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.

The Beneficial Sinergy of MW Irradiation and Ionic Liquids in Catalysis of Organic Reactions

The quest for sustainable processes is becoming more and more important, with catalysis playing a major role in improving atom economy and reducing waste. Organic syntheses with less need of protecting/de-protecting steps are highly desirable. The combination of microwave irradiation, as energy source, with ionic liquids, as both solvents and catalysts, offered interesting solutions in recent years. The literature data of the last 15 years concerning selected reactions are presented, highlighting the importance of microwave (MW) technology coupled with ionic liquids.

Microwave-promoted solventless Mizoroki–Heck reactions catalysed by Pd nanoparticles supported on laponite clay

Palladium nanoparticles supported on laponite efficiently catalyse solventless Mizoroki–Heck reactions activated by microwaves. High yields are obtained in a few minutes and the catalyst can be efficiently recovered and reused up to thirteen times.

Bis(N-substituted oxamate)palladate(ii) complexes as effective catalysts for sustainable Heck carbon–carbon coupling reactions in n-Bu4NBr as the solvent

Bis(oxamato)palladate(ii) complexes are structurally well-defined precatalysts for the Heck vinylation of aryl halide derivatives inn-Bu₄NBr as benign ionic liquid.

Development of a mild and efficient protocol for the protection and O-alkylation of allyl alcohols

An efficient, pyridine-free protocol has been developed for the protection of 3°-allyl alcohol of oxindole using a mild base of potassium carbonate under microwave irradiation conditions. The methodology has been tested with a variety of substrates and protecting group reagents, which provides a clean and good yield of desired products within a short reaction time.