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.

Magnetic silica/graphene oxide nanocomposite supported ionic liquid-manganese complex as a powerful catalyst for the synthesis of tetrahydrobenzopyrans

A novel magnetic silica/graphene oxide nanocomposite supported ionic liquid/manganese complex (Fe3O4@SiO2-NH2/GO/IL-Mn) is prepared, characterized and its catalytic application is investigated. The Fe3O4@SiO2-NH2/GO/IL-Mn catalyst was synthesized via chemical immobilization of graphene oxide on Fe3O4@SiO2 nanoparticles followed by modification with ionic liquid/Mn complex. This nanocomposite was characterized by using SEM, TGA, FT-IR, PXRD, EDX, TEM, nitrogen adsorption-desorption, and VSM analyses. The catalytic application of Fe3O4@SiO2-NH2/GO/IL-Mn was studied in the synthesis of tetrahydrobenzo[b]pyrans (THBPs) in water solvent at RT. This nanocatalyst was successfully recovered and reused at least eight times without a significant decrease in its activity.

Catalytic asymmetric Friedel-Crafts alkylation of unprotected indoles with nitroalkenes using a novel chiral Yb(OTf)3-pybox complex

Chiral chloro-indeno pybox has served as a new ligand for the Yb(OTf)3-catalyzed asymmetric Friedel-Crafts alkylation reaction of indoles with nitroalkenes. The tunable nature of pybox ligands enables the rational design of catalysts for optimal performance in terms of both activity and stereoselectivity in a Friedel-Crafts-type reaction. Good to excellent yields and enantioselectivities were obtained for a relatively wide range of substrates, including sterically hindered compounds, under optimized reaction conditions.

The assembly of “S3N”-ligands decorated with an azo-dye as potential sensors for heavy metal ions

The synthesis and complexation of azo dye-S₃N crown conjugates with Ag(i), Cu(ii) and Hg(ii) is described.

Thiopropyl-containing ionic liquid based periodic mesoporous organosilica as a novel and efficient adsorbent for the removal of Hg(ii) and Pb(ii) ions from aqueous solutions

In the present study, a novel thiol-functionalized ionic liquid based periodic mesoporous organosilica (PMO-IL-SH) is prepared, characterized and its efficiency for the removal of mercury and lead ions from aqueous solutions is investigated.

Synergistic catalysis within TEMPO-functionalized periodic mesoporous organosilica with bridge imidazolium groups in the aerobic oxidation of alcohols

Anchoring TEMPO within the nanospaces of a PMO with bridged imidazolium groups led to an powerful bifunctional catalyst (TEMPO@PMO-IL-Br), which showed enhanced activity in the metal-free aerobic oxidation of alcohols.

Nanostructured oxytyramine catalyst for the facile one-pot synthesis of cyclohexanecarbonitrile derivatives

A magnetic, recyclable heterogeneous organocatalyst, OT@Si@SPIONs, has been developed for the facile synthesis of cyclohexanecarbonitriles.

Catalytic Synthesis of α-Aminonitriles Using Nano Copper Ferrite CuFe2O4 under Green Conditions

Copper ferrite nanomaterial CuFe2O4 as reusable heterogeneous initiator in the synthesis of α-aminonitriles. The nanocatalyst is easily recovered and its reusability is recorded. Synthesis of α-aminonitriles derivatives by one-pot reaction of different aldehydes with amines and trimethylsilyl cyanides has been developed using nano copper ferrite CuFe2O4 catalyst under room temperature and green solvent (water as solvent) conditions. α-aminonitriles are important in preparing a wide variety of amino acids, amides, diamines, and nitrogen containing heterocycles.

Imidazolium-based ionic liquids grafted on solid surfaces

Supported ionic liquids (SILs), which refer to ionic liquids (ILs) immobilized on supports, are among the most important derivatives of ILs.

Enantioselective hydrocyanation of N-protected aldimines

Enantioselective hydrocyanation of N-benzyloxycarbonyl aldimines catalyzed by a Ru[(S)-phgly](2)[(S)-binap]/C(6)H(5)OLi system or a bimetallic complex [Li{Ru[(S)-phgly](2)[(S)-binap]}]Cl affords the amino nitriles in 92-99% ee. The reaction is carried out in tert-C(4)H(9)OCH(3) with a substrate-to-catalyst molar ratio in the range of 500-5000 at -20 to 0 °C. Primary, secondary, and tertiary alkyl imines as well as the aryl and heteroaryl substrates are smoothly cyanated to produce the desired products in high yield.

A truly green synthesis of α-aminonitriles via Strecker reaction

Background

The classical Strecker reaction is one of the simplest and most economical methods for the synthesis of racemic α-aminonitriles (precursor of α-amino acids) and pharmacologically useful compounds.

Results

Indium powder in water is shown to act as a very efficient catalyst for one-pot, three-component synthesis of α-aminonitriles from diverse amines, aldehydes and TMSCN. This general rapid method is applicable to a wide range of amines and aldehydes and produces products in excellent yield.

Conclusions

The present one-pot, three-component environmentally benign procedure for the synthesis of α-aminonitriles will find application in the synthesis of complex biologically active molecules.