Research Journal of Chemical Sciences ______________________________________________ ISSN 2231-606X Vol. 5(3), 77-89, March (2015) Res. J. Chem. Sci. International Science Congress Association 77 Review Paper Use of Non-Conventional Reaction Media - A Green Approach Ratti Rajni Motilal Nehru College, New-Delhi, INDIAAvailable online at: www.isca.in, www.isca.me Received 11th February 2015, revised 10th March 2015, accepted 16th March 2015 AbstractUse of volatile organic solvents, particularly the chlorinated hydrocarbons, lead to serious environmental issues like air and water pollution. It has been realized that the replacement of these environmentally harmful solvents with benign non-conventional media will be a great step towards achieving sustainable processes. The most prevalent of these new solvent systems include, but not exclusively, water, supercritical fluids (like supercritical CO), ionic liquids, solvent-less processes and fluorous solvents. Keywords: Non-Conventional media, supercritical fluids, ionic liquids, fluorous media. Introduction Most chemical processes involve solvents in the reaction and separation step to dissolve solids, reduce viscosity, modulate temperature, and recover products by means of extraction or recrystallization as reaction media or for cleaning purposes. Solvents not only dissolve the reactants but they also affect the rates, chemo-, regio- and stereoselectivities of reaction. However, majority of the organic solvents used in industry, despite their inherent advantages, are associated with several ill effects on human health and environment. Moreover, these solvents are derived from non-renewable resources like petroleum. These parameters are in contradiction to the very basics of Green Chemistry. Due to these reasons, the only alternative available is to substitute these environmentally harmful solvents with some benign solvents. Hungerbuhler et al discussed the following four directions towards the development of green solvents. Substitution of hazardous solvents with one that show better EHS (Environment, Health, Safety) properties such as increased biodegradability or reduced ozone depletion potential. Use of “bio-solvents” i.e solvents produced from renewable resources such as ethanol produced by fermentation of sugar-containing feeds, starchy feed materials or lignocellulosic materials. Substitution of organic solvents with supercritical CO in polymer processing avoids the use of chlorofluorocarbons, and reduces the ozone depletion. With ionic liquids that show low or negligible vapour pressure, and thus fewer emissions to air. Sustainable processes can be developed using all the alternatives in different ways as it is unlikely that only one solvent will be the panacea for various chemical protocols7,8. Various Non-Conventional Approaches Solvent-free Reactions: Solvent-free processes or reactions are the best solution for minimizing the solvent losses as they are clean, safer, efficient and economical9-11. They can be efficiently coupled to non-classical methods of activation like ultrasound and microwave12-15. The best solvent is no solvent (prevention is better than cure). A reaction can be carried out without a solvent when the reagents are liquids or the reaction mixture can be melted to produce a liquid. Solvent-free separation step includes mechanical separation instead of extraction with an organic solvent. The work-up is considerably simplified, cost is reduced, energy consumption is lowered and an increased amount of reactants can be used in the same equipment with the added advantage of enhanced reactivity and selectivity in some cases as illustrated by the examples discussed below: Pelphrey and co-workers demonstrated efficient solvent-free reactions involving donor/acceptor substituted rhodium carbenoids16 (Scheme-1). Cruz et al carried out synthesis of a series of N-alkylpyrrolidino [60] fullerenes without solvent by phase transfer catalysis under microwave irradiation17 (scheme-2). Scheme-1 Research Journal of Chemical Sciences ___________________________________________________________ ISSN 2231-606XVol. 5(3), 77-89, March (2015) Res. J. Chem. Sci. International Science Congress Association 78 A one-pot synthesis of substituted coumarins via Pechmann condensation has been efficiently catalyzed by silica-gel supported sulfuric acid under solvent-free conditions18 (scheme-3).Jiang et al carried out solvent-free synthesis of substituted ureas from CO and amines using [bmim]OH as catalyst19 (scheme-4). A chemoselective solvent-free protocol was developed by Hua and co-workers for the reaction between ortho-aminocinnamate and isothiocyanates20. It has been found that when Yb(OTf)was used as a catalyst 2-Amino-3,1-benzothiazines were obtained in high yields whereas [(MeSi)N]La(-Cl)Li(THF)leads to 3,4- dihydroquinazoline-2-thiones (scheme-5). Pooladian and co-workers developed a solvent-free and catalyst- free, one-pot protocol for the synthesis of novel symmetrical bisthioglycolic acid derivatives starting from thioglycolic acid and aldehydes/ketones21. The green attributes of the reaction are absence of organic solvents at any stage of reaction, shorter reaction times, easy work-up, no requirement of purification of products by column chromatography (scheme-6). Aurones and hydroxyaurones have been efficiently prepared by grinding aldehydes with substituted 2-hydroxyphenacyl chlorides under solvent-free conditions using activated barium hydroxide as solid base22 (scheme-7). Supercritical Fluids: Supercritical fluids have emerged as useful solvents for extractions, chromatography and some specific chemical reactions23-25. They differ from ordinary liquids and gases in their properties which can be tuned as per the requirement of a process simply by changing the temperature and pressure. Scheme 2 Scheme 3 Scheme 4 Scheme-5 Scheme-6 Research Journal of Chemical Sciences ___________________________________________________________ ISSN 2231-606XVol. 5(3), 77-89, March (2015) Res. J. Chem. Sci. International Science Congress Association 79 Scheme 7The most popular supercritical fluid is supercritical carbon-dioxide (scCO26. Supercritical carbon-dioxide is readily available, with a critical temperature (T) of 31.1C and critical pressure (P) of 72.9 atm. There are various advantages associated with the use of scCO and are discussed in a number of recent articles27-31. CO is available in abundance, non-toxic, non-flammable, and relatively inert towards reactive compounds. The most remarkable property of scCO2 is that by changing the pressure and temperature it can be made to behave like a gas or a liquid, giving it the ability to diffuse or solvate respectively. Moreover the critical temperature being very low, allows the heat sensitive reactions to be carried out at ease. The use of scCO permits selective extraction as all chemical reactants do not solubilize in it easily. Moreover, it’s removal from the reaction mixture is quite easy by depressurization. The use of CO do not lead to global warming as its usage involve no net addition to the atmosphere, it is taken from atmosphere and returned there. Supercritical carbon-dioxide find application in a number of industrial processes. Poliakoff pioneered the use of scCO as a solvent for catalytic hydrogenation and Thomas Swan and Co. commercialized it for the manufacture of trimethyl cyclohexanone by palladium catalyzed hydrogenation of isophorone32 (scheme-8). Scheme 8 Recently, much interest has also been inclined towards catalytic oxidations with hydrogen peroxide, generated in situ by Pd-catalyzed reaction of hydrogen with oxygen, in scCO-water mixtures. This system was effectively used by Danciu et al for the direct epoxidation of propylene to propylene oxide over a Pd/TS-1 catalyst (scheme-9)33. Scheme 9 Supercritical carbon-dioxide is an ideal solvent for metathesis reactions because of high solubility of alkenes in it. Selva et al used scCO as a reaction media to execute the selective self metathesis of -olefins (1-hexene, 1-heptene and 1-octene) in the presence of heterogeneous Re catalyst34 (scheme-10). Effect of carbon-dioxide pressure, amount of catalyst and nature of catalytic support were studied extensively. It was observed that Re-oxide showed good activity when supported on -Alwhile silica supported systems were found to be inactive. The self metathesis of 1-octene at 35C in scCO gave conversion over 35% higher than the conventional solvents. Under the optimized conditions, the recyclability was successfully studied upto two cycles. Supercritical water (374C, 218 atm) has been recognized as an attractive and green reaction medium due to its unique properties and environmentally favorable nature35,36. Dielectric constant of supercritical water roughly corresponds to that of common organic solvents so organic reactions get facilitated in this medium. Lower viscosity (2.98 x 10-5 PaS) at critical point provides high diffusion coefficient. Hayashi and Hakuta carried out the synthesis of metal oxide particles in supercritical water which allows control of the crystal phase, morphology, and particle size. They emphasize the use of supercritical water in the formation of fine particles37. Korzenski and Kolis performed Diel’s Alder reaction of cyclopentadiene and various electron poor dienophiles in supercritical water and obtained medium to high yields of clean products in the absence of catalysts38 (scheme-11). Scheme10 Research Journal of Chemical Sciences ___________________________________________________________ ISSN 2231-606XVol. 5(3), 77-89, March (2015) Res. J. Chem. Sci. International Science Congress Association 80 + COOEt EtOOC 375C, 1 h COOEt COOEt Scheme 11 Dreher and co-workers carried out the conversion of biomass into methane in supercritical water using carbon-supported ruthenium catalyst in a realistic continuous flow process39. In-situ XAS studies revealed that sulphur poisoning of Ru/C is an irreversible process and possible regeneration procedure may involve chemical treatment of sulphur poisoned catalyst. Fluorous Media: “Fluorous” is the term coined for highly fluorinated (or perflourinated) solvents by Horvath40,41. Now a days, fluorine chemistry constitutes an important part of clean technology, both in catalysis and as an alternative reaction media42. Fluorous solvents possess unique physico-chemical properties, such as low dielectric constant, high chemical and thermal stability, and low toxicity. Due to temperature-dependent miscibility with organic solvents, fluorous solvents find numerous applications in biphasic catalysis43,44. Juliette et al have reported hydroboration in perfluoromethyl cyclohexane and toluene using a rhodium complex catalyst with fluorous ligands (scheme-12). After the reaction was complete, the product was separated and the fluorous phase containing the catalyst was reused45,46. Using fluorous solvent as reaction media and Hafnium (IV) bis (perfluorooctanesulfonyl) imide complex as catalyst, Hantzsch synthesis of polyhydroquinoline derivatives was executed in an efficient way 47 (scheme-13). Shorter reaction time, easy work-up, reusability of catalyst and excellent yields are the highlighting advantages of this methodology. Yu et al synthesized a novel Pd-NHC complex bearing fluorous tags. Using a reaction medium consisting of ethanol and perfluorobenzene (1:1 v/v), the Pd-NHC complex was used as an efficient catalyst to execute Suzuki coupling of aryl halides with aryl boronic acids48 (scheme-14). The catalytic system could be recycled thrice without any appreciable loss of activity. Due to their disadvantages like high cost, low biodegradability and global warming issues, perflourinated solvents are now days replaced by hydrofluoroethers (HFEs). Commercial HFEs, such as HFE-7100, HFE-7500 and F- 626 possess a higher polarity than perflourinated solvents due to the presence of an oxygen atom between a fluoroalkyl group and alkyl group (figure-1). + O O HB RhCl[P[CH(CFCFCF11/toluene, 40C, 14h B O O Scheme 12 Scheme 13 Scheme 14 Research Journal of Chemical Sciences ___________________________________________________________ ISSN 2231-606XVol. 5(3), 77-89, March (2015) Res. J. Chem. Sci. International Science Congress Association 81 O F F F F F F F F F O F F F F F F F F F HFE-7100 F F F F F F F F F F F F O F F F F F F F F F F F F F HFE-7500F-626Figure 1 The fluorous ether F-626 was used by Ryu et al as the reaction medium in the Heck - arylation of , -unsaturated acids and esters with aryl iodides, in the presence of a fluorous palladium carbene complex49 (scheme-15). After work-up the recovered F-626 phase containing the palladium catalyst was reused for further five runs without any appreciable loss in catalytic activity. Aqueous Media: Water has emerged as a versatile green solvent for organic reactions in recent years50. It is not only cheap, eco-friendly, innocuous but also exhibits an entirely new reactivity owing to its unique physico-chemical properties. Research, using water as a solvent, is focused on the development of environmentally friendly and recyclable techniques, which can be commercialized for large scale applications51. Water also finds application in biphasic processes in combination with other solvents. The use of water as a solvent generally eliminates the requirement of protection-deprotection of sensitive functional groups, thereby enhancing the overall synthetic efficiency. Due to its high dielectric constant, water is an appropriate solvent for microwave mediated synthesis52. The type of organic reactions studied in aqueous media are wide including pericyclic reactions, reactions of carbocation equivalent, reactions of radicals, reactions of carbanion equivalent,and carbenes, transition metal catalyzed reactions and various redox reactions53,54. Narayan et al reported 2 + 2 + 2 cycloaddition of quadricyclane with azidocarboxylates at room temperature which occurs at a faster rate in water than in other organic solvents55 (scheme-16). Suzuki-Miyaura coupling reaction has been reported in water at room temperature using a palladacycle catalyst by Marziale and co-workers. Under the optimized reaction conditions, a broad range of products has been obtained in good to excellent yields and high purity by simple filtration56 (scheme-17). Buxaderas and collegues developed a protocol for Sonogashira coupling of deactivated and hindered aryl bromides and chlorides using a chloro-bridged oxime derived palladacycles, 2-dicyclohexylphosphanyl-2,4,6-triisopropylbiphenyl (XPhos) as ancillary ligand, pyrrolidine as base, and SBDS as surfactant in aqueous media57. The main green attributes of the reaction are air and moisture insensitive catalyst, execution of reaction in aqueous media under microwave irradiation, requirement of catalyst in low concentration (0.1- 1 mol%) and short reaction time (scheme-18). Scheme 15 +N COOMe MeOOC rt N N COOMe COOMe Scheme 16 Scheme 17 Research Journal of Chemical Sciences ___________________________________________________________ ISSN 2231-606XVol. 5(3), 77-89, March (2015) Res. J. Chem. Sci. International Science Congress Association 82 Scheme 18 Scheme 19 A sustainable protocol was developed for the synthesis of 1,8-dioxo octahydroxanthenes in aqueous hydrotropic solution by Kamble et al. Increase in reaction rate was observed for NaPTSA58 (scheme-19). Short reaction time, use of water as reaction medium, recyclability and excellent yields are the advantages of developed methodology. Ionic Liquids: Ionic liquids, a new class of non-molecular ionic solvents, have emerged as an important alternative to the volatile organic solvents59-62 Ionic liquids (ILs) are broadly defined as low melting salts that have melting points below 10063. They consist of an organic asymmetric cation and an anion as shown in figure-2. A CationAlkyl ChainAnion [NR[PR[SR Linear/ Branched/Chiral/Achiral/other functionalitiesBF, PFSbF, NOCFSO, ArSOCl, Br, NTfSO, HSOFigure-2 Diagrammatic representation of various components of ionic liquids Ionic liquids have been described as “designer solvents” which implies that their properties can be tuned to meet the requirements of a particular reaction64. Properties such as melting point, viscosity, density and hydrophobicity can be modulated by simple variations in the structure of the ions65-70. As solvents, ionic liquids are versatile as they are reusable, increases the reactivity and selectivity of chemical transformations, simplify product isolation and facilitate the catalyst recycling71-73. Reaction product can be selectively extracted from the ionic liquid phase by water, organic solvent like diethyl ether, ScCO2 andper-vaporation. Due to the possession of these unique properties, ionic liquids are increasingly finding applications in both academia and industry74-77. Ionic liquids have been used as solvents in various transition metal catalyzed reactions, multicomponent reactions, esterification, biocatalytic reactions, redox reactions and cycloaddition reactions to mention a few78-85. Handy prepared a base-stable imidazolium based room temperature ionic liquid which was used as a solvent for the addition of Grignard reagents to carbonyl compounds (scheme-20). Good to excellent yields of alcohols have been obtained at ambient temperature. Moreover, the ionic liquid has been recycled and reused several times without any difficulty86. O MgBr NN NTf R R' OH Scheme 20 Anjaiah et al used [bmim]BF and [bmim]NTf as efficient, reusable solvents in ytterbium triflate catalyzed carbon-Ferrier Research Journal of Chemical Sciences ___________________________________________________________ ISSN 2231-606XVol. 5(3), 77-89, March (2015) Res. J. Chem. Sci. International Science Congress Association 83 rearrangement of triacetyl glucal with allyl silanes, propargyl silane, and silyl enolethers87 (scheme-21). O OAc AcO AcO R1 OTMS R2 Yb (Tf) 5 mol%[bmim] [NTf OAc AcO R1 O Scheme 21 Co(CO) catalyzed intramolecular and intermolecular PausonKhand annelation have been efficiently carried in various imidazolium based ionic liquids under a CO pressure of 10 bar88 (scheme-22). +CO Co(CO) 10 mol%ionic liquids O Scheme 22 Suzuki-Miyuara reaction of aryl bromides and aryl boronic acids gave good to excellent yields in pyrrolidinium ionic liquids. A pre-formed air stable and easily handled triethylammonium-tagged diphenylphosphine palladium (II) complex was used as a catalyst. The ionic liquid containing the catalyst was recycled for six times, with no appreciable loss of activity89 (scheme-23). Ionic liquid has been used both as a reaction media as well as a promoter for the synthesis of optically active O- acetyl cyanohydrins via one-pot lipase catalyzed kinetic resolution of the in-situ generated racemic cyanohydrins or O-acetyl cyanohydrins by Shen and co-workers90 (scheme-24). The room temperature ionic liquid [bmim]PF has been used as an efficient and recyclable medium for highly chemoselective synthesis of 2,2-dimethyl-6-substituted 4-piperidones via a L-proline catalyzed tandem Mannich reaction of ammonia, aldehydes and acetone. Both aryl and alkyl aldehydes gave good yields in this reaction91 (scheme-25). Singh et al reported an efficient synthesis of selenoesters from acyl chlorides catalyzed by CuO nanopowder using onic liquid as a recyclable solvent. This methodology exhibits high efficiency than the previous protocols due to non-residual methodological design92 (scheme-26). Br B(OH) + PdL, KPO, 65C, 2h[bmpy] [NTf]/ HO (2:1) Scheme 23 H O R CN OAc 1. TMSCN, [emim] PF2. Ac3. Candida antartica lipase n-BuOH/Ac 1. TMSCN, [emim] PF2.Pseudomonas cepacia lipase vinyl acetate CN OAc Scheme 24 O +PhCHO Ammonia gas[bmim] PF, rt, 20 h O +N O Ph Ph + Ph O OH + Ph O Scheme 25 Research Journal of Chemical Sciences ___________________________________________________________ ISSN 2231-606XVol. 5(3), 77-89, March (2015) Res. J. Chem. Sci. International Science Congress Association 84 R Cl O -Se-Se-RCuO nanopowder[bmim]PF, base, 80 Se O R1 Scheme 26 Ionic liquids have been used as reaction media for theatom transfer carbonylation reaction using a variety of alkyl iodides catalyzed by a palladium-carbene complex. The palladium catalyst and ionic liquid were recycled93 (scheme-27). [bmim] BF has been used as a solvent for the efficient oxidation of benzylic alcohols to aldehydes and ketones using N-chlorosuccinimide/AlCl.6HO as catalytic system94 (scheme-28). Alkene copolymerization with carbon monoxide has been carried out in a number of N-alkyl pyridinium, 1,3-dialkylimidazolium, tetraalkylammonium, and tetraalkyl phosphonium based [NTf] ionic liquids and catalyzed by palladium complexes95 (scheme-29). Singh et al efficiently carried out Mizoroki-Heck and Sonogashira reaction in an ammonium based ionic liquid [TMBA] NTf using an ammonium tagged palladacycle and its clay hybrid96 (scheme-30, 31). The catalytic system, which includes palladacycles and ionic liquid, was found to be recyclable upto seven cycles. Phan and Collegues used chitosan as a heterogeneous catalyst in ionic liquid solvent to execute Knoevengeal condensation97 (scheme-32). The catalytic system could be efficiently recycled several times. R-I+CO+RNH Pd-catalystIonic Liquids NR O R NR O O Scheme 27 R1 OH R3 R2 NCS, AlCl.6H[bmim] BF R1 O R3 R2 Scheme 28 Palladium complexes[Cpyr] [NTfCO (40 bar), 70 O O Scheme 29 Scheme 30 Research Journal of Chemical Sciences ___________________________________________________________ ISSN 2231-606XVol. 5(3), 77-89, March (2015) Res. J. Chem. Sci. International Science Congress Association 85 Scheme 31 Scheme 32 Schenzel et al developed a sustainable protocol for transesterification of cellulose using [bmim]Cl as solvent, DMSO as co-solvent. The developed methodology is quite versatile as promising results are obtained for aromatic, aliphatic and fatty acid cellulose esters98. [bmim]Cl-DMSO mixture can be recycled and reused thereby avoiding the use of volatile organic solvents. Not only in laboratories, ionic liquids have paved their way into industries too99-101. BASF pioneered the application of ionic liquids on a commercial scale with a number of BASIL (Biphasic Acid Scavenging utilizing Ionic Liquids) processes. One of these processes replaced triethyl amine with 1-methylimidazolium ion as an acid scavenger of HCl, thereby, facilitating the work-up greatly102. Rogers and Seddon reported that, for one particular BASIL process, the productivity had been increased by 80,000 compared to the conventional methodology103. Similarly, Degussa has commercialized the usage of ionic liquids as secondary dispersive agents in paints, thereby, minimizing the use of hazardous volatile organic solvents104. Though ionic liquids possess numerous advantages still owing to their high cost, the number of industrial processes using them is. Research efforts, now a day, are focused on the development of cheap and easily biodegradable ionic liquids for commercial purposes. Conclusion The review is focused on the use of non-conventional reaction media for organic synthesis which is a pre-requisite for making chemistry green. Applications of supercritical fluids, Ionic liquids, water and fluorous media in organic reactions have been discussed in detail. Choice of solvent is, indeed, decided by the nature of reaction. Combination of these non-conventional solvents can be used in reactions requiring bi-phasic conditions. As solvents constitute a major part of industrial processes so using an appropriate non-conventional solvent can improve the economy as well as green attributes of commercial processes. References 1.Anastas P.T. and Williamson T.C., Green Chemistry: Frontiers in Benign Chemical Syntheses and Processes, Oxford University Press, (1998)2.Capello C., Fischer U. and Hungerbuhler K, What is a green solvent?, A comprehensive framework for the environmental assessment of solvents, Green Chem., , 927-934, (2007)3.Gani R., Gonzalez C.J., Kate A., Crafts P.A., Jones M., Powell L., Atherton J.H. and Cordiner J.L., A Modern approach to solvent selection, Chem. Eng., , 30-41 (2006)4.Savaiko B., A promising future for ethanol, World ethanol and biofuels report., , 20-22 (2004)5.Noyori R., Supercritical Fluids : Introduction, Chem. Rev., 99, 353-354 (1999)6.Petkovic M., Seddon K.R., Rebelo L.P.N. and Pereira C.S., Ionic liquids: A pathway to environmental acceptability, Chem. Soc. Rev., 40, 1383-1403 (2011)7.Andrade C.K.Z. and Alves L.M., Environmentally benign solvents in organic synthesis: Current Topics, Curr. Org. Chem., , 195-218 (2005)8.Pollet P., Davey E.A., Ureña-Benavides E.E., Eckerta C.A., Liotta C.L., Solvents for sustainable chemical processes, Green Chem., 16, 1034-1055 (2014)9.Metzer J.O., Solvent-Free Organic Syntheses, Angew. Chem. Int. Ed.,37, 2975-2978 (1998) Research Journal of Chemical Sciences ___________________________________________________________ ISSN 2231-606XVol. 5(3), 77-89, March (2015) Res. J. Chem. Sci. International Science Congress Association 86 10.Cave G.W.V., Raston C.L. and Scott J.L., Recent advances in solventless organic reactions: Towards benign synthesis with remarkable versatility, Chem. Commun., 2159-2169 (2001)11.Loupy A., Solvent-free reactions, Top. Curr. Chem.,206, 153-207 (1999)12.Gawande M.B., Bonifacio V.D.B., Luque R., Branco P.S. and Varma R.S., Solvent-free and catalyst free chemistry: A benign pathway to sustainability, Chem Sus Chem., 7, 24-44 (2014)13.Singh M.S. and Chowdhury S., Recent developments in solvent–free multicomponent reactions : A perfect synergy for eco-compatible organic synthesis, RSC Adv., 2, 4547-4592 (2012)14.He J.Y., Xin H.X., Yan H., Song X.Q. and Zhong R.G., Convenient ultrasound-mediated synthesis of 1, 4-diazabutadienes under solvent-free conditions, Ultrason. Sonochem.,18, 466-469 (2011) 15.Varma R.S., Solvent-free organic syntheses using supported reagents and microwave irradiation, Green Chem., , 43-55 (1999)16.Pelphrey P., Hansen J. and Davies H.M.L., Solvent-free catalytic enantioselective C–C bond forming reactions with very high catalyst turnover numbers, Chem. Sci., , 254-257 (2010)17.Cruz P.de la., Hoz A.de la., Font L.M., Langa F. and Perez-Rodriguez M.C., Solvent-free phase transfer catalysis under microwaves in fullerene chemistry: A convenient preparation of N-alkylpyrrolidino [60] fullerenes, Tetrahedron Lett., 39, 6053-6056 (1998) 18.Reddy B.M., Thirupathi B. and Patil M.K., One-pot synthesis of substituted coumarins catalyzed by silica gel supported sulfuric acid under solvent-free conditions, The Open Catal. J., , 33-39 (2009)19.Jiang T., Ma X., Zhou Y., Liang S., Zhang J. and Han B., Solvent-free synthesis of substituted ureas from CO and amines with a functional ionic liquid as the catalyst, Green Chem., 10, 465-469 (2008)20.Hua L., Yao Z., Xu F. and Shen Q., Chemoselective reactions under solvent-free conditions: lanthanidecatalyzed syntheses of 2-amino-3,1-benzothiazines and 3,4-dihydroquinazoline-2-thiones, RSC Adv., , 3113-3120 (2014)21.Poolandian B., Ghasemi E. and Jaberi Z.A., Catalyst free and solvent free synthesis of novel symmetrical bisthioglycolic acid derivatives, Green Chem. Lett. Rev., 7, 60-63 (2014)22.Kumar S., An Improved one pot and eco friendly synthesis of aurones under solvent free conditions, Green Chem. Lett. Rev., 7, 95-99 (2014)23.Oakes R.S., Clifford A.A. and Rayner C.M., The use of supercritical fluids in synthetic organic chemistry, J. Chem. Soc.,Perkin Trans., , 917-941 (2001)24.Brunner G., Applications of supercritical fluids, Annu. Rev. Chem. Biomol. Eng., 1, 321-342 (201025.Skouta R., Selective chemical reactions in supercritical carbon dioxide, water and ionic liquids, Green Chem. Lett. Rev., 2, 121-156 (2009) 26.Munshi P. and Bhaduri S., Supercritical Carbon-dioxide: A twenty first century solvent for the chemical industry, Curr. Sci., 97, 63-72 (2009) 27.Sokolov V.I., Bulygina L.A., Khrustalev V.N., Starikova Z.A., Nikitin L.N. and Khokhlov A.R. Supercritical carbon dioxide as a solvent for crystallization and a reaction medium for metallocene derivatives, Dokl. Chem., 431, 65-70 (2010) 28.Mayadevi S., Reactions in supercritical carbon dioxide, Ind. J. Chem., 51A, 1298-1305 (2012) 29.Jiang H., Jia L. and Li J., Wacker reaction in supercritical carbon-dioxide, Green Chem., , 161-164 (2000) 30.Lee C.K.Y., Holmes A.B., Al-Duri B., Leeke G.A., Santos R.C.D. and Seville J.P.K., Nitrile oxide cycloadditions in supercritical carbon dioxide, Chem. Commun., 2622-2623 (2004) 31.Kimmerle B.M., Grunwalst J.D. and Baiker A., Gold catalysed selective oxidation of alcohols in supercritical carbon dioxide, Top. Catal., 44, 285-292 (2007) 32.Licence P., Ke J., Sokolova M., Ross S.K. and Poliakoff M., Chemical reactions in supercritical carbon dioxide: From laboratory to commercial plant, Green Chem., 5,99–104 (2003) 33.Danciu T., Beckman E.J., Hancu D., Cochran R., Grey R., Hajnik D. and Jewson J., Direct Synthesis of Propylene Oxide with CO as the Solvent, Angew. Chem., Int. Ed., 42, 1140-1142 (2003) 34.Selva M., Perosa A., Fabris M. and Canton P., The metathesis of -olefins over supported Re-catalysts in supercritical CO, Green Chem., 11, 229-238 (2009) 35.Serani A.L., Aymonier C. and Cansell F., Supercritical water for environmental technologies, J. Chem. Technol. Biotechnol., 85, 583-589 (2010) 36.Savage P.E., Organic chemical reactions in supercritical water, Chem. Rev., 99, 603-621 (1999) 37.Hayashi H. and Hakuta Y., Hydrothermal Synthesis of Metal Oxide Nanoparticles in Supercritical Water, Mater., , 3794-3817 (2010) 38.Korzenski M.B. and Kolis J.W., Diels-Alder reactions using supercritical water as an aqueous solvent medium, Tetrahedron Lett., 38, 5611-5614 (1997) Research Journal of Chemical Sciences ___________________________________________________________ ISSN 2231-606XVol. 5(3), 77-89, March (2015) Res. J. Chem. Sci. International Science Congress Association 87 39.Dreher M., Johnson B., Peterson A.P., Nachtegaal M., Wambach J. and Vogel F., Catalysis in supercritical water: Pathway of the methanation reaction and sulfur poisoning over a Ru/C catalyst during the reforming of biomolecules, J. Catal., 301, 38-45 (2013) 40.Horvath I.T. and Rabai J., Facile catalyst separation without water: Fluorous biphase hydroformylation of olefins, Science,266, 72-75 (199441.Dobbsa A.P. and Kimberley M.R., Fluorous phase chemistry: A new industrial technology, J. Fluorine Chem., 118, 3-17 (2002) 42.Curran D.P., Fluorous methods for synthesis and separation of organic molecules, Pure Appl. Chem., 72, 1649-1653 (2000) 43.Klement I., Lutjens H. and Knochel P., Transition metal catalyzed oxidations in perfluorinated solvents, Angew. Chem., Int. Ed., 36, 1454-1456 (1997) 44.Maayan G., Fish R.H. and Neumann R., Polyfluorinated quaternary ammonium salts of polyoxometalate anions: Fluorous biphasic oxidation catalysis with and without fluorous solvent, Org. Lett., 5, 3547-3550 (2003) 45.Juliette J.J.J., Horvath I.T. and Gladysz J.A., Transition metal catalysis in fluorous media: Practical application of a new immobilization principle to Rhodium-catalyzed hydroboration, Angew. Chem., Int. Ed., 36, 1610-1612 1997) 46.Juliette J.J.J., Rutherford D, Horvath I.T. and Gladysz J.A., Transition metal catalysis in fluorous media:Practical application of a new immobilization principle to Rhodium-catalyzed hydroborations of alkenes and alkyne, J. Am. Chem. Soc., 121, 2696-2704 (199947.Hong M., Cai C. and Yi W.B., Hafnium (IV) bis (perfluorooctanesulfonyl) imide complex catalyzed synthesis of polyhydroquinoline derivatives via unsymmetrical Hantzsch reaction in fluorous media, J. Fluorine Chem., 131, 111-114 (201048.Yu H., Wan L., Cai C., A Novel system for the Suzuki cross-coupling reaction catalyzed with light fluorous palladium-NHC complex, J. Fluorine Chem., 144, 143-146 (201249.Fukuyama T., Arai M., Matsubara H. and Ryu I., Mizoroki-Heck Arylation of -Unsaturated Acids with a Hybrid Fluorous Ether, F-626: Facile filtrative separation of products and efficient recycling of a reaction medium containing a catalyst, J. Org. Chem., 69,8105-8107 (2004) 50.Wei W., Keh C.C.K., Li C.J. and Varma R.S., Water as a reaction medium for clean chemical processes, Clean Techn. Environ. Policy, 6, 250-257 (2004) 51.Moulay S., Towards water-borne organic synthesis: An education in chemistry research. Chemistry, 18, 1-21 2009) 52.Dallinger D. and Kappe C.O., Microwave-assisted synthesis in water as solvent, Chem. Rev., 107, 2563-2591 (2007) 53.Lubineau A. and Auge J., Water as a solvent in organic synthesis, Top. Curr. Chem., 206, 1-39 (1999) 54.Li C.J., Organic reactions in aqueous media with a focus on carbon-carbon coupling reactions, Chem. Rev., 93, 2023-2035 (1993) 55.Narayan S., Muldoon J., Finn M.G., Fokin V.V., Kolb H.C. and Sharpless K.B., On Water: Unique reactivity of organic compounds in aqueous suspension, Angew. Chem., Int. Ed., 44, 3275-3279 (2005) 56.Marziale A.N., Faul S.H., Reiner T., Schneider S. and Eppinger J., Facile palladium catalyzed Suzuki–Miyaura coupling in air and water at ambient temperature, Green Chem., 12, 35- 38 (2010) 57.Buxaderas E., Alonso D.A. and Nájera C., Copper-free oxime–palladacycles catalyzed Sonogashira alkynylation of deactivated aryl bromides and chlorides in water under microwave irradiation, Eur. J. Org. Chem., 2013, 5864- 5870 (2013) 58.Kamble S., Rashinkar G., Kumbhar A. and Salunkhe R., Hydrotrope induced synthesis of 1,8 -dioxo- octahydroxanthenes in aqueous media, Green Chem. Lett. Rev., 5, 101-107 (2012) 59.Rogers R.D. and Seddon K.R., Ionic Liquids as Green Solvents : Progress and Prospects, Am. Chem. Soc., 856,ACS Symposium series (200360.Wassercheid P. and WeltonT., Ionic Liquids in Synthesis, 2nd ed, Wiley-VCH (2008) 61.Bourbigou H.O., Magna L. and Morvan D., Ionic liquids and catalysis: Recent progress from knowledge to applications, Appl. Catal. A: Gen., 373, 1-56 (2010) 62.Ranke J., Stolte S., Stormann R., Arning J. and Jastorff B., Design of sustainable chemical products-The example of ionic liquids, Chem. Rev., 107, 2183-2206 (2007) 63.Welton T., Room-Temperature Ionic Liquids. Solvents for synthesis and catalysis, Chem. Rev., 99, 2071-2083 1999) 64.Freemantle M.,Ionic liquids may boost clean technology development, Chem. Eng. News, 76, 32-37 (1998) 65.Seddon K.R., Stark A. and Torres M.J., Influence of chloride, water, and organic solvents on the physical properties of ionic liquids, Pure Appl. Chem., 72, 2275-2287 (2000) 66.Gordon C.M., Holbrey J.D., Kennedy A.R. and Seddon K.R., Ionic liquid crystals: hexafluorophosphate salts, J. Mater. Chem., 8, 2627-2636 (1998) 67.Reichert W.M., The Effects of Cation-Anion Interactions Research Journal of Chemical Sciences ___________________________________________________________ ISSN 2231-606XVol. 5(3), 77-89, March (2015) Res. J. Chem. Sci. International Science Congress Association 88 On the Physical and Solvent Properties of Ionic Liquids, Ph.D dissertation, The University of Albama: USA, 2006) 68.Shimoyama Y. and Ito A., Predictions of cation and anion effects on solubilities, selectivities and permeabilities for CO in ionic liquid using COSMO based activity coefficient model, Fluid Phase equilib., 297, 178-182 (201069.Seki S., Kobayashi T., Kobatashi Y., Takei K., Miyashiro H., Hayamizu K., Tsuzuki S., Mitsugi T. and Umebayashi Y., Effects of cation and anion on physical properties of room-temperature ionic liquids, J. Mol. Liq., 152, 9-13 (201070.Zhang S., Sun N., He X., Lu X. and Zhang X., Physical Properties of Ionic Liquids: Database and Evaluation, J. Phys. Chem. Ref. Data,35, 1475-1517 (2006) 71.Ganeshpure P.A., Ionic Liquids: Environment-friendly solvents and catalysts for the future, Asian J. Exp. Sci., 22, 113-115 (2008) 72.Dyson P.J. and Geldbach T.J., Applications of Ionic Liquids in Synthesis and Catalysis, The Electrochem. Soc. Interface, 50-53 (2007) 73.Bourbigou H.O. and Magna L., Ionic liquids: Perspectives for organic and catalytic reactions, J. Mol. Catal A: Chem., 182-183, 419-437 (2002) 74.Plechkova N.V. and Seddon K.R., Applications of ionic liquids in the chemical industry, Chem. Soc. Rev., 37,123-150 (2008) 75.Weyershausen B. and Lehmann K., Industrial application of ionic liquids as performance additives, Green Chem., 7, 15-19 (2005) 76.Laus G., Bentivoglio G., Schottenberger H., Kahlenberg V., Kopacka H., Roder T.and Sixta H., Ionic Liquids: Current developments, potential and drawbacks for industrial applications, Lenzinger Berichte, 84, 71-85 2005) 77.Weyershausen B., Hell K. and Hesse U., Industrial application of ionic liquids as process aid, Green Chem., 7, 283-287 (2005) 78.Singh R., Sharma M., Mamgain R. and Rawat D.S., Ionic Liquids: A versatile medium for palladium-catalyzed reactions, J. Braz. Chem. Soc., 19, 357-359 (2008) 79.Vallette H., Pican S., Boudou C., Levillain J., Plaquevent J.C. and Gaumont A.C., Ionic Liquids: Valuable solvents for palladium catalyzed C-P cross coupling reactions, Ind. J. Chem., 45B., 2286-2290 (2006) 80.Shi F., Gu Y., Zhang Q. and Deng Y., Development of ionic liquids as green reaction media and catalysts, Catal. Surv. Asia, 8, 179-186 (2004) 81.Isambert N., Duque M.del.M.S., Plaquevent J.C., Genisson Y., Rodriguez J. and Constantieux T. Multicomponent reactions and ionic liquids: a perfect synergy for eco-compatible heterocyclic synthesis, Chem. Soc. Rev., 40, 1347-1357 (2011) 82.Gok Y., Alici B., Centinkaya E., Ozdemir I. and Ozeroglu O., Ionic liquids as solvent for efficientesterication of carboxylic acids with alkyl halides, Turk. J. Chem., 34, 187-191 (2010) 83.Song C.E., Enantioselective chemo- and bio-catalysis in ionic liquids, Chem. Commun., 1033-1043 (2004) 84.Martinez J.A.B., Tang L., Belleres J.P., Zeller R., Angell C. and Friesen C., Hydrogen redox in protic ionic liquids and a direct measurement of proton thermodynamics, J. Phys. Chem. C., 113, 12586-12593 (2009) 85.Xiao Y. and Malhotra S.V., Diels–Alder reactions in pyridinium based ionic liquids, Tetrahedron Lett., 45,8339-8342 (2004) 86.Handy S.T., Grignard Reactions in imidazolium ionic liquids, J. Org. Chem., 71, 4659-4662 (200687.Anjaiah S., Chandrasekhar S. and Gree R., Carbon-Ferrier rearrangements in ionic liquids using Yb(OTf) as catalyst, J. Mol. Catal. A: Chem., 214, 133-136 (2004) 88.Mastrorili P., Nobile C.F., Paolillo R. and Suranna G.P., Catalytic Pauson–Khand reaction in ionic liquids, J. Mol. Catal. A: Chem., 214, 103-106 (2004) 89.Lombardo M., Chiarucci M. and Trombini C., A recyclable triethylammonium ion-tagged diphenylphosphine palladium complex for the Suzuki–Miyaura reaction in ionic liquids, Green Chem., 11, 574-579 (2009) 90.Shen Z.L., Zhou W.J., Liu Y.T., Ji S.J. and Loh T.P., One-pot chemoenzymatic syntheses of enantiomerically-enriched -acetyl cyanohydrins from aldehydes in ionic liquid, Green Chem., 10, 283- 286 (2008) 91.Feng L.C., Sun Y.W., Tang W.J., Xiu L.J., Lam K.L.,Zhou Z. and Chan A.S.C., Highly efficient chemoselective construction of 2,2-dimethyl-6-substituted 4-piperidones via multicomponent tandem Mannich reaction in ionic liquids, Green Chem., 12, 949-952 (2010) 92.Singh D., Narayanaperumal S., Gul K., Godoi M., Rodrigues O.E.D. and Braga A.L., Efficient synthesis of selenoesters from acyl chlorides mediated by CuO nanopowder in ionic liquid, Green Chem., 12, 957-960 2010) 93.Fukuyama T., Inouye T. and Ryu I., Atom transfer carbonylation using ionic liquids as reaction media, J. Organomet. Chem., 692, 685-690 (2007) 94.Chang S.U., Cho J.H. and Lee J.C., Efficient Oxidation of Benzylic Alcohols to Aldehydes and Ketones in Ionic Research Journal of Chemical Sciences ___________________________________________________________ ISSN 2231-606XVol. 5(3), 77-89, March (2015) Res. J. Chem. Sci. International Science Congress Association 89 Liquid Using N-Chlorosuccinimide/AlCl·6HO, Bull. Korean Chem. Soc., 29, 27-28 (2008) 95.Klingshirn M.A., Broker G.A., Holbrey J.D., Shaughnessy K.H. and Rogers, R.D., Polar, non-coordinating ionic liquids as solvents for the alternating copolymerization of styrene and CO catalyzed by cationic palladium catalysts, Chem. Commun., 1394-1395 2002) 96.Singh V., Ratti R. and Kaur S., Synthesis and characterization of recyclable and recoverable MMT-clay exchanged ammonium tagged carbapalladacycle catalyst for Mizoroki–Heck and Sonogashira reactions in ionic liquid media, J. Mol. Catal. A: Chem.,334, 13-19 (2011) 97.Phan N.T.S., Le K.K.A., Nguyen T.V. and Le N.T.H., Chitosan as a renewable heterogeneous catalyst for the Knoevenagel reaction in ionic liquid as Green Solvent. ISRN Org. Chem., Article ID 928484, 9, (2012)98.Schenzel A., Hufendiek. A, Kowollik C.B. and Meier M.A.R., Catalytic transesterification of cellulose in ionic liquids: Sustainable access to cellulose esters, Green Chem., 16, 3266-3271 (2014) 99.Sekhon B.S., Ionic Liquids: Pharmaceutical and biotechnological applications, Asian J. Pharma. Biol. Res., , 395-411 (2011) 100.Swapnil D.A., Ionic Liquids: The green solvents for petroleum and hydrocarbon industries, Res. J. Chem. Sci., 2, 80-85 (2012) 101.Siodmiak T., Marszall M.P. and Proszowska A., Ionic Liquids: A new strategy in pharmaceutical synthesis, Mini Rev. Org. Chem., 9, 1-6 (2012) 102.http://www.basf.com/group/corporate/en/innovations/innovationaward/2004/basil., (2004)103.Rogers R.D. and Seddon K.R., Ionic Liquids: Solvents of the future?, Science, 302, 792-793 (2003) 104.Hoff A., Jost C., Schwab A.P., Schmidt F.G., Weyershausen, B. Ionic Liquids: New designer compounds for more efficient chemistry, Elements: Degussa Sci. New. lett., 9, 10-15 (2004)