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Synthesis of 14-aryl-14H-dibenzo[a,j]xanthenes using CuSO4·5H2O as a green and reusable catalyst
⁎Corresponding author. Tel.: +98 0261 448145; fax: +98 0261 4418156. farahnazkargar@yahoo.com (Farahnaz K. Behbahani)
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Received: ,
Accepted: ,
This article was originally published by Elsevier and was migrated to Scientific Scholar after the change of Publisher.
Peer review under responsibility of King Saud University.
Abstract
The synthesis of 14-aryl-14H-dibenzno[a,j]xanthenes has attracted considerable attention in organic synthesis. In this article, aromatic aldehydes have been employed with 2-naphthol in the presence of CuSO4·5H2O under solvent-free conditions to afford the corresponding benzoxanthenes in very good yields. The use of readily available CuSO4·5H2O as a reusable and recyclable catalyst makes this process quite simple, convenient, and environmentally friendly.
Keywords
Dibenzoxanthenes
CuSO4·5H2O
Catalyst
Synthesis
1 Introduction
Green chemistry is a quickly developing new field that provides us a proactive path for the sustainable progress of future science and technology (Varma, 1999). Green chemistry uses highly efficient and environmentally benign synthetic procedures to deliver lifesaving medicines and optimization processes in drug discovery with reduced needless environmental impact. Green chemistry also offers enhanced chemical process economics concomitant with a reduced environmental burden (Li and Chen, 2006).
Xanthenes and benzoxanthenes, owing to the possession of useful biological activities such as anti-inflammatory (Poupelin et al., 1978), antiviral (Lambert et al., 1997) and antibacterial activities (Hideo, 1981), as antagonists for the paralyzing action of oxazolamine (Saint-Ruf et al., 1972) in photodynamic therapy (Ion et al., 1998), as leuco-dyes in laser technology (Menchen et al., 2003) and as pH-sensitive fluorescent materials for the visualization of biomolecules (Knight and Stephens, 1989), have been of great interest.
Recently, the synthesis of benzoxanthenes has been achieved by the condensation of aldehydes with β-naphthol by cyclodehydration in the presence of various catalysts (Kumar et al., 2010) such as AcOH-H2SO4, p-TSA, MeSO3H, sulfamic acid, ionic liquid, iodine, heteropolyacid, silica sulfuric acid, Amberlyst-15, cyanuric chloride, LiBr, CoPy2Cl2, Yb(OTf)3, Sc[N(SO2C8F17)2]3, NaHSO4 and Al(HSO4)3, and the other references therein.
CuSO4·5H2O, as a Lewis acid catalyst has been used for various organic transformations such as four-component synthesis of β-acetamido carbonyl compounds (Behbahani et al., 2012) and the other references therein including the synthesis of tetrahydropyranylation/depyranylation of alcohols and phenols, protection of alcohols and phenols using hexamethyldisilazane, the one-pot conversion of tetrahydropyrane (THP) ethers to acetates, the chemoselective synthesis of 1,1-diacetates from aldehydes, the synthesis of quinoxaline derivatives, the synthesis of β-keto esters, the one-pot synthesis of β-hydroxytriazoles from epoxides and the synthesis of 1,2,3-triazoles.
From this point of view, it is desirable that the preparation of 14-aryl-14H-dibezno[a,j]xanthenes from the condensation of various aromatic aldehydes and 2-naphthol, respectively takes place in the presence of a catalytic amount of a green and reusable catalyst under solvent-free conditions (Scheme 1). To the best of our knowledge in the open literature, one-pot synthesis of benzoxanthenes catalyzed by CuSO4·5H2O has not been reported.
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2 Results and discussion
We started to study this condensation reaction using a catalytic amount of CuSO4·5H2O by examining the reaction times involving benzaldehyde (1 mmol) and 2-naphthol (2 mmol) to afford the product under solvent-free conditions at 80 °C (Table 1). As can be seen from Table 1, the best results were obtained at 10 mol% of the catalyst under solvent-free conditions and gave 14-phenyl-14H-dibenzo[a,j]xanthene in 95% yield. The catalyst played a crucial role in the success of the reaction in terms of time and the yields. In the absence of the catalyst, the reaction of benzaldehyde with β-naphthol as an example, could be carried out but the product was obtained in very low yield (10%) after prolonged reaction time.
As listed in Table 2, a variety of aromatic aldehydes has been used to evaluate this procedure. The electronic effects and the nature of the substituents on the aromatic ring showed relatively strong obvious effects in terms of yields under reaction conditions. Benzaldehyde and other aromatic aldehydes containing electron-withdrawing and electron-donating groups were used and reacted to give the corresponding dibenzoxanthenes. In these cases the yields were very good and electron withdrawing groups were more effective than electron donating groups on reaction rates.
Entry
Aldehyde
Product
Time (h)
Yield%
M.p (°C)[Ref.]
1
C6H5CHO
3a
5
95
180–185Kumar et al. (2006)
2
4-CH3OC6H4CHO
3b
6
89
203–205 Kumar et al. (2006)
3
4-ClC6H4CHO
3c
5
90
283–285Kumar et al. (2006)
4
3-O2NC6H4CHO
3d
5.5
90
212–215Kumar et al. (2006)
5
2-O2NC6H4CHO
3e
6.5
88
288–290Kumar et al. (2006)
6
4-F-C6H4CHO
3f
4
95
235–238Kumar et al. (2006)
7
4-H3CC6H4CHO
3g
6
85
224–227Kumar et al. (2006)
8
2.4- DiClC6H4CHO
3h
5
92
260–265 Kumar et al. (2010)
9
2-ClC6H4CHO
3i
7
90
214–215Kumar et al. (2006)
10
3-OHC6H4CHO
3j
7
90
240–242Kumar et al. (2010)
The suggested mechanism (Kumar et al., 2010) of CuSO4·5H2O-catalyzed transformation is shown in Scheme 2. CuSO4 activated carbonyl group of aldehyde was treated by 2-naphthol, followed by the elimination of water and catalyst then formed in the reaction with 2-naphthol, which then undergoes dehydration to afford the desired product.
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3 Experimental
Melting points were measured by using the capillary tube method with an electro thermal 9200 apparatus. IR spectra were recorded on Perkin Elmer FT-IR spectrophotometer scanning between 4000 and 400 cm−1. 1H NMR and 13C NMR spectra were obtained on a Bruker DRX-300 MHZ NMR instrument in CDC13. Mass spectra were taken on an Agilent 5973 Network Mass Selective Detector instrument. All starting materials were purchased from the Merck Company.
3.1 General procedure for synthesis of 14-substituted-14H-dibenzo[a,j]xanthenes
To a mixture of 2-naphthol (2 mmol) and aldehyde (1 mmol), CuSO4·5H2O (10 mol%) was added and the reaction mixture was mixed at 80 °C for appropriate times (Table 2). After completion of the reaction (monitored by TLC, ethylacetate:n-hexane; 1:3), water (50 ml) was added and extracted with ethyl acetate (3 × 20 ml). Then the organic layer was dried over anhydrous Na2SO4 and the filtrate evaporated to dryness under vacuum to give the crude product, which was recrystallized from ethanol/water. The desired pure products were characterized by spectra (FT-IR and 1HNMR) and by comparison of their physical and spectral methods with those of known benzoxanthenes (Rajitha et al., 2005; Wu et al., 2009).
3.2 Physical and spectra data
3.2.1 14-(phenyl)-14H-dibenzo[a,j]xanthene (3a)
White solid: mp 180–185 °C. IR (KBr, cm−1): 3074, 3020, 2887, 1620, 1591, 1512, 1489, 1457, 1402, 1253, 1079, 1026, 964, 827, 744, 700. 1H NMR (300 MHz, CDCl3, ppm): δ 8.41 (2H, d, J = 8.5 Hz), 7.83-7.00 (15H, m), 6.50 (1H, s). 13CNMR (300 MHz, CDCl3, ppm): δ 44.7, 117.4, 118.8, 123, 127, 129, 129.3 133.5, 144, 153.8; Mass (m/z): 358 (24.7.0%), 281 (100%), 77 (43%). Anal. Calcd for C27H18O: C, 90.47; H, 5.06. Found: C, 90.38; H; 5.01
3.2.2 14-(4-methoxyphenyl)-14H-dibenzo[a,j]xanthene (3b)
White solid: mp 203–205 °C. IR (KBr, cm−1): 3039, 2833, 1591, 1508, 1457, 1430, 1399, 1247, 1027, 958, 829, 807, 740 cm−1. 1H NMR (300 MHz, CDCl3, ppm): δ 8.35 (d, J = 8.6 Hz, 2H), 7.32–7.85 (m, 12H), 6.65 (d, J = 8.7 Hz, 2H), 6.40 (s, 1H), 3.58 (s, 3H). 13CNMR (300 MHz, CDCl3, ppm): δ 37, 54.2, 114, 117.2, 118.3, 123.5, 124.1, 127.4, 129.1, 129.4, 131.4, 133.7, 137.2, 149.3, 158.2. Mass (m/z): 388 (M+, 24.8%), 281 (100%), 261 (6.8%), 207 (6.8%), 136 (26.2%), 107 (15.1%), 83 (27.5%), 69 (41.3%), 55 (53.7%). Anal. Calcd for C28H20O2: C, 86.57; H; 5.19. Found: C, 86.41; H; 5.20.
3.2.3 14-(4-Chlorophenyl)-14H-dibenzo[a,j]xanthene (3c)
White solid: mp 286–283 °C. IR (KBr, cm−1): 3037, 1620, 1580; 1495, 1389, 1236, 1027, 858. 1H NMR (300 MHz, CDCl3, ppm): δ 6.48 (s, 1H), 7.10–8.34 (m, 16H); 13CNMR (300 MHz, CDCl3, ppm): δ 37.47, 116, 118, 122.40, 124.37, 127, 128.64, 128.91, 129.09, 129.49, 131, 131.24, 132.17, 143.46, 148.6. Mass (m/z): 394 (M + 2+, 10%), 392 (M+, 25%), 281 (100%), 252 (45%), 75 (34%). Anal. Calcd for C27H17ClO: C, 82.54; H, 4.36; Cl, 9.02. Found: C, 82.50; H, 4.31; Cl, 9.03.
3.2.4 14-(3-Nitrophenyl)-14H-dibenzo[a,j]xanthene (3d)
Yellow solid: mp 212–215 °C. IR (KBr, cm−1): 3084, 1529, 1350, 1259, 1059, 798; 1H NMR (300 MHz, CDCl3, ppm): δ 6.58 (1H, s), 8.42 (s, 1H) 7.10–8.56 (m, 16H). 13C NMR (300 MHz, CDCl3, ppm): δ 32.9, 118.0, 118.4, 123.0, 124.6, 125.0, 125.3, 127.8, 128.0, 129.4, 129.5, 129.9, 130.8, 132.1, 132.6, 134.5, 141.3, 147.5, 149.8. Mass (m/z): 403 (M+, 21%), 281 (100%), 122 (6.5%), 76 (55%), 51 (38%), 65 (7.5%). Anal. Calcd for C27H17NO3: C, 80.38; H, 4.25; N, 3.47, Found: C, 80.25; H, 4.24, N, 3.57.
3.2.5 14-(2-Nitrophenyl)-14H-dibenzo[a,j]xanthene (3e)
Yellow solid: mp 288–290 °C. IR (KBr, cm−1): 3070, 1615, 1540, 1355, 1240, 1142, 810, 748; 1H NMR (300 MHz, CDCl3, ppm): δ 7.52 (s, 1H) 7.10–8.56 (m, 16H). 13C NMR (300 MHz, CDCl3, ppm): δ 32.9, 118.0, 118.4, 123.0, 124.6, 125.0, 125.3, 127.8, 128.0, 129.4, 129.5, 129.9, 130.8, 132.1, 132.6, 134.5, 141.3, 147.5, 149.8, 153.35. Mass (m/z): 403 (M+, 23%), 281 (100%), 122 (6.3%), 76 (65%), 51 (35%), 65 (8.5%). Anal. Calcd for C27H17NO3: C, 80.38; H, 4.25; N, 3.47, Found: C, 80.24; H, 4.25, N, 3.56.
3.2.6 14-(4-Fluorophenyl)-14H-dibenzo[a,j]xanthene (3f)
White solid: mp 235–238 °C. IR (KBr, cm−1): 3078, 1604, 1593, 1450, 1242, 1092, 816, 746. 1H NMR (300 MHz, CDCl3, ppm): δ 6.47 (s, 1H), 6.85 (d, 2H, J = 9.5 Hz), 7.03 (d, 2H, J = 9.7 Hz) 7.25–8.34 (m, 12H); 13C NMR (300 MHz, CDCl3, ppm): δ 37.46, 116.64, 118.02, 120.21, 122.39, 124.38, 126.93, 128.91, 129.12, 129.88, 131.03, 131.23, 131.58, 143.98, 148.65, 153.44, 158.63. Mass (m/z): 376 (M+, 20%), 281 (100%), 95 (8.5%), 76 (45%). Anal. Calcd for C27H17FO: C, 86.15; H, 4.55; F, 5.05. Found: C, 86.14; H, 4.45, F, 5.06.
3.2.7 14-(4-Methylphenyl)-14H-dibenzo[a,j]xanthene (3g)
White solid: mp 224–227 °C. IR (KBr, cm−1): 3043, 2913, 2835, 1604, 1595, 1403, 1254, 1169, 847, 758, 744. 1H NMR (300 MHz, CDCl3, ppm): δ 2.15 (s, 3H), 6.46 (s, 1H), 8.39 (2H, d, J = 8.4 Hz), 7.83 (2H, d, J = 8.9 Hz), 7.78–6.95 (m, 12H). 13C NMR (300 MHz, CDCl3, ppm): δ 20.5, 37, 117.3, 117.4, 117.5, 123.3, 124.5, 126.7, 127.8, 128.4, 130.6, 136, 142.5, 147.8, 147.9. Mass (m/z): 372 (M+, 28%), 281 (100%), 91 (55%), 76 (65%). Anal. Calcd for C28H20O: C, 90.29; H, 5.41. Found: C, 90.24; H, 5.45.
3.2.8 14-(2,4-Dichlorophenyl)-14H-dibenzo[a,j]xanthene (3h)
White solid: mp 220–225 °C. IR (KBr, cm−1): 3058, 1620, 1593, 1459, 1248, 837, 808, 743, 607. 1H NMR (300 MHz, CDCl3, ppm): δ 6.73 (s, 1H), 6.88 (d, 1H, J = 8.5 Hz), 7.27 (s, 1H), 7.31 (d, 1H, J = 8.7 Hz), 8.8–7.25 (m, 12 H). 13C NMR (300 MHz, CDCl3, ppm): δ 36.6, 117.3, 11.5 118.4, 123.3, 126.7, 127.5, 128.4, 130.8, 133.5, 135, 141.5, 150.9. Mass (m/z): 430 (M + 4+, 3%), 428 (M + 2+, 10%), 426 (M+, 24%), 281 (100%), 144 (35%), 75 (45%). Anal. Calcd for C27H16Cl2O: C, 75.89; H, 3.77; Cl, 16.59. Found: C, 75.84; H, 3.75, Cl, 16.56.
3.2.9 14-(2-Chlorophenyl)-14H-dibenzo[a,j]xanthene (3i)
White solid: mp 175–178 °C. IR (KBr, cm−1): 3071, 1697, 1593, 1430, 1243, 749, 692.
1H NMR (300 MHz, CDCl3, ppm): δ 6.47 (s, 1H), 8.75 (d, 2H, J = 9.01 Hz), 7.84–6.90 (m, 14H). 13C NMR (300 MHz, CDCl3, ppm): δ 36.4, 117.9, 123.3, 124.6, 125.5, 127.8, 128.6, 129.4, 129.5, 131, 132.5, 132.6, 134.5, 141.3, 147.5, 149.8, 152. Mass (m/z): 394 (M + 2+, 10%), 392 (M+, 29%), 281 (100%), 111 (65%), 76 (55%). Anal. Calcd for C27H17ClO: C, 82.54; H, 4.36; Cl, 9.02. Found: C, 82.65; H, 4.38, Cl, 9.04.
3.2.10 14-(3-Hydroxyphenyl)-14H-dibenzo[a,j]-xanthene (3j)
White solid mp 240–242 °C. IR (KBr, cm−1): 3412, 1588, 1507, 1413, 1258, 1237, 813; 1H NMR (300 MHz, CDCl3, ppm): δ 4.54 (s, 1H), 6.86 (s, 1H), 7.83–6.43 (m, 12H), 8.37 (d, J = 8.7 Hz, 2H); 13C NMR (300 MHz, CDCl3, ppm): δ 37.0. 112.8, 114.6, 116.3, 117.2, 120.1, 121.9, 123.5, 126.0, 128.0, 128.1, 128.6, 130.2, 130.6, 145.9, 147.9, 154.8. Mass (m/z): 374 (M+, 24%), 281 (100%), 93 (75%), 76 (45%), 51 (65%). Anal. Calcd for C27H18O2: C, 86.61; H, 4.85. Found: C, 86.50; H, 4.73.
3.3 Reusability of the catalyst
To evaluate of reusability of the catalyst, model reaction (entry 1, Table 2) was repeated. After completion of the reaction, water and ethyl acetate were added, and the aqueous layer was separated, evaporated and dried at 50 °C. The catalyst was recovered and reused for three runs and the product was obtained in good yields (88, 85, 86) %.
4 Conclusion
This paper describes a general method for the synthesis of dibenzoxanthenes utilizing CuSO4·5H2O as a reusable catalyst. The catalyst is mild which has an advantage in that only 10 mol% is required for the reactions. In addition to its efficiency, operational simplicity, mild reaction conditions and easier work-up procedure make it a useful method for the synthesis of fused 14-aryl-14H-dibenzo[a,j]xanthenes.
References
- Synthetic Commun.. 2012;42:705.
- Biochemistry. 1989;258:683.
- Kumar, P.S.; Kumar, B.S.; Rajitha, B.; Reddy, P.N.; Sreenivasulu, N.; Reddy Y.T. ARKIVOC 2006, xii, 46.
- Tetrahedron Lett.. 2010;51:442.
- Chem. Soc. Rev.. 2006;5:68.
- Menchen, S. M.; Benson, S. C.; Lam, J. Y. L.; Zhen, W.; Sun, D.; Rosenblum, S.; Khan, H.; Taing, M. US Patent, 6,583,168, 2003; Chem. Abstr. 139, 54287f.
- Eur. J. Med. Chem.. 1978;13:67.
- Tetrahedron Lett. 2005:8691.
- Bull. Chim. Ther.. 1972;7:83.
- Green Chem.. 1999;1:43.
- Synthetic. Commun. 2009:3762.
