Polyethylene Glycol as a Green and Biocompatible Reaction Media for the Catalyst Free Synthesis of Organic Compounds

Rezvan       Kardooni; Ali    Reza    Kiasat
Abstract

Replacing harmful organic solvents that caused environmental pollution with an alternative medium for the development of ideal synthetic strategies is one of the primary focal points of green chemistry. Utilizing polyethylene glycol (PEG) as a nonvolatile solvent and promotor for the evaluation of safe processes has made a considerable contribution to the reduction of pollution problems. The current review summarizes the recent well-known catalyst-free organic reaction performed in polyethylene glycol as a green and biocompatible reaction medium.
Keywords: Polyethylene glycol, catalyst-free, organic compounds, green synthesis, reaction media, non-volatile solvent.
Graphical Abstract

[1] 
Safari, E.; Maryamabadi, A.; Hasaninejad, A. Highly efficient, one-pot synthesis of novel bis-spirooxindoles with skeletal diversity via sequential multi-component reaction in PEG-400 as a biodegradable solvent. RSC Advances,  2017, 7(63), 39502-39511.
[http://dx.doi.org/10.1039/C7RA06017C] 
[2] 
Sharma, N.; Sharma, P.; Bhagat, S. Eco-friendly reactions in PEG-400: a highly efficient and green approach for stereoselective access to multisubstituted 3,4-dihydro-2 (1H)-quinazolines using 2-aminobenzylamines. RSC Advances,  2018, 8(16), 8721-8731.
[http://dx.doi.org/10.1039/C7RA13487H] 
[3] 
Chen, J.; Spear, S.K.; Huddleston, J.G.; Rogers, R.D. Polyethylene glycol and solutions of polyethylene glycol as green reaction media. Green Chem.,  2005, 7(2), 64-82.
[http://dx.doi.org/10.1039/b413546f] 
[4] 
Patil, A.; Gajare, S.; Rashinkar, G.; Salunkhe, R. β-CD-SO3H: Synthesis, characterization and its application for the synthesis of benzylpyrazolyl naphthoquinone and pyrazolo pyranopyrimidine derivatives in water. Catal. Lett.,  2020, 150(1), 127-137.
[http://dx.doi.org/10.1007/s10562-019-02928-y] 
[5] 
Vafaeezadeh, M.; Hashemi, M.M. Polyethylene glycol (PEG) as a green solvent for carbon–carbon bond formation reactions. J. Mol. Liq.,  2015, 207, 73-79.
[http://dx.doi.org/10.1016/j.molliq.2015.03.003] 
[6] 
Patil, A.; Lohar, T.; Mane, A.; Kamat, S.; Salunkhe, R. Deep eutectic solvent an efficient reaction medium for the synthesis of chromeno pyrazolo and indazolo phthalazine derivatives. J. Heterocycl. Chem.,  2019, 56(11), 3145-3151.
[http://dx.doi.org/10.1002/jhet.3713] 
[7] 
Patil, A.; Mane, A.; Kamat, S.; Lohar, T.; Salunkhe, R. Aqueous hydrotropic solution: green reaction medium for synthesis of pyridopyrimidine carbonitrile and spiro-oxindole dihydroquinazolinone derivatives. Res. Chem. Intermed.,  2019, 45(6), 3441-3452.
[http://dx.doi.org/10.1007/s11164-019-03801-8] 
[8] 
Kumar, R.; Chaudhary, P.; Nimesh, S.; Chandra, R. Polyethylene glycol as a non-ionic liquid solvent for Michael addition reaction of amines to conjugated alkenes. Green Chem.,  2006, 8(4), 356-358.
[http://dx.doi.org/10.1039/b517397c] 
[9] 
Sheldon, R.A. Green solvents for sustainable organic synthesis: state of the art. Green Chem.,  2005, 7(5), 267-278.
[http://dx.doi.org/10.1039/b418069k] 
[10] 
Kunz, W.; Häckl, K. The hype with ionic liquids as solvents. Chem. Phys. Lett.,  2016, 661, 6-12.
[http://dx.doi.org/10.1016/j.cplett.2016.07.044] 
[11] 
Rajanarendar, E.; Govardhan Reddy, K.; Nagi Reddy, M.; Raju, S.; Rama Murthy, K. Polyethylene glycol (PEG) mediated synthesis of pyrrolo-[2,3-d] isoxazoles by using NaOCl reagent- a green chemistry approach. Green Chem. Lett. Rev.,  2011, 4(3), 257-260.
[http://dx.doi.org/10.1080/17518253.2011.560126] 
[12] 
Shedge, A.S.; Kavitake, B.P.; Desai, U.V.; Wadgaonkar, P.P. A simple method for synthesis of methylene dioximes using poly (ethylene glycol)‐400 as a phase transfer catalyst. Synth. Commun.,  2004, 34(24), 4483-4486.
[http://dx.doi.org/10.1081/SCC-200043184] 
[13] 
Balasubramanian, D.; Chandani, B. Poly (ethylene glycol): a poor chemist’s crown. J. Chem. Educ.,  1983, 60(1), 77-78.
[http://dx.doi.org/10.1021/ed060p77] 
[14] 
Alessi, M.L.; Norman, A.I.; Knowlton, S.E.; Ho, D.L.; Greer, S.C. Helical and coil conformations of poly (ethylene glycol) in isobutyric acid and water. Macromolecules,  2005, 38(22), 9333-9340.
[http://dx.doi.org/10.1021/ma051339e] 
[15] 
Kardooni, R.; Kiasat, A.R. Bifunctional PEG/NH2 silica-coated magnetic nanocomposite: An efficient and recoverable core-shell-structured catalyst for one pot multicomponent synthesis of 3-alkylated indoles via Yonemitsu-type condensation. J. Taiwan Inst. Chem. Eng.,  2018, 87, 241-251.
[http://dx.doi.org/10.1016/j.jtice.2018.03.029] 
[16] 
Patil, A.; Salunkhe, R. Metal free green protocol for the synthesis of bis-spiro piperidine and pyrimidine derivatives. Res. Chem. Intermed.,  2018, 44(5), 3337-3348.
[http://dx.doi.org/10.1007/s11164-018-3310-7] 
[17] 
Shinde, P.V.; Kategaonkar, A.H.; Shingate, B.B.; Shingare, M.S. Polyethylene glycol (PEG) mediated expeditious synthetic route to 1,3-oxazine derivatives. Chin. Chem. Lett.,  2011, 22(8), 915-918.
[http://dx.doi.org/10.1016/j.cclet.2011.01.011] 
[18] 
Kardooni, R.; Kiasat, A.R.; Motamedi, H. Designing of a novel dual-function silica-iron oxide hybrid based nanocomposite, Fe3O4@SiO2-PEG/NH2, and its application as an eco-catalyst for the solvent-free synthesis of polyhydroacridines and polyhydroquinolines. J. Taiwan Inst. Chem. Eng.,  2017, 81, 373-382.
[http://dx.doi.org/10.1016/j.jtice.2017.10.013] 
[19] 
Kardooni, R.; Kiasat, A.R.; Eskandari Sabzi, N. Hyper-cross-linked β-cyclodextrin nanosponge: a three-dimensional, porous and biodegradable catalyst in the one-pot synthesis of kojic acid-based heterocyclic compounds. Res. Chem. Intermed.,  2020, 46(3), 1857-1868.
[http://dx.doi.org/10.1007/s11164-019-04067-w] 
[20] 
Jain, S.L.; Singhal, S.; Sain, B. PEG-assisted solvent and catalyst free synthesis of 3,4-dihydropyrimidinones under mild reaction conditions. Green Chem.,  2007, 9(7), 740-741.
[http://dx.doi.org/10.1039/b702311a] 
[21] 
Kamble, V.T.; Davane, B.S.; Chavan, S.A.; Bhosale, R.B. An efficient and green procedure for the preparation of 2-2-[N′-(2-hydroxybenzylidene) hydrazino] thiazol-4-yl phenols. Aust. J. Chem.,  2007, 60(4), 302-304.
[http://dx.doi.org/10.1071/CH06377] 
[22] 
Wang, X.C.; Gong, H.P.; Quan, Z.J.; Li, L.; Ye, H.L. PEG-400 as an efficient reaction medium for the synthesis of 2,4,5-triaryl-1H-imidazoles and 1,2,4, 5-tetraaryl-1H-imidazoles. Chin. Chem. Lett.,  2009, 20(1), 44-47.
[http://dx.doi.org/10.1016/j.cclet.2008.10.005] 
[23] 
Nalage, V.S.P.; Nikum, A.B.; Kalyankar, M.S.; Patil, V.D.; Patil, U.R.; Desale, K.L.; Patil, S.V.; Bhosale, S. One-pot four component synthesis of 4, 6-disubstituted 3-cyano-2-pyridones in polyethylene glycol. Lett. Org. Chem.,  2010, 7(5), 406.
[http://dx.doi.org/10.2174/157017810791514832] 
[24] 
Dawane, B.S.; Konda, S.G.; Bodade, R.G.; Bhosale, R.B. An efficient one‐pot synthesis of some new 2,4‐diaryl pyrido [3,2‐c] coumarins as potent antimicrobial agents. J. Heterocycl. Chem.,  2010, 47(1), 237-241.
[25] 
Das, B.; Sudhakar, C.; Srinivas, Y. Efficient synthesis of 5-substituted 2,3-diphenyl and 5-substituted 1-aryl-2, 3-diphenyl imidazoles using polyethylene glycol. Synth. Commun.,  2010, 40(18), 2667-2675.
[http://dx.doi.org/10.1080/00397910903318633] 
[26] 
Mallepalli, R.; Yeramanchi, L.; Bantu, R.; Nagarapu, L. Polyethylene glycol (PEG-400) as an efficient and recyclable reaction medium for the one-pot synthesis of N-substituted azepines under catalyst-free conditions. Synlett,  2011, 2011(18), 2730-2732.
[http://dx.doi.org/10.1055/s-0031-1289542] 
[27] 
Kidwai, M.; Mishra, N.K.; Bhatnagar, D.; Jahan, A. A green methodology for one-pot synthesis of polysubstituted-tetrahydropyrimidines using PEG. Green Chem. Lett. Rev.,  2011, 4(2), 109-115.
[http://dx.doi.org/10.1080/17518253.2010.512565] 
[28] 
Nagarapu, L.; Mallepalli, R.; Yeramanchi, L.; Bantu, R. Polyethylene glycol (PEG-400) as an efficient and recyclable reaction medium for one-pot synthesis of polysubstituted pyrroles under catalyst-free conditions. Tetrahedron Lett.,  2011, 52(26), 3401-3404.
[http://dx.doi.org/10.1016/j.tetlet.2011.04.095] 
[29] 
Wang, X.; Gong, H.; Quan, Z.; Li, L.; Ye, H. One-pot, three-component synthesis of 1,4-dihydropyridines in PEG-400. Synth. Commun.,  2011, 41(21), 3251-3258.
[http://dx.doi.org/10.1080/00397911.2010.517888] 
[30] 
Konkala, K.; Murthy, S.N.; Ramesh, K.; Satish, G.; Nanubolu, J.B.; Nageswar, Y. Polyethylene glycol (PEG-400): an efficient and recyclable reaction medium for the synthesis of pyrazolo [3,4-b] quinoline derivatives. Tetrahedron Lett.,  2012, 53(23), 2897-2903.
[http://dx.doi.org/10.1016/j.tetlet.2012.03.135] 
[31] 
Pal, S.; Singh, V.; Das, P.; Choudhury, L.H. PEG-mediated one-pot multicomponent reactions for the efficient synthesis of functionalized dihydropyridines and their functional group dependent DNA cleavage activity. Bioorg. Chem.,  2013, 48, 8-15.
[http://dx.doi.org/10.1016/j.bioorg.2013.03.003 PMID: 23639829] 
[32] 
Paidepala, H.; Nagendra, S.; Saddanappu, V.; Addlagatta, A.; Das, B. Catalyst-free efficient synthesis of polyhydroquinolines using polyethylene glycol as a solvent and evaluation of their cytotoxicity. Med. Chem. Res.,  2014, 23(2), 1031-1036.
[http://dx.doi.org/10.1007/s00044-013-0706-1] 
[33] 
Reddy, M.V.; Kim, J.S.; Lim, K.T.; Jeong, Y.T. Polyethylene glycol (PEG-400): an efficient green reaction medium for the synthesis of benzo [4,5] imidazo [1,2-a]-pyrimido [4,5-d] pyrimidin-4 (1H)-ones under catalyst-free conditions. Tetrahedron Lett.,  2014, 55(47), 6459-6462.
[http://dx.doi.org/10.1016/j.tetlet.2014.09.135] 
[34] 
Khan, M.N.; Karamthulla, S.; Choudhury, L.H.; Faizi, M.S.H. Ultrasound assisted multicomponent reactions: a green method for the synthesis of highly functionalized selenopyridines using reusable polyethylene glycol as reaction medium. RSC Advances,  2015, 5(28), 22168-22172.
[http://dx.doi.org/10.1039/C5RA02403J] 
[35] 
Rao, K.R.; Mekala, R.; Raghunadh, A.; Meruva, S.B.; Kumar, S.P.; Kalita, D.; Laxminarayana, E.; Prasad, B.; Pal, M. A catalyst-free rapid, practical and general synthesis of 2-substituted quinazolin-4 (3H)-ones leading to luotonin B and E, bouchardatine and 8-norrutaecarpine. RSC Advances,  2015, 5(76), 61575-61579.
[http://dx.doi.org/10.1039/C5RA10928K] 
[36] 
Maryamabadi, A.; Hasaninejad, A.; Nowrouzi, N.; Mohebbi, G.; Asghari, B. Application of PEG-400 as a green biodegradable polymeric medium for the catalyst-free synthesis of spiro-dihydropyridines and their use as acetyl and butyrylcholinesterase inhibitors. Bioorg. Med. Chem.,  2016, 24(6), 1408-1417.
[http://dx.doi.org/10.1016/j.bmc.2016.02.019 PMID: 26879857] 
[37] 
Penumati, N.R.; Rajaka, L.; Kommu, N. PEG-400 as an efficient and recyclable reaction medium for the synthesis of 2-aryl-2-methyl-4,5-diphenyl-2,3-dihydro-2H-imidazoles. Synth. Commun.,  2016, 46(4), 367-373.
[http://dx.doi.org/10.1080/00397911.2016.1139721] 
[38] 
Mallepalli, R.; Vennam, D.K.R.; Perali, R.S. PEG-400 mediated sp3 CH functionalization of aza-arenes: an enroute to the synthesis of 2-(2-(6-methylpyridin/quinolin-2-yl)-1-phenylethyl) malononitriles. Tetrahedron Lett.,  2016, 57(41), 4541-4543.
[http://dx.doi.org/10.1016/j.tetlet.2016.08.083] 
[39] 
Firoj Basha, S.; Prasad, T.N.; Gudise, V.B.; Kumar, V.S.; Mulakayala, N.; Anwar, S. An efficient, multicomponent, green protocol to access 4,7-dihydrotetrazolo [1,5-a] pyrimidines and 5,6,7,9-tetrahydrotetrazolo[5,1-b]quinazolin-8(4H)-ones using PEG-400 under microwave irradiation. Synth. Commun.,  2019, 49(22), 3181-3190.
[http://dx.doi.org/10.1080/00397911.2019.1659973] 
[40] 
Maryamabadi, A.; Hasaninejad, A.; Nowrouzi, N.; Mohebbi, G. Green synthesis of novel spiro-indenoquinoxaline derivatives and their cholinesterases inhibition activity. Bioorg. Med. Chem.,  2017, 25(7), 2057-2064.
[http://dx.doi.org/10.1016/j.bmc.2017.02.017 PMID: 28279561] 
[41] 
Kardooni, R.; Kiasat, A.R. Polyethylene glycol (PEG-400): a green reaction medium for one-pot, three component synthesis of 3-substituted indoles under catalyst free conditions. Polycycl. Aromat. Compd.,  2019, 2019, 1-9.
[http://dx.doi.org/10.1080/10406638.2019.1703764] 
[42] 
Reddy, B.S.; Somashekar, D.; Reddy, A.M.; Yadav, J.; Sridhar, B. PEG-400 as a reusable solvent for 1,4-dipolar cycloadditions via a three-component reaction. Synthesis,  2010, 2010(12), 2069-2074.
[http://dx.doi.org/10.1055/s-0029-1218762] 
[43] 
Shitole, N.V.; Shelke, K.F.; Sadaphal, S.A.; Shingate, B.B.; Shingare, M.S. PEG-400 remarkably efficient and recyclable media for one-pot synthesis of various 2-amino-4H-chromenes. Green Chem. Lett. Rev.,  2010, 3(2), 83-87.
[http://dx.doi.org/10.1080/17518250903567246] 
[44] 
Das, B.; Balasubramanyam, P.; Chinna Reddy, G.; Salvanna, N. Simple, efficient, and catalyst‐free synthesis of (2‐amino‐4H‐1‐benzopyran‐4‐yl) phosphonates in polyethylene glycol. Helv. Chim. Acta,  2011, 94(7), 1347-1350.
[http://dx.doi.org/10.1002/hlca.201000461] 
[45] 
Meshram, H.M.; Kumar, D.A.; Prasad, B.R.V.; Goud, P.R. Efficient and convenient polyethylene glycol (PEG)‐mediated synthesis of spiro‐oxindoles. Helv. Chim. Acta,  2010, 93(4), 648-653.
[http://dx.doi.org/10.1002/hlca.200900273] 
[46] 
Bhosle, M.R.; Mali, J.R.; Mulay, A.A.; Mane, R.A. Polyethylene glycol mediated one‐pot three‐component synthesis of new 4‐thiazolidinones. Heteroatom Chem.,  2012, 23(2), 166-170.
[http://dx.doi.org/10.1002/hc.20766] 
[47] 
Pandey, S.K.; Ahamd, A.; Pandey, O.; Nizamuddin, K. Polyethylene glycol mediated, one‐pot, three‐component synthetic protocol for novel 3‐[3‐substituted‐5‐mercapto‐1,2,4‐triazol‐4‐yl]‐spiro‐(indan‐1′, 2‐thiazolidin)‐4‐ones as new class of potential antimicrobial and antitubercular agents. J. Heterocycl. Chem.,  2014, 51(5), 1233-1239.
[http://dx.doi.org/10.1002/jhet.1605] 
[48] 
Karnakar, K.; Ramesh, K.; Reddy, K.H.V.; Kumar, B.A.; Nanubonula, J.B.; Nageswar, Y. A novel one pot four-component reaction for the efficient synthesis of spiro [indoline-3,4′-pyrano [2,3-c] pyrazole]-3′-carboxylate and trifluoromethylated spiro [indole-3,4′-pyrano [2,3-c] pyrazole] derivatives using recyclable PEG-400. New J. Chem.,  2015, 39(11), 8978-8983.
[http://dx.doi.org/10.1039/C5NJ01448D] 
[49] 
Modugu, N.R.; Pittala, P.K. Polyethylene glycol (PEG-400) promoted as an efficient and recyclable reaction medium for the one-pot eco-friendly synthesis of functionalized isoxazole substituted spirooxindole derivatives. New J. Chem.,  2017, 41(23), 14062-14066.
[http://dx.doi.org/10.1039/C7NJ03515B] 
[50] 
Raut, D.G.; Bhosale, R.B. One-pot PEG-mediated syntheses of 2-(2-hydrazinyl) thiazole derivatives: novel route. J. Sulfur Chem.,  2018, 39(1), 1-7.
[http://dx.doi.org/10.1080/17415993.2017.1371175] 
[51] 
Kardooni, R.; Kiasat, A.R. A green, catalyst-free synthesis of pyrazolopyranopyrimidines in polyethylene glycol as a biodegradable medium at ambient temperature. Mol. Divers.,  2019, 23(3), 639-649.
[http://dx.doi.org/10.1007/s11030-018-9898-0 PMID: 30547372] 
[52] 
Sujatha, K.; Vedula, R.R. Polyethylene glycol (PEG-400) promoted one-pot, five-component synthesis of (E)-ethyl2-(2-((E)-2-(1-(4-methyl-2-(phenyl-amino)thiazol-5yl)ethylidene)hydrazinyl)-4-oxothiazol-5(4H)-ylidene)aceta-tes. Mol. Divers.,  2019, 2019, 1-9.
[http://dx.doi.org/10.1007/s11030-019-09962-3 PMID: 31123896] 
[53] 
Zeynizadeh, B.; Dilmaghani, K.A.; Yari, M. NaHSO4‧H2O as a heterogeneous acidic reagent for mild and convenient synthesis of 3,4-dihydropyrimidin-2 (1H)-ones and their sulfur derivatives. Phosphorus. Sulfur Relat. Elem.,  2009, 184(9), 2465-2471.
[http://dx.doi.org/10.1080/10426500802501274] 
[54] 
Ramalingan, C.; Kwak, Y-W. Tetrachlorosilane catalyzed multicomponent one-step fusion of biopertinent pyrimidine heterocycles. Tetrahedron,  2008, 64(22), 5023-5031.
[http://dx.doi.org/10.1016/j.tet.2008.03.078] 
[55] 
Srinivas, K.V.N.S.; Das, B. Iodine catalyzed one-pot synthesis of 3,4-dihydropyrimidin-2(1H)-ones and thiones: a simple and efficient procedure for the Biginelli reaction. Synthesis,  2004, 2004(13), 2091-2093.
[http://dx.doi.org/10.1055/s-2004-829170] 
[56] 
Kumar, V.N.; Kumar, B.S.; Reddy, P.N.; Reddy, Y.T.; Rajitha, B. Selectfluor™ catalyzed one pot synthesis of dihydropyrimidinones: an improved protocol for the biginelli reaction. Heterocycl. Commun.,  2007, 13(1), 29-32.
[http://dx.doi.org/10.1515/HC.2007.13.1.29] 
[57] 
Rafiee, E.; Jafari, H. A practical and green approach towards synthesis of dihydropyrimidinones: using heteropoly acids as efficient catalysts. Bioorg. Med. Chem. Lett.,  2006, 16(9), 2463-2466.
[http://dx.doi.org/10.1016/j.bmcl.2006.01.087 PMID: 16464580] 
[58] 
Reddy, C.V.; Mahesh, M.; Raju, P.V.K.; Babu, T.R.; Reddy, V.V.N. Zirconium(IV) chloride catalyzed one-pot synthesis of 3,4-dihydropyrimidin-2(1H)-ones. Tetrahedron Lett.,  2002, 43(14), 2657-2659.
[http://dx.doi.org/10.1016/S0040-4039(02)00280-0] 
[59] 
Kumar, K.A.; Kasthuraiah, M.; Reddy, C.S.; Reddy, C.D. Mn(OAc)3‧2H2O-mediated three-component, one-pot, condensation reaction: an efficient synthesis of 4-aryl-substituted 3,4-dihydropyrimidin-2-ones. Tetrahedron Lett.,  2001, 42(44), 7873-7875.
[http://dx.doi.org/10.1016/S0040-4039(01)01603-3] 
[60] 
Paraskar, A.S.; Dewkar, G.K.; Sudalai, A. Cu(OTf)2: a reusable catalyst for high-yield synthesis of 3,4-dihydropyrimidin-2(1H)-ones. Tetrahedron Lett.,  2003, 44(16), 3305-3308.
[http://dx.doi.org/10.1016/S0040-4039(03)00619-1] 
[61] 
Shen, M-G.; Cai, C.; Yi, W-B. Ytterbium perfluorooctanesulfonate as an efficient and recoverable catalyst for the synthesis of trisubstituted imidazoles. J. Fluor. Chem.,  2008, 129(6), 541-544.
[http://dx.doi.org/10.1016/j.jfluchem.2008.03.009] 
[62] 
Safari, J.; Zarnegar, Z. A highly efficient magnetic solid acid catalyst for synthesis of 2,4,5-trisubstituted imidazoles under ultrasound irradiation. Ultrason. Sonochem.,  2013, 20(2), 740-746.
[http://dx.doi.org/10.1016/j.ultsonch.2012.10.004 PMID: 23137656] 
[63] 
Khaksar, S.; Alipour, M. Lewis acid catalyst free synthesis of substituted imidazoles in 2,2,2-trifluoroethanol. Monatsh. Chem.,  2013, 144(3), 395-398.
[http://dx.doi.org/10.1007/s00706-012-0834-1] 
[64] 
Khoshneviszadeha, M.; Mahdavib, M. Appel reagent as novel promoter for
the synthesis of polysubstituted imidazoles. ARKIVOK, 2017, ((part iv)),
343-352. 
[65] 
Behbahani, F.K.; Yektanezhad, T.; Khorrami, A.R. Anhydrous FePO4: a green and cost-effective catalyst for the one-pot three component synthesis of 2,4,5-triarylated imidazoles. Heterocycles,  2010, 81(10), 2313-2321.
[http://dx.doi.org/10.3987/COM-10-12019] 
[66] 
Marques, M.V.; Ruthner, M.M.; Fontoura, L.A.; Russowsky, D. Metal chloride hydrates as Lewis acid catalysts in multicomponent synthesis of 2,4,5-triarylimidazoles or 2,4,5-triaryloxazoles. J. Braz. Chem. Soc.,  2012, 23(1), 171-179.
[http://dx.doi.org/10.1590/S0103-50532012000100024] 
[67] 
Mohammadi, A.A.; Mivechi, M.; Kefayati, H. Potassium aluminum sulfate (alum): an efficient catalyst for the one-pot synthesis of trisubstituted imidazoles. Monatsh. Chem.,  2008, 139(8), 935.
[http://dx.doi.org/10.1007/s00706-008-0875-7] 
[68] 
Peng, H-N.; Peng, X-M.; Zheng, D-G.; Yu, F.; Rao, M. Sulfamic acid as an efficient and cost-effective catalyst for the synthesis of 2,4,5-triarylimidazoles and 2-arylphenanthrimidazoles. Heterocycl. Commun.,  2011, 17(5-6), 223-226.
[http://dx.doi.org/10.1515/HC.2011.040] 
[69] 
Das, B.; Ravikanth, B.; Ramu, R.; Vittal Rao, B. An efficient one-pot synthesis of polyhydroquinolines at room temperature using HY-zeolite. Chem. Pharm. Bull. (Tokyo),  2006, 54(7), 1044-1045.
[http://dx.doi.org/10.1248/cpb.54.1044 PMID: 16819229] 
[70] 
Reddy, C.S.; Raghu, M. Cerium (IV) ammonium nitrate catalysed facile and efficient synthesis of polyhydroquinoline derivatives through Hantzsch multicomponent condensation. Chin. Chem. Lett.,  2008, 19(7), 775-779.
[http://dx.doi.org/10.1016/j.cclet.2008.04.040] 
[71] 
Rajini, A.; Nookaraju, M.; Reddy, I.A.K.; Narayanan, V. Vanadium dodecylamino phosphate: a novel efficient catalyst for synthesis of polyhydroquinolines. Chem. Pap.,  2014, 68(2), 170-179.
[http://dx.doi.org/10.2478/s11696-013-0441-6] 
[72] 
Saha, M.; Pal, A.K. Palladium(0) nanoparticles: an efficient catalyst for the one-pot synthesis of polyhydroquinolines. Tetrahedron Lett.,  2011, 52(38), 4872-4877.
[http://dx.doi.org/10.1016/j.tetlet.2011.07.031] 
[73] 
Kiyani, H.; Ghiasi, M. Solvent-free efficient one-pot synthesis of Biginelli and Hantzsch compounds catalyzed by potassium phthalimide as a green and reusable organocatalyst. Res. Chem. Intermed.,  2015, 41(8), 5177-5203.
[http://dx.doi.org/10.1007/s11164-014-1621-x] 
[74] 
Yü, S-J.; Wu, S.; Zhao, X-M.; Lü, C-W. Green and efficient synthesis of acridine-1,8-diones and hexahydroquinolines via a KH2PO4 catalyzed Hantzsch-type reaction in aqueous ethanol. Res. Chem. Intermed.,  2017, 43(5), 3121-3130.
[http://dx.doi.org/10.1007/s11164-016-2814-2] 
[75] 
Cherkupally, S.R.; Mekala, R. P-TSA catalyzed facile and efficient synthesis of polyhydroquinoline derivatives through hantzsch multi-component condensation. Chem. Pharm. Bull. (Tokyo),  2008, 56(7), 1002-1004.
[http://dx.doi.org/10.1248/cpb.56.1002 PMID: 18591819] 
[76] 
Hong, M.; Cai, C.; Yi, W-B. Hafnium (IV) bis(perfluorooctanesulfonyl) imide complex catalyzed synthesis of polyhydroquinoline derivatives via unsymmetrical Hantzsch reaction in fluorous medium. J. Fluor. Chem.,  2010, 131(1), 111-114.
[http://dx.doi.org/10.1016/j.jfluchem.2009.10.009] 
[77] 
Jin, T.S.; Zhang, J.S.; Liu, L.B.; Wang, A.Q.; Li, T.S. Clean, one‐pot synthesis of naphthopyran derivatives in aqueous media. Synth. Commun.,  2006, 36(14), 2009-2015.
[http://dx.doi.org/10.1080/00397910600632096] 
[78] 
Heravi, M.M.; Bakhtiari, K.; Zadsirjan, V.; Bamoharram, F.F.; Heravi, O.M. Aqua mediated synthesis of substituted 2-amino-4H-chromenes catalyzed by green and reusable Preyssler heteropolyacid. Bioorg. Med. Chem. Lett.,  2007, 17(15), 4262-4265.
[http://dx.doi.org/10.1016/j.bmcl.2007.05.023 PMID: 17537629] 
[79] 
Heravi, M.M.; Baghernejad, B.; Oskooie, H.A. A novel and efficient catalyst to one‐pot synthesis of 2‐amino‐4H‐chromenes by methanesulfonic acid. J. Chin. Chem. Soc. (Taipei),  2008, 55(3), 659-662.
[http://dx.doi.org/10.1002/jccs.200800098] 
[80] 
Han, G.F.; Wang, M.; Jin, Y.; Chen, L.Z. Synthesis and characterization of benzochromeno [2,3‐b] tetrahydroquinolinone derivatives. J. Heterocycl. Chem.,  2014, 51(3), 648-655.
[http://dx.doi.org/10.1002/jhet.1101] 
[81] 
Verma, S.; Jain, S.L. Thiourea dioxide catalyzed multi-component coupling reaction for the one step synthesis of naphthopyran derivatives. Tetrahedron Lett.,  2012, 53(45), 6055-6058.
[http://dx.doi.org/10.1016/j.tetlet.2012.08.118] 
[82] 
Eshghi, H.; Damavandi, S.; Zohuri, G. Efficient one-pot synthesis of 2-amino-4 H-chromenes catalyzed by ferric hydrogen sulfate and Zr-based catalysts of FI. Synth. React. Inorg. Met.-Org. Nano-Met. Chem.,  2011, 41(9), 1067-1073.
[http://dx.doi.org/10.1080/15533174.2011.591347] 
[83] 
Monadi, N.; Moradi, E. A molybdenum(VI) Schiff base complex immobilized on functionalized Fe3O4 nanoparticles as a recoverable nanocatalyst for synthesis of 2-amino-4H-benzo[h]chromenes. Synth. React. Inorg. Met.-Org. Nano-Met. Chem.,  2018, 43(2), 161-170.
[84] 
Farahi, M.; Karami, B.; Alipour, S.; Moghadam, L.T. Silica tungstic acid as an efficient and reusable catalyst for the one-pot synthesis of 2-amino-4H-chromene derivatives. Acta Chim. Slov.,  2014, 61(1), 94-99.
[PMID: 24664332] 
[85] 
Wang, G.D.; Zhang, X.N.; Zhang, Z.H. One‐pot three‐component synthesis of spirooxindoles catalyzed by hexamethylenetetramine in water. J. Heterocycl. Chem.,  2013, 50(1), 61-65.
[http://dx.doi.org/10.1002/jhet.994] 
[86] 
Jamatia, R.; Gupta, A.; Pal, A.K. Nano-FGT: a green and sustainable catalyst for the synthesis of spirooxindoles in aqueous medium. RSC Advances,  2016, 6(25), 20994-21000.
[http://dx.doi.org/10.1039/C5RA27552K] 
[87] 
Esmaeilpour, M.; Javidi, J.; Divar, M. A green one-pot three-component synthesis of spirooxindoles under conventional heating conditions or microwave irradiation by using Fe3O4@SiO2-imid-PMAn magnetic porous nanospheres as a recyclable catalyst. J. Magn. Magn. Mater.,  2017, 423, 232-240.
[http://dx.doi.org/10.1016/j.jmmm.2016.09.020] 
[88] 
Zhu, S-L.; Ji, S-J.; Zhang, Y. A simple and clean procedure for three-component synthesis of spirooxindoles in aqueous medium. Tetrahedron,  2007, 63(38), 9365-9372.
[http://dx.doi.org/10.1016/j.tet.2007.06.113] 
[89] 
Sridhar, R.; Srinivas, B.; Madhav, B.; Reddy, V.P.; Nageswar, Y.V.D.; Rao, K.R. Multi-component supramolecular synthesis of spirooxindoles catalyzed by β-cyclodextrin in water. Can. J. Chem.,  2009, 87(12), 1704-1707.
[http://dx.doi.org/10.1139/V09-137] 
[90] 
Li, Y.; Chen, H.; Shi, C.; Shi, D.; Ji, S. Efficient one-pot synthesis of spirooxindole derivatives catalyzed by L-proline in aqueous medium. J. Comb. Chem.,  2010, 12(2), 231-237.
[http://dx.doi.org/10.1021/cc9001185 PMID: 20085353] 
[91] 
Azizi, N.; Dezfooli, S.; Mahmoudi Hashemi, M. Greener synthesis of spirooxindole in deep eutectic solvent. J. Mol. Liq.,  2014, 194, 62-67.
[http://dx.doi.org/10.1016/j.molliq.2014.01.009] 
[92] 
Mobinikhaledi, A.; Jabbarpour, M. A facile multi component synthesis of some functionalized chromenes and spiroindole derivatives using dabco as an efficient catalyst. J. Chem. Soc. Pak.,  2013, 35(4), 1211-1218.
[93] 
Kiasat, A.; Mehrjardi, M.F. An efficient catalyst-free ring opening of epoxides in peg-300: a versatile method for the synthesis of vicinal azidoalcohols. J. Iran. Chem. Soc.,  2009, 6(3), 542-546.
[http://dx.doi.org/10.1007/BF03246533] 
[94] 
Mehrjardi, M.F.; Kiasat, A.R.; Niknam, K. Nucleophilic ring-opening of epoxides: trends in β-substituted alcohols synthesis. J. Iran. Chem. Soc.,  2018, 15(9), 2033-2081.
[http://dx.doi.org/10.1007/s13738-018-1400-5] 
[95] 
Das, B.; Reddy, V.S.; Krishnaiah, M. An efficient catalyst-free synthesis of thiiranes from oxiranes using polyethylene glycol as the reaction medium. Tetrahedron Lett.,  2006, 47(48), 8471-8473.
[http://dx.doi.org/10.1016/j.tetlet.2006.09.153] 
[96] 
Das, B.; Reddy, V.S.; Tehseen, F.; Krishnaiah, M. Catalyst-free highly regio-and stereoselective ring opening of epoxides and aziridines with sodium azide using poly (ethylene glycol) as an efficient reaction medium. Synthesis,  2007, 2007(05), 666-668.
[http://dx.doi.org/10.1055/s-2007-965921] 
[97] 
Das, B.; Krishnaiah, M.; Thirupathi, P.; Laxminarayana, K. An efficient catalyst-free regio-and stereoselective ring-opening of epoxides with phenoxides using polyethylene glycol as the reaction medium. Tetrahedron Lett.,  2007, 48(24), 4263-4265.
[http://dx.doi.org/10.1016/j.tetlet.2007.04.062] 
[98] 
Kiasat, A.R.; Fallah-Mehrjardi, M. Polyethylene glycol: a cheap and efficient medium for the thiocyanation of alkyl halides. Bull. Korean Chem. Soc.,  2008, 29(12), 2346-2348.
[http://dx.doi.org/10.5012/bkcs.2008.29.12.2346] 
[99] 
Zeng, H.; Tian, Q.; Shao, H. PEG-400 promoted nucleophilic substitution reaction of halides into organic azides under mild conditions. Green Chem. Lett. Rev.,  2011, 4(3), 281-287.
[http://dx.doi.org/10.1080/17518253.2011.571717] 
[100] 
Guravaiah, N.; Rao, V.R. Facile polyethylene glycol (PEG-400) promoted synthesis of some new heteryl (E)-styryl sulfones. J. Chem. Res.,  2009, 2009(4), 237-239.
[http://dx.doi.org/10.3184/030823409X430176] 
[101] 
Suryakiran, N.; Reddy, T.S.; Ashalatha, K.; Lakshman, M.; Venkateswarlu, Y. Facile polyethylene glycol (PEG-400) promoted synthesis of β-ketosulfones. Tetrahedron Lett.,  2006, 47(23), 3853-3856.
[http://dx.doi.org/10.1016/j.tetlet.2006.03.181] 
[102] 
Siddaiah, V.; Basha, G.M.; Srinuvasarao, R.; Yessayya, V. Polyethylene glycol mediated facile protocol for N-Cbz protection of amines. Green Chem. Lett. Rev.,  2012, 5(3), 337-342.
[http://dx.doi.org/10.1080/17518253.2011.633567] 
[103] 
Zhang, C.L.; Zhang, D.F.; Zhao, H.Y.; Lin, Z.Y.; Huang, H.H. A facile protocol for N-Cbz protection of amines in PEG-600. Chin. Chem. Lett.,  2012, 23(7), 789-792.
[http://dx.doi.org/10.1016/j.cclet.2012.05.012] 
[104] 
Zeng, H.; Shao, H. Convenient synthesis of sulfonyl azides using PEG-400 as an efficient and eco-friendly reaction medium. Green Chem. Lett. Rev.,  2013, 6(3), 222-227.
[http://dx.doi.org/10.1080/17518253.2012.750688] 
[105] 
Reddy, Y.D.; Kumar, P.P.; Devi, B.R.; Dubey, P.K.; Kumari, Y.B. PEG-600 mediated facile and green synthesis of novel imide derivatives and their biological activity evaluation. Lett. Drug Des. Discov.,  2013, 10(3), 226-238.
[106] 
Naidu, M.K.R.; Dadapeer, E.; Reddy, C.B.; Rao, A.J.; Reddy, C.S.; Raju, C.N. Polyethylene glycol-promoted dialkyl, aryl/heteroaryl phosphonates. Synth. Commun.,  2011, 41(23), 3462-3468.
[http://dx.doi.org/10.1080/00397911.2010.518279] 
[107] 
Zeng, H.; Li, Y.; Shao, H. Simple and efficient method for N-boc protection of amines using PEG-400 as a reaction medium under mild conditions. Synth. Commun.,  2012, 42(1), 25-32.
[http://dx.doi.org/10.1080/00397911.2010.520831] 
[108] 
Close, A.J.; Kemmitt, P.; Emmerson, M.K.; Spencer, J. Microwave-mediated synthesis of N-methyliminodiacetic acid (MIDA) boronates. Tetrahedron,  2014, 70(47), 9125-9131.
[http://dx.doi.org/10.1016/j.tet.2014.09.044] 
[109] 
Xing, T.; Wei, K-J.; Quan, Z-J.; Wang, X-C. Nucleophilic substitution reaction of pyrimidin-2-yl phosphates using amines and thiols as nucleophiles mediated by PEG-400 as an environmentally friendly solvent. Synthesis,  2015, 47(24), 3925-3935.
[http://dx.doi.org/10.1055/s-0035-1560175] 
[110] 
Campos, J.F.; Loubidi, M.; Scherrmann, M-C.; Raboin, S.B. A greener and efficient method for nucleophilic aromatic substitution of nitrogen-containing fused heterocycles. Molecules,  2018, 23(3), 684.
[http://dx.doi.org/10.3390/molecules23030684 PMID: 29562645] 
[111] 
Dubey, P.; Venkatanarayana, M. PEG-600: a facile and eco-friendly reaction medium for the synthesis of N-alkyl derivatives of indole-3-carboxyalde-hyde. Green Chem. Lett. Rev.,  2010, 3(4), 257-261.
[http://dx.doi.org/10.1080/17518251003749379] 
[112] 
Rao, A.H.; Babu, P.K.; Rao, V.L.; Shree, A.J. PEG-600 Mediated phase transfer catalyst free N-alkylations of 2-butyl-5-chloro-1H-imidazole-4-carbaldehyde. Asian J. Chem.,  2015, 27(5), 1910.
[http://dx.doi.org/10.14233/ajchem.2015.18495] 
[113] 
Cho, B.T.; Kang, S.K.; Shin, S.H. Application of optically active 1,2-diol monotosylates for synthesis of β-azido and β-amino alcohols with very high enantiomeric purity. Synthesis of enantiopure (R)-octopamine, (R)-tembamide and (R)-aegeline. Tetrahedron Asymmetry,  2002, 13(11), 1209-1217.
[http://dx.doi.org/10.1016/S0957-4166(02)00322-1] 
[114] 
Chini, M.; Crotti, P.; Macchia, F. Efficient metal salt catalyzed azidolysis of epoxides with sodium azide in acetonitrile. Tetrahedron Lett.,  1990, 31(39), 5641-5644.
[http://dx.doi.org/10.1016/S0040-4039(00)97921-8] 
[115] 
Sabitha, G.; Babu, R.S.; Rajkumar, M.; Yadav, J.S. Cerium(III) chloride promoted highly regioselective ring opening of epoxides and aziridines using NaN3 in acetonitrile: a facile synthesis of 1,2-azidoalcohols and 1,2-azidoamines. Org. Lett.,  2002, 4(3), 343-345.
[http://dx.doi.org/10.1021/ol016979q PMID: 11820875] 
[116] 
Yadollahi, B.; Danafar, H. A facile synthesis of 1,2-azidoalcohols by (TBA)4PFeW11O39‧3H2O-catalyzed azidolysis of epoxides with NaN3. Catal. Lett.,  2007, 113(3), 120-123.
[http://dx.doi.org/10.1007/s10562-007-9021-0] 
[117] 
Tamami, B.; Mahdavi, H. Synthesis of azidohydrins from epoxides using quaternized amino functionalized cross-linked polyacrylamide as a new polymeric phase-transfer catalyst. Tetrahedron Lett.,  2001, 42(49), 8721-8724.
[http://dx.doi.org/10.1016/S0040-4039(01)01891-3] 
[118] 
Fringuelli, F.; Piermatti, O.; Pizzo, F.; Vaccaro, L. Ring opening of epoxides with sodium azide in water. A regioselective pH-controlled reaction. J. Org. Chem.,  1999, 64(16), 6094-6096.
[http://dx.doi.org/10.1021/jo990368i] 
[119] 
Mirkhani, V.; Tangestaninejad, S.; Alipanah, L. Mild, efficient, and convenient conversion of oxiranes to thiiranes with ammonium thiocyanate and thiourea in the presence of cerium (IV) polyoxometallate. Synth. Commun.,  2002, 32(4), 621-626.
[http://dx.doi.org/10.1081/SCC-120002409] 
[120] 
Kazemi, F.; Kiasat, A. Efficient conversion of epoxides to episulfides with thiourea catalysed with cerium (IV). J. Chem. Res.,  2003, 2003(5), 290-291.
[http://dx.doi.org/10.3184/030823403103173831] 
[121] 
Surendra, K.; Krishnaveni, N.S.; Rao, K.R. A new and efficient method for the synthesis of thiiranes from oxirane–β-cyclodextrin complexes and thiourea in water. Tetrahedron Lett.,  2004, 45(34), 6523-6526.
[http://dx.doi.org/10.1016/j.tetlet.2004.06.111] 
[122] 
Baltork, I.M.; Khosropour, A. Bi(TFA)3 and Bi(OTf)3 catalyzed conversions of epoxides to thiiranes with ammonium thiocyanate and thiourea under non-aqueous conditions. Molecules,  2001, 6(12), 996-1000.
[http://dx.doi.org/10.3390/61200996] 
[123] 
Iranpoor, N.; Firouzabadi, H.; Jafari, A.A. A green protocol for the easy synthesis of thiiranes from epoxides using thiourea/silica gel in the absence of solvent. Phosphorus Sulfur Silicon Relat. Elem.,  2005, 180(8), 1809-1814.
[http://dx.doi.org/10.1080/104265090889404] 
[124] 
Firouzabadi, H.; Iranpoor, N.; Khoshnood, A. Aluminum tris (dodecyl sulfate) trihydrate Al(DS)3‧3H2O as an efficient Lewis acid-surfactant-combined catalyst for organic reactions in water: Efficient conversion of epoxides to thiiranes and to amino alcohols at room temperature. J. Mol. Catal. Chem.,  2007, 274(1), 109-115.
[http://dx.doi.org/10.1016/j.molcata.2007.04.035] 
[125] 
Zeynizadeh, B.; Yeghaneh, S. A green protocol for solvent-free conversion of epoxides to thiiranes with Dowex-50WX8-supported thiourea. Phosphorus Sulfur Silicon Relat. Elem.,  2009, 184(2), 362-368.
[http://dx.doi.org/10.1080/10426500802157515] 
[126] 
Behrouz, S.; Soltani Rad, M.N.; Piltan, M.A. Ultrasound promoted rapid and
green synthesis of thiiranes from epoxides in water catalyzed by chitosansilica sulfate nano hybrid (CSSNH) as a green, novel and highly proficient
heterogeneous nano catalyst Ultrason. Sonochem., 2018.40(Pt A) 517-526.. 
[http://dx.doi.org/10.1016/j.ultsonch.2017.07.046] [PMID: 28946453] 
[127] 
Li, J.; Cao, J.J.; Wei, J.F.; Shi, X.Y.; Zhang, L.H.; Feng, J.J.; Chen, Z.G. Ionic liquid brush as a highly efficient and reusable catalyst for on‐water nucleophilic substitutions. Eur. J. Org. Chem.,  2011, 2011(2), 229-233.
[http://dx.doi.org/10.1002/ejoc.201001227] 
[128] 
Kiasat, A.R.; Nazari, S. β-Cyclodextrin conjugated magnetic nanoparticles as a novel magnetic microvessel and phase transfer catalyst: synthesis and applications in nucleophilic substitution reaction of benzyl halides. J. Incl. Phenom. Macrocycl. Chem.,  2013, 76(3-4), 363-368.
[http://dx.doi.org/10.1007/s10847-012-0207-8] 
[129] 
Varma, R.S.; Naicker, K.P.; Aschberger, J. A facile preparation of alkyl azides from alkyl bromides and sodium azide using 18-crown-6 ether doped clay. Synth. Commun.,  1999, 29(16), 2823-2830.
[http://dx.doi.org/10.1080/00397919908086450] 
[130] 
Varma, R.S.; Naicker, K.P.; Kumar, D. Can ultrasound substitute for a phase-transfer catalyst? Triphase catalysis and sonochemical acceleration in nucleophilic substitution of alkyl halides and α-tosyloxyketones: synthesis of alkyl azides and α-azidoketones. J. Mol. Catal. Chem.,  1999, 149(1-2), 153-160.
[http://dx.doi.org/10.1016/S1381-1169(99)00168-5] 
[131] 
Godajdar, B.M.; Ansari, B. Preparation of novel magnetic dicationic ionic liquid polymeric phase transfer catalyst and their application in nucleophilic substitution reactions of benzyl halides in water. J. Mol. Liq.,  2015, 202, 34-39.
[http://dx.doi.org/10.1016/j.molliq.2014.12.009] 
[132] 
Goodajdar, B.M.; Akbari, F.; Davarpanah, J. PEG‐DIL‐based MnCl42−: A novel phase transfer catalyst for nucleophilic substitution reactions of benzyl halides. Appl. Organomet. Chem.,  2019, 33(2)e4647
[133] 
Kiasat, A.R.; Nazari, S. Magnetic nanoparticles grafted with β-cyclodextrin-polyurethane polymer as a novel nanomagnetic polymer brush catalyst for nucleophilic substitution reactions of benzyl halides in water. J. Mol. Catal. Chem.,  2012, 365, 80-86.
[http://dx.doi.org/10.1016/j.molcata.2012.08.012] 
[134] 
Varma, R.S.; Naicker, K.P. Surfactant pillared clays in phase transfer catalysis: A new route to alkyl azides from alkyl bromides and sodium azide. Tetrahedron Lett.,  1998, 39(19), 2915-2918.
[http://dx.doi.org/10.1016/S0040-4039(98)00416-X] 
[135] 
Lenardão, E.J.; Silva, M.S.; Sachini, M.; Lara, R.G.; Jacob, R.G.; Perin, G. Synthesis of alkenyl selenides and tellurides using PEG-400. ARKIVOC,  2009, 11, 221-227.
[136] 
Chandrasekhar, S.; Saritha, B.; Jagadeshwar, V.; Narsihmulu, C.; Vijay, D.; Sarma, G.D.; Jagadeesh, B. Hydroxy-assisted catalyst-free Michael addition-dehydroxylation of Baylis-Hillman adducts in poly(ethylene glycol). Tetrahedron Lett.,  2006, 47(17), 2981-2984.
[http://dx.doi.org/10.1016/j.tetlet.2006.02.104] 
[137] 
Kumar, D.; Patel, G.; Mishra, B.G.; Varma, R.S. Eco-friendly polyethylene glycol promoted Michael addition reactions of α,β-unsaturated carbonyl compounds. Tetrahedron Lett.,  2008, 49(49), 6974-6976.
[http://dx.doi.org/10.1016/j.tetlet.2008.09.116] 
[138] 
Nagarapu, L.; Mallepalli, R.; Kumar, U.N.; Venkateswarlu, P.; Bantu, R.; Yeramanchi, L. Synthesis of α1-oxindole-α-hydroxyphosphonates under catalyst-free conditions using polyethylene glycol (PEG-400) as an efficient and recyclable reaction medium. Tetrahedron Lett.,  2012, 53(14), 1699-1700.
[http://dx.doi.org/10.1016/j.tetlet.2012.01.045] 
[139] 
Bi, J.; Zhang, Z.; Liu, Q.; Zhang, G. Catalyst-free and highly selective electrophilic mono-fluorination of acetoacetamides: facile and efficient preparation of 2-fluoroacetoacetamides in PEG-400. Green Chem.,  2012, 14(4), 1159-1162.
[http://dx.doi.org/10.1039/c2gc16661e] 
[140] 
Kumar, D.; Arun, V.; Pilania, M.; Shekar, K.C. A metal-free and microwave-assisted efficient synthesis of diaryl sulfones. Synlett,  2013, 24(07), 831-836.
[http://dx.doi.org/10.1055/s-0032-1317803] 
[141] 
Kantam, M.L.; Laha, S.; Yadav, J.; Jha, S. Nanocrystalline copper(II) oxide catalyzed aza-Michael reaction and insertion of α-diazo compounds into N–H bonds of amines. Tetrahedron Lett.,  2009, 50(31), 4467-4469.
[http://dx.doi.org/10.1016/j.tetlet.2009.05.059] 
[142] 
Surendra, K.; Krishnaveni, N.S.; Sridhar, R.; Rao, K.R. β-Cyclodextrin promoted aza-Michael addition of amines to conjugated alkenes in water. Tetrahedron Lett.,  2006, 47(13), 2125-2127.
[http://dx.doi.org/10.1016/j.tetlet.2006.01.124] 
[143] 
Yadav, J.S.; Reddy, B.V.S.; Basak, A.K.; Narsaiah, A.V. Aza-Michael reactions in ionic liquids. A facile synthesis of β-amino compounds. Chem. Lett.,  2003, 32(11), 988-989.
[http://dx.doi.org/10.1246/cl.2003.988] 
[144] 
Dai, L.; Zhang, Y.; Dou, Q.; Wang, X.; Chen, Y. Chemo/regioselective Aza-Michael additions of amines to conjugate alkenes catalyzed by polystyrene-supported AlCl3. Tetrahedron,  2013, 69(6), 1712-1716.
[http://dx.doi.org/10.1016/j.tet.2012.12.037] 
[145] 
Chen, X.; She, J.; Shang, Z.; Wu, J.; Zhang, P. A catalytic method for room-temperature Michael additions using 12-tungstophosphoric acid as a reusable catalyst in water. Synthesis,  2008, 2008(24), 3931-3936.
[http://dx.doi.org/10.1055/s-0028-1083254] 
[146] 
Fetterly, B.M.; Jana, N.K.; Verkade, J.G. [HP(HNCH2CH2)3N]NO3: an efficient homogeneous and solid-supported promoter for aza and thia-Michael reactions and for Strecker reactions. Tetrahedron,  2006, 62(2), 440-456.
[http://dx.doi.org/10.1016/j.tet.2005.09.117] 
[147] 
Hussain, S.; Bharadwaj, S.K.; Chaudhuri, M.K.; Kalita, H. Borax as an efficient metal-free catalyst for hetero-Michael reactions in an aqueous medium. Eur. J. Org. Chem.,  2007, 2007(2), 374-378.
[http://dx.doi.org/10.1002/ejoc.200600691] 
[148] 
Dhake, K.P.; Tambade, P.J.; Singhal, R.S.; Bhanage, B.M. Promiscuous Candida antarctica lipase B-catalyzed synthesis of β-amino esters via aza-Michael addition of amines to acrylates. Tetrahedron Lett.,  2010, 51(33), 4455-4458.
[http://dx.doi.org/10.1016/j.tetlet.2010.06.089] 
[149] 
Alamgholiloo, H.; Rostamnia, S.; Hassankhani, A.; Banaei, R. Synthesis of a zeolitic imidazolate-zinc metal-organic framework and the combination of its catalytic properties with 2,2,2-trifluoroethanol for N-formylation. Synlett,  2018, 29(12), 1593-1596.
[http://dx.doi.org/10.1055/s-0037-1610159] 
[150] 
Kim, J-G.; Jang, D.O. Facile and highly efficient N-formylation of amines using a catalytic amount of iodine under solvent-free conditions. Synlett,  2010, 2010(14), 2093-2096.
[http://dx.doi.org/10.1055/s-0030-1258518] 
[151] 
Azizi, N.; Edrisi, M.; Abbasi, F. Mesoporous silica SBA-15 functionalized with acidic deep eutectic solvent: A highly active heterogeneous N-formylation catalyst under solvent-free conditions. Appl. Organomet. Chem.,  2018, 32(1)e3901
[http://dx.doi.org/10.1002/aoc.3901] 
[152] 
Hong, M.; Xiao, G. Hafnium(IV) bis(perfluorooctanesulfonyl)imide complex supported on fluorous silica gel catalyzed N-formylation of amines using aqueous formic acid. J. Fluor. Chem.,  2013, 146, 11-14.
[http://dx.doi.org/10.1016/j.jfluchem.2012.12.010] 
[153] 
Majumdar, S.; De, J.; Hossain, J.; Basak, A. Formylation of amines catalysed by protic ionic liquids under solvent-free condition. Tetrahedron Lett.,  2013, 54(3), 262-266.
[http://dx.doi.org/10.1016/j.tetlet.2012.11.017] 
[154] 
Tamaddon, F.; Aboee, F.; Nasiri, A. ZnO nanofluid as a structure base catalyst for chemoselective amidation of aliphatic carboxylic acids. Catal. Commun.,  2011, 16(1), 194-197.
[http://dx.doi.org/10.1016/j.catcom.2011.09.023] 
[155] 
Nishikawa, Y.; Nakamura, H.; Ukai, N.; Adachi, W.; Hara, O. Tetraethylorthosilicate as a mild dehydrating reagent for the synthesis of N-formamides with formic acid. Tetrahedron Lett.,  2017, 58(9), 860-863.
[http://dx.doi.org/10.1016/j.tetlet.2017.01.056] 
[156] 
Kim, J-G.; Jang, D.O. Indium-catalyzed N-formylation of amines under solvent-free conditions. Synlett,  2010, 2010(08), 1231-1234.
[http://dx.doi.org/10.1055/s-0029-1219784] 
[157] 
Das, B.; Krishnaiah, M.; Balasubramanyam, P.; Veeranjaneyulu, B.; Kumar, D.N. A remarkably simple N-formylation of anilines using polyethylene glycol. Tetrahedron Lett.,  2008, 49(14), 2225-2227.
[http://dx.doi.org/10.1016/j.tetlet.2008.02.050] 
[158] 
Eshghi, H.; Gordi, Z. P2O5/SiO2 as an efficient reagent for the preparation of Z-aldoximes under solvent-free conditions. Phosphorus Sulfur Silicon Relat. Elem.,  2005, 180(7), 1553-1557.
[http://dx.doi.org/10.1080/10426500590924148] 
[159] 
Setamdideh, D.; Khezri, B.; Esmaeilzadeh, S. Synthesis of oximes with NH2OH.HCl/DOWEX(R)50WX4 system. J. Chin. Chem. Soc. (Taipei),  2012, 59(9), 1119-1124.
[http://dx.doi.org/10.1002/jccs.201200011] 
[160] 
Talaei, F.; Setamdideh, D. NH2OH.Hcl/BaCl2: a convenient system for synthesis of oximes from the corresponding of organic carbonyl compounds. Orient. J. Chem.,  2016, 32(3), 1583-1587.
[http://dx.doi.org/10.13005/ojc/320334] 
[161] 
Sharghi, H.; Sarvari, M.H. Selective synthesis of E and Z isomers of oximes. Synlett,  2001, 2001(01), 99-101.
[http://dx.doi.org/10.1055/s-2001-9719] 
[162] 
Ghozlojeh, N.P.; Setamdideh, D. Synthesis of oximes from the corresponding of organic carbonyl compounds with NH2OH. HCl and oxalic acid. Orient. J. Chem.,  2015, 31(3), 1823-1825.
[http://dx.doi.org/10.13005/ojc/310365] 
[163] 
Guo, J-J.; Jin, T-S.; Zhang, S-L.; Li, T-S. TiO2/SO42-: an efficient and convenient catalyst for preparation of aromatic oximes. Green Chem.,  2001, 3(4), 193-195.
[http://dx.doi.org/10.1039/b102067f] 
[164] 
Karthikeyan, P.; Aswar, S.A.; Muskawar, P.N.; Sythana, S.K.; Bhagat, P.R.; Kumar, S.S.; Satvat, P.S. A novel l-amino acid ionic liquid for quick and highly efficient synthesis of oxime derivatives - an environmental benign approach. Arab. J. Chem.,  2016, 9, S1036-S1039.
[http://dx.doi.org/10.1016/j.arabjc.2011.11.007] 
[165] 
Damljanović, I.; Vukićević, M.; Vukićević, R.D. A simple synthesis of oximes. Monatsh. Chem.,  2006, 137(3), 301-305.
[http://dx.doi.org/10.1007/s00706-005-0427-3] 
[166] 
Dutta, P.; Dutta, A.K.; Sarma, P.; Borah, R. Dual nature of polyethylene glycol under microwave irradiation for the clean synthesis of oximes. Monatsh. Chem.,  2014, 145(3), 505-508.
[http://dx.doi.org/10.1007/s00706-013-1101-9] 
[167] 
Kadam, S.N.; Ambhore, A.N.; Hebade, M.J.; Kamble, R.D.; Hese, S.V.; Gaikwad, M.V.; Gavhane, P.D.; Dawane, B.S. Metal-free one-pot chemoselective thiocyanation of imidazothiazoles and 2-aminothiazoles with in situ generated N-thiocyanatosuccinimide. Synlett,  2018, 29(14), 1902-1908.
[http://dx.doi.org/10.1055/s-0037-1609553] 
[168] 
Bandgar, B.P.; Korbad, B.L.; Patil, S.A.; Bandgar, S.B.; Chavan, H.V.; Hote, B.S. Uncatalyzed Knoevenagel condensation in PEG-600 at room temperature. Aust. J. Chem.,  2008, 61(9), 700-703.
[http://dx.doi.org/10.1071/CH08106] 
[169] 
Firouzeh, N.; Hossein, K. A green and highly efficient protocol for catalyst‐free Knoevenagel condensation and Michael addition of aromatic aldehydes with 1, 3‐cyclic diketones in PEG‐400. Chin. J. Chem.,  2011, 29(11), 2407-2410.
[http://dx.doi.org/10.1002/cjoc.201100005] 
[170] 
Kumar, D.; Sandhu, J.S. Uncatalysed Knoevenagel condensation of 3-formylchromones in green media: polyethylene glycol-400 (PEG-400). Indian J. Chem.,  2012, 51B, 1743-1748.
[171] 
Metwally, N.H. A simple green synthesis of (Z)-5-arylmethylene-4-thioxothiazolidines and thiopyrano [2,3-d] thiazolidine-2-thiones in PEG-400 under catalyst-free conditions. J. Sulfur Chem.,  2014, 35(5), 528-537.
[http://dx.doi.org/10.1080/17415993.2014.933341] 
[172] 
Gupta, A.K.; Bharadwaj, M.; Mehrotra, R. Eco‐friendly polyethylene glycol‐400 as a rapid and efficient recyclable reaction medium for the synthesis of anticancer isatin‐linked chalcones and their 3‐hydroxy precursor. J. Heterocycl. Chem.,  2019, 56(2), 703-709.
[http://dx.doi.org/10.1002/jhet.3424] 
[173] 
Hasaninejad, A.; Zare, A.; Shekouhy, M.; Golzar, N. Efficient synthesis of 4, 4′-(arylmethylene)-bis (3-methyl-1-phenylpyrazol-5-ol) derivatives in PEG-400 under catalyst-free conditions. Org. Prep. Proced. Int.,  2011, 43(1), 131-137.
[http://dx.doi.org/10.1080/00304948.2010.526827] 
[174] 
Raghu, M.; Rajasekhar, M.; Reddy, B.C.O.; Reddy, C.S.; Reddy, B.S. Polyethylene glycol (PEG-400): a mild and efficient reaction medium for one-pot synthesis of 3-hydroxy-3-(pyridin-2-ylmethyl) indolin-2-ones. Tetrahedron Lett.,  2013, 54(27), 3503-3506.
[http://dx.doi.org/10.1016/j.tetlet.2013.04.089] 
[175] 
Huang, T.Q.; Qu, W.Y.; Ding, J.C.; Liu, M.C.; Wu, H.Y.; Chen, J.X. Catalyst‐free protocol for the synthesis of quinoxalines and pyrazines in PEG. J. Heterocycl. Chem.,  2013, 50(2), 293-297.
[http://dx.doi.org/10.1002/jhet.1043] 
[176] 
Nagarapu, L.; Mallepalli, R.; Arava, G.; Yeramanchi, L. Polyethylene glycol (PEG-400) mediated synthesis of quinoxalines. Eur. J. Chem.,  2010, 1(3), 228-231.
[http://dx.doi.org/10.5155/eurjchem.1.3.228-231.172] 
[177] 
Bassaco, M.M.; Fortes, M.P.; Kaufman, T.S.; Silveira, C.C. Metal-free synthesis of 3, 5-disubstituted 1H-and 1-aryl-1H-pyrazoles from 1,3-diyne-indole derivatives employing two successive hydroaminations. RSC Advances,  2015, 5(27), 21112-21124.
[http://dx.doi.org/10.1039/C4RA16439C] 
[178] 
Zhu, D.; Chen, J.; Xiao, H.; Liu, M.; Ding, J.; Wu, H. Efficient and expeditious synthesis of di-and trisubstituted thiazoles in PEG under catalyst-free conditions. Synth. Commun.,  2009, 39(16), 2895-2906.
[http://dx.doi.org/10.1080/00397910802691874] 
[179] 
Babu, B.H.; Vijay, K.; Krishna, K.B.M.; Sharmila, N.; Ramana, M.B. An efficient PEG-400 mediated catalyst free green synthesis of 2-amino-thiazoles from α-diazoketones and thiourea. J. Chem. Sci.,  2016, 128(9), 1475-1478.
[http://dx.doi.org/10.1007/s12039-016-1130-0] 
[180] 
Phatangare, K.R.; Padalkar, V.S.; Gupta, V.D.; Patil, V.S.; Umape, P.G.; Sekar, N. Phosphomolybdic acid: an efficient and recyclable solid acid catalyst for the synthesis of 4,4′-(arylmethylene)bis(1H-pyrazol-5-ols). Synth. Commun.,  2012, 42(9), 1349-1358.
[http://dx.doi.org/10.1080/00397911.2010.539759] 
[181] 
Niknam, K.; Saberi, D.; Sadegheyan, M.; Deris, A. Silica-bonded S-sulfonic acid: an efficient and recyclable solid acid catalyst for the synthesis of 4,4′-(arylmethylene)bis(1H-pyrazol-5-ols). Tetrahedron Lett.,  2010, 51(4), 692-694.
[http://dx.doi.org/10.1016/j.tetlet.2009.11.114] 
[182] 
Tayebi, S.; Baghernejad, M.; Saberi, D.; Niknam, K. Sulfuric acid ([3-(3-silicapropyl)sulfanyl]propyl)ester as a recyclable catalyst for the synthesis of 4,4′-(arylmethylene)bis(1H-pyrazol-5-ols). Chin. J. Catal.,  2011, 32(9), 1477-1483.
[http://dx.doi.org/10.1016/S1872-2067(10)60260-4] 
[183] 
Bhardwaj, M.; Sahi, S.; Mahajan, H.; Paul, S.; Clark, J.H. Novel heterogeneous catalyst systems based on Pd(0) nanoparticles onto amine functionalized silica-cellulose substrates [Pd(0)-EDA/SCs]: synthesis, characterization and catalytic activity toward C–C and C–S coupling reactions in water under limiting basic conditions. J. Mol. Catal. Chem.,  2015, 408, 48-59.
[http://dx.doi.org/10.1016/j.molcata.2015.07.005] 
[184] 
Mosaddegh, E.; Hassankhani, A.; Baghizadeh, A. Cellulose sulfuric acid as a new, biodegradable and environmentally friendly bio-polymer for synthesis of 4,4′-(arylmethylene) bis(3-methyl-1-phenyl-1H-pyrazo-4-ols). J. Chil. Chem. Soc.,  2010, 55(4), 419-420.
[http://dx.doi.org/10.4067/S0717-97072010000400001] 
[185] 
Baghernejad, M.; Niknam, K. Synthesis of 4,4′-(Arylmethylene)bis(1H-pyrazol-5-ols) using silica-bonded ionic liquid as recyclable catalyst. Int. J. Chem.,  2012, 4(3)
[http://dx.doi.org/10.5539/ijc.v4n3p52] 
[186] 
Iravani, N.; Albadi, J.; Momtazan, H.; Baghernejad, M. Melamine trisulfunic acid: an efficient and recyclable solid acid catalyst for the synthesis of 4,4′-(arylmethylene)-bis-(1H-pyrazol-5-ols). J. Chin. Chem. Soc. (Taipei),  2013, 60(4), 418-424.
[http://dx.doi.org/10.1002/jccs.201200345] 
[187] 
Tale, N.P.; Tiwari, G.B.; Karade, N.N. Un-catalyzed tandem Knoevenagel–Michael reaction for the synthesis of 4,4′-(arylmethylene)bis(1H-pyrazol-5-ols) in aqueous medium. Chin. Chem. Lett.,  2011, 22(12), 1415-1418.
[http://dx.doi.org/10.1016/j.cclet.2011.09.004] 
[188] 
Harsha, K.B.; Rangappa, K.S. One-step approach for the synthesis of functionalized quinoxalines mediated by T3P®-DMSO or T3P® via a tandem oxidation–condensation or condensation reaction. RSC Advances,  2016, 6(62), 57154-57162.
[http://dx.doi.org/10.1039/C6RA03078E] 
[189] 
Ghosh, P.; Mandal, A. Synthesis of functionalized benzimidazoles and quinoxalines catalyzed by sodium hexafluorophosphate bound Amberlite resin in aqueous medium. Tetrahedron Lett.,  2012, 53(48), 6483-6488.
[http://dx.doi.org/10.1016/j.tetlet.2012.09.045] 
[190] 
Jeganathan, M.; Dhakshinamoorthy, A.; Pitchumani, K. One-pot synthesis of 2-substituted quinoxalines using K10-montmorillonite as heterogeneous catalyst. Tetrahedron Lett.,  2014, 55(9), 1616-1620.
[http://dx.doi.org/10.1016/j.tetlet.2014.01.087] 
[191] 
Emmadi, N.R.; Atmakur, K. Sodium dodecylsulfate induced synthesis of quinoxalines. Indian J. Chem.,  2013, 52B, 1500-1504.
[192] 
Ghosh, P.; Mandal, A.; Subba, R. γ-Maghemite-silica nanocomposite: A green catalyst for diverse aromatic N-heterocycles. Catal. Commun.,  2013, 41, 146-152.
[http://dx.doi.org/10.1016/j.catcom.2013.06.026] 
[193] 
Huang, T.; Zhang, Q.; Chen, J.; Gao, W.; Ding, J.; Wu, H. Synthesis of quinoxalines catalysed by cetyltrimethyl ammonium bromide (CTAB) in aqueous media. J. Chem. Res.,  2009, 2009(12), 761-765.
[194] 
Wan, J-P.; Gan, S-F.; Wu, J-M.; Pan, Y. Water mediated chemoselective synthesis of 1,2-disubstituted benzimidazoles using o-phenylenediamine and the extended synthesis of quinoxalines. Green Chem.,  2009, 11(10), 1633-1637.
[http://dx.doi.org/10.1039/b914286j] 
[195] 
Dhakshinamoorthy, A.; Alvaro, M.; Garcia, H. Deactivation of Cu3(BTC)2 in the synthesis of 2-phenylquinoxaline. Catal. Lett.,  2015, 145(8), 1600-1605.
[http://dx.doi.org/10.1007/s10562-015-1497-4] 
[196] 
Balalaie, S.; Nikoo, S.; Haddadi, S. Aqueous-phase synthesis of 2-aminothiazole and 2-iminothiazolidine derivatives catalyzed by diammonium hydrogen phosphate and DABCO. Synth. Commun.,  2008, 38(15), 2521-2528.
[http://dx.doi.org/10.1080/00397910802219155] 
[197] 
Potewar, T.M.; Ingale, S.A.; Srinivasan, K.V. Efficient synthesis of 2,4-disubstituted thiazoles using ionic liquid under ambient conditions: a practical approach towards the synthesis of Fanetizole. Tetrahedron,  2007, 63(45), 11066-11069.
[http://dx.doi.org/10.1016/j.tet.2007.08.036] 
[198] 
Lobo, H.R.; Singh, B.S.; Shankarling, G.S. Lipase and deep eutectic mixture catalyzed efficient synthesis of thiazoles in water at room temperature. Catal. Lett.,  2012, 142(11), 1369-1375.
[http://dx.doi.org/10.1007/s10562-012-0902-5] 
[199] 
Narender, M.; Reddy, M.S.; Sridhar, R.; Nageswar, Y.V.D.; Rao, K.R. Aqueous phase synthesis of thiazoles and aminothiazoles in the presence of β-cyclodextrin. Tetrahedron Lett.,  2005, 46(35), 5953-5955.
[http://dx.doi.org/10.1016/j.tetlet.2005.06.130] 
[200] 
Rostamizadeh, S.; Aryan, R.; Ghaieni, H.R.; Amani, A.M. Aqueous NaHSO4 catalyzed regioselective and versatile synthesis of 2-thiazolamines. Monatsh. Chem.,  2008, 139(10), 1241-1245.
[http://dx.doi.org/10.1007/s00706-008-0906-4] 
[201] 
Bhosale, P.; Chavan, R.; Bhosale, A. Design, synthesis, biological evaluation of thiazolyl Schiff base derivatives as novel anti-inflammatory agents. Indian J. Chem.,  2012, 51B, 1649-1654.
[202] 
Muthyala, M.K.; Kumar, A. A novel and efficient one pot synthesis of 2,4-disubstituted thiazoles and oxazoles using phenyltrimethylammoniumtribromide in ionic liquid. J. Heterocycl. Chem.,  2012, 49(4), 959-964.
[http://dx.doi.org/10.1002/jhet.904] 
[203] 
Yang, X-D. One-pot synthesis under ultrasonic irradiation of N-(substituted phenyl)-N´-(5-methylisoxazoyl)-thiourea derivatives. Asian J. Chem.,  2008, 20(3), 2147-2150.
[204] 
Deligeorgiev, T.G.; Kaloyanova, S.S.; Lesev, N.Y.; Vaquero, J.J. An environmentally benign procedure for the synthesis of substituted 2-thiobenzothiazoles, 2-thiobenzoxazoles, 2-thiobenzimidazoles, and 1,3-oxazolopyridine-2-thiols. Monatsh. Chem.,  2011, 142(9), 895-899.
[http://dx.doi.org/10.1007/s00706-011-0551-1] 
[205] 
Mungara, A.K.; Park, Y-K.; Lee, K.D. Synthesis and antiproliferative activity of novel α-aminophosphonates. Chem. Pharm. Bull. (Tokyo),  2012, 60(12), 1531-1537.
[PMID: 22986831] 
[206] 
Srinivasa Reddy, B.; Naidu, A.; Dubey, P. PEG-600-mediated, green and efficient, tandem syntheses of N-subtituted-2-styrylquinazolin-4-ones. Green Chem. Lett. Rev.,  2013, 6(3), 254-261.
[http://dx.doi.org/10.1080/17518253.2012.742142] 
[207] 
Rafeeq, M.; Reddy, B.S.; Reddy, C.V.R.; Naidu, A.; Dubey, P. Green and efficient synthesis of 2-(4-oxo-3,4-dihydroquinazolin-2-yl)-2,3-dihydroptha-lazine-1,4-dione. Indian J. Chem.,  2015, 54B, 412-417.
[http://dx.doi.org/10.1002/chin.201545174] 
[208] 
Akbarzadeh, A.; Dekamin, M.G. A facile and environmentally benign polyethylene glycol 600-mediated method for the synthesis of densely functionalized 2-aminothiophene derivatives under ultrasonication. Green Chem. Lett. Rev.,  2017, 10(4), 315-323.
[http://dx.doi.org/10.1080/17518253.2017.1380234] 
[209] 
Sampath, C.; Harika, P.; Revaprasadu, N. Design, green synthesis, anti-microbial, and anti-oxidant activities of novel α-aminophosphonates via Kabachnik-Fields reaction. Phosphorus Sulfur Silicon Relat. Elem.,  2016, 191(8), 1081-1085.
[http://dx.doi.org/10.1080/10426507.2015.1035379] 
[210] 
Dharavath, N.; Eligeti, R.; Reddy, Y.; Pittala, P.K.; Modugu, N.R. PEG‐400 mediated an efficient green synthesis of isoxazolyl indole‐3‐carboxylic acid esters via Nentizescu condensation reaction and their anti‐inflammatory and analgesic activity. ChemistrySelect,  2017, 2(18), 5110-5114.
[http://dx.doi.org/10.1002/slct.201700640] 
[211] 
Gawande, S.S.; Bandgar, B.P.; Kadam, P.D.; Sable, S.S. Uncatalyzed synthesis of thiomorpholide using polyethylene glycol as green reaction media. Green Chem. Lett. Rev.,  2010, 3(4), 315-318.
[http://dx.doi.org/10.1080/17518253.2010.486772] 
Cite As
Current Organic Chemistry

Polyethylene Glycol as a Green and Biocompatible Reaction Media for the Catalyst Free Synthesis of Organic Compounds

Abstract

Graphical Abstract
