https://www.chem.ccu.edu.tw/~joyce/referance/gump/IL/Chem.%20Rev.%201999,%2099,%202071.pdf

Room-Temperature Ionic Liquids. Solvents for Synthesis and Catalysis

Ionic liquids are salts that are liquid at low temperature (<100 degrees C) which represent a new class of solvents with nonmolecular, ionic character. Even though the first representative has been known since 1914, ionic liquids have only been investigated as solvents for transition metal catalysis in the past ten years. Publications to date show that replacing an organic solvent by an ionic liquid can lead to remarkable improvements in well-known processes. Ionic liquids form biphasic systems with many organic product mixtures. This gives rise to the possibility of a multiphase reaction procedure with easy isolation and recovery of homogeneous catalysts. In addition, ionic liquids have practically no vapor pressure which facilitates product separation by distillation. There are also indications that switching from a normal organic solvent to an ionic liquid can lead to novel and unusual chemical reactivity. This opens up a wide field for future investigations into this new class of solvents in catalytic applications.

Ionic Liquids-New "Solutions" for Transition Metal Catalysis.

s, or keywords if they used Heck-type chemistry in their syntheses, because it became one of basic tools of organic preparations, a natural way to

http://aether.cmi.ua.ac.be/artikels/Artikels%20Gitte/Artikels/Reviews/Heck%20reactie%20Beletskaya%20%20Chem.%20Rev.%20003009.pdf

The heck reaction as a sharpening stone of palladium catalysis.

Interest in catalysis by metal nanoparticles (NPs) is increasing dramatically, as reflected by the large number of publications in the last five years. This field, "semi-heterogeneous catalysis", is at the frontier between homogeneous and heterogeneous catalysis, and progress has been made in the efficiency and selectivity of reactions and recovery and recyclability of the catalytic materials. Usually NP catalysts are prepared from a metal salt, a reducing agent, and a stabilizer and are supported on an oxide, charcoal, or a zeolite. Besides the polymers and oxides that used to be employed as standard, innovative stabilizers, media, and supports have appeared, such as dendrimers, specific ligands, ionic liquids, surfactants, membranes, carbon nanotubes, and a variety of oxides. Ligand-free procedures have provided remarkable results with extremely low metal loading. The Review presents the recent developments and the use of NP catalysis in organic synthesis, for example, in hydrogenation and C--C coupling reactions, and the heterogeneous oxidation of CO on gold NPs.

Nanoparticles as Recyclable Catalysts: The Frontier between Homogeneous and Heterogeneous Catalysis

Catalytic reactions in ionic liquids

A fast, pH-responsive DNA hydrogel (see picture; right) was prepared by a three-armed DNA nanostructure (left) assembling together through the formation of intermolecular i-motif structures (middle). The hydrogel can be switched to the non-gel state in minutes by simply using environmental pH changes.

A pH-triggered, fast-responding DNA hydrogel.

Heck Reaction in Ionic Liquids and the in Situ Identification of N-Heterocyclic Carbene Complexes of Palladium

Room-temperature ionic liquids (RTILs) have recently received a great deal of attention as alternative reaction media. Numerous catalytic reactions have proven feasible in a variety of ionic liquids, with many reactions displaying enhanced reactivities and selectivities, and some of which were not possible in common organic solvents. Furthermore, RTILs have served as a promising means to immobilize a catalyst, therefore facilitating product isolation and offering an opportunity to reuse the catalyst. However, the use of RTILs in asymmetric catalytic reactions is still limited. The recycling and reuse of chiral catalysts in ionic liquids have often been problematic because of the instability and/or leaching of the catalysts. From a practical standpoint, development of highly effective and recyclable catalysts in ionic liquids for use in asymmetric hydrogenation remains a challenge: in particular for heteroaromatic substrates which are difficult to hydrogenate. Although a variety of chiral Rh, Ru, and Ir complexes have been efficient and enantioselective reagents for the hydrogenation of prochiral olefins, ketones, and imines, most of these catalysts failed to give satisfactory results in the asymmetric hydrogenation of heteroaromatic compounds. A few successful examples for the asymmetric hydrogenation of quinolines have recently been reported. However, all catalysts for such reactions have at least one phosphine ligand around the metal center and are often air sensitive. From the viewpoints of both scientific interest and practical application, it is highly desirable to develop recyclable and phosphine-free chiral catalysts for the highly enantioselective hydrogenation of quinolines. Few examples of phosphine-free homogeneous catalysts capable of activating molecular hydrogen have been reported. Recently, Noyori and co-workers reported that chiral h-arene/Ntosylethylenediamine–Ru complexes (which are known as excellent catalysts for asymmetric transfer hydrogenation, for example Ru/Ts-dpen) can be used for the asymmetric hydrogenation of prochiral ketones under slightly acidic conditions. Inspired by this important breakthrough and following our continued pursuit of developing effective and environmentally benign catalyst systems for asymmetric hydrogenations, herein we report a practical and efficient catalyst system of Ru/Ts-dpen in [BMIM]PF6 (BMIM = 1-nbutyl-3-methylimidazolium) for the enantioselective hydrogenation of quinolines (Scheme 1).

Hydrogenation of Quinolines Using a Recyclable Phosphine‐Free Chiral Cationic Ruthenium Catalyst: Enhancement of Catalyst Stability and Selectivity in an Ionic Liquid

Palladium-catalyzed regioselective Heck arylation of the electron-rich olefins, vinyl ethers 1a-d, enamides 1e-g, and allyltrimethylsilane 1h, has been accomplished in imidazolium ionic liquids with a wide range of aryl bromides and iodides instead of the commonly used, but commercially unavailable and expensive, aryl triflates. The reaction proceeded with high efficiency and remarkable regioselectivity without the need for costly or toxic halide scavengers, leading exclusively to substitution by aryl groups of diverse electronic and steric properties at the olefinic carbon alpha to the heteroatom of 1a-g and beta to the heteroatom of 1h. In contrast, the arylation reaction in molecular solvents led to mixtures of regioisomers under similar conditions. Several lines of evidence point to the unique regiocontrol stemming from the ionic environment provided by the ionic liquid that alters the reaction pathway. The chemistry provides a simple, effective method for preparing branched, arylated olefins and contributes to the extension of Heck reaction to a wider range of substrates.

Ionic Liquid-Promoted, Highly Regioselective Heck Arylation of Electron-Rich Olefins by Aryl Halides

Air-stable Ir-(P-Phos) complex for highly enantioselective hydrogenation of quinolines and their immobilization in poly(ethylene glycol) dimethyl ether (DMPEG)

Lijin Xu

Papers

A pH-triggered, fast-responding DNA hydrogel.

Heck Reaction in Ionic Liquids and the in Situ Identification of N-Heterocyclic Carbene Complexes of Palladium

Hydrogenation of Quinolines Using a Recyclable Phosphine‐Free Chiral Cationic Ruthenium Catalyst: Enhancement of Catalyst Stability and Selectivity in an Ionic Liquid

Ionic Liquid-Promoted, Highly Regioselective Heck Arylation of Electron-Rich Olefins by Aryl Halides

Air-stable Ir-(P-Phos) complex for highly enantioselective hydrogenation of quinolines and their immobilization in poly(ethylene glycol) dimethyl ether (DMPEG)