Ionic liquids microwave-assisted synthesis

Microwave-Assisted Synthesis of a Substituted Pyran Using Ionic Liquid Tagging... 

In microwave-assisted synthesis, a homogeneous mixture is preferred to obtain a uniform heating pattern. For this reason, silica gel is used for solvent-free (open-vessel) reactions or, in sealed containers, dipolar solvents of the DMSO type. Welton (1999), in a review, recommends ionic liquids as novel alternatives to the dipolar solvents. Ionic liquids are environmentally friendly and recyclable. They have excellent dielectric properties and absorb microwave irradiation in a very effective manner. They exhibit a very low vapor pressure that is not seriously enhanced during microwave heating. This makes the process not so dangerous as compared to conventional dipolar solvents. The polar participants of organic ion-radical reactions are perfectly soluble in polar ionic liquids. 

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... 

The specific microwave effects were presumably responsible for the observed 40-fold acceleration in microwave-assisted synthesis of 1,3,5-triazines 107 compared to conventional thermal conditions. Thus, microwave heating of benzonitrile and dicyandiamide 106 in an ionic liquid ([bmim]PF6) in the presence of powdered KOH at 130 °C for just 12 min afforded 2,4-diaminotriazine 107 in 87% yield. Under otherwise identical conditions the reaction in a pre-heated oil-bath (130 °C temperature) took 8 hours to afford the target heterocycle 107 in 79% yield [140] (Scheme 57). 

Martinez-Palou R (2010) Microwave-assisted synthesis using ionic liquids. Mol Divers 14 3-25... 

Pal SK, Kumar S (2006) Microwave-assisted synthesis of novel imidazolium-based ionic liquid crystalline dimers. Tetrahedron Lett 47 8993-8997... 

Hu X, Qi R, Wang W, Zhu Y. 2004. Microwave-assisted synthesis of singlecrystalline tellurium nanorods and nanowires in ionic liquids. Angew Chem Int Ed 45 1410-1414. 

A microwave dielectric heating assisted TSIL phase synthesis [45] of 1,4-dihydropyridines, 3,4-dihydropyrimidin-2(lH)-ones, pyridines and polyhydroquinolines using a TSIL as a soluble support was described. The efficiency of the ionic liquid phase organic synthesis (loLiPOS) methodology was demonstrated by using a one-pot three-component condensation. The stmcture of the intermediates... 

Buehler, G., and Feldmann, C. (2006]. Microwave-assisted synthesis of luminescent LaP04 Ce,Tb nanocrystals in ionic liquids. Angew. Chem. Int Edit, 45, pp. 4864-4867. 

The novice reader may think that the subject is an emerging field however, the green chemistry name is an umbrella for many well-established ideas and techniques that already exist in the literature. None of the techniques under the green technology label can therefore be considered new. For example, the first room-temperature ionic liquid, ethylammonium nitrate [EtNH3] [N03] , which melts at 12°C was discovered by Paul Walden in 1914 [40], Ionic liquids were also observed in Friedel-Crafts acylation and alkylation reactions [41,42], The reader is directed to two reviews that chronicle the historical development of ionic liquids [43,44]. Microwave-assisted synthesis was developed by Gedeye and Westaway at Laurentian University in Sudbury, Canada [45-48],... 

Abstract The quinoxaline (Qx) nucleus is present in various bioactive molecules. Thus, synthesis of Qxs continues to draw the attention of synthetic oiganic/medici-nal chemists. The contemporary interest in search for newer synthetic methods for this privileged class of compounds rcmains unabated and a vast number of publications continue to appear. The focus of this chapter is on the research woiks pubhshed in this area after the year 2000 with the inherent objective to attain sustainability towards the synthesis. The attention will be on the key sustainable approaches of pharmaceutical industries like the solvent-fiee reactions, use of alternate reaction media (e g., water, fluorous alcohols, polyethylene glycols, and ionic liquids), and alternate modes of synthesis such as microwave-assisted synthesis and flow reactions. 

Chen HT, Gao J, Wang G, Shi SQ, Zhang SB, Cai LP (2004) Effect on temperature on calcium carbonate deposition in situ on bamboo fiber and polymer interfaces. Wood Fiber Sci 46 1-12 Datta C, Basu D, Baneijee AN (2002) Mechanical and dynamical mechanical properties of jute fibers-Novolac-Epoxy composite laminates. J App Polym Sci 85 2800-2807 Garea SA, Nicolescu A, Deleanu C, lovu H (2010) New nanocomposites based on epoxy resins reinforced with modified montmorillonite. Int J Polym Anal Charact 15 497-508 Ghosh P, Mitra PS, Baneijee AN (2003) Photopolymerization of methyl methacrylate with the use of bromine as photoinitiator. J Polym Sci Polym Chem Ed ll(8) 2021-2030 Jia N, Li SM, Ma MG, Sun RC, Zhu L (2011) Green microwave-assisted synthesis of cellulose/ calcium silicate nanocomposites in ionic liquids and recycled ionic liquids. Caibohydr Res 34 2970-2974... 

S. Thummanagoti, G.S. YeUol, C.M. Sun, Microwave-assisted tandem transformation on an ionic-liquid support efficient synthesis of pyrrolo/pyridobenzimidazolones and isoindoUnone-fusedbenzimidazoles, Chem. Asian). 6 (2011) 2471-2480. 

Importantly, ionic liquids show excellent properties on the adsorption of microwave. The combination of microwave-assisted synthesis and ionothermal synthesis opens up an efficient and safe route to prepare zeolite materials [60]. Tian and coworkers reported the microwave-assisted ionothermal synthesis of AlPO-ll using [EmimJBr [61]. Silicon element was also successfully introduced to the framework forming SAPO-11 with potential catalytic applications. In addition, Yan and coworkers developed the ambient pressure synthesis method for silicate zeolites by combining the advantages of ionothermal synthesis, dry-gel conversion, and microwave irradiation [62]. With the assistance of microwave-assisted synthesis, the safe and fast process of ionothermal synthesis has shown to be a promising synthetic route for a variety of zeolite structures. 

Labrini et al. (2005) have reported a rapid synthesis of 2,5-disubstituted-1,3,4-thiadiazoles via the one pot condensation reaction of aromatic aldehydes, hydrazine, and sulfur in ethanol under microwave irradiation. Microwave-assisted synthesis of 2-aminothiophene-3-carboxylic derivatives (Gewald synthesis) has been reported by Hu et al. (2006) under microwave conditions using a functional ionic liquid as a soluble support. 

Jiang, Y. Zhu, Y. J. (2005) Microwave-assisted synthesis of sulfide M2S3 (M = Bi, Sb) nanorods using an ionic liquid J. Phys. Chem. B 109,10,4361-4364,1520-6106... 

Liu, Z. Sun, Z. Han, B., Zhang, J. Huang, J. Du, J. Miao, S. (2006) Microwave-Assisted Synthesis of Pt Nanocrystals and Deposition on Carbon Nanotubes in Ionic Liquids, / Nanosci Nanotech, 2006,6,1,175-179,1550-7033 Movahedi, M. Kowsari, E. Mahjoub, A. R. Yavari, I. (2008) A task specific basic ionic liquid for synthesis of flower-like ZnO by hydrothermal method. Mater lett, 62, 23, 3856-3858, 0167-577X... 

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. 

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