Functionalized ionic liquid

Microwave-Enhanced Synthesis Using Functional Ionic Liquid Supports. 115... 

Abstract Current microwave-assisted protocols for reaction on solid-phase and soluble supports are critically reviewed. The compatibility of commercially available polymer supports with the relatively harsh conditions of microwave heating and the possibilities for reaction monitoring are discussed. Instrmnentation available for microwave-assisted solid-phase chemistry is presented. This review also summarizes the recent applications of controlled microwave heating to sohd-phase and SPOT-chemistry, as well as to synthesis on soluble polymers, fluorous phases and functional ionic liquid supports. The presented examples indicate that the combination of microwave dielectric heating with solid- or soluble-polymer supported chemistry techniques provides significant enhancements both at the level of reaction rate and ease of purification compared to conventional procedures. 

In addition to the examples described above, functionalized ionic liquids have been recently introduced as microwave-compatible soluble supports [137,138]. 

Preparation of a 4-thiazolidinone Library Employing a Functional Ionic Liquid Support... 

Sulfonamido-l,3,4-oxadiazoles 141 Sulfonyloximes 147 Supports, functional, ionic liquid 115 Suzuki couplings 21,122 Suzuki-Miyaura reaction 164... 

Zhang, FI. and FI. Cui, Synthesis and characterization of functionalized ionic liquid-stabilized metal (gold and platinum) nanoparticles and metal nanoparticle/carbon nanotube hybrids. Langmuir, 2009. 25(5) p. 2604-2612. 

Peng YQ, Song GH (2007) Amino-functionalized ionic liquid as catalytically active solvent for microwave-assisted synthesis of 4H-pyrans. Catal Commun 8 111-114... 

To explain the difficulties encountered in the reuse of sulfonyl chloride functionalized ionic liquids during Beckmann rearrangement, Deng and colleagues proposed a mechanism for rearrangement of cyclohexanone oxime (equation 97). 

Saha, S., and Hamaguchi, H., Effect of water on the molecular structure and arrangement of nitrile-functionalized ionic liquids, /. Phys. Ghem. B, 110, 2777-2781, 2006. 

Gurkan BE, de la Fuente JC, Mindrup EM et al (2010) Equimolar C02 absorption by anion-functionalized ionic liquids. J Am Chem Soc 132(7) 2116-2117... 

Galan Sanchez LM, Meindersma GW, de Haan AB (2007) Solvent properties of functionalized ionic liquids for C02 absorption. Chem Eng Res Des 85(1) 31—39... 

Scheme 5.5 Structures of PEG-functionalized ionic liquids for the synthesis of cyclic carbonates. Reproduced from Ref. [15] by permission of The Royal Society of Chemistry...

Zhou, L. and Wang, L. (2006) Functionalized Ionic Liquid as an Efficient and Recyclable Reaction Medium for Phosphine-Free Palladium-Catalyzed Heck Reaction. Synthesis, 2653-2658, DOI 10.1055/S-2006-942466. 

Song, G., Cai, Y., and Peng, Y. (2005) Amino-functionalized ionic liquid as a nucleophilic scavenger in solution phase combinatorial synthesis./. Comb. Chem., 7, 561-566. 

Cai, Y., Peng, Y, and Song, G. 2006. Amino-functionalized ionic liquid as an efficient and recyclable catalyst for Knoevenagel reactions in water. Catalysis letters, 109 61-64. 

Yu G, Zhou F, Liu W, et al. Preparation of functional ionic liquids and tribological investigation of their ultra-thin films. Wear. 2006. 260, 1076-1080. 

Hu S Q, Jiang T, Zhang Z F, et al. Functional ionic liquid from biorenewable materials Synthesis and application as a catalyst in direct aldol reactions. Tetrahedron Lett. 2007. 48, 5613-5617. 

Recent advances in ionic liquids research has provided routes for achieving functionalized ionic liquids (Fig. 4) in which a functional group is covalently tethered to the cation or anion of the ionic liquid, especially to the two N atoms of the... 

In 1998, Dupont et al. [68] reported the synthesis of [C4mim]2[PdCl4] (Fig. 11). Solid IL-coordinated Pd2+ complex 13 was synthesized by the reaction of a nitrile functionalized ionic liquid with PdCl2 at room temperature. [69] Shreeve and co-workers [70] synthesized the IL-coordinated compound 14 (Fig. 11). 

During the last 8 years [82, 83], various types of functionalized ionic liquids (Fig. 13) expressly categorized as being task-specific ionic liquids have been designed and synthesized for specific purposes such as catalysis, organic synthesis, separation of specific materials, as well as for the construction of nanostructure materials and ion conductive materials, etc. The salts are defined as functionalized ionic liquids when they are ionic liquids in which a functional group is covalently tethered to (1) the cation, (2) the anion, or (3) a zwitterionic form of the salt. It is typically the cation that bears the reactive moiety. In fact, instances in which the anion comprises the active constituent are few. 

Recently, novel sulphonyl-functionalized ionic liquids with S03H and S02C1 groups have been designed, synthesized and characterized. First reported were Bronsted-acidic functionalized ionic liquids bearing an alkane sulphonic acid group in an imidazole or triphenylphosphine cation (Fig. 15a) [86] or in a pyridinium cation (Fig. 15b) [87],... 

Functionalized ionic liquids possessing two Bronsted acid sites with COOH, HS04 or H2P04 groups were reported by Dan [40] in 2007 ... 

Recently, ionic liquids with amino acids as anions were synthesized by neutralization between [C2mim][OH] and amino acids [88], Tetrabutylphosphonium amino acids [P(C4)4][AA] were synthesized by the reaction of tetrabutylphosphonium hydroxide [P(C4)4][OH] with amino acids, including glycine, L-alanine, l-/1-alanine, L-serine and L-lysine [89], The esters or amide derivatives of bromoacetic acid were either commercially available or formed in one step via the reaction of bromoacetyl bromide with the appropriate alcohol or amine [90-92], An advantage of this route is that a wide range of ester and amide side chains can be prepared easily. For ionic liquids with anions other than bromide, a metathesis reaction was employed to introduce the counter ion of choice. Additionally, functionalized ionic liquids with electrophilic alkene-type appendages were synthesized. 

Scheme 16 Ester and carbonyl groups appended functionalized ionic liquid phases...

Bazureau et al. reported the synthesis of poly(ethyleneglycol) functionalized -ionic liquid phases as functionalized ionic liquids which are promising tools for synthetic applications in ionic-phase combinatorial chemistry [97], Moreover, several research groups have described ionic liquids with imidazolium cations carrying amino functionality. Davis et al. [98] reported for the first time a functionalized ionic liquid with NH2 group, n-propylamine-3-butylimidazohum tetrafluoroborate 18, for capturing C02 (Scheme 17). 

Electroactive, functionalized ionic liquid, tetraalkylphosphonium polyoxometalates were synthesized by the substitution of sodium tungstate with tetaralkylphosphoni-umbromide [(C6H13)3P(C14H29)]2W6019 [99],... 

Scheme 17 Functionalized ionic liquids with NH2 group...

Recently, Wasserscheid and co-workers [103] introduced a complementary method for functionalized ionic liquid synthesis (11). In a one-pot, two step synthesis, the protonation of an imidazolium or pyridinium cation followed by a Michael-type addition to methyl vinyl ketone was reported. The only drawback is the limited thermal stability of the cations, which at moderately elevated temperatures undergo a retro-Michael reaction ... 

---