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Current Organic Chemistry

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ISSN (Print): 1385-2728
ISSN (Online): 1875-5348

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Research Article

Using Supercritical Diethyl Ether as the Reaction Medium for the Synthesis of 3-Acetyl and 4-Methyl Substituted Coumarins

Author(s): Zeynep Özsırkıntı, Abdul Hakim Hakimi, Mehmet Erşatır, Murat Türk, Onur Demirkol and Elife Sultan Giray*

Volume 28, Issue 10, 2024

Published on: 27 February, 2024

Page: [789 - 798] Pages: 10

DOI: 10.2174/0113852728284871240215103216

Price: $65

Abstract

Due to very good biological activity and use as fluorescent probes, coumarin synthesis and developing new synthesis methods are still an attractive area for many research groups. In this work, for the first time, a novel, mild, and green method has been developed for coumarin synthesis by using supercritical diethyl ether as a reaction medium. The optimum conditions for the synthesis of 3-acetylcoumarins and 4-methylcoumarins have been explored. These newly established techniques could be a favourable approach against two traditional synthetic routes in terms of green chemistry criteria for the synthesis of important intermediates, 3-acetyl coumarins and 4-methyl coumarins. 4-Methyl coumarins have been obtained in good-to-excellent yields (63-87%); for example, bmethylumbelliferone, a naturally bioactive coumarin compound, was synthesised in 30 min at 200oC, resulting in 87% yield, while several 3-acetyl coumarins were synthesized in very good yields (28- 96%).

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[1]
Horváth, I.T. Introduction: Sustainable chemistry. Chem. Rev., 2018, 118(2), 369-371.
[http://dx.doi.org/10.1021/acs.chemrev.7b00721] [PMID: 29361827]
[2]
Zangade, S.; Patil, P. A review on solvent-free methods in organic synthesis. Curr. Org. Chem., 2020, 23(21), 2295-2318.
[http://dx.doi.org/10.2174/1385272823666191016165532]
[3]
Li, C.J. Organic reactions in aqueous media with a focus on carbon-carbon bond formations: A decade update. Chem. Rev., 2005, 105(8), 3095-3166.
[http://dx.doi.org/10.1021/cr030009u] [PMID: 16092827]
[4]
Kacem, S.; Qiao, Y.; Wirtz, C.; Theyssen, N.; Bordet, A.; Leitner, W. Supercritical carbon dioxide as reaction medium for selective hydrogenation of fluorinated arenes. Green Chem., 2022, 24(22), 8671-8676.
[http://dx.doi.org/10.1039/D2GC02623F]
[5]
Gooden, P.N.; Bourne, R.A.; Parrott, A.J.; Bevinakatti, H.S.; Irvine, D.J.; Poliakoff, M. Continuous acid-catalyzed methylations in supercritical carbon dioxide: Comparison of methanol dimethyl ether and dimethyl carbonate as methylating agents. Org. Process Res. Dev., 2010, 14(2), 411-416.
[http://dx.doi.org/10.1021/op900307w]
[6]
Xu, X.; De Almeida, C.P.; Antal, M.J., Jr Mechanism and kinetics of the acid-catalyzed formation of ethene and diethyl ether from ethanol in supercritical water. Ind. Eng. Chem. Res., 1991, 30(7), 1478-1485.
[http://dx.doi.org/10.1021/ie00055a012]
[7]
Jakob, A.; Likozar, B.; Grilc, M. Aqueous conversion of monosaccharides to furans: Were we wrong all along to use catalysts? Green Chem., 2022, 24(21), 8523-8537.
[http://dx.doi.org/10.1039/D2GC02736D]
[8]
şirin, Z.; Demirkol, O.; Akbaşlar, D.; Giray, E.S. Clean and efficient synthesis of flavanone in sub-critical water. J. Supercrit. Fluids, 2013, 81, 217-220.
[http://dx.doi.org/10.1016/j.supflu.2013.05.014]
[9]
Ulusal, H.; Fındıkkıran, G.; Demirkol, O.; Akbaşlar, D.; Giray, E.S. Supercritical diethylether: A novel solvent for the synthesis of aryl-3,4,5,6,7,9-hexahydroxanthene-1,8-diones. J. Supercrit. Fluids, 2015, 105, 146-150.
[http://dx.doi.org/10.1016/j.supflu.2014.12.020]
[10]
Iranshahi, M.; Askari, M.; Sahebkar, A.; Hadjipavlou-Litina, D. Evaluation of antioxidant, anti-inflammatory and lipoxygenase inhibitory activities of the prenylated coumarin umbelliprenin. Daru, 2009, 17, 99-103.
[11]
Demirkol, O.; Erşatır, M.; Giray, E.S.; Kırıcı, S. Comparison of the effects of green and sustainable extraction methods on the extraction yield and chemical composition of Ruta chalepensis roots. Sustain. Chem. Pharm., 2022, 29, 100750.
[http://dx.doi.org/10.1016/j.scp.2022.100750]
[12]
Liang, X-T.; Fang, W.S. Medicinal chemistry of bioactive natural product. In: Chinese academy of medical sciences; Liang, X-T.; Fang, W.S., Eds.; John Wiley & Sons, Inc.: Beijing, China, 2005.
[http://dx.doi.org/10.1002/0471739340]
[13]
Hosseini Nasab, N.; Azimian, F.; Kruger, H.G.; Kim, S.J. Reaction of 3-Acetylcoumarin: From methods to mechanism. Arab. J. Chem., 2023, 16(2), 104472.
[http://dx.doi.org/10.1016/j.arabjc.2022.104472]
[14]
Anand, P.; Singh, B.; Singh, N. A review on coumarins as acetylcholinesterase inhibitors for Alzheimer’s disease. Bioorg. Med. Chem., 2012, 20(3), 1175-1180.
[http://dx.doi.org/10.1016/j.bmc.2011.12.042] [PMID: 22257528]
[15]
Sednev, M.V.; Belov, V.N.; Hell, S.W. Fluorescent dyes with large Stokes shifts for super-resolution optical microscopy of biological objects: A review. Methods Appl. Fluoresc., 2015, 3(4), 042004.
[http://dx.doi.org/10.1088/2050-6120/3/4/042004] [PMID: 29148519]
[16]
Emami, S.; Dadashpour, S. Current developments of coumarin-based anti-cancer agents in medicinal chemistry. Eur. J. Med. Chem., 2015, 102, 611-630.
[http://dx.doi.org/10.1016/j.ejmech.2015.08.033] [PMID: 26318068]
[17]
Nasr, T.; Bondock, S.; Youns, M. Anticancer activity of new coumarin substituted hydrazide–hydrazone derivatives. Eur. J. Med. Chem., 2014, 76, 539-548.
[http://dx.doi.org/10.1016/j.ejmech.2014.02.026] [PMID: 24607878]
[18]
Menezes, J.C.J.M.D.S.; Diederich, M. Translational role of natural coumarins and their derivatives as anticancer agents. Future Med. Chem., 2019, 11(9), 1057-1082.
[http://dx.doi.org/10.4155/fmc-2018-0375] [PMID: 31140865]
[19]
Ashton, T.D.; Jolliffe, K.A.; Pfeffer, F.M. Luminescent probes for the bioimaging of small anionic species in vitro and in vivo. Chem. Soc. Rev., 2015, 44(14), 4547-4595.
[http://dx.doi.org/10.1039/C4CS00372A] [PMID: 25673509]
[20]
Frath, D.; Massue, J.; Ulrich, G.; Ziessel, R. Luminescent materials: Locking π-conjugated and heterocyclic ligands with boron(III). Angew. Chem. Int. Ed., 2014, 53(9), 2290-2310.
[http://dx.doi.org/10.1002/anie.201305554] [PMID: 24482312]
[21]
Ko, K.C.; Wu, J.S.; Kim, H.J.; Kwon, P.S.; Kim, J.W.; Bartsch, R.A.; Lee, J.Y.; Kim, J.S. Rationally designed fluorescence ‘turn-on’ sensor for Cu2+. Chem. Commun. (Camb.), 2011, 47(11), 3165-3167.
[http://dx.doi.org/10.1039/c0cc05421f] [PMID: 21283852]
[22]
Wu, J.S.; Hwang, I.C.; Kim, K.S.; Kim, J.S. Rhodamine-based Hg2+-selective chemodosimeter in aqueous solution: Fluorescent OFF-ON. Org. Lett., 2007, 9(5), 907-910.
[http://dx.doi.org/10.1021/ol070109c] [PMID: 17286411]
[23]
Yuan, L.; Lin, W.; Xie, Y.; Chen, B.; Zhu, S. Single fluorescent probe responds to H2O2, NO, and H2O2/NO with three different sets of fluorescence signals. J. Am. Chem. Soc., 2012, 134(2), 1305-1315.
[http://dx.doi.org/10.1021/ja2100577] [PMID: 22148503]
[24]
Yuan, L.; Lin, W.; Zhao, S.; Gao, W.; Chen, B.; He, L.; Zhu, S. A unique approach to development of near-infrared fluorescent sensors for in vivo imaging. J. Am. Chem. Soc., 2012, 134(32), 13510-13523.
[http://dx.doi.org/10.1021/ja305802v] [PMID: 22816866]
[25]
Yuan, L.; Lin, W.; Zheng, K.; He, L.; Huang, W. Far-red to near infrared analyte-responsive fluorescent probes based on organic fluorophore platforms for fluorescence imaging. Chem. Soc. Rev., 2013, 42(2), 622-661.
[http://dx.doi.org/10.1039/C2CS35313J] [PMID: 23093107]
[26]
Sharma, G.V.M.; Janardhan Reddy, J.; Sree Lakshmi, P.; Radha Krishna, P. An efficient ZrCl4 catalyzed one-pot solvent free protocol for the synthesis of 4-substituted coumarins. Tetrahedron Lett., 2005, 46(36), 6119-6121.
[http://dx.doi.org/10.1016/j.tetlet.2005.06.166]
[27]
Kalita, P.; Baskar, A.V.; Choy, J.H.; Lakhi, K.S.; El-Newehy, M.; Lawrence, G.; Al-deyab, S.S.; Balasubramanian, V.V.; Vinu, A. Preparation of highly active triflic acid functionalized SBA‐15 catalysts for the synthesis of coumarin under solvent‐free conditions. ChemCatChem, 2016, 8(2), 336-344.
[http://dx.doi.org/10.1002/cctc.201500884]
[28]
Vahabi, V.; Hatamjafari, F. Microwave assisted convenient one-pot synthesis of coumarin derivatives via Pechmann condensation catalyzed by FeF3 under solvent-free conditions and antimicrobial activities of the products. Molecules, 2014, 19(9), 13093-13103.
[http://dx.doi.org/10.3390/molecules190913093] [PMID: 25255747]
[29]
Uroos, M.; Javaid, A.; Bashir, A.; Tariq, J.; Khan, I.H.; Naz, S.; Fatima, S.; Sultan, M. Green synthesis of coumarin derivatives using Brønsted acidic pyridinium based ionic liquid [MBSPy][HSO4] to control an opportunistic human and a devastating plant pathogenic fungus Macrophomina phaseolina. RSC Advances, 2022, 12(37), 23963-23972.
[http://dx.doi.org/10.1039/D2RA03774B] [PMID: 36093243]
[30]
Avdović, E.H.; Milanović, Ž.; Simijonović, D.; Antonijević, M.; Milutinović, M.; Nikodijević, D.; Filipović, N.; Marković, Z.; Vojinović, R. An effective, green synthesis procedure for obtaining coumarin–hydroxybenzohydrazide derivatives and assessment of their antioxidant activity and Redox status. Antioxidants, 2023, 12(12), 2070.
[http://dx.doi.org/10.3390/antiox12122070]
[31]
Borah, B.; Dwivedi, K.D.; Kumar, B.; Chowhan, L.R. Recent advances in the microwave- and ultrasound-assisted green synthesis of coumarin-heterocycles. Arab. J. Chem., 2022, 15(3), 103654.
[http://dx.doi.org/10.1016/j.arabjc.2021.103654]
[32]
Fetzer, D.E.L.; Kanda, L.R.S.; Xavier, L.A.; da Cruz, P.N.; Errico, M.; Corazza, M.L. Lipids and coumarin extraction from cumaru seeds (Dipteryx odorata) using sequential supercritical CO2+ solvent and pressurized ethanol. J. Supercrit. Fluids, 2022, 188, 105688.
[http://dx.doi.org/10.1016/j.supflu.2022.105688]
[33]
Torres, F. C.; Medeiros-Neves, B.; Teixeira, H.F.; Kawanoa, D.; Eifler-Lima, V. L.; Cassel, E.; Vargas, R. M. F.; von Poser, G. L. Supercritical CO2 extraction as a selective method for the obtainment of coumarins from Pterocaulon balansae (Asteraceae). J. CO2 Util., 2017, 18, 303-308.
[http://dx.doi.org/10.1016/j.jcou.2017.02.008]
[34]
Oliveira, A.L.; Pozza, L.N.L.; Santos, D.N.; Kamimura, E.S.; Vicente, E.; Cabral, F.A. Supercritical extraction of coumarin from guaco (Mikania laevigata and Mikania glomerata) for pharmaceutical applications. J. Supercrit. Fluids, 2013, 83(1), 65-71.
[http://dx.doi.org/10.1016/j.supflu.2013.07.019]
[35]
Vishnumurthy, K.; Guru Row, T.N.; Venkatesan, K. Unusual photodimerization of 7-fluoro-4-methylcoumarin and 6-fluoro-4-methylcoumarin in the solid state. Tetrahedron, 1998, 54(37), 11235-11246.
[http://dx.doi.org/10.1016/S0040-4020(98)00656-5]
[36]
Borges, F.; Roleira, F.; Milhazes, N.; Santana, L.; Uriarte, E. Simple coumarins and analogues in medicinal chemistry: Occurrence, synthesis and biological activity. Curr. Med. Chem., 2005, 12(8), 887-916.
[http://dx.doi.org/10.2174/0929867053507315] [PMID: 15853704]
[37]
Abdallah, M.; Hijazi, A.; Graff, B.; Fouassier, J.P.; Dumur, F.; Lalevée, J. In silico design of nitrocoumarins as near-uv photoinitiators: Toward interesting opportunities in composites and 3d printing technologies. ACS Appl. Polym. Mater., 2020, 2(7), 2890-2901.
[http://dx.doi.org/10.1021/acsapm.0c00409]
[38]
Erşatır, M.; Türk, M.; Giray, E.S. An efficient and green synthesis of 1,4-dihydropyridine derivatives through multi-component reaction in subcritical EtOH. J. Supercrit. Fluids, 2021, 176, 105303.
[http://dx.doi.org/10.1016/j.supflu.2021.105303]
[39]
Erşatır, M.; Yıldırım, M.; Giray, E.S.; Yalın, S. Synthesis and antiproliferative evaluation of novel biheterocycles based on coumarin and 2-aminoselenophene-3-carbonitrile unit. Monatsh. Chem., 2020, 151(4), 625-636.
[http://dx.doi.org/10.1007/s00706-020-02573-x]
[40]
Mohamed, H.M.; El-Wahab, A.H.F.A.; Ahmed, K.A.; El-Agrody, A.M.; Bedair, A.H.; Eid, F.A.; Khafagy, M.M. Synthesis, reactions and antimicrobial activities of 8-ethoxycoumarin derivatives. Molecules, 2012, 17(1), 971-988.
[http://dx.doi.org/10.3390/molecules17010971] [PMID: 22258342]
[41]
Mohareb, R.M.; Fleita, D.H.; Sakka, O.K. Novel synthesis of hydrazide-hydrazone derivatives and their utilization in the synthesis of coumarin, pyridine, thiazole and thiophene derivatives with antitumor activity. Molecules, 2010, 16(1), 16-27.
[http://dx.doi.org/10.3390/molecules16010016] [PMID: 21187814]
[42]
Matiadis, D.; Stefanou, V.; Athanasellis, G.; Hamilakis, S.; McKee, V.; Igglessi-Markopoulou, O.; Markopoulos, J. Synthesis, X-ray crystallographic study, and biological evaluation of coumarin and quinolinone carboxamides as anticancer agents. Monatsh. Chem., 2013, 144(7), 1063-1069.
[http://dx.doi.org/10.1007/s00706-013-0986-7]
[43]
Kusanur, R.A.; Ghate, M.; Kulkarni, M.V. Synthesis of spiro[indolo-1,5-benzodiazepines] from 3-acetyl coumarins for use as possible antianxiety agents. J. Chem. Sci., 2004, 116(5), 265-270.
[http://dx.doi.org/10.1007/BF02708277]
[44]
Aydıner, B.; Yalçın, E.; Korkmaz, V.; Seferoğlu, Z. Efficient one-pot three-component method for the synthesis of highly fluorescent coumarin-containing 3,5-disubstituted-2,6-dicyanoaniline derivatives under microwave irradiation. Synth. Commun., 2017, 47(23), 2174-2188.
[http://dx.doi.org/10.1080/00397911.2017.1362438]
[45]
Tapanyiğit, O.; Demirkol, O.; Güler, E.; Erşatır, M.; Çam, M.E.; Giray, E.S. Synthesis and investigation of anti-inflammatory and anticonvulsant activities of novel coumarin-diacylated hydrazide derivatives. Arab. J. Chem., 2020, 13(12), 9105-9117.
[http://dx.doi.org/10.1016/j.arabjc.2020.10.034]
[46]
Nofal, Z.; El-Zahar, M.; Abd El-Karim, S. Novel coumarin derivatives with expected biological activity. Molecules, 2000, 5(12), 99-113.
[http://dx.doi.org/10.3390/50200099]
[47]
Erşatır, M.; Yıldırım, M.; Giray, E.S. Carbostyril derivatives: Synthesis of novel carbostyril-3′-carbonitrilselenophene hybrid compounds and investigation of their antiproliferative properties on prostate and breast cancer. Synth. Commun., 2021, 51(2), 290-301.
[http://dx.doi.org/10.1080/00397911.2020.1825744]
[48]
Togna, A.R.; Firuzi, O.; Latina, V.; Parmar, V.S.; Prasad, A.K.; Salemme, A.; Togna, G.I.; Saso, L. 4-Methylcoumarin derivatives with anti-inflammatory effects in activated microglial cells. Biol. Pharm. Bull., 2014, 37(1), 60-66.
[http://dx.doi.org/10.1248/bpb.b13-00568] [PMID: 24389482]
[49]
Pankaj, A.; Sanjib, D.; Namita, A.; Ashish, G.; Baghel, U.S. Synthesis and screening of some novel 7-hydroxy-4-methyl coumarin derivatives for antipsychotic activity. Int. J. Pharm. Life Sci., 2010, 1, 113-118.
[50]
Pal, R.; Salkar, T.; Khasnobis, S. Amberlyst-15 in organic synthesis amberlyst-15 in organic synthesis. Arch. Org. Chem, 2012, 570-609.
[http://dx.doi.org/10.3998/ark.5550190.0013.114]
[51]
Adharvana Chari, M. Amberlyst-15: An efficient and reusable catalyst for multi-component synthesis of 3,4-dihydroquinoxalin-2-amine derivatives at room temperature. Tetrahedron Lett., 2011, 52(46), 6108-6112.
[http://dx.doi.org/10.1016/j.tetlet.2011.09.015]
[52]
Bora, P.P.; Vanlaldinpuia, K.; Rokhum, L.; Bez, G. Amberlyst-15 catalyzed Cbz protection of amines under solvent-free conditions. Synth. Commun., 2011, 41(18), 2674-2683.
[http://dx.doi.org/10.1080/00397911.2010.515341]
[53]
Chao, S.; Lu, G.; Wu, L. Amberlyst-15 catalyzed synthesis of 12-aryl-12h-benzo[i][1,3]-dioxolo[4,5-b]xanthene-6,11- diones and 14-aryl-14h-dibenzo[a,i]xanthene-8,13-diones under solvent-free condition. Asian J. Chem., 2011, 23, 3865-3869.
[54]
Lenin, R.; Rallabandi, M.R. A simple and efficient thiocyanation of indoles, anilines and keto compounds catalyzed by a polystyrene resin amberlyst-15. Lett. Org. Chem., 2010, 7, 392-395.
[http://dx.doi.org/10.2174/157017810791514878]
[55]
Brufani, G.; Valentini, F.; Sabatelli, F.; Di Erasmo, B.; Afanasenko, A.M.; Li, C.J.; Vaccaro, L. Valorisation of phenols to coumarins through one-pot palladium-catalysed double C–H functionalizations. Green Chem., 2022, 24(23), 9094-9100.
[http://dx.doi.org/10.1039/D2GC03579K]
[56]
Rather, I.A.; Ali, R. An efficient and versatile deep eutectic solvent-mediated green method for the synthesis of functionalized coumarins. ACS Omega, 2022, 7(12), 10649-10659.
[http://dx.doi.org/10.1021/acsomega.2c00293] [PMID: 35382332]
[57]
Wang, D.; Wang, Y.; Zhao, J.; Shen, M.; Hu, J.; Liu, Z.; Li, L.; Xue, F.; Yu, P. Strategic approach to 8-azacoumarins. Org. Lett., 2017, 19(5), 984-987.
[http://dx.doi.org/10.1021/acs.orglett.6b03771] [PMID: 28186758]
[58]
Atkins, R.L.; Bliss, D.E. Substituted coumarins and azacoumarins. Synthesis and fluorescent properties. J. Org. Chem., 1978, 43(10), 1975-1980.
[http://dx.doi.org/10.1021/jo00404a028]
[59]
Narumi, T.; Takano, H.; Ohashi, N.; Suzuki, A.; Furuta, T.; Tamamura, H. Isostere-based design of 8-azacoumarin-type photolabile protecting groups: A hydrophilicity-increasing strategy for coumarin-4-ylmethyls. Org. Lett., 2014, 16(4), 1184-1187.
[http://dx.doi.org/10.1021/ol5000583] [PMID: 24495035]
[60]
Takano, H.; Narumi, T.; Ohashi, N.; Suzuki, A.; Furuta, T.; Nomura, W.; Tamamura, H. Development of the 8-aza-3-bromo-7-hydroxycoumarin-4-ylmethyl group as a new entry of photolabile protecting groups. Tetrahedron, 2014, 70(29), 4400-4404.
[http://dx.doi.org/10.1016/j.tet.2014.04.063]
[61]
Takano, H.; Narumi, T.; Nomura, W.; Furuta, T.; Tamamura, H. Utilization of the heavy atom effect for the development of a photosensitive 8-azacoumarin-type photolabile protecting group. Org. Lett., 2015, 17(21), 5372-5375.
[http://dx.doi.org/10.1021/acs.orglett.5b02720] [PMID: 26469518]
[62]
Gorjian, H.; Khaligh, N.G. The liquid phase of 4,4′-trimethylenedipiperidine: A safe and greener dual-task agent for clean and facile synthesis of coumarin derivatives. Mol. Divers., 2022, 26(6), 3047-3055.
[http://dx.doi.org/10.1007/s11030-021-10364-7]
[63]
Potdar, M.K.; Rasalkar, M.S.; Mohile, S.S.; Salunkhe, M.M. Convenient and efficient protocols for coumarin synthesis via Pechmann condensation in neutral ionic liquids. J. Mol. Catal. Chem., 2005, 235, 249-252.
[http://dx.doi.org/10.1016/j.molcata.2005.04.007]
[64]
Gu, Y.; Zhang, J.; Duan, Z.; Deng, Y. Pechmann reaction in non-chloroaluminate acidic ionic liquids under solvent-free conditions. Adv. Synth. Catal., 2005, 347(4), 512-516.
[http://dx.doi.org/10.1002/adsc.200404316]
[65]
Singh, V.; Kaur, S.; Sapehiyia, V.; Singh, J.; Kad, G.L. Microwave accelerated preparation of [bmim][HSO4] ionic liquid: An acid catalyst for improved synthesis of coumarins. Catal. Commun., 2005, 6(1), 57-60.
[http://dx.doi.org/10.1016/j.catcom.2004.10.011]
[66]
Heravi, M.M.; Khorasani, M.; Derikvand, F.; Oskooie, H.A.; Bamoharram, F.F.; Bamoharram, F.F. Highly efficient synthesis of coumarin derivatives in the presence of H14[NaP5W30O110] as a green and reusable catalyst. Catal. Commun., 2007, 8(12), 1886-1890.
[http://dx.doi.org/10.1016/j.catcom.2007.02.030]
[67]
Amoozadeh, A.; Ahmadzadeh, M.; Kolvar, E. Easy access to coumarin derivatives using aluminasulfuric acid as an efficient and reusable catalyst under solvent-free conditions. J. Chem., 2013, 2013, 767825.
[http://dx.doi.org/10.1155/2013/767825]
[68]
Shirini, F.; Yahyazadeh, A.; Mohammadi, K. A solvent-free synthesis of coumarins using 1,3-disulfonic acid imidazolium hydrogen sulfate as a reusable and effective ionic liquid catalyst. Res. Chem. Intermed., 2015, 41(9), 6207-6218.
[http://dx.doi.org/10.1007/s11164-014-1733-3]

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