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1-Hexanesulphonic acid sodium salt promoted the one-pot synthesis of amidoalkyl naphthols under microwave-irradiation
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Chinese Chemical Letters 22 (2011) 551–554 www.elsevier.com/locate/cclet
1-Hexanesulphonic acid sodium salt promoted the one-pot synthesis of amidoalkyl naphthols under microwave-irradiation Kirti S. Niralwad, Bapurao B. Shingate, Murlidhar S. Shingare * Organic Research Laboratory, Department of Chemistry, Dr. Babasaheb Ambedkar Marathwada University, Aurangabad, M.S. 431004, India Received 1 September 2010 Available online 3 March 2011
Abstract Amidoalkyl naphthols have been synthesized in high yields in the presence of 1-hexanesulphonic acid sodium salt as an inexpensive solid catalyst under solvent-free conditions and microwave-irradiation. This catalyst provides clean conversion; greater selectivity and easy workup make this protocol practical and economically attractive. # 2010 Murlidhar S. Shingare. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved. Keywords: Aldehydes; Naphthols; 1-Hexanesulphonic acid sodium salt; Amidoalkyl naphthols; Microwave-irradiation
During last 10 years our interest in an efficient and economical technology for the preparation of some organic synthones has promoted the research in the field of microwave irradiation [1–3]. The use of such non-conventional reaction conditions reveals several features like: a short reaction time compared to conventional heating, ease of workup after a reaction and reduction in the usual thermal degradation and better selectivity [4,5]. In recent years some important reviews, concerning study of microwave assisted organic reactions, have been published [6,7]. Solvent-free methods are specially adapted to green chemistry principles [8]. When coupled to microwave irradiation, they result in very efficient and clean procedures with noticeable improvements over classical methods. Multi-component reactions (MCRs) play an important role in combinatorial chemistry because of its ability to synthesize small drug-like molecules with several degrees of structural diversity [9,10]. Compounds bearing 1,3-amino oxygenated functional groups are ubiquitous to a variety of biologically important natural products and potent drugs including a number of nucleoside antibiotics and HIV protease inhibitors, such as ritonavir and lipinavir [11]. The preparation of 1-amidoalkyl-2-naphthols can be carried out in the presence of various catalysts such as montmorillonite K10 clay [12], Ce(SO4)2 [13], iodine [14], K5COW12O403H2O [12], p-toluene sulphonic acid ( p-TSA) [13], sulphamic acid [14], cation-exchanged resins [15], silica–sulphuric acid [16], SiO2–HClO4 [17] and NaHSO4H2O [18]. Some of these methods, however, suffer from drawbacks, which include the use of hazardous materials, commercially non-available or highly corrosive and difficult-to-handle reagents, long reaction times, low yields, drastic reaction conditions and tedious workup procedures.
* Corresponding author. E-mail address: [email protected] (M.S. Shingare). 1001-8417/$ – see front matter # 2010 Murlidhar S. Shingare. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved. doi:10.1016/j.cclet.2010.11.018
[()TD$FIG] 552
K.S. Niralwad et al. / Chinese Chemical Letters 22 (2011) 551–554 R' OH R'CHO
R''CONH2
MW 1
2(a-j)
NHCOR''
1-Hexanesulphonic acid sodiun salt
3 R''=NH2,CH3,C6H5
OH
4(a-j)
Scheme 1. Synthesis of amidoalkyl naphthol using 1-hexanesulphonic acid sodium salt.
A search of the literature revealed that the 1-hexanesulphonic acid sodium salt [19] liberates corresponding acid with extreme wide applications such as sulphonation of alkanes [20]. However, there are very few reports using hexane sulphonic acid sodium salt as a catalyst in the organic transformation [21]. For the first time we herein report the use of 1-hexanesulphonic acid sodium salt for the synthesis of a amidoalkyl naphthols under microwave-irradiation and solvent-free condition. 1. Experimental Microwave oven (LG Smart Chef MS-255R operating at 2450 MHz having maximum out put power of 960 W) was used for microwave irradiation. 1H NMR spectra were recorded on Mercury plus Varian at 400 MHz in DMSO-d6 as a Table 1 Synthesis of amidoalkyl naphthols catalysed by 1-hexanesulphonic acid sodium salt under microwave-irradiation.a Entry 4d
Aldehydes [TD$INLE]
CHO
4e [TD$INLE]
4f
[TD$INLE] Br
4a [TD$INLE]
4b
[TD$INLE] Cl
CHO
Cl
CHO
4c
CHO
CHO
[TD$INLE]
CHO
Urea/amide
Time (min)
Yield (%) b
M.P. (8C)
CH3CONH2
3
95
229–231
CH3CONH2
4
94
229–230
CH3CONH2
5
90
205–207
H2NCONH2
4
90
170–172
H2NCONH2
7
88
167–169
H2NCONH2
6
90
192–194
C6H5CONH2
8
92
235–237
C6H5CONH2
10
87
177–179
C6H5CONH2
7
80
192–194
CH3CONH2
20
35
173–175
ON
4g [TD$INLE]
4h
[TD$INLE]Cl
4i
[TD$INLE] F
4j
[TD$INLE]
a b
CHO
CHO
CHO
CHO
Reaction conditions: 1 (1 mmol), 2 (1 mmol), and 3 urea (1.5 mmol) catalyst (10 mol%). Isolated yield.
[()TD$FIG]
K.S. Niralwad et al. / Chinese Chemical Letters 22 (2011) 551–554 R OH +
R
O C
1-Hexanesulphonic acid sodium salt H
H
R
O O
R'
553
NH2
O H N C R' OH
MW O-QMs
Scheme 2. Mechanism of amidoalkyl naphthols.
solvent and TMS as an internal standard. IR spectra were recorded on a PerkinElmer FTIR using KBr discs. Mass spectra were recorded on Micromass Quattro II using electrospray ionization technique. The appropriate b-naphthol 1 (1 mmol), aldehydes 2(a–j) (1 mmol), urea 3 (1.5 mmol) and the appropriate catalyst (10 mol%) were introduced into a beaker and mixed. The mixture was irradiated under microwave-irradiation for an appropriate time, the progress of reaction was monitored by TLC. After completion of reaction the mixture was cooled to room temperature and was washed with cold water, and then the crude product was recrystallized from 96% ethanol to obtain the pure product. All the products were characterized from their spectral data. 2. Result and discussion As a part of our ongoing research devoted to the development of useful synthetic methodologies [22], herein we report an efficient and practical method for the synthesis of amidoalkyl naphthols using 1-hexanesulphonic acid sodium salt which makes use of mild catalyst under solvent-free condition and microwave-irradiation (Scheme 1). Herein, we have carried out the reaction by adding the three components, a-naphthol, benzaldehyde, and urea to 1hexanesulphonic acid sodium salt affords the mixture of regioisomers, while same the reaction was carried out using b-naphthol it gave the corresponding product in excellent yield. We have also examined the reaction with aliphatic aldehydes but the yield was low as compared to aromatic aldehydes. After optimizing the conditions, the generality of this method was examined by the reaction of b-naphthol with several substituted aldehydes and urea/amides using 1-hexanesulphonic acid as a catalyst under microwaveirradiation, the results are shown in Table 1. A possible mechanism for this transformation is the reaction of 2-naphthol with aromatic aldehydes in the presence of 1-hexanesulphonic acid sodium salt give ortho-quinone methides (o-QMs). The same o-QMs, generated in situ, have been reacted with urea/amide via conjugate addition to form 1-amidoalkyl-2-naphthol derivatives (Scheme 2). Here we extended this reaction on several substituted aromatic aldehydes, b-naphthol, and urea/amide under similar conditions, furnishing the respective amidoalkyl naphthols in excellent yields (80–95%). In all cases, aromatic aldehydes with substituent carrying either electron-donating or electron withdrawing groups reacted successfully and gave the products in excellent yields. Also we have found that the reaction with liquid aldehydes required less time than that required for solid aldehydes. All the synthesized compounds were characterized by spectral data and compared (MS and NMR) with authentic sample [23]. 3. Conclusion In conclusion, 1-hexanesulphonic acid sodium salt was found to be an efficient catalyst for the reaction of substituted aldehydes, phenol, and urea/amide to afford the corresponding product in excellent yields. The notable advantages of the present protocol are mild, solvent-free conditions, ecofriendly catalyst and easy reaction work-up procedure. We believe this will provide a better and more practical alternative to be existing methodologies for the synthesis of amidoalkyl naphthols. Acknowledgments The authors are thankful to University Grant Commission, New Delhi, for awarding the Rajiv Gandhi fellowship and to The Head, Department of Chemistry, Dr. Babasaheb Ambedkar Marathwada University, Aurangabad-431 004, MS, India for providing the laboratory facility.
554
K.S. Niralwad et al. / Chinese Chemical Letters 22 (2011) 551–554
References [1] (a) R. Gedye, F. Smith, K. Westaway, et al. Tetrahedron Lett. 27 (1986) 279; (b) A. Loupy, Microwave in Organic Synthesis, Wiley-VCH, Weinheim, 2006. [2] R.J. Giguere, T.L. Bray, S.M. Duncan, G. Majetich, Tetrahedron Lett. 27 (1986) 4945. [3] (a) D.R. Hwang, S.M. Moerlein, M.J. Welch, J. Chem. Soc., Chem. Commun. 23 (1987) 1799; (b) A. Gourdenne, Q. Le Van, Polym. Prep. 22 (1981) 125; (c) H. Jullien, H. Valot, Polymer 24 (1983) 810; (d) A. Loupy, S.J. Song, S.J. Cho, et al. Synth. Commun. 35 (2005) 79. [4] A. Loupy, A. Haudrechy, Effect de Milieu en Synthese Organique, Masson, Paris, 1996. [5] (a) D.A. Lewis, J.D. Summers, T.C. Ward, et al. J. Polym. Sci. Part A 30 (1992) 1647; (b) J. Berlan, P. Giboreau, S. Lefeuvre, et al. Tetrahedron Lett. 32 (1991) 2363. [6] C.R. Strauss, R.S. Varma, Top. Curr. Chem. 266 (2006) 199. [7] (a) I. Ugi, A. Domling, W. Horl, Endeavour 18 (1994) 115; (b) L.F. Tietze, A. Modi, Med. Res. Rev. 20 (2000) 304; (c) I. Ugi, A. Domling, B. Werner, J. Heterocycl. Chem. 37 (2000) 647; (d) R.V.A. Orru, M. de Greef, Synthesis (2003) 1471. [8] (a) E. Juaristi, Enantioselective Synthesis of Amino-acids, John Wiley & Sons, New York, 1997.; (b) T. Dingermann, D. Steinhilber, G. Folkers, Wiley-VCH, Weinheim, 2004. [9] S. Kantevari, S.V.N. Vuppalapati, L. Nagarapu, Catal. Commun. 8 (2007) 1857. [10] N.P. Selvam, P.T. Perumal, Tetrahedron Lett. 47 (2006) 7481. [11] B. Das, K. Laxminarayana, B. Ravikanth, et al. J. Mol. Catal. A: Chem. 261 (2007) 180. [12] L. Nagarapu, M. Baseeruddin, S. Apuri, et al. Catal. Commun. 8 (2007) 1729. [13] M.M. Khodaei, A.R. Khosropour, H.A. Moghanian, Synlett 6 (2006) 916. [14] S.B. Patil, P.R. Singh, M.P. Surpur, S.D. Samant, Ultrason. Sonochem. 14 (2007) 515. [15] S.B. Patil, P.R. Singh, M.P. Surpur, S.D. Samant, Synth. Commun. 37 (2007) 1659. [16] G. Srihari, M. Nagaraju, M.M. Murthy, Helv. Chim. Acta 90 (2007) 1497. [17] H.R. Shaterian, H. Yarahmadi, M. Ghashang, Tetrahedron 64 (2008) 1263. [18] H.R. Shaterian, H. Yarahmadi, Arkivoc 2 (2008) 105. [19] (a) J. Weiss, V.C.H. Verlags gesellschaft mbH, IInd ed., VCH Publisher, Inc., New York, Weinheim, Germany, 1995; (b) H. Small, Ion Chromatography, Plenum Press, New York and London, 1989. [20] J.L. Boyer, B. Gilot, J.P. Canselierm, Phosphorus Sulphur Silicon Relat. Elem. 20 (1984) 259. [21] (a) R.S. Joshi, P.G. Mandhane, S.D. Diwakar, C.H. Gill, Ultrason. Sonochem. 17 (2010) 298; (b) K.S. Niralwad, B.B. Shingate, M.S. Shingare, Ultrason. Sonochem. 17 (2010) 760. [22] (a) K.S. Niralwad, B.B. Shingate, M.S. Shingare, Bull. Korean Chem. Soc. 31 (2010) 981; (b) S.B. Sapkal, K.F. Shelke, B.B. Shingate, M.S. Shingare, Tetrahedron Lett. 50 (2009) 1754; (c) K.S. Niralwad, B.B. Shingate, M.S. Shingare, Tetrahedron Lett. 51 (2010) 3616; (d) S.A. Sadaphal, K.F. Shelke, S.S. Sonar, M.S. Shingare, Central Eur. J. Chem. 6 (2008) 622. [23] Spectral data of principal compounds: (2-Hydroxynaphthalen-1-yl)-phenylmethylurea (4a): 1H NMR (400 MHz, DMSO-d6): d 10.30 (s, 1H), 7.84–7.14 (m, 12H), 6.89 (s, 2H), 5.72 (s, 2H); Mass (ES/MS): m/z 291 (M H, 100%); Anal. calcd. for C18H16N2O2: C 73.96, H 5.52, N 9.58; found: C 73.51, H 5.55, N 9.60. (4-Chlorophenyl)-(2-hydroxynaphthelene-1-yl)-methylurea (4b): 1H NMR (400 MHz, DMSO-d6): d 10.31 (s, 1H), 7.93–7.74 (m, 3H, Ar–H), 7.52–7.13 (m, 7H, Ar–H), 6.80 (s, 2H), 5.85 (s, 2H); Mass (ES/MS): m/z 325 (M H, 100%); Anal. calcd. for C18H15ClN2O2: C 66.16, H 4.63, N 8.57; found: C 66.20, H 4.58, N 8.62. (3Nitrophenyl)-(2-hydroxynaphthalen-1-yl)-methylurea (4d): 1H NMR (400 MHz, DMSO-d6): d 10.28 (s, 1H), 8.04–7.92 (m, 2H), 7.54–6.87 (m, 8H), 6.75 (bs, 2H), 5.83 (s, 2H); Mass (ES/MS): m/z 336 (M H, 100%); Anal. calcd. for C18H15N3O4: C 64.09, H 4.48, N 12.46; found C 64.37, H 4.53, N 12.52. N-(4-Bromophenyl)(2hydroxynaphthalen-1-yl)-methylacetamide (4f): 1H NMR (400 MHz, DMSO-d6): d 9.84 (s, 1H), 8.11 (d, J = 8.1 Hz, 1H), 7.92 (d, J = 11.3 Hz, 1H), 7.80–7.66 (m, 2H), 7.42–7.05 (m, 8H), 2.02 (s, 3H); Anal. calcd. for C19H16BrNO2: C, 61.64; H, 4.36; N, 3.78; found: C, 61.76; H, 4.40; N, 3.62. N-((4-fluorophenyl)(2-hydroxynaphthalen-1-yl)-methyl)benzamide (4i): 1H NMR (300 MHz, DMSO-d6): d 10.36 (s, 1H), 9.37 (d, J = 9 Hz, 1H), 8.08–7.06 (m, 16H); Anal. calcd. for C24H18FNO2: C, 77.61; H, 4.88; N, 3.77; F, 5.12; found: C, 77.52; H, 4.90; N, 3.76; F, 5.10. 1-(2-Hydroxynaphthalen-1-yl)-propylurea (4j): 1H NMR (400 MHz, DMSO-d6): d 10.37 (s, 1H), 7.66–6.97 (m, 6H), 6.45 (bs, 1H), 5.64 (bs, 2H), 4.86 (m, 1H), 1.74 (m, 2H), 1.05 (t, 3H); Mass (ES/MS): m/z 243 (M H, 100%); Anal. calcd. for C14H16N2O2: C 68.83, H 6.60, N 11.47; found C 69.11, H 6.62, N 11.54.
Chinese Chemical Letters 22 (2011) 551–554 www.elsevier.com/locate/cclet
1-Hexanesulphonic acid sodium salt promoted the one-pot synthesis of amidoalkyl naphthols under microwave-irradiation Kirti S. Niralwad, Bapurao B. Shingate, Murlidhar S. Shingare * Organic Research Laboratory, Department of Chemistry, Dr. Babasaheb Ambedkar Marathwada University, Aurangabad, M.S. 431004, India Received 1 September 2010 Available online 3 March 2011
Abstract Amidoalkyl naphthols have been synthesized in high yields in the presence of 1-hexanesulphonic acid sodium salt as an inexpensive solid catalyst under solvent-free conditions and microwave-irradiation. This catalyst provides clean conversion; greater selectivity and easy workup make this protocol practical and economically attractive. # 2010 Murlidhar S. Shingare. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved. Keywords: Aldehydes; Naphthols; 1-Hexanesulphonic acid sodium salt; Amidoalkyl naphthols; Microwave-irradiation
During last 10 years our interest in an efficient and economical technology for the preparation of some organic synthones has promoted the research in the field of microwave irradiation [1–3]. The use of such non-conventional reaction conditions reveals several features like: a short reaction time compared to conventional heating, ease of workup after a reaction and reduction in the usual thermal degradation and better selectivity [4,5]. In recent years some important reviews, concerning study of microwave assisted organic reactions, have been published [6,7]. Solvent-free methods are specially adapted to green chemistry principles [8]. When coupled to microwave irradiation, they result in very efficient and clean procedures with noticeable improvements over classical methods. Multi-component reactions (MCRs) play an important role in combinatorial chemistry because of its ability to synthesize small drug-like molecules with several degrees of structural diversity [9,10]. Compounds bearing 1,3-amino oxygenated functional groups are ubiquitous to a variety of biologically important natural products and potent drugs including a number of nucleoside antibiotics and HIV protease inhibitors, such as ritonavir and lipinavir [11]. The preparation of 1-amidoalkyl-2-naphthols can be carried out in the presence of various catalysts such as montmorillonite K10 clay [12], Ce(SO4)2 [13], iodine [14], K5COW12O403H2O [12], p-toluene sulphonic acid ( p-TSA) [13], sulphamic acid [14], cation-exchanged resins [15], silica–sulphuric acid [16], SiO2–HClO4 [17] and NaHSO4H2O [18]. Some of these methods, however, suffer from drawbacks, which include the use of hazardous materials, commercially non-available or highly corrosive and difficult-to-handle reagents, long reaction times, low yields, drastic reaction conditions and tedious workup procedures.
* Corresponding author. E-mail address: [email protected] (M.S. Shingare). 1001-8417/$ – see front matter # 2010 Murlidhar S. Shingare. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved. doi:10.1016/j.cclet.2010.11.018
[()TD$FIG] 552
K.S. Niralwad et al. / Chinese Chemical Letters 22 (2011) 551–554 R' OH R'CHO
R''CONH2
MW 1
2(a-j)
NHCOR''
1-Hexanesulphonic acid sodiun salt
3 R''=NH2,CH3,C6H5
OH
4(a-j)
Scheme 1. Synthesis of amidoalkyl naphthol using 1-hexanesulphonic acid sodium salt.
A search of the literature revealed that the 1-hexanesulphonic acid sodium salt [19] liberates corresponding acid with extreme wide applications such as sulphonation of alkanes [20]. However, there are very few reports using hexane sulphonic acid sodium salt as a catalyst in the organic transformation [21]. For the first time we herein report the use of 1-hexanesulphonic acid sodium salt for the synthesis of a amidoalkyl naphthols under microwave-irradiation and solvent-free condition. 1. Experimental Microwave oven (LG Smart Chef MS-255R operating at 2450 MHz having maximum out put power of 960 W) was used for microwave irradiation. 1H NMR spectra were recorded on Mercury plus Varian at 400 MHz in DMSO-d6 as a Table 1 Synthesis of amidoalkyl naphthols catalysed by 1-hexanesulphonic acid sodium salt under microwave-irradiation.a Entry 4d
Aldehydes [TD$INLE]
CHO
4e [TD$INLE]
4f
[TD$INLE] Br
4a [TD$INLE]
4b
[TD$INLE] Cl
CHO
Cl
CHO
4c
CHO
CHO
[TD$INLE]
CHO
Urea/amide
Time (min)
Yield (%) b
M.P. (8C)
CH3CONH2
3
95
229–231
CH3CONH2
4
94
229–230
CH3CONH2
5
90
205–207
H2NCONH2
4
90
170–172
H2NCONH2
7
88
167–169
H2NCONH2
6
90
192–194
C6H5CONH2
8
92
235–237
C6H5CONH2
10
87
177–179
C6H5CONH2
7
80
192–194
CH3CONH2
20
35
173–175
ON
4g [TD$INLE]
4h
[TD$INLE]Cl
4i
[TD$INLE] F
4j
[TD$INLE]
a b
CHO
CHO
CHO
CHO
Reaction conditions: 1 (1 mmol), 2 (1 mmol), and 3 urea (1.5 mmol) catalyst (10 mol%). Isolated yield.
[()TD$FIG]
K.S. Niralwad et al. / Chinese Chemical Letters 22 (2011) 551–554 R OH +
R
O C
1-Hexanesulphonic acid sodium salt H
H
R
O O
R'
553
NH2
O H N C R' OH
MW O-QMs
Scheme 2. Mechanism of amidoalkyl naphthols.
solvent and TMS as an internal standard. IR spectra were recorded on a PerkinElmer FTIR using KBr discs. Mass spectra were recorded on Micromass Quattro II using electrospray ionization technique. The appropriate b-naphthol 1 (1 mmol), aldehydes 2(a–j) (1 mmol), urea 3 (1.5 mmol) and the appropriate catalyst (10 mol%) were introduced into a beaker and mixed. The mixture was irradiated under microwave-irradiation for an appropriate time, the progress of reaction was monitored by TLC. After completion of reaction the mixture was cooled to room temperature and was washed with cold water, and then the crude product was recrystallized from 96% ethanol to obtain the pure product. All the products were characterized from their spectral data. 2. Result and discussion As a part of our ongoing research devoted to the development of useful synthetic methodologies [22], herein we report an efficient and practical method for the synthesis of amidoalkyl naphthols using 1-hexanesulphonic acid sodium salt which makes use of mild catalyst under solvent-free condition and microwave-irradiation (Scheme 1). Herein, we have carried out the reaction by adding the three components, a-naphthol, benzaldehyde, and urea to 1hexanesulphonic acid sodium salt affords the mixture of regioisomers, while same the reaction was carried out using b-naphthol it gave the corresponding product in excellent yield. We have also examined the reaction with aliphatic aldehydes but the yield was low as compared to aromatic aldehydes. After optimizing the conditions, the generality of this method was examined by the reaction of b-naphthol with several substituted aldehydes and urea/amides using 1-hexanesulphonic acid as a catalyst under microwaveirradiation, the results are shown in Table 1. A possible mechanism for this transformation is the reaction of 2-naphthol with aromatic aldehydes in the presence of 1-hexanesulphonic acid sodium salt give ortho-quinone methides (o-QMs). The same o-QMs, generated in situ, have been reacted with urea/amide via conjugate addition to form 1-amidoalkyl-2-naphthol derivatives (Scheme 2). Here we extended this reaction on several substituted aromatic aldehydes, b-naphthol, and urea/amide under similar conditions, furnishing the respective amidoalkyl naphthols in excellent yields (80–95%). In all cases, aromatic aldehydes with substituent carrying either electron-donating or electron withdrawing groups reacted successfully and gave the products in excellent yields. Also we have found that the reaction with liquid aldehydes required less time than that required for solid aldehydes. All the synthesized compounds were characterized by spectral data and compared (MS and NMR) with authentic sample [23]. 3. Conclusion In conclusion, 1-hexanesulphonic acid sodium salt was found to be an efficient catalyst for the reaction of substituted aldehydes, phenol, and urea/amide to afford the corresponding product in excellent yields. The notable advantages of the present protocol are mild, solvent-free conditions, ecofriendly catalyst and easy reaction work-up procedure. We believe this will provide a better and more practical alternative to be existing methodologies for the synthesis of amidoalkyl naphthols. Acknowledgments The authors are thankful to University Grant Commission, New Delhi, for awarding the Rajiv Gandhi fellowship and to The Head, Department of Chemistry, Dr. Babasaheb Ambedkar Marathwada University, Aurangabad-431 004, MS, India for providing the laboratory facility.
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