Keggin type heteropolyacids-catalyzed synthesis of quinoxaline derivatives in water

Available online at www.sciencedirect.comCHINESEScienceDirectC HEMICALL .ETTERSELSEVIERChinese Chemical Letters 20 (2009) 161-164www.elsevier.com/locate/ccletKeggin type heteropolyacids-catalyzed synthesis of quinoxalinederivatives in waterTai Kun Huang, Lin Shi, Rui Wang, Xing Zhou Guo, Xiao Xia LuChengduu Institute of Biology Chinese Academy of Sciences, Chengdu 610041, PR ChinaReceived 3 July 2008AbstractKeggin type heteropolyacids was found to be an efficient and reusable catalyst for the synthesis of biologically activequinoxaline derivatives from the condensation of 1,2-diamine with 1,2-dicarbonyl compounds in excellent yields in water. Thismethod provides a new and efficient protocol in terms of small quantity of catalyst, a wide scope of substrates, and simple work-upprocedure.C 2008 Xiao Xia Lu. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.Keywords: Keggin type heteropolyacids; 1,2-Diamines; 1,2- Diketones; Quinoxaline derivatives; WaterQuinoxalines are important compounds from both academic and industrial perspective because they are significantintermediates for the manufacturing of pharmaceuticals and advanced materials [1]. There is an increasing interest indeveloping environmentally benign reactions and atom-economic catalytic processes that employ 1,2-diamine and1,2-dicarbonyl compounds for the synthesis of quinoxaline derivatives in recent years [2]. Reactions that areperformed in water have attracted a great deal of attention in synthetic organic chemistry over past decades [3],because water is safe, cheap, and environmentally friendly. Despite a number of synthetic strategies have beendeveloped for the preparation of quinoxalines, most of them are preformed in organic solvents, with the use of water asa sole medium being very rare [4]. Moreover, most of synthetic strategies for the synthesis of quinoxaline derivativessuffer from several drawbacks including the use of a large amount of catalysts, unsatisfactory product yields, andcritical product isolation procedures. Especially the limited application of less-reactive aromatic diamine such as 4-nitrophenylenediamine. Therefore the search continues for a better catalyst for the quinoxaline derivatives in water interms of a wide scope of substrates, economic viability and reusability.Heteropolyacids (HPAs) are environmentally benign and economically feasible solid catalysts that offer severaladvantages such as excellent solubility in water, high catalytic activities and reactivates, ease of handling, cleanerreactions in comparison to conventional catalysts (less waste production), non-toxicity and experimental simplicity[5]. It is attractive that HPAs have hierarchical structure [6], which are important for the forming of active pseudoliquidphases and keeping high catalytic activities. HPAs are strong Bronsted acid and most of them are stronger in aciditythan the usual inorganic acids (HCl, H2SO4, HNO3, HBr), even stronger than HClO4 and CFSO3H. Both its structuralCorresponding author.E-mail address: xlua71 @ yahoo.com.cn (X.X. Lu).中国煤化工1001-8417/$ - see front matter◎2008 Xiao Xia Lu. Published by Elsevier B.V. on beMYHCNMH GAll rights reseved.doi: 10.1016/.cclet.2008.10.048162T.K. Huang et al./Chinese Chemical Letters 20 (2009) 161-164Table 1Synthesis of quinoxalines under different catalysts and different conditions' .EntryCatalyst (mol%)TimeSolventYield (%) .NH2SO,H (1)1hH2O42Mont. K-10 (1).h57p-TsOH (1)!h50HsSiW 12O40 (10))6H2SiW12O40 (5))5H4SiW12O4o (1)H4SiW 12O40 (0.5)hH,O2HzSiW i2O40 (0.1)8h96HzSiW12O40 (1)15 minCH,OH10010H4SiW12O4o(1)11HsSiW 12O40(1)CHCl3 .12H4SiW2O4o (1)AcOHa Reaction conditions: 1,2 diaminobenene (1.0 mmol) and benzil (1.0 mmol) in solvent (3 mL) at room temperature.Isolated yield.features [6] and synthetic potential [7] have been extensively studied. Due to strong catalytic activity as Bronsted acid,HPAs have been usedextensively as catalyst in: esterification [7(a)], Friedel- Crafts reactions [7(b)], cyanosilylation[7(c)], ring-opening of epoxides [7(d)], and dehydration [7(e)].In continuation of the studies on the new variants, of a one pot synthesis of quinoxaline derivatives and our ongoinggreen organic chemistry program that uses water as a reaction medium, Wells-Dawson type heteropolyacids(H6P2W 18O62) which is ellipsoidal structure [8] as catalyst for synthesis of quinoxaline derivatives has been reported,however use of water as solvent in this reaction gave very low yields of products (30% after 24 h) [9]. Keggin typeheteropolyacids (H4SiW 12O40) are roughly spherical and involves 4 threefold M3O13 groups. The total assemblagecontains 40 close-packed oxygens and has a tetrahedron pocket in its center for the heteroatom [10]. To the best of ourknowledge, there are no examples of the use of Keggin type heteropolyacids as catalyst for the synthesis ofquinoxaline derivatives. Following our previous work on the synthesis of quinoxaline derivatives [11], and in view ofthe importance of heterogeneous solid acids as reusable catalyst in organic synthesis, herein, we describe a green andeficient method for the synthesis of quinoxaline derivatives in high yields by the condensation 1,2- diamine with 1,2-dicarbonyl compounds catalyzed by Keggin type heteropolyacids in water (Scheme 1).Initally, following the report by Heravi et al. [9], we attempted the condensation of o phenylenediamine and benzil(PhCOCOPh) using 1 mol% different solid acids, such as NH2SO3H, Mont K- 10 and p-TsOH, in place of Wells-Dawson type heteropolyacids, at room temperature in water for the synthesis of quinoxaline, only providing moderateyield of a condensation product 3a after 1 h (Table 1, entries 1-3). Thus, using Wells-Dawson type heteropolyacids,NH2SO3H, Mont K 10 and p-TsOH, as catalyst in water, the reaction was slow with unsatisfactory yields. While usingKeggin type heteropolyacids (H4SiW 12O40) as catalyst with similar substrates in water, to our surprise, the reactionproceeded smoothly after 1 h and afforded the products 3a in 96% yield (Table 1, entry 6). In order to determine theoptimum conditions, we examined the influence of the proportions of H4SiW 12O40 to substrate. The condensation wascompleted in the formation of quinoxaline ring using 1 mol% of H4SiW12O40 after 1h (Table 1, entry 6, 96%).Decreasing the amount of H4SiW 12O40 to 0.5 mol% resulted in lower yields (Table 1, entry 7, 72% ), while increasingthe amount of H4SiW 12O40 to 5 mol% showed no substantial improvement in the yield (Table 1, entry 5, 95%). We alsoobserved that the reaction proceeded with 0.1 mol% of H4SiW 12O40, longer time (8 h) is typical to achieve comparableyields to those obtained with 1 mol% of H4SiW 12O40 (Table 1, entry 8, 96%). The reaction was also carried out insome organic solvents (Table 1, entries 9-12). Organic solvents stood out as the solvent of choice, with their fastR1YNH20yR2 H4SiW1204o(1 mol%) RiyA .Ny ,Rz .o个R3H2O, r.t.中国煤化工1MYHCNMHGScheme 1.T.K. Huang et al. / Chinese Chemical Letters 20 (2009) 161-164163conversion and quantitative yields, organ solvents are proved to be better than water which requires longer time tocomplete. However, the use of hazardous organic solvents often results in environmental pollution. The reaction inwater is green, environmental friendly, clean, can be performed easily at room temperature and no undesirable sidereactions were observed. Moreover H4SiW 12O40 is highly soluble in water and can be easily removed from thereaction mixture by simple filtration.Encouraged by the remarkable results obtained with the above reaction conditions, and in order to show thegenerality and scope of this new protocol, we used various 1,2-diamine and 1,2-dicarbonyl compounds in the presenceof HsSiW 12O40 and the results were summarized in Table 2. Most of the reactions proceeded very cleanly at roomtemperature and no undesirable side reactions were observed. The variations in the yields were very small and bothsubstituted aromatic diamines such as 4-methyl and 4-chloro gave the condensed products in excellent yields (Table 2,entries 2 and 3). However, less-reactive aromatic diamines such as 4-nitro, gave the desired product in low yield inwater similar to the results we found for both CAN and CuSO4:5H2O under the same conditions (Table 2, entry 4).Importantly, when the reaction was carried out in CH3OH, the yield was dramatically improved to 96%, whilst the useof sulfamic acid/MeOH catalytic system to ensure a complete reaction was required more loading of catalyst (80 mol%of sulfamic acid) and longer time (5 h) [12]. To check the versatility of this method, we have also studied compoundssuch as furil and 1-phenyl-1,2-propanedione, and obtained the products in high yields (Table 2, entries 6 and 7). Thegenerality of this system was also confirmed by the use of other dicarbonyls, i.e. diacetyl (CH3COCOCH3) and otherdiamine, i.e. 1,2-ethylenediamine (NH2CH2CH2NH2) (Table 2, entries 8 and 9).Table 2Synthesis of quinoxaline derivatives catalyzed by HSiW i2O4o using different diamines and 1,2-diketones".EntryDiamine1,2-DiketoneProductTime (h)Yield (%)中3a96“企o1.02416, 149, 13", 96°O2NONLCNHCH1AcHs6ENH路量3f9273g91oCHs8ONhOqCHslXCH3h959[NH23i1.590NH2a Reaction conditions: 1,2-diamine (1.0 mmol), 1,2-diketone (1.0 mmol), and H4SiWb Isolated yield confirmed by 'H NMR.中国煤化工roo eperure。 The reaction was crried out in the presence of CAN (5 mol%) in water (3 mL) at:0HCNMH G,。24h.d The reaction was carried out in the presence of CuSO45H2O (10 mol%) in water (The reaction was carried out in the presence of H4SiW 12O40 (1 mol%) in CH3OH (3 mL) at room temperature during 30 min.164T.K. Huang et al. /Chinese Chemical Letters 20 (2009) 161-164To investigate the reusability of the catalyst, the reaction of o-phenylenediamine and benzil in water at roomtemperature in the presence of H4SiW 12O40 was studied. When the reaction was completed, the solid was fitered andthe aqueous solution was saved for the next reaction. The recycled catalyst could be directly reused for five timeswithout any treatment and, there was no observation of appreciable loss in its catalytic activities (96%, 95%, 93%,92%, 91%).In conclusion, we developed the use of the Keggin-type heteropolyacid (H4SiW 12O40) as an inexpensive, reusable,easy to handle, non-corrosive, and environmentally benign catalyst for the synthesis of biologically activequinoxalines from 1 ,2-diamines and 1 ,2-dicarbonyl compounds.1. ExperimentalGeneral experimental procedure. A mixture of 1,2-diamine 1 (1 mmol), 1,2-diketone 2 (1 mmol) and H4SiW 12040(1 mol%) in water (3 mL) was stirred at room temperature. The progress of the reaction was monitored by TLC. Aftercompletion of the reaction, the crude product was filtered, washed with water (3 X 10 mL) and then recrystallizedfrom ethanol to afford pure quinoxaline 3.References[1] (a) N. Sato, in: A.R. Katritzky, C.W. Rees, EFV. Scrivon (Eds.), Comprehensive Heterocyclic Chemistry II, EIsevier Science Ltd., Oxford,1996;(b) M. Matsuoka, I. Iwamoto, N. Furukawa, T. Kitao, J. Heterocyel. Chem. 29 (1992) 439;(c) A.R. Ahmad, LK. Mehta, J. Parrick, Tetrahedron 51 (1995) 12899;(d) A. Gazit, H. App, G. McMahon, J. Chen, A. Levitzki, FD. Bohmer, J. Med. Chem. 39 (1996) 2170; .(e) LE. Seitz, WJ. Suling, R.C. Reynolds, J. Med. Chem.45 (2002) 5604.[2] (a) Z. Zhao, D.D. Wisnoski, S.E. Wolkenberg, W.H. Leister, Y. Wang, C. W. Lindsley, Tetrahedron Lett. 45 (2004) 4873;(b) S.V. More, M.N.V. Sastry, C.C. Wang, CF. Yao, Tetrahedron Lett. 46 (2005) 6345;(c) R.S. Bhosale, S.R. Sarda, S.S. Ardhapure, W.N. Jadhav, S.R. Bhusare, R.P. 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