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Efficient one-pot synthesis of 14-substituted-14H-dibenzo[a,j]xanthenes using boric acid under solvent-free conditions
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Chinese Chemical Letters 21 (2010) 547–549 www.elsevier.com/locate/cclet
Efficient one-pot synthesis of 14-substituted-14H-dibenzo[a,j]xanthenes using boric acid under solvent-free conditions Zahed Karimi-Jaberi *, Mohsen Keshavarzi Department of Chemistry, Islamic Azad University of Firoozabad, P.O. Box 74715-117 Firoozabad, Fars, Iran Received 16 September 2009
Abstract Boric acid efficiently catalysed the one-pot reaction of alkyl or aryl aldehydes with 2-naphthol to afford the corresponding 14alkyl- or aryl-14H-dibenzo[a,j]xanthenes in good yields under solvent-free conditions. # 2010 Zahed Karimi-Jaberi. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved. Keywords: Boric acid; 2-Naphthol; Dibenzoxanthenes; Solvent-free synthesis
Xanthenes and benzoxanthenes are biologically important drug intermediates. They are cited as active oxygen heterocycles possessing antiviral, antibacterial and antiflammatory activities [1] as well as efficacy in photodynamic therapy and antagonists for paralyzing action of zoxazolamine [2]. The other useful applications of these heterocycles are as dyes [3], fluorescent materials for visualization of biomolecules [4] and in laser technologies [5]. Consequently, the development of novel synthetic methods for their synthesis has attracted sustained interest in organic synthesis. A number of synthetic methods have been developed for the synthesis of xanthenes and benzoxanthenes [6–10]. In addition, the synthesis of dibenzoxanthenes by the reaction of aldehydes with 2-naphthol is the most convenient method. In this context some catalysts have been reported such as acetic acid and sulfuric acid [11], acetic acid and hydrochloric acid [12], H3PO4 or HClO4 [13], p-toluene sulfonic acid [14], sulfamic acid [15], I2 [16], oxalic acid [17], K5CoW12O40 [18], cyanuric chloride [19], silica sulfuric acid [20], and NH4H2PO4 [21]. However, these methods suffer from one or more disadvantages such as low yields, prolonged reaction times, use of toxic organic solvents, the requirement of special apparatus, or harsh reaction conditions. Thus, there is a certain need for the development of an alternative route for the production of xanthenes derivatives, which surpasses those limitations. During the course of our systematic studies directed towards the development of environmentally friendly procedures for several important organic transformations [22], we have recently developed catalytic method based on sodium hydrogen sulfate for the synthesis of 14-alkyl- or aryl-14H-dibenzo[a,j]xanthenes [23]. We report here a new
* Corresponding author. E-mail address: [email protected] (Z. Karimi-Jaberi). 1001-8417/$ – see front matter # 2010 Zahed Karimi-Jaberi. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved. doi:10.1016/j.cclet.2010.01.014
548
Z. Karimi-Jaberi, M. Keshavarzi / Chinese Chemical Letters 21 (2010) 547–549
Scheme 1. Synthesis of dibenzoxanthenes using boric acid.
and very convenient procedure for the condensation of aldehydes with 2-naphthol to the corresponding 14-alkyl- or aryl-14H-dibenzo[a,j]xanthanes using catalytic amounts of boric acid under solvent-free conditions (Scheme 1). Boric acid (H3BO3) is a useful and environmentally benign catalyst which has been successfully utilized in numerous reactions, for example, the aza-Michael addition [24], the thia Michael addition [25], Biginelli reaction [26], transesterification of ethyl acetoacetate [27], decarboxylation of cyclic b-enaminoketoesters [28] and Mannich reaction [29]. It offers milder conditions relative to common mineral acids. Boric acid is a readily available and inexpensive reagent and can conveniently be handled and removed from the reaction mixture. Thus, the remarkable catalytic activities together with its operational simplicity make it the most suitable catalyst for the synthesis of dibenzoxanthenes. To optimize the reaction conditions, the reaction of benzaldehyde with 2-naphthol was used as a model reaction. Reactions at different conditions and various molar ratios of substrates in the presence of boric acid revealed that the best conditions were solvent-free at 120 8C and a molar ratio of 2-naphthol/aldehyde/boric acid of 2:1:0.2. After completion of the reaction, the catalyst (boric acid) can easily be separated from the reaction mixture by washing the product with water. To show the generality of this method the optimized system was used for the synthesis of other derivatives 3a–3k. Several examples illustrating this novel and general method for the synthesis of dibenzoxanthenes are summarized in Table 1. All products are known compounds and structures of them were confirmed by comparison with their known physical and spectral (NMR and IR) data [11–21]. The reaction proceeds via condensation of 1 mol of aldehyde with 2 mol of 2-naphthol followed by intramolecular elimination of water from two hydroxyl groups to form the corresponding dibenzoxanthene as has been suggested earlier [23]. In conclusion this paper describes a convenient and efficient process for the synthesis of 14-alkyl- or aryl-14Hdibenzo[a,j]xanthenes by one-pot reaction of alkyl or aryl aldehydes and 2-naphthol in the presence of catalytic amount of boric acid at 120 8C under solvent-free conditions. This method offers some advantages in terms of simplicity of performance, solvent-free condition, low cost, and it follows along the line of green chemistry. The catalyst is readily available and inexpensive and can conveniently be handled and removed from the reaction mixture. We believe that this procedure is convenient, economic, and a user-friendly process for the synthesis of 14-alkyl- or aryl-14H-dibenzo[a,j]xanthenes of biological and medicinal importance. Table 1 Synthesis of 14-alkyl- or aryl-14-H-dibenzo[a,j]xanthanes in the presence of boric acid. Entry
R
Time (h)
Yield (%)
3a 3b 3c 3d 3e 3f 3g 3h 3i 3j 3k
C6H5 4-ClC6H4 4-NO2C6H4 3-NO2C6H4 4-CNC6H4 4-CH3C6H4 4-CH3OC6H4 4-OHC6H4 2,4-Cl2C6H3 CH3CH2 CH3
2 2 2 1.5 2 2 3 2 1.5 2 2
94 97 98 89 98 90 89 85 98 97 84
Z. Karimi-Jaberi, M. Keshavarzi / Chinese Chemical Letters 21 (2010) 547–549
549
1. Experimental 1.1. Synthesis of 14-alkyl- or aryl dibenzo[a,j]xanthenes 3a–3k. General procedure A mixture of aldehyde (1 mmol), 2-naphthol (2 mmol) and boric acid (20 mol%) was stirred at 120 8C for the appropriate time indicated in Table 1. The progress of reactions was monitored by TLC (ethyl acetate/n-hexane = 1/4). After completion of the reaction, the reaction mixture was cooled to 25 8C, and water (10 cm3) was added, and the mixture was stirred for 10 min. The obtained solid was collected by filtration and purified by recrystallization from ethanol. Products were characterized by comparison of their physical and spectral data with those of authentic samples [11–21]. Spectral data for selected products: compound 3a: 1H NMR (500 MHz, CDCl3): d 8.41 (d, 2H, J = 8.5 Hz), 7.85 (d, 2H, J = 8.0 Hz), 7.82 (d, 2H, J = 8.8 Hz), 7.60 (t, 2H, J = 7.7 Hz), 7.54 (d, 2H, J = 7.5 Hz), 7.51 (d, 2H, J = 8.8 Hz), 7.43 (t, 2H, J = 7.5 Hz), 7.18 (t, 2H, J = 7.5 Hz), 7.02 (t, 1H, J = 7.5 Hz), 6.50 (s, 1H). References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26] [27] [28] [29]
J.P. Poupelin, G. Saint-Rut, O. Foussard-Blanpin, et al. Eur. J. Med. Chem. 13 (1978) 67. R.M. Ion, D. Frackowiak, A. Planner, et al. Acta Biochim. Pol. 45 (1998) 833. S.M. Menchen, S.C. Benson, J.Y.L. Lam, et al. Chem. Abstr. 139 (2003) p54287f (U.S. Patent US6583168 (2003)). C.G. Knight, T. Stephens, Biochem. J. 258 (1989) 683. M. Ahmad, T.A. King, D. Ko, et al. J. Phys. D: Appl. Phys. 35 (2002) 1473. D.W. Knight, P.B. Little, J. Chem. Soc. Perkin Trans. 1 (2001) 1771. A. Jha, J. Beal, Tetrahedron Lett. 45 (2004) 8999. C.W. Kuo, J.M. Fang, Synth. Commun. 31 (2001) 877. F.M. Dean, H.D. Lockstely, J. Chem. Soc. (1963) 393. J.Q. Wang, R.G. Harvey, Tetrahedron 58 (2002) 5927. R.J. Sarma, J.B. Baruah, Dyes Pigments 64 (2005) 91. (a) J.A. Van Allan, D.D. Giannini, T.H. Whitesides, J. Org. Chem. 47 (1982) 820; (b) O. Sirkecioglu, N. Talinli, A. Akar, J. Chem. Res. (S) (1995) 502. A. Khoramabadi-zad, Z. Kazemi, H.A. Rudbari, J. Korean Chem. Soc. 46 (2002) 541. A.R. Khosropour, M.M. Khodaei, H. Moghannian, Synlett (2005) 955. B. Rajitha, B.S. Kumar, Y.T. Reddy, et al. Tetrahedron Lett. 46 (2005) 8691. (a) B. Das, B. Ravikanth, R. Ramu, et al. J. Mol. Catal. A: Chem. 255 (2006) 74; (b) M.A. Pasha, V.P. Jayashankara, Bioorg. Med. Chem. Lett. 17 (2007) 621. N.D. Kokare, J.N. Sangshetti, D.B. Shinde, Chin. Chem. Lett. 19 (2008) 1186. L. Nagarapu, S. Kantevari, V.C. Mahankhali, et al. Catal. Commun. 8 (2007) 1173. M.A. Bigdeli, M.M. Heravi, G.H. Mahdavinia, Catal. Commun. 8 (2007) 1595. H.R. Shaterian, M. Ghashang, A. Hassankhani, Dyes Pigments 67 (2008) 564. S. Rostamizadeh, A.M. Amani, G.H. Mahdavinia, et al. Chin. Chem. Lett. 20 (2009) 779. (a) M.M. Hashemi, Z. Karimi-Jaberi, Monatsh. Chem. 135 (2004) 41; (b) M.M. Hashemi, M. Bakhtiari, Z. Karimi-Jaberi, Russ. J. Org. Chem. 43 (2007) 621. Z. Karimi-Jaberi, M.M. Hashemi, Monatsh. Chem. 139 (2008) 605. M.K. Chaudhuri, S. Hussain, M.L. Kantam, et al. Tetrahedron Lett. 46 (2005) 8329. M.K. Chaudhuri, S. Hussain, J. Mol. Catal. A: Chem. 269 (2007) 214. S. Tu, F. Fang, C. Miao, et al. Tetrahedron Lett. 44 (2003) 6153. G.C.M. Kondaiah, L.A. Reddy, K.S. Babu, et al. Tetrahedron Lett. 49 (2008) 106. P. Delbecq, J. Celerier, G. Lhommet, Tetrahedron Lett. 31 (1990) 4873. C. Mukhopadhyay, A. Datta, R.J. Butcher, Tetrahedron Lett. 50 (2009) 4246.
Chinese Chemical Letters 21 (2010) 547–549 www.elsevier.com/locate/cclet
Efficient one-pot synthesis of 14-substituted-14H-dibenzo[a,j]xanthenes using boric acid under solvent-free conditions Zahed Karimi-Jaberi *, Mohsen Keshavarzi Department of Chemistry, Islamic Azad University of Firoozabad, P.O. Box 74715-117 Firoozabad, Fars, Iran Received 16 September 2009
Abstract Boric acid efficiently catalysed the one-pot reaction of alkyl or aryl aldehydes with 2-naphthol to afford the corresponding 14alkyl- or aryl-14H-dibenzo[a,j]xanthenes in good yields under solvent-free conditions. # 2010 Zahed Karimi-Jaberi. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved. Keywords: Boric acid; 2-Naphthol; Dibenzoxanthenes; Solvent-free synthesis
Xanthenes and benzoxanthenes are biologically important drug intermediates. They are cited as active oxygen heterocycles possessing antiviral, antibacterial and antiflammatory activities [1] as well as efficacy in photodynamic therapy and antagonists for paralyzing action of zoxazolamine [2]. The other useful applications of these heterocycles are as dyes [3], fluorescent materials for visualization of biomolecules [4] and in laser technologies [5]. Consequently, the development of novel synthetic methods for their synthesis has attracted sustained interest in organic synthesis. A number of synthetic methods have been developed for the synthesis of xanthenes and benzoxanthenes [6–10]. In addition, the synthesis of dibenzoxanthenes by the reaction of aldehydes with 2-naphthol is the most convenient method. In this context some catalysts have been reported such as acetic acid and sulfuric acid [11], acetic acid and hydrochloric acid [12], H3PO4 or HClO4 [13], p-toluene sulfonic acid [14], sulfamic acid [15], I2 [16], oxalic acid [17], K5CoW12O40 [18], cyanuric chloride [19], silica sulfuric acid [20], and NH4H2PO4 [21]. However, these methods suffer from one or more disadvantages such as low yields, prolonged reaction times, use of toxic organic solvents, the requirement of special apparatus, or harsh reaction conditions. Thus, there is a certain need for the development of an alternative route for the production of xanthenes derivatives, which surpasses those limitations. During the course of our systematic studies directed towards the development of environmentally friendly procedures for several important organic transformations [22], we have recently developed catalytic method based on sodium hydrogen sulfate for the synthesis of 14-alkyl- or aryl-14H-dibenzo[a,j]xanthenes [23]. We report here a new
* Corresponding author. E-mail address: [email protected] (Z. Karimi-Jaberi). 1001-8417/$ – see front matter # 2010 Zahed Karimi-Jaberi. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved. doi:10.1016/j.cclet.2010.01.014
548
Z. Karimi-Jaberi, M. Keshavarzi / Chinese Chemical Letters 21 (2010) 547–549
Scheme 1. Synthesis of dibenzoxanthenes using boric acid.
and very convenient procedure for the condensation of aldehydes with 2-naphthol to the corresponding 14-alkyl- or aryl-14H-dibenzo[a,j]xanthanes using catalytic amounts of boric acid under solvent-free conditions (Scheme 1). Boric acid (H3BO3) is a useful and environmentally benign catalyst which has been successfully utilized in numerous reactions, for example, the aza-Michael addition [24], the thia Michael addition [25], Biginelli reaction [26], transesterification of ethyl acetoacetate [27], decarboxylation of cyclic b-enaminoketoesters [28] and Mannich reaction [29]. It offers milder conditions relative to common mineral acids. Boric acid is a readily available and inexpensive reagent and can conveniently be handled and removed from the reaction mixture. Thus, the remarkable catalytic activities together with its operational simplicity make it the most suitable catalyst for the synthesis of dibenzoxanthenes. To optimize the reaction conditions, the reaction of benzaldehyde with 2-naphthol was used as a model reaction. Reactions at different conditions and various molar ratios of substrates in the presence of boric acid revealed that the best conditions were solvent-free at 120 8C and a molar ratio of 2-naphthol/aldehyde/boric acid of 2:1:0.2. After completion of the reaction, the catalyst (boric acid) can easily be separated from the reaction mixture by washing the product with water. To show the generality of this method the optimized system was used for the synthesis of other derivatives 3a–3k. Several examples illustrating this novel and general method for the synthesis of dibenzoxanthenes are summarized in Table 1. All products are known compounds and structures of them were confirmed by comparison with their known physical and spectral (NMR and IR) data [11–21]. The reaction proceeds via condensation of 1 mol of aldehyde with 2 mol of 2-naphthol followed by intramolecular elimination of water from two hydroxyl groups to form the corresponding dibenzoxanthene as has been suggested earlier [23]. In conclusion this paper describes a convenient and efficient process for the synthesis of 14-alkyl- or aryl-14Hdibenzo[a,j]xanthenes by one-pot reaction of alkyl or aryl aldehydes and 2-naphthol in the presence of catalytic amount of boric acid at 120 8C under solvent-free conditions. This method offers some advantages in terms of simplicity of performance, solvent-free condition, low cost, and it follows along the line of green chemistry. The catalyst is readily available and inexpensive and can conveniently be handled and removed from the reaction mixture. We believe that this procedure is convenient, economic, and a user-friendly process for the synthesis of 14-alkyl- or aryl-14H-dibenzo[a,j]xanthenes of biological and medicinal importance. Table 1 Synthesis of 14-alkyl- or aryl-14-H-dibenzo[a,j]xanthanes in the presence of boric acid. Entry
R
Time (h)
Yield (%)
3a 3b 3c 3d 3e 3f 3g 3h 3i 3j 3k
C6H5 4-ClC6H4 4-NO2C6H4 3-NO2C6H4 4-CNC6H4 4-CH3C6H4 4-CH3OC6H4 4-OHC6H4 2,4-Cl2C6H3 CH3CH2 CH3
2 2 2 1.5 2 2 3 2 1.5 2 2
94 97 98 89 98 90 89 85 98 97 84
Z. Karimi-Jaberi, M. Keshavarzi / Chinese Chemical Letters 21 (2010) 547–549
549
1. Experimental 1.1. Synthesis of 14-alkyl- or aryl dibenzo[a,j]xanthenes 3a–3k. General procedure A mixture of aldehyde (1 mmol), 2-naphthol (2 mmol) and boric acid (20 mol%) was stirred at 120 8C for the appropriate time indicated in Table 1. The progress of reactions was monitored by TLC (ethyl acetate/n-hexane = 1/4). After completion of the reaction, the reaction mixture was cooled to 25 8C, and water (10 cm3) was added, and the mixture was stirred for 10 min. The obtained solid was collected by filtration and purified by recrystallization from ethanol. Products were characterized by comparison of their physical and spectral data with those of authentic samples [11–21]. Spectral data for selected products: compound 3a: 1H NMR (500 MHz, CDCl3): d 8.41 (d, 2H, J = 8.5 Hz), 7.85 (d, 2H, J = 8.0 Hz), 7.82 (d, 2H, J = 8.8 Hz), 7.60 (t, 2H, J = 7.7 Hz), 7.54 (d, 2H, J = 7.5 Hz), 7.51 (d, 2H, J = 8.8 Hz), 7.43 (t, 2H, J = 7.5 Hz), 7.18 (t, 2H, J = 7.5 Hz), 7.02 (t, 1H, J = 7.5 Hz), 6.50 (s, 1H). References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26] [27] [28] [29]
J.P. Poupelin, G. Saint-Rut, O. Foussard-Blanpin, et al. Eur. J. Med. Chem. 13 (1978) 67. R.M. Ion, D. Frackowiak, A. Planner, et al. Acta Biochim. Pol. 45 (1998) 833. S.M. Menchen, S.C. Benson, J.Y.L. Lam, et al. Chem. Abstr. 139 (2003) p54287f (U.S. Patent US6583168 (2003)). C.G. Knight, T. Stephens, Biochem. J. 258 (1989) 683. M. Ahmad, T.A. King, D. Ko, et al. J. Phys. D: Appl. Phys. 35 (2002) 1473. D.W. Knight, P.B. Little, J. Chem. Soc. Perkin Trans. 1 (2001) 1771. A. Jha, J. Beal, Tetrahedron Lett. 45 (2004) 8999. C.W. Kuo, J.M. Fang, Synth. Commun. 31 (2001) 877. F.M. Dean, H.D. Lockstely, J. Chem. Soc. (1963) 393. J.Q. Wang, R.G. Harvey, Tetrahedron 58 (2002) 5927. R.J. Sarma, J.B. Baruah, Dyes Pigments 64 (2005) 91. (a) J.A. Van Allan, D.D. Giannini, T.H. Whitesides, J. Org. Chem. 47 (1982) 820; (b) O. Sirkecioglu, N. Talinli, A. Akar, J. Chem. Res. (S) (1995) 502. A. Khoramabadi-zad, Z. Kazemi, H.A. Rudbari, J. Korean Chem. Soc. 46 (2002) 541. A.R. Khosropour, M.M. Khodaei, H. Moghannian, Synlett (2005) 955. B. Rajitha, B.S. Kumar, Y.T. Reddy, et al. Tetrahedron Lett. 46 (2005) 8691. (a) B. Das, B. Ravikanth, R. Ramu, et al. J. Mol. Catal. A: Chem. 255 (2006) 74; (b) M.A. Pasha, V.P. Jayashankara, Bioorg. Med. Chem. Lett. 17 (2007) 621. N.D. Kokare, J.N. Sangshetti, D.B. Shinde, Chin. Chem. Lett. 19 (2008) 1186. L. Nagarapu, S. Kantevari, V.C. Mahankhali, et al. Catal. Commun. 8 (2007) 1173. M.A. Bigdeli, M.M. Heravi, G.H. Mahdavinia, Catal. Commun. 8 (2007) 1595. H.R. Shaterian, M. Ghashang, A. Hassankhani, Dyes Pigments 67 (2008) 564. S. Rostamizadeh, A.M. Amani, G.H. Mahdavinia, et al. Chin. Chem. Lett. 20 (2009) 779. (a) M.M. Hashemi, Z. Karimi-Jaberi, Monatsh. Chem. 135 (2004) 41; (b) M.M. Hashemi, M. Bakhtiari, Z. Karimi-Jaberi, Russ. J. Org. Chem. 43 (2007) 621. Z. Karimi-Jaberi, M.M. Hashemi, Monatsh. Chem. 139 (2008) 605. M.K. Chaudhuri, S. Hussain, M.L. Kantam, et al. Tetrahedron Lett. 46 (2005) 8329. M.K. Chaudhuri, S. Hussain, J. Mol. Catal. A: Chem. 269 (2007) 214. S. Tu, F. Fang, C. Miao, et al. Tetrahedron Lett. 44 (2003) 6153. G.C.M. Kondaiah, L.A. Reddy, K.S. Babu, et al. Tetrahedron Lett. 49 (2008) 106. P. Delbecq, J. Celerier, G. Lhommet, Tetrahedron Lett. 31 (1990) 4873. C. Mukhopadhyay, A. Datta, R.J. Butcher, Tetrahedron Lett. 50 (2009) 4246.