Surfactant-assisted synthesis of bis(indolyl)methanes in water

Available online at www.sciencedirect.comCHINES EScienceDirectCH EMICALL .ETTERSEL SEVIERChinese Chemical Letters 22 (2011) 1305- -1308www.elsevier.com/locate/ccletSurfactant-assisted synthesis of bis(indolyl)methanes in waterEskandar Kolvari a.*, Mohammad Ali Zolfigol b, Hoda Banarya*Department of Chemistry; Faculty of Science, Semnan University, Semnan, lranb Faculty of Chemistry; Bu-Ali Sina Universit, Hamnedan, lranReceived 1 April 2011Available online 6 September 2011AbstractAn environmentally friendly synthesis method for bis(indoly)methanes has been developed in the presence of sodium laurylether sulfate (SLES), electrophilic substitution reactions of indoles with aldehydes were accomplished in water as solvent at roomtemperature without any Bronested or Lewis acid catalysts.◎2011 Eskandar Kolvani. Published by Elsevier B.V. on behalf of Chinese Chemical Society, All rights reserved.Keywords: Sodium lauryl etber sulfate; Bis(indolyI) methanes; Indoles; AldehydesIndoles and bis(indolyl)methanes (BIMs) are important class of heterocyclic compounds in the pharmaceutical aswell as synthetic chemistry [1,2] They are important antibiotics in the field of pharmaceuticals [3] or the precursor ofbioactive metabolites of terrestrial and marine origin [4 6]. They are also know as antitumor compounds [7,8] and areeffective in the prevention of cancer and found in cruciferous plants and known to promote beneficial estrogenmetabolism and induce apoptosis in human cancer cell [9]. In the analytical chemistry they can be used as anionreceptors [10] or in solid-phase extraction [11].Due to importance of bis(indolyl)methanes in pharmaceutical chemistry, their synthesis have received increasingattention. Several methods have been reported in the literature for the preparation of bis(indolyl)methanes fromindoles and aldehydes or ketones using protic acids [12-17] and Lewis acids [18 -23]. Many Lewis acids like BF3 andAlCl3 promote this type of reaction but they generate harmful wastes, which pose environmental problems.Use of environmentally friendly reaction medium is one of the fundamental principles of green chemistry [24].Water as a reaction solvent has received much attention in synthesis of organic compounds, because it would beconsiderably safe, non-toxic, environmentally friendly, and cheap compared to organic solvents [25]. Moreover, whena water soluble catalyst is used, the insoluble products can be separated by simple filtration and the catalyst system canbe recycled. Using water as solvent in the synthesis of BIMs is accompanied with some problems; the most commonand noticeable of these problems are low solubility of reactants and sensitivity of Lewis acids to the water. Theseproblems can be solved to some extent using water tolerant Lewis acids such as metal trifate and surfactant-type Lewisand Bronested acids or using surfactant assisted reactions [26 -30].# Corresponding author.中国煤化工E-mail address: kolvari@semnan.ac.ir (E. Kolvari).MYHCNMHG1001-8417/$S- sce front matter◎2011 Eskandar Kolvari. Publisbed by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.doi:10.101j.cl.2011.0.00130E. Kolvani et al./Chinese Chemical Letters 22 (2011) 1305-1308CHOSLESooH2O,rtScbeme 1. The reaction of indole with benzaldehyde as a model reaction.Table 1Effect of amount of SLES on the reaction yicld of 3,3'-bis(indoly)phenylmethane. 'EntryMol%Yield (%)5NoneN.R031542070●Indole (2.0 mmol), benzaldehyde (1.0 mmol) in the presence of diferent amount of SLES.b Isolated yield.In order to develop a new method for the synthesis of bis(indoly1)methanes we report here the surfactant assistedsynthesis of bis(indoly)methanes from the condensation of various aldehydes and indoles in water as solvent at roomtemperature in the absence of any catalyst.To optimize the reaction conditions, the reaction of indole and benzaldehyde was selected as the model reaction.Model reaction has been carried out at room temperature in water as solvent (Scheme |).To find the optimum amount of SLES, the yields of the model reaction using various amounts of SLES (5, 10, 15 and20 mol%) were obtained and compared. The results were summarized in Table 1. From these results, it can be concludedthat the yields of reaction in the presence small amount of SLES were good to high and the optimum amount of surfactantwas 10 mol%, the desired product was obtained in 93% yield within 2.5 h. Presence of surfactant is essential for thisreaction and the reaction did not occur in the absence of SLES even after a long time (Table 1, entry 1).In addition to SLES, we screened the effect of other surfactants such as cetyl trimethylammonium bromide(CTAB), tetradecyl trimethyl ammonium bromide (TTAB), dodecyl trimethyl ammonium bromide (DTAB), andEsterquat (Scheme 2), on the time and yield of the model reaction (Table 2). As can be seen from this table SLESperforms better than other surfactants regard to time and yield of the reaction.Based on these observations we extended the study to the reaction of indoles with other aldehydes all the resultswere summarized in Table 3.prionCHzOS03n=12Scbeme 2. Chemical structure of Esterquate as a cationice surfactantTable 2Effect of diferent surfactants on the reaction time and yield of 3.3'-bis(indolyl)phenaylmethane."EntrSurfactant (10 mol%)Time (b)Yicld (%)TTAB35DETAB30CTAB中国煤化工EsterquatYHCNMHG92' Indole (2.0 mmol), benzaldebyde (1.0 mmol) in the presence of 10 mol% of various surfactants.E. Kolvari et al./Chinese Chemical Letters 22 (2011) 1305 -13081307Table 3Synthesis of bis(indolyI)methancs via the condensation of indoles with aldchydes using SLES in aqueous media at room temperature.EntryIndoleBenzaldehydeProductTime (b)Yicld (%)1.5σ°9P2.CH2.5qMe'%3心.070a-MeAMe M4QMe,.085MeO'唧s90咖686。点7。O°8530973σNHPh NAorl.5”中国煤化工12CH2CHOMYHCNMHG1 Yields refer to isolated products.”All the products gave stisfactoy spectroscopic IR, H, and "c NMR) analyis.1308E. Kolvari et al./Chinese Chemical Letters 22 (2011) 1305-1308SLES forms micelles in water and can dissolves insoluble starting materials. The dissolved material reactedgradually on sirring the reaction mixture at room temperature and was complete in 2.5 5 h giving 70 -94% yields ofbis(indolyl)methanes.In conclusion, we have presented a green procedure for the synthesis of bis(indolyI)methanes from indoles andaromatic aldehydes in the presence of SLES in water as green solvent. The present procedure has many advantagessuch as mild conditions, easy operation procedures and environment friendly.General experimental procedure for synthesis of bis(indolyl)methanes: To a mixture of indole (2 mmol), aldehyde(1 mmol) in water (5 mL), SLES (10 mol%) was added and stired at room temperature. The mixture became emulsiveand the product gradually precipitated. The progress of reaction monitored byTLC and the reaction went to completion inappropriate time (Table 3). After completion of the reaction the almost pure insoluble bis(indoly)-methane was filteredand recrystallized from suitable solvent like ethanol- water for further purification.AcknowledgmentsWe thank Semnan University research councils for financial support of this work. Also we would like toacknowledge and thank the Condor Company for their generous support.References[1] RJ. Sundberg, The Chemistry of Indoles, Academic Press, New York, 1996.[2] M Shin, M.A. Zolfigol, H.G. Kruger, et al. Chem. Rev. 110 (2010) 2250.[3] P. aletti, A. Quintavalla, C. Ventrici, et al. New J. Chem.34 (2010) 2861.[4] G. Bifulco, I. Bruno, R. Riccio, et al. J. Nat. Prod. 58 (1995) 1254.[5] TR. Garbe, M. Kobayashi, N. Shimizu, et al. J. Nat. Prod. 63 (2000) 596.[6] T. Osawa, M. Narmik, Tetrabedron Lett. 24 (1983) 4719.[7] N. Ichite, M. Chougule, A.R. Patel, et al. Mol. Cancer Ther. 9 (2010) 3003.[8] P. Diana, A. Carbone, P. Barraja, et al. Bioorg. Med. Chem. 18 (2010) 4524.[9] J.S. Glasby, Encyclopedia of the Alkaloids, Plenum Press, New York, 1975.[10] L. Wang, W. Wei, Y. Guo, et al. Spectrochim. Acta A 78 (2011) 726.[11] M. Ghaedi, K. Nikmam, K. Taberi, et al. Food Chem. Toxicol. 48 (2010) 891.[12] M.A. Naik, D. Sachdev, A. Dubey, Catal. Commun. 11 (2010) 1148.[13] E. Rafice, Z. Zolfaghanifar, M. Joshaghani, et al. Synth. Commun.41 (2011) 459.[14] S.A. Sadaphal, A.H. Kategaonkar, V.B. Labade, et al. Chin. Chem. Lett. 21 (2010) 39.[15] F. Shirini, A. Yahyazadeh, M. Abedini, et al. Bull. Korean Chem. Soc. 31 (2010) 1715.[16] J.S. Yadav, M.K. Gupta, R. Jain, et al. Monatsh. Chem. 141 (2010) 1001.[17] MA. Zolfigol, A. Khazaei, A.R. Moosavi-Zare, et al. Org. Prep. Proced. Int. 42 (2010) 95.[18] s. Amiya, PD. Deo, Res. J. Chem. Env. 14 (2010) 19.[19] M. Kidwai, N. Bura, NK. Mishra, Indian J. Chem. Sect. B 50 (2011) 229.[20] G.A. Meshram, V.D. Pati, Synth. Commun. 40 (2010) 29.[21] M. Rahimizadeh, z. Bakhtiarpoor, H. Esbghi, et al. Monatsh. Chem.140 (2009) 1465.[22] C.C. Silveira, S.R. Mendes, FM. Libero, et al. Tetrahedron Lett. 50 (2009) 6060.[23] F Shirini, M.S. Langroodi, M. Abedini, Chin. Chem. Lt 21 (2010) 1342.[24] PT. Anastas, J.C. Warner, Green Chemistry: Theory and Practice, Oxford University Press, London, 1998.[25] U.M. Lindstrom, Organic Reactions in Water: Principles, Strategies and Applications, Blackwell, Oxford, 2007.[26] J.T. Li, M.X. Sum, G.Y. He, et al. Utrason. Sonochem. 18 (2011) 412.[27] MA. Zoligol, P. Salchi, M. Shiri, et al. Catal. Commun. 8 (2007) 173.[28] Y.Y. Peng, QL. Zhang. JJ. Yuan, et al. Chin. J. Chem. 26 (2008) 2282.[29] M.L Deb, PJ. Bhuyan, Tetrahedron Ltt 47 (2006) 1441.[30} R. Ghorbani-Vaghei, H. Veisi, H. Keypour, et al. Mol. Diversity 14 (2010) 87.中国煤化工MYHCNMHG