PtO2

Adams' catalyst in poly(ethylene glycol) (PEG) (400) has been found to be a superior solvent over the ionic liquids by severalfold in promoting the hydrogenation of various functional groups. Both the catalyst and PEG were recycled efficiently over 10 runs without loss of activity, and substrate cross contamination was not observed despite a change in the substrate four times.

Copper(II)-Catalyzed Aerobic Oxidation of Primary Alcohols to Aldehydes in Ionic Liquid [bmpy]PF6

A room-temperature aerobic oxidation of primary alcohols to aldehydes catalyzed by the three-component system acetamido-TEMPO/Cu(ClO(4))(2)/DMAP in the ionic liquid [bmpy]PF(6) has been developed, and the catalysts can be recycled and reused for five runs without any significant loss of catalytic activity. [reaction: see text]

Ionic Liquid as Catalyst and Reaction Medium. The Dramatic Influence of a Task-Specific Ionic Liquid, [bmIm]OH, in Michael Addition of Active Methylene Compounds to Conjugated Ketones, Carboxylic Esters, and Nitriles

[reaction: see text] A task-specific ionic liquid, [bmIm]OH, has been introduced as a catalyst and as a reaction medium in Michael addition. Very interestingly, although the addition to alpha,beta-unsaturated ketones proceeds in the usual way, giving the monoaddition products, this ionic liquid always drives the reaction of open-chain 1,3-dicarbonyl compounds with alpha,beta-unsaturated esters and nitriles toward bis-addition to produce exclusively bis-adducts in one stroke.