Ionic Liquids as Reaction Media for Palladium-Catalysed Cross-Coupling of Aryldiazonium Tetrafluoroborates with Potassium Organotrifluoroborates

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.

Ultra-fast Suzuki and Heck reactions for the synthesis of styrenes and stilbenes using arenediazonium salts as super-electrophiles

The reliable and convenient procedure for the ultrafast conversion of potassium vinyltrifluoroborate to stilbenes and styrenes with impressive TOFs is proposed.

Suzuki-Miyaura cross-coupling reaction of 1-aryltriazenes with arylboronic acids catalyzed by a recyclable polymer-supported N-heterocyclic carbene-palladium complex catalyst

The Suzuki–Miyaura cross-coupling reaction of 1-aryltriazenes with arylboronic acids catalyzed by a recyclable polymer-supported Pd–NHC complex catalyst has been realized for the first time. The polymer-supported catalyst can be re-used several times still retaining high activity for this transformation. Various aryltriazenes were investigated as electrophilic substrates at room temperature to give biaryls in good to excellent yields and showed good chemoselectivity over aryl halides in the reactions.

Ionic Solid-State Dimers and Polymers Derived from Imidazolium Dicarboxylic Acids

A series of imidazolium dicarboxylic acids have been prepared from the reaction of the 1,3-bis(carboxymethyl)imidazolium zwitterion with the Brønsted acids HX (X = F, Br, Cl, ClO4). The structures of these acids have been established in the solid state by single-crystal X-ray diffraction, which revealed that the cations and anions form strong hydrogen bonds through O-H...X interactions, leading to the formation of dimeric and polymeric networks. These acids react with elemental zinc and cobalt to form stable polymeric coordination complexes, some of which have also been characterised by X-ray diffraction.

Pyrazolyl-functionalized 2-methylimidazolium-based ionic liquids and their palladium(ii) complexes as recyclable catalysts

A series of pyrazolyl- and 3,5-dimethylpyrazolyl-functionalized 2-methylimidazolium-based salts have been prepared through neat reactions of 1-pyrazolylmethylene-2-methylimidazole and 1-(3,5-dimethylpyrazolylmethylene)-2-methylimidazole with alkyl or polyfluoroalkyl iodides or 1-bromohexane, followed by anion exchange with LiN(SO2CF3)2 or KPF6. Their thermal properties were determined by DSC and TGA. Most of the bis(trifluoromethanesulfonyl)amide salts are room temperature ionic liquids. The influence of anions and of the structural variation in the 2-methylimidazolium-based cations on the physicochemical properties is discussed. These salts reacted easily with palladium(II) chloride to generate mononuclear palladium ionic liquid complexes. The catalytic activity and recyclability of the palladium complexes in the corresponding ionic liquids were preliminarily examined using Heck, Suzuki and Sonogashira cross-coupling reactions in the absence of phosphine ligands.