Ionic Liquids as Organocatalysts for Nucleophilic Fluorination: Concepts and Perspectives

Abstract

Besides their extremely useful properties as solvent, ionic liquids (ILs) are now considered to be highly instructive tools for enhancing the rates of chemical reactions. The ionic nature of the IL anion and cation seems to be the origin of this fascinating function of ILs as organocatalyst/promoter through their strong Coulombic forces on other ionic species in the reaction and also through the formation of hydrogen bonds with various functional groups in substrates. It is now possible to tailor-make ILs for specific purposes as solvent/promoters in a variety of situations by carefully monitoring these interactions. Despite the enormous potentiality, it seems that the application of ILs as organocatalysts/promoters for chemical reactions have not been fully achieved so far. Herein, we review recent developments of ILs for promoting the nucleophilic reactions, focusing on fluorination. Various aspects of the processes, such as organocatalytic capability, reaction mechanisms and salt effects, are discussed.

Advances in organocatalyzed synthesis of organic compounds

“…Synthesis of benzil bis-hydrazones. Novel bioactive benzil bis-hydrazone derivatives (17)(18)(19) were synthesized by solvent-free mechanical grinding of benzil bis(cyanoacetylhydrazone) (25a) with aldehydes (26a-c) employing L-proline as an effective organocatalyst (Scheme 14). The precursor 25a was synthesized by heating benzil (23a) and 2-cyanoacetohydrazide (24a) in EtOH with HCl.…”

“…[4][5][6][7] This article aims to quickly display certain classic and contemporary publications explaining, how these catalysts play crucial role in synthesis of organic components. In literature, recent work reported on organocatalysis includes organocatalysis of pyrrole and amino acids, 8,9 dehydroabietane-type bifunctional organocatalysis, 10 degradation of polluting dyes, [11][12][13] asymmetric photocatalysis, 14 proline derivatives catalyzed reactions in aqueous media, [15][16][17] ionic liquid as organocatalysts, 18,19 guanidinium catalyzed hypoiodite mediated reactions, 20 asymmetric organocatalysis in drug discovery, 21 enantioselective organocatalysis in disguise, 22 asymmetric micheal addition of unactivated ketones and uorination reaction. 23,24 In this study, we gave a general overview of the methods and reaction mechanism (Table 1) for obtaining organocatalyzed synthetic organic compounds which have vast industrial applications such as sensors, 25,26 fertilizers, pesticides, 27,28 synthetic polymers, cosmetics, and platform chemicals are all utilized to improve people's standards of life.…”

Efficient dimerization of perfluoroolefin catalyzed by strong nucleophilic bifunctional ionic liquids

“…One of the wellknown features of ionic liquids is their unique adjustable properties via the precise design of cations and anions, which make them appealing as catalysts or green solvents across various applications, especially in the field of fluorine chemistry. 9,10 In numerous literature reports on olefin oligomerization, there has been successive development of both homogeneous and heterogeneous catalyst systems aimed at enhancing the efficiency of this process. These catalysts include liquid acid, solid phosphoric acid, zeolite, ion exchange resin, nickel catalyst, and ionic liquids.…”

Poly Caprolactam Supported Hexaethylene Glycolic Imidazolium Ionic Liquid as a Heterogeneous Promoter for Nucleophilic Fluorination

“…For functional group transformation in organic synthesis, ionic liquids (ILs) have attracted increasing attention recently, and have succeeded to some extent [ 11 , 12 , 13 ]. In particular, imidazolium-based ILs are a well-known IL series, with potential phase transfer catalytic activity that improves the solubility of alkali metal salts, resulting in easy nucleophilic substitution reactions of fluorination [ 14 , 15 , 16 ]. On the other hand, for the preparation of fluorinated molecules available, a range of direct C–F bond formation methods have integrated technologies for the molecular incorporation of other heteroatoms [ 2 , 3 , 4 ].…”