Accepted Manuscript Natrolite zeolite supported copper nanoparticles as an efficient heterogeneous catalyst for the 1,3-diploar cycloaddition and cyanation of aryl iodides under ligand-free conditions Mahmoud Nasrollahzadeh, S. Mohammad Sajadi, Akbar Rostami-Vartooni PII: DOI: Reference:
S0021-9797(15)00424-5 http://dx.doi.org/10.1016/j.jcis.2015.04.047 YJCIS 20427
To appear in:
Journal of Colloid and Interface Science
Received Date: Accepted Date:
31 March 2015 23 April 2015
Please cite this article as: M. Nasrollahzadeh, S. Mohammad Sajadi, A. Rostami-Vartooni, Natrolite zeolite supported copper nanoparticles as an efficient heterogeneous catalyst for the 1,3-diploar cycloaddition and cyanation of aryl iodides under ligand-free conditions, Journal of Colloid and Interface Science (2015), doi: http://dx.doi.org/ 10.1016/j.jcis.2015.04.047
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Natrolite zeolite supported copper nanoparticles as an efficient heterogeneous catalyst for the 1,3-diploar cycloaddition and cyanation of aryl iodides under ligand-free conditions Mahmoud Nasrollahzadeha,*, S. Mohammad Sajadib and Akbar Rostami-Vartoonia a
b
Department of Chemistry, Faculty of science, University of Qom, P. O. Box 37185-359, Qom, Iran.
Department of Petroleum Geoscience, Faculty of Science, Soran University, PO Box 624, Soran, Kurdistan Regional Government, Iraq *Corresponding author. Tel: +98 25 32850953; Fax: +98 25 32103595.
E-mail address: [email protected]
ABSTRACT In this paper, we report the preparation of Natrolite zeolite supported copper nanoparticles as a heterogeneous catalyst for 1,3-diploar cycloaddition and synthesis aryl nitriles from aryl iodides under ligand-free conditions. The catalyst was characterized using XRD, SEM, TEM, EDS and TG-DTA. The experimental procedure is simple, the products are formed in high yields and the catalyst can be recycled and reused several times without any significant loss of catalytic activity.
Keywords: Cu NPs, Natrolite zeolite, Nitrile, Triazole, Green synthesis
1. Introduction Due to the importance of nitriles in the construction of various pharmaceutical compounds, agrochemicals and dyes and also in synthetic organic chemistry for the manufacture of nitrogen-containing heterocycles, aldehydes, acids and acid derivatives [1-3], we turned our attention to applying new method for the preparation of nitriles. Most of the methods for the synthesis of nitriles have disadvantages such as long reaction times, formation of side products, use of homogeneous catalysts, use of toxic, hazardous, sensitive to moisture, expensive reagents, several-step methods and low yields. Among cyanation agents in the synthesis of nitriles, CuCN and Zn(CN)2 lead to heavy metal waste [1-3]. Recently, K4Fe(CN)6 as a cyanation agent has received much attention because
1
of its interest properties such as nonexplosive, nonflammable and nonexpensive. Also, it can be easily stored and is neither moisture sensitive and nor very volatile. It is used in the food industry for metal precipitation and cheaper than KCN and NaCN. Several syntheses of aryl nitriles have been reported using K4Fe(CN)6 in the presence of palladium or copper homogeneous catalysts [4-8], while less expensive copper heterogeneous catalysts have less received attention. In the recent years, synthesis of metallic nanoparticles has gained great significance due to their unique size dependant electronic, optical and catalytic properties [9]. Among many metal nanoparticles, Cu is the most common used as catalyst in organic chemistry [10-12]. However, Cu nanoparticles have some drawbacks characteristic of homogeneous catalysis such as difficulties in quantitative separation (purity of the product), recovery, and regeneration of the catalyst. Immobilization of catalysts on solid supports is one of the best methods to improve the efficiency and recovery of catalysts. To prevent the agglomeration of metal nanoparticles (MNPs) and the over-stoichiometric use of Cu reagents, several inorganic materials such as alumina and silica have been used as a support for MNPs [13]. Among heterogeneous catalysts, zeolites have been used widely as efficient support and catalysts in organic reactions due to their high catalytic activity, ease of handling, reusability, and benign character [14-18]. The framework structure of zeolite consists of a three dimensional network of SiO4 and AlO4 tetrahedra linked together by oxygen (Figure 1) which the ordered Na+ ions and H2O molecules fill the voids of the framework [14-18].The Natrolite zeolite is one of zeolites with Al2Si3O10 main structural unit. The Natrolite zeolite can be classified as fibrous zeolites with small pores (channels in the framework structure) which mostly consist of 8 members of oxygen ring systems (the diameter of their pores < 4.5 Å), and the Na+ cations occupy positions in the eight-ring channels. Our recent study has shown that the Natrolite zeolite can be used as a very active catalyst in the organic synthesis [14-18].
Figure 1. Aluminosilicate framework of zeolite. In continuation of our efforts to develop environmentally friendly synthetic methodologies [19-25], we report the synthesis of natural Na zeolite-supported copper NPs and its application for synthesis of 1,2,3-triazoles and
2
substituted benzonitriles under ligand-free conditions (Scheme 1). The synthesis procedure followed by us is very simple and environmental friendly.
2. Experimental High-purity chemical reagents were purchased from the Merck and Aldrich chemical companies. All materials were of commercial reagent grade. Melting points were deter-mined in open capillaries using a BUCHI 510 melting point apparatus and are uncorrected. 1H NMR and 13C NMR spectra were recorded on a Bruker Avance DRX spectrometer at 250, 400 and 90 MHz, respectively. FT-IR spectra were recorded on a Nicolet 370 FT/IR spectrometer (Thermo Nicolet, USA) using pressed KBr pellets. The element analyses (C, H, N) were obtained from a Carlo ERBA Model EA 1108 analyzer carried out on Perkin-Elmer 240c analyzer. The natural zeolite used in this study originated from Hormak area, Iran. X-ray diffraction (XRD) measurements were carried out using a Philips powder diffractometer type PW 1373 goniometer (Cu Kα = 1.5406 A˚). The scanning rate was 2º/min in the 2θ range from 10 to 80˚. Scanning electron microscopy (SEM) was performed on a Cam scan MV2300. EDS (S3700N) was utilized for chemical analysis of preparednanostructures. Thermogravimetricdifferential thermal analysis (TG-DTA) was performed using STA 1500 Rheometric Scientific (England). The flow rate of air was 120 ml/min and the ramping rate of sample was 2 oC/min. Preparation of extract of the leaves of Euphorbia esula L 50 g of dried powder of the leaves of Euphorbia esula L [26,27] was extracted using boiling in 300 mL double distillated water for 20 min and aqueous extract was centrifuged in 7000 rpm to obtain the supernatant as extract [28].
3
Green synthesis of copper nanoparticles using Euphorbia esula L leaves extract The copper nanoparticles were synthesized by the following process. In a 250 mL conical flask, 10 mL solution of CuCl2⋅2H2O 5 mM was mixed with 100 mL of the aqueous plant extract (100 g dried leaves of the plant extracted using 500 mL of deionized water while heating at 80 °C and pH 9 for 30 min then filtered) along with vigorous shaking until gradually changing the color of the mixture during 20 min from yellow to dark indicating the formation of Cu nanoparticles (as monitored by UV-vis and FT-IR spectra of the solution). The well shaked mixture then filtered and centrifuged at 6500 rpm for 30 min and obtained precipitation washed with absolute ethanol and double distillated water, respectively. Then, Cu NPs were calcined at 600 ˚C [28]. Preparation of Natrolite zeolite/Cu NPs The Natrolite zeolite/Cu NPs was prepared by supporting in an aqueous solution of Cu NPs synthesized using aqueous extract of the leaves of Euphorbia esula. Approximately, 1.0 g of Natrolite zeolite was dispersed in 15 mL of an aqueous Cu NPs solution (0.05 M) and stirred for 15 h at 100 ˚C. Then, the mixture was cooled down to room temperature, filtered, washed with water, and dried. This procedure was carried out twice. General procedure for the cyanation of aryl iodides A mixture of aryl iodide (1.0 mmol), K4Fe(CN)6 (0.66 mmol), Et3N (2.0 mmol) and Natrolite zeolite/Cu NPs (0.05 g) in a 1:1 mixture of DMF and water (6 mL) was heated with stirring at 120 °C for 15 h (TLC). After completion of the reaction, the reaction mixture was cooled to room temperature and filtered to separate the solid catalyst which was used for successive cycles. The filtrate was extracted with Et2O. The extract was washed with water, brine and then dried (MgSO4). Evaporation of the solvent left the crude product which was purified by column chromatography over silica gel to provide pure product. All the products are known compounds and the spectral data and melting points were identical to those reported in the literature [1-8]. General procedure for the synthesis of 1,2,3-triazoles A mixture of benzyl azide (1.0 mmol), alkyne (1.0 mmol), Et3N (1.0 mmol) and Natrolite zeolite/Cu NPs (0.05 g) in water (10 mL) was stirred at room temperature for the appropriate time. After completion of the reaction, the ethyl acetate was added to reaction mixture and the catalyst was separated. The recovered catalyst was dried and reused at least five times without losing its activity. The organic extract was washed with water, dried over MgSO4 and concentrated to give the crude product. The products were purified by simple crystallization or by
4
performing column chromatography. All the products are known compounds and the spectral data and melting points were identical to those reported in the literature [29-37].
3. Results and discussion In this paper, we report on the “green-chemical” synthesis of Cu NPs by the reduction of Cu2+ ions by aqueous extract of the leaves of a naturally available material, Euphorbia esula L under alkaline pH conditions. The methodology which we have adopted was totally hazard free, clean, nontoxic and environment friendly. Euphorbia esula L, commonly known as green spurge or leafy spurge, is a species of spurge native to central and southern Europe, and eastward through most of Asia north of the Himalaya to Korea and eastern Siberia [26,27]. This unique material is the source of various potentially bioactive chemical constituents, mainly terpenoids, flavonoids, tannins, sterols. For this reason, Euphorbia esula L has become the subject of intense pharmacological and chemical studies [26,27]. However, in spite of its ready natural availability, non-toxicity and biological relevance’s, Euphorbia esula L has never been explored for the green synthesis of metal nanoparticles. In this paper, metal ions were reduced to nano zero valent (NZV) metallic particles by flavonoid and phenolics acids present in the extract of the leaves of Euphorbia esula L. The formation of copper NPs with flavonoid and phenolics acids takes place via the following steps: (1) complexation with copper metal salts, (2) simultaneous reduction of copper metal, and (3) capping with oxidized polyphenols/caffeine. The progress of the reaction between metal ions and aqueous extract of the leaves of Euphorbia esula L and the Cu NPs production was monitored by recording the absorption spectra as a function of time. UV-vis spectra of Cu NPs in times 20 and 30 min (Figure 2) indicate that the typical surface resonance peak of Cu NPs is at around 580 nm [28].
5
Figure 2. UV-vis spectrum of Cu NPs synthesized using aqueous extract of the leaves of Euphorbia esula L (A; 20 min and B; 30 min).
The XRD pattern (Figure 3) shows that the Cu NPs are crystalline. Reflection peaks appeared at 43.7°, 50.7° and 74.5° which correspond to (1 1 1), (2 0 0) and (2 2 0) miller indices, respectively (JCPDS no. 71-4610) [28]. These are characteristic of fcc (face centered cubic) structure. As shown in Figure 3, the intensity of diffraction peaks of copper oxides is very low, which indicates high purity of Cu NPs. The particles size can be found by applying Sherrer’s equation and the average particles size is found to be 69 nm.
Figure 3. X-ray diffraction pattern of the synthesized Cu NPs (Source: Adapted from Ref. 28).
3.1. Preparation of Na zeolite/Cu NPs The Na zeolite/Cu NPs was fabricated via a simple synthetic process by supporting in an aqueous solution of Cu NPs synthesized using aqueous extract of the leaves of Euphorbia esula and was characterized by using the powder XRD, TG-DTA, SEM, and EDS. Natural Natrolite zeolite was obtained from Hormak area, Sistan and Baluchestan province, Iran and was characterized by our group using the powder XRD, SEM, XRF and FT-IR spectroscopy [14-18].
6
The elemental composition of the Natrolite zeolite was also analyzed by the Energy Dispersive X-ray Spectroscopy (EDS). This technique further confirmed that Natrolite zeolite was composed of aluminium, silicon, calcium and oxygen (Figure 4).
Figure 4.EDS spectrum of Natrolite zeolite.
XRD patterns of the Na zeolite and Natrolite zeolite/Cu NPs are shown in Figure 5 and 6. The comparison of the X-ray diffractogram pattern of Na zeolite with X-ray diffractogram pattern of the standard sample (International Zeolite Association) show which pattern was completely matched with that of the Natrolite zeolite. The actual phases for the natural Iranian Natrolite zeolite were silicon oxide cristobalite-SiO2 (cubic) and aluminium silicate zeolite. The presence of copper was confirmed with powder XRD measurements. The results reveal that Cu loading and thermal treatment did not alter the Natrolite zeolite structure [17]. A comparison of the XRD patterns with the one of Na zeolite clearly shows that the host framework remains intact at the end of the procedure, no observable alteration in the framework lattice and no lost in the crystallinity of Na zeolite. Furthermore, one observes a Bragg peak of copper nanoparticles (2 0 0) at 2θ = 48.10° in the Natrolite zeolite/Cu NPs sample. The detection limit of XRD is normally 3-5 wt.%. It is possible that the corresponding peaks of CuO and Cu2O might be below the detection limit of this technique. Thus, no CuO or Cu2O peak was detected. These results indicate that Cu nanoparticles have been combined with Natrolite zeolite.
7
Figure 5.XRD powder pattern of Na zeolite.
Figure 6.XRD powder pattern of Natrolite zeolite/Cu NPs.
The size and shape of the products were examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Figure 7 shows typical large-scale FE-SEM images of the as-produced Natrolite zeolite/Cu NPs. It is clearly observed that the Cu grain pervaded into zeolite surface, which displays a good combination between natural Natrolite zeolite and Cu NPs.
Figure 7. FE-SEM images of Natrolite zeolite/Cu NPs.
8
The size of as-prepared Natrolite zeolite/Cu NPs was further examined by TEM (Figure 8). The average size of Cu NPs determined from Figure 8 was under 40 nm. The particles exhibited spherical morphology with low tendency to agglomeration.
Figure 8. Typical TEM images of as-prepared Natrolite zeolite/Cu NPs.
The elemental composition of Natrolite zeolite/Cu NPs was also analyzed by the Energy Dispersive X-ray Spectroscopy (EDS) spectrum. It further confirmed that Natrolite zeolite/Cu NPs was composed of Si, Al, Ca, Na, Fe, Cu and oxygen (Figure 9).
3000
SiKα 2500
O Kα
AlKα
2000
1500
CaLα 1000
CuLα FeLα NaKα
500
CaKα AuMβ AuMα
FeKα AuLl CuKα
CaKβ
FeKβ
CuKβ AuLα
0 0
5
10
Figure 9. EDS spectrum ofNatrolite zeolite/Cu NPs.
9
keV
Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) were carried out in flowing air (120 ml min-1) at a heating rate of 2 °C min-1 on an autonomic TG/DTA. In the TG/DTA data of Natrolite zeolite [17] a gradual weight decreasing was only observed between 300 and 400 °C, while as seen in Figure 10, two weight loss stages were observed in flowing air. About 5.0 wt % weight loss was observed in the first stage at 160-260 ºC corresponding to desorption of surface water or decomposition of the organic content (leaves extract) present in the sample. In the second stage at 370-440 ºC, weight loss is about 6.0 wt %, which can be attributed to desorption of lattice water.
Figure 10.TG-DTA data measured for Natrolite zeolite/Cu NPs.
3.2. Evaluation of the catalytic activity of Natrolite zeolite/Cu NPs through the preparation of nitriles Herein, in this paper, we describe here a simple method of synthesis of aryl nitriles in high yields by the reaction of aryl bromides and K4Fe(CN)6 in the presence of Natrolite zeolite/Cu NPs as a as stable, heterogeneous and environmentally benign catalyst. We initially selected 4-iodotoluene and non-toxic potassium ferrocyanide as a model reaction. As expected, no target product could be detected in the absence of catalyst or base. The results indicated that base had a remark effect on the yield of product. Among the various bases (K2CO3, Et3N, Na2CO3 and KOAc) tested in the presence of Natrolite zeolite/Cu NPs in a 1:1 mixture of DMF and water, Et3N led to significant conversion. The best result was obtained with 4-iodotoluene (1.0 mmol), K4Fe(CN)6 (0.66 mmol), Natrolite zeolite/Cu NPs (0.05 g), Et3N (2.0 mmol), in a 1:1 mixture of DMF and water at 120 ºC, which obtained the product in a good yield (93%). We have examined the reaction of various aryl iodides containing electron-withdrawing or electrondonating groups with K4Fe(CN)6. As shown in Table 1, substituted aryl iodides were converted into the corresponding products in high yields under ligand-free and aerobic conditions.
10
Table 1. Synthesis of aryl nitriles.
Entry
a
ArI
ArB(OH)2
Yielda (%)
1
92 (89)b
2
90
3
89
4
86
5
84
6
89
7
90
Yields are after work-up. bYield after the 5th cycle.
3.3. Evaluation of the catalytic activity of Natrolite zeolite/Cu NPs through the preparation of 1,2,3-triazoles Due to the importance of 1,2,3-triazoles in synthetic organic chemistry and in industry for the manufacture of pharmaceuticals and medicinal compounds and their application as photostabilizers, agrochemicals, optical brighteners, corrosion inhibitors etc. [29-37], we next turned our attention to applying Natrolite zeolite/Cu NPs to the synthesis of 1,2,3-triazoles via the 1,3-dipolar cycloaddition reactions between azides and terminal alkynes in the presence of Et3N and water as a green solvent at room temperature. The desired products are obtained in excellent yields. As shown in Table 2, benzylic azides coupled with acetylenes to generate a range of triazoles in water as the. The reactions were completed within 3-5 hours to give high yields of the corresponding products. Table 2. Synthesis of 1,2,3-triazoles.a
11
Time (h)
Yieldb(%)
1
3
96 (93)c
2
3
97
3
3
96
4
5
93
5
5
95
6
5
96
7
5
93
8
5
95
9
5
94
Entry
a
Benzyl azide
Alkyne
Product
Conditions: Benzyl azide (1.0 mmol), alkyne (1.0 mmol), catalyst (50 mg), Et3N (1.0 mmol), H2O (10 mL),
room temperature. bIsolated yield. cYield after the 5th cycle.
12
3.4. Catalyst recyclability The high catalytic activity, easy preparation, isolability, bottleability, and reusability of Natrolite zeolite/Cu NPs raise the prospect of using this type of materials for the hydration of cyanamides and synthesis of nitriles in industrial applications as well as in small scale organic synthesis. The work-up procedure is straightforward due to the heterogeneous nature of the catalyst. The reusability of the catalysts is one of the most important benefits and makes them useful for commercial applications. The reusability of the Natrolite zeolite/Cu NPs was studied for both transformations. After completion of the reaction, the catalyst was separated and was washed with ethanol, dried in a hot air oven at 100 °C for 2 h and the recycled catalyst was saved for the next reaction. The recycled catalyst could be reused five times with no loss of activity (Figure 11). Thus, the catalyst is stable during the reaction. The reusability of the catalyst was also studied for the synthesis of 1,2,3-triazoles (Table 2, entry 1) under the present reaction conditions. The catalytic activity did not decrease considerably after five catalytic cycles.
4. Conclusions In conclusion, we have fabricated a heterogeneous and stable catalyst using the prepared Cu NPs and natural Na-zeolite. We demonstrate that the Natrolite zeolite/Cu NPs have potential for various catalytic applications. The study provides a green synthetic route for preparing nitriles and 1,2,3-triazoles. The catalyst can be readily recovered and reused for several cycles with only a slight decrease in activity.
Acknowledgements
13
We gratefully acknowledge from the Iranian Nano Council and University of Qom for the support of this work.
References [1] Z. Rappoport, In Chemistry of the Cyano Group; John Wiley & Sons: London, 1970, p. 121. [2] M. Nasrollahzadeh, Y. Bayat, D. Habibi, S. Moshaee, Tetrahedron Lett. 50 (2009) 4435. [3] D. Habibi, S. Heydari, M. Nasrollahzadeh, J. Chem. Res. 36 (2012) 573. [4] N. S. Nandurkar, B. M. Bhanage, Tetrahedron 64 (2008) 3655. [5] Y.-N. Cheng, Z. Duan, L. Yu, Z. Li, Y. Zhu, Y. Wu, Org. Lett. 10 (2008) 901. [6] A. Littke, M. Soumeillant, R. F. III Kaltenbach, R. J. Cherney, C. M. Tarby, S. Kiau, Org. Lett. 9 (2007) 1711. [7] S. Kim, K. Y. Yi, Tetrahedron Lett. 27 (1986) 1925. [8] M. Hatsuda, M. Seki, Tetrahedron 61 (2005) 9908. [9] M.; Nasrollahzadeh, F. Babaei, S. M. Sajadi, A. Ehsani, Spectrochim. Acta A 132 (2014) 423. [10] P. Fakhri, B. Jaleh, M. Nasrollahzadeh, J. Mol. Catal. A Chem. 383-384 (2014) 17. [11] Y. Isomura, T. Narushima, H. Kawasaki, T. Yonezawa, Y. Obora, Chem. Commun. 48 (2012) 3784. [12] F. Benaskar, V. Engels, N. Patil, E. V. Rebrov, J. Meuldijk, V. Hessel, L. A. Hulshof, D. A. Jefferson, J. C. Schouten, A. E. H. Wheatley, Tetrahedron Lett. 51 (2010) 248. [13] P. Roisson, J. P. Brunelle, P. Nortier, Boston: Butterworth, 1987. [14] M. Nasrollahzadeh, D. Habibi, Z. Shahkarami, Y. Bayat, Tetrahedron 66 (2009) 3866. [15] D. Habibi, M. Nasrollahzadeh, T. A. Kamali, Green Chem. 13 (2011) 3499. [16] D. Habibi, M. Nasrollahzadeh, H. Sahebekhtiari, J. Mol. Catal. A Chem. 378 (2013) 148. [17] M. Nasrollahzadeh, A. Ehsani, A. Rostami-Vartouni, Ultrason. Sonochem. 21 (2014) 275.
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[18] M. Nasrollahzadeh, M. Enayati, M. Khalaj, RSC Adv. 4 (2014) 26264. [19] M. Nasrollahzadeh, M. Maham, A. Ehsani, M. Khalaj, RSC Adv. 4 (2014) 19731. [20] M. Nasrollahzadeh, A. Rostami-Vartouni, A. Ehsani, M. Moghadam, J. Mol. Catal. A Chem. 387 (2014) 123. [21] M. Nasrollahzadeh, A. Zahraei, A. Ehsani, M. Khalaj, RSC Adv. 4 (2014) 20351. [22] M. Nasrollahzadeh, M. Maham, M. M. Tohidi, J. Mol. Catal. A Chem. 391 (2014) 83. [23] M. Nasrollahzadeh, A. Azarian, A. Ehsani, A. Zahraei, Tetrahedron Lett. 55 (2014) 2813. [24] M. Nasrollahzadeh, A. Ehsani, M. Maham, Synlett 25 (2014) 505. [25] M. Nasrollahzadeh, RSC Adv. 4 (2014) 29089. [26] V. Mozaffarian, A Dictionary of Iranian Plant Names; Farhang Mo’aser, Tehran, 1996. p. 219. [27] M. Nasrollahzadeh, S. M. Sajadi, M. Maham, P. Salaryan, A. Enayati, S. A. Sajjadi, K. Naderi, Chem. Nat. Compd. 47 (2011) 434. [28] M. Nasrollahzadeh, S. M. Sajadi, M. Khalaj, RSC Adv. 4 (2014) 47313. [29] V. V. Rostovtsev, L. G. Green, V. V. Fokin, K. B. Sharpless, Angew. Chem., Int. Ed. 41 (2002) 2596. [30] C.D. Hein, X. M. Liu, D. Wang, Pharm. Res. 25 (2008) 2216. [31] R. Alvarez, S. Velazquez, A. San-Felix, S. Aquaro, E. De Clercq, C.-F. Perno, A. Karlsson, J. Balzarini, M. J. Camarasa, J. Med. Chem. 37 (1994) 4185. [32] G. C. Tron, T. Pirali, R. A. Billington, P. L. Canonico, G. Sorba, A. A. Genazzani, Med. Res. Rev. 28 (2008) 278. [33] E. K. Moltzen, H. Pedersen, K. P. Bogeso, E. Meier, K. Frederiksen, C. Sanchez, H. L. Lembol, J. Med. Chem. 37 (1994) 4085. [34] C. L. Droumaguet, C. Wang, Q. Wang, Chem. Soc. Rev. 39 (2010) 1233. [35] S. K. Yousuf, D. Mukherjee, B. Singh, S. Maity, S. C. Taneja, Green Chem. 12 (2010) 1568.
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[36] D. Kumar, V. B. Reddy, R. S. Varma, Tetrahedron Lett. 50 (2009) 2065. [37] C. Shao, R. Zhu, S. Luo, Q. Zhang, X. Wang, Y. Hu, Tetrahedron Lett. 52 (2011) 3782.
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Graphical Abstract Natrolite zeolite supported copper nanoparticles as an efficient heterogeneous catalyst for the 1,3-diploar cycloaddition and cyanation of aryl iodides under ligand-free conditions Mahmoud Nasrollahzadeh*, S. Mohammad Sajadi and Akbar Rostami-Vartooni
17
S0021-9797(15)00424-5 http://dx.doi.org/10.1016/j.jcis.2015.04.047 YJCIS 20427
To appear in:
Journal of Colloid and Interface Science
Received Date: Accepted Date:
31 March 2015 23 April 2015
Please cite this article as: M. Nasrollahzadeh, S. Mohammad Sajadi, A. Rostami-Vartooni, Natrolite zeolite supported copper nanoparticles as an efficient heterogeneous catalyst for the 1,3-diploar cycloaddition and cyanation of aryl iodides under ligand-free conditions, Journal of Colloid and Interface Science (2015), doi: http://dx.doi.org/ 10.1016/j.jcis.2015.04.047
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Natrolite zeolite supported copper nanoparticles as an efficient heterogeneous catalyst for the 1,3-diploar cycloaddition and cyanation of aryl iodides under ligand-free conditions Mahmoud Nasrollahzadeha,*, S. Mohammad Sajadib and Akbar Rostami-Vartoonia a
b
Department of Chemistry, Faculty of science, University of Qom, P. O. Box 37185-359, Qom, Iran.
Department of Petroleum Geoscience, Faculty of Science, Soran University, PO Box 624, Soran, Kurdistan Regional Government, Iraq *Corresponding author. Tel: +98 25 32850953; Fax: +98 25 32103595.
E-mail address: [email protected]
ABSTRACT In this paper, we report the preparation of Natrolite zeolite supported copper nanoparticles as a heterogeneous catalyst for 1,3-diploar cycloaddition and synthesis aryl nitriles from aryl iodides under ligand-free conditions. The catalyst was characterized using XRD, SEM, TEM, EDS and TG-DTA. The experimental procedure is simple, the products are formed in high yields and the catalyst can be recycled and reused several times without any significant loss of catalytic activity.
Keywords: Cu NPs, Natrolite zeolite, Nitrile, Triazole, Green synthesis
1. Introduction Due to the importance of nitriles in the construction of various pharmaceutical compounds, agrochemicals and dyes and also in synthetic organic chemistry for the manufacture of nitrogen-containing heterocycles, aldehydes, acids and acid derivatives [1-3], we turned our attention to applying new method for the preparation of nitriles. Most of the methods for the synthesis of nitriles have disadvantages such as long reaction times, formation of side products, use of homogeneous catalysts, use of toxic, hazardous, sensitive to moisture, expensive reagents, several-step methods and low yields. Among cyanation agents in the synthesis of nitriles, CuCN and Zn(CN)2 lead to heavy metal waste [1-3]. Recently, K4Fe(CN)6 as a cyanation agent has received much attention because
1
of its interest properties such as nonexplosive, nonflammable and nonexpensive. Also, it can be easily stored and is neither moisture sensitive and nor very volatile. It is used in the food industry for metal precipitation and cheaper than KCN and NaCN. Several syntheses of aryl nitriles have been reported using K4Fe(CN)6 in the presence of palladium or copper homogeneous catalysts [4-8], while less expensive copper heterogeneous catalysts have less received attention. In the recent years, synthesis of metallic nanoparticles has gained great significance due to their unique size dependant electronic, optical and catalytic properties [9]. Among many metal nanoparticles, Cu is the most common used as catalyst in organic chemistry [10-12]. However, Cu nanoparticles have some drawbacks characteristic of homogeneous catalysis such as difficulties in quantitative separation (purity of the product), recovery, and regeneration of the catalyst. Immobilization of catalysts on solid supports is one of the best methods to improve the efficiency and recovery of catalysts. To prevent the agglomeration of metal nanoparticles (MNPs) and the over-stoichiometric use of Cu reagents, several inorganic materials such as alumina and silica have been used as a support for MNPs [13]. Among heterogeneous catalysts, zeolites have been used widely as efficient support and catalysts in organic reactions due to their high catalytic activity, ease of handling, reusability, and benign character [14-18]. The framework structure of zeolite consists of a three dimensional network of SiO4 and AlO4 tetrahedra linked together by oxygen (Figure 1) which the ordered Na+ ions and H2O molecules fill the voids of the framework [14-18].The Natrolite zeolite is one of zeolites with Al2Si3O10 main structural unit. The Natrolite zeolite can be classified as fibrous zeolites with small pores (channels in the framework structure) which mostly consist of 8 members of oxygen ring systems (the diameter of their pores < 4.5 Å), and the Na+ cations occupy positions in the eight-ring channels. Our recent study has shown that the Natrolite zeolite can be used as a very active catalyst in the organic synthesis [14-18].
Figure 1. Aluminosilicate framework of zeolite. In continuation of our efforts to develop environmentally friendly synthetic methodologies [19-25], we report the synthesis of natural Na zeolite-supported copper NPs and its application for synthesis of 1,2,3-triazoles and
2
substituted benzonitriles under ligand-free conditions (Scheme 1). The synthesis procedure followed by us is very simple and environmental friendly.
2. Experimental High-purity chemical reagents were purchased from the Merck and Aldrich chemical companies. All materials were of commercial reagent grade. Melting points were deter-mined in open capillaries using a BUCHI 510 melting point apparatus and are uncorrected. 1H NMR and 13C NMR spectra were recorded on a Bruker Avance DRX spectrometer at 250, 400 and 90 MHz, respectively. FT-IR spectra were recorded on a Nicolet 370 FT/IR spectrometer (Thermo Nicolet, USA) using pressed KBr pellets. The element analyses (C, H, N) were obtained from a Carlo ERBA Model EA 1108 analyzer carried out on Perkin-Elmer 240c analyzer. The natural zeolite used in this study originated from Hormak area, Iran. X-ray diffraction (XRD) measurements were carried out using a Philips powder diffractometer type PW 1373 goniometer (Cu Kα = 1.5406 A˚). The scanning rate was 2º/min in the 2θ range from 10 to 80˚. Scanning electron microscopy (SEM) was performed on a Cam scan MV2300. EDS (S3700N) was utilized for chemical analysis of preparednanostructures. Thermogravimetricdifferential thermal analysis (TG-DTA) was performed using STA 1500 Rheometric Scientific (England). The flow rate of air was 120 ml/min and the ramping rate of sample was 2 oC/min. Preparation of extract of the leaves of Euphorbia esula L 50 g of dried powder of the leaves of Euphorbia esula L [26,27] was extracted using boiling in 300 mL double distillated water for 20 min and aqueous extract was centrifuged in 7000 rpm to obtain the supernatant as extract [28].
3
Green synthesis of copper nanoparticles using Euphorbia esula L leaves extract The copper nanoparticles were synthesized by the following process. In a 250 mL conical flask, 10 mL solution of CuCl2⋅2H2O 5 mM was mixed with 100 mL of the aqueous plant extract (100 g dried leaves of the plant extracted using 500 mL of deionized water while heating at 80 °C and pH 9 for 30 min then filtered) along with vigorous shaking until gradually changing the color of the mixture during 20 min from yellow to dark indicating the formation of Cu nanoparticles (as monitored by UV-vis and FT-IR spectra of the solution). The well shaked mixture then filtered and centrifuged at 6500 rpm for 30 min and obtained precipitation washed with absolute ethanol and double distillated water, respectively. Then, Cu NPs were calcined at 600 ˚C [28]. Preparation of Natrolite zeolite/Cu NPs The Natrolite zeolite/Cu NPs was prepared by supporting in an aqueous solution of Cu NPs synthesized using aqueous extract of the leaves of Euphorbia esula. Approximately, 1.0 g of Natrolite zeolite was dispersed in 15 mL of an aqueous Cu NPs solution (0.05 M) and stirred for 15 h at 100 ˚C. Then, the mixture was cooled down to room temperature, filtered, washed with water, and dried. This procedure was carried out twice. General procedure for the cyanation of aryl iodides A mixture of aryl iodide (1.0 mmol), K4Fe(CN)6 (0.66 mmol), Et3N (2.0 mmol) and Natrolite zeolite/Cu NPs (0.05 g) in a 1:1 mixture of DMF and water (6 mL) was heated with stirring at 120 °C for 15 h (TLC). After completion of the reaction, the reaction mixture was cooled to room temperature and filtered to separate the solid catalyst which was used for successive cycles. The filtrate was extracted with Et2O. The extract was washed with water, brine and then dried (MgSO4). Evaporation of the solvent left the crude product which was purified by column chromatography over silica gel to provide pure product. All the products are known compounds and the spectral data and melting points were identical to those reported in the literature [1-8]. General procedure for the synthesis of 1,2,3-triazoles A mixture of benzyl azide (1.0 mmol), alkyne (1.0 mmol), Et3N (1.0 mmol) and Natrolite zeolite/Cu NPs (0.05 g) in water (10 mL) was stirred at room temperature for the appropriate time. After completion of the reaction, the ethyl acetate was added to reaction mixture and the catalyst was separated. The recovered catalyst was dried and reused at least five times without losing its activity. The organic extract was washed with water, dried over MgSO4 and concentrated to give the crude product. The products were purified by simple crystallization or by
4
performing column chromatography. All the products are known compounds and the spectral data and melting points were identical to those reported in the literature [29-37].
3. Results and discussion In this paper, we report on the “green-chemical” synthesis of Cu NPs by the reduction of Cu2+ ions by aqueous extract of the leaves of a naturally available material, Euphorbia esula L under alkaline pH conditions. The methodology which we have adopted was totally hazard free, clean, nontoxic and environment friendly. Euphorbia esula L, commonly known as green spurge or leafy spurge, is a species of spurge native to central and southern Europe, and eastward through most of Asia north of the Himalaya to Korea and eastern Siberia [26,27]. This unique material is the source of various potentially bioactive chemical constituents, mainly terpenoids, flavonoids, tannins, sterols. For this reason, Euphorbia esula L has become the subject of intense pharmacological and chemical studies [26,27]. However, in spite of its ready natural availability, non-toxicity and biological relevance’s, Euphorbia esula L has never been explored for the green synthesis of metal nanoparticles. In this paper, metal ions were reduced to nano zero valent (NZV) metallic particles by flavonoid and phenolics acids present in the extract of the leaves of Euphorbia esula L. The formation of copper NPs with flavonoid and phenolics acids takes place via the following steps: (1) complexation with copper metal salts, (2) simultaneous reduction of copper metal, and (3) capping with oxidized polyphenols/caffeine. The progress of the reaction between metal ions and aqueous extract of the leaves of Euphorbia esula L and the Cu NPs production was monitored by recording the absorption spectra as a function of time. UV-vis spectra of Cu NPs in times 20 and 30 min (Figure 2) indicate that the typical surface resonance peak of Cu NPs is at around 580 nm [28].
5
Figure 2. UV-vis spectrum of Cu NPs synthesized using aqueous extract of the leaves of Euphorbia esula L (A; 20 min and B; 30 min).
The XRD pattern (Figure 3) shows that the Cu NPs are crystalline. Reflection peaks appeared at 43.7°, 50.7° and 74.5° which correspond to (1 1 1), (2 0 0) and (2 2 0) miller indices, respectively (JCPDS no. 71-4610) [28]. These are characteristic of fcc (face centered cubic) structure. As shown in Figure 3, the intensity of diffraction peaks of copper oxides is very low, which indicates high purity of Cu NPs. The particles size can be found by applying Sherrer’s equation and the average particles size is found to be 69 nm.
Figure 3. X-ray diffraction pattern of the synthesized Cu NPs (Source: Adapted from Ref. 28).
3.1. Preparation of Na zeolite/Cu NPs The Na zeolite/Cu NPs was fabricated via a simple synthetic process by supporting in an aqueous solution of Cu NPs synthesized using aqueous extract of the leaves of Euphorbia esula and was characterized by using the powder XRD, TG-DTA, SEM, and EDS. Natural Natrolite zeolite was obtained from Hormak area, Sistan and Baluchestan province, Iran and was characterized by our group using the powder XRD, SEM, XRF and FT-IR spectroscopy [14-18].
6
The elemental composition of the Natrolite zeolite was also analyzed by the Energy Dispersive X-ray Spectroscopy (EDS). This technique further confirmed that Natrolite zeolite was composed of aluminium, silicon, calcium and oxygen (Figure 4).
Figure 4.EDS spectrum of Natrolite zeolite.
XRD patterns of the Na zeolite and Natrolite zeolite/Cu NPs are shown in Figure 5 and 6. The comparison of the X-ray diffractogram pattern of Na zeolite with X-ray diffractogram pattern of the standard sample (International Zeolite Association) show which pattern was completely matched with that of the Natrolite zeolite. The actual phases for the natural Iranian Natrolite zeolite were silicon oxide cristobalite-SiO2 (cubic) and aluminium silicate zeolite. The presence of copper was confirmed with powder XRD measurements. The results reveal that Cu loading and thermal treatment did not alter the Natrolite zeolite structure [17]. A comparison of the XRD patterns with the one of Na zeolite clearly shows that the host framework remains intact at the end of the procedure, no observable alteration in the framework lattice and no lost in the crystallinity of Na zeolite. Furthermore, one observes a Bragg peak of copper nanoparticles (2 0 0) at 2θ = 48.10° in the Natrolite zeolite/Cu NPs sample. The detection limit of XRD is normally 3-5 wt.%. It is possible that the corresponding peaks of CuO and Cu2O might be below the detection limit of this technique. Thus, no CuO or Cu2O peak was detected. These results indicate that Cu nanoparticles have been combined with Natrolite zeolite.
7
Figure 5.XRD powder pattern of Na zeolite.
Figure 6.XRD powder pattern of Natrolite zeolite/Cu NPs.
The size and shape of the products were examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Figure 7 shows typical large-scale FE-SEM images of the as-produced Natrolite zeolite/Cu NPs. It is clearly observed that the Cu grain pervaded into zeolite surface, which displays a good combination between natural Natrolite zeolite and Cu NPs.
Figure 7. FE-SEM images of Natrolite zeolite/Cu NPs.
8
The size of as-prepared Natrolite zeolite/Cu NPs was further examined by TEM (Figure 8). The average size of Cu NPs determined from Figure 8 was under 40 nm. The particles exhibited spherical morphology with low tendency to agglomeration.
Figure 8. Typical TEM images of as-prepared Natrolite zeolite/Cu NPs.
The elemental composition of Natrolite zeolite/Cu NPs was also analyzed by the Energy Dispersive X-ray Spectroscopy (EDS) spectrum. It further confirmed that Natrolite zeolite/Cu NPs was composed of Si, Al, Ca, Na, Fe, Cu and oxygen (Figure 9).
3000
SiKα 2500
O Kα
AlKα
2000
1500
CaLα 1000
CuLα FeLα NaKα
500
CaKα AuMβ AuMα
FeKα AuLl CuKα
CaKβ
FeKβ
CuKβ AuLα
0 0
5
10
Figure 9. EDS spectrum ofNatrolite zeolite/Cu NPs.
9
keV
Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) were carried out in flowing air (120 ml min-1) at a heating rate of 2 °C min-1 on an autonomic TG/DTA. In the TG/DTA data of Natrolite zeolite [17] a gradual weight decreasing was only observed between 300 and 400 °C, while as seen in Figure 10, two weight loss stages were observed in flowing air. About 5.0 wt % weight loss was observed in the first stage at 160-260 ºC corresponding to desorption of surface water or decomposition of the organic content (leaves extract) present in the sample. In the second stage at 370-440 ºC, weight loss is about 6.0 wt %, which can be attributed to desorption of lattice water.
Figure 10.TG-DTA data measured for Natrolite zeolite/Cu NPs.
3.2. Evaluation of the catalytic activity of Natrolite zeolite/Cu NPs through the preparation of nitriles Herein, in this paper, we describe here a simple method of synthesis of aryl nitriles in high yields by the reaction of aryl bromides and K4Fe(CN)6 in the presence of Natrolite zeolite/Cu NPs as a as stable, heterogeneous and environmentally benign catalyst. We initially selected 4-iodotoluene and non-toxic potassium ferrocyanide as a model reaction. As expected, no target product could be detected in the absence of catalyst or base. The results indicated that base had a remark effect on the yield of product. Among the various bases (K2CO3, Et3N, Na2CO3 and KOAc) tested in the presence of Natrolite zeolite/Cu NPs in a 1:1 mixture of DMF and water, Et3N led to significant conversion. The best result was obtained with 4-iodotoluene (1.0 mmol), K4Fe(CN)6 (0.66 mmol), Natrolite zeolite/Cu NPs (0.05 g), Et3N (2.0 mmol), in a 1:1 mixture of DMF and water at 120 ºC, which obtained the product in a good yield (93%). We have examined the reaction of various aryl iodides containing electron-withdrawing or electrondonating groups with K4Fe(CN)6. As shown in Table 1, substituted aryl iodides were converted into the corresponding products in high yields under ligand-free and aerobic conditions.
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Table 1. Synthesis of aryl nitriles.
Entry
a
ArI
ArB(OH)2
Yielda (%)
1
92 (89)b
2
90
3
89
4
86
5
84
6
89
7
90
Yields are after work-up. bYield after the 5th cycle.
3.3. Evaluation of the catalytic activity of Natrolite zeolite/Cu NPs through the preparation of 1,2,3-triazoles Due to the importance of 1,2,3-triazoles in synthetic organic chemistry and in industry for the manufacture of pharmaceuticals and medicinal compounds and their application as photostabilizers, agrochemicals, optical brighteners, corrosion inhibitors etc. [29-37], we next turned our attention to applying Natrolite zeolite/Cu NPs to the synthesis of 1,2,3-triazoles via the 1,3-dipolar cycloaddition reactions between azides and terminal alkynes in the presence of Et3N and water as a green solvent at room temperature. The desired products are obtained in excellent yields. As shown in Table 2, benzylic azides coupled with acetylenes to generate a range of triazoles in water as the. The reactions were completed within 3-5 hours to give high yields of the corresponding products. Table 2. Synthesis of 1,2,3-triazoles.a
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Time (h)
Yieldb(%)
1
3
96 (93)c
2
3
97
3
3
96
4
5
93
5
5
95
6
5
96
7
5
93
8
5
95
9
5
94
Entry
a
Benzyl azide
Alkyne
Product
Conditions: Benzyl azide (1.0 mmol), alkyne (1.0 mmol), catalyst (50 mg), Et3N (1.0 mmol), H2O (10 mL),
room temperature. bIsolated yield. cYield after the 5th cycle.
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3.4. Catalyst recyclability The high catalytic activity, easy preparation, isolability, bottleability, and reusability of Natrolite zeolite/Cu NPs raise the prospect of using this type of materials for the hydration of cyanamides and synthesis of nitriles in industrial applications as well as in small scale organic synthesis. The work-up procedure is straightforward due to the heterogeneous nature of the catalyst. The reusability of the catalysts is one of the most important benefits and makes them useful for commercial applications. The reusability of the Natrolite zeolite/Cu NPs was studied for both transformations. After completion of the reaction, the catalyst was separated and was washed with ethanol, dried in a hot air oven at 100 °C for 2 h and the recycled catalyst was saved for the next reaction. The recycled catalyst could be reused five times with no loss of activity (Figure 11). Thus, the catalyst is stable during the reaction. The reusability of the catalyst was also studied for the synthesis of 1,2,3-triazoles (Table 2, entry 1) under the present reaction conditions. The catalytic activity did not decrease considerably after five catalytic cycles.
4. Conclusions In conclusion, we have fabricated a heterogeneous and stable catalyst using the prepared Cu NPs and natural Na-zeolite. We demonstrate that the Natrolite zeolite/Cu NPs have potential for various catalytic applications. The study provides a green synthetic route for preparing nitriles and 1,2,3-triazoles. The catalyst can be readily recovered and reused for several cycles with only a slight decrease in activity.
Acknowledgements
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We gratefully acknowledge from the Iranian Nano Council and University of Qom for the support of this work.
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Graphical Abstract Natrolite zeolite supported copper nanoparticles as an efficient heterogeneous catalyst for the 1,3-diploar cycloaddition and cyanation of aryl iodides under ligand-free conditions Mahmoud Nasrollahzadeh*, S. Mohammad Sajadi and Akbar Rostami-Vartooni
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