Chitosan supported ionic liquid: a recyclable wet and dry catalyst for the direct conversion of aldehydes into nitriles and amides under mild conditions

Abstract

A green and highly efficient chitosan supported magnetic ionic liquid (CSMIL) was synthesized with chitosan (the most abundant biopolymer in nature and a cheap industrial waste product), methyl imidazole and anhydrous/hydrous FeCl₃. The heterogeneous catalyst thus obtained was used for the direct conversion of aldehydes to the corresponding nitriles in the presence of NH₂OH·HCl/dry-CSMIL/MeSO₂Cl and amides with NH₂OH·HCl/wet-CSMIL/MeSO₂Cl. A highlight of our approach is the easy separation of the catalyst from the reaction medium and thus the recyclability of the catalyst. This simple method can be applied to obtain a wide range of aromatic, heterocyclic, and aliphatic nitriles and amides.

---

1. Introduction

In recent years, the development of pollution prevention research has been broad due to growing environmental concerns. In this respect, heterogeneous catalysis is generally preferable to homogeneous catalysis, mainly because of the easy recovering and possible recycling of the catalyst, simple experimental procedures, mild reaction conditions and minimization of chemical wastes as compared to its liquid phase counterparts. Very recently, natural materials for catalytic applications, in particular biopolymers, have been attracting increasing interest as environmentally benign polymeric supports for catalysts.¹ Carbohydrates are one of the most diverse and important classes of biomolecules in nature. These renewable polymers are largely used in applications such as adhesives, absorbents, lubricants, soil conditioners, drug delivery systems, textiles and high strength structural materials.²

Among biopolymers, chitosan (CS), is the second most abundant polysaccharide in nature next to cellulose, and is estimated to be produced annually almost as much as cellulose. It can also be found in industrial waste.³ Chitosan is a potentially excellent material to be used as a support for catalytic applications in heterogeneous molecular catalysis, due to its hydrophilicity, chemical reactivity, unique three-dimensional structure, hydroxyl and amino groups, excellent chelating properties, and mechanical properties.^4,5 Moreover, chitosan is environmentally friendly because it can be degraded by microorganisms in soil and water. There has been much scientific and industrial interest in utilizing chitin and chitosan for different applications such as pharmaceutical, waste water treatment, cosmetics, drug delivery, heavy metal chelation, heterogeneous catalysts and many other attractive utilizations.^6,7

The unique and tunable physical and chemical properties of ionic liquids (IL) make this class of molecules particularly suitable as green solvents for a range of organic reactions, as they provide possibilities such as control of product distribution,⁸ enhanced rates⁹ and/or reactivity,¹⁰ ease of product recovery,¹¹ catalyst immobilization,¹² and recycling.^13,14

In this work, we reveal a new biopolymer supported ionic liquid based on dry FeCl₃ and FeCl₃·3H₂O, which can be used to produce both wet and dry heterogeneous catalysts.

The nitrile moiety is an important constituent in different natural products, and a considerable precursor for the synthesis of amines, amides, ketones, carboxylic acids and esters. There are diverse methods for the synthesis of nitrile groups from different organic functional groups.¹⁵ Among these, the direct conversion of aldehydes into the corresponding nitriles has been shown to be an attractive and important strategy for the preparation of nitriles in organic transformations.¹⁶ Until now, several methods have been reported for the conversion of aldehydes to nitriles via the dehydration of aldoximes, such as using Pd(OAc)₂/PPh₃,¹⁷ N-(p-toluenesulfonyl) imidazole (TsIm),¹⁸ [RuCl₂(p-cymene)]₂/molecular sieves,¹⁹ 2-chloro-1-methyl pyridinium iodide,²⁰ triethyl amine/SO₂,²¹ PPh₃/CCl₄,²² acetic anhydride,²³ Vilsmeier reagent,²⁴ Burgess reagent,²⁵ cyanuric chloride,²⁶ di-2-pyridylsulfite,²⁷ AlI₃,²⁸ TiCl₃(OTf),²⁹ AlCl₃·6H₂O/KI,³⁰ chlorosulfonic acid,³¹ and S,S-dimethyl dithiocarbonate.³²

Although all of these methods are valuable, most of them have one or more of the following drawbacks: less readily available reagents, harsh reaction conditions, low yields, refluxing for a prolonged period of time, tedious work-up of the reaction mixture, use of expensive metals and toxic oxidants. Hence, it is of great practical importance to develop a more efficient and also environmentally benign method that avoids all of these drawbacks for the conversion of aldoximes into nitriles.

Herein, as part of our ongoing study on the application of this new green catalyst in organic synthesis,³³ we would like to present the direct oxidative conversion of aldehydes into the corresponding nitriles and amides by treatment with hydroxyl amine hydrochloride and mesyl chloride under solvent free conditions at 70 °C in the presence of dry and wet chitosan supported magnetic ionic liquid (CSMIL) (Scheme 1).

Scheme 1 Direct conversion of aldehydes into the corresponding nitriles (method A), and amides (method B) in the presence of CSMIL.

Result and discussion

Catalyst preparation

Dry and wet catalysts were prepared and characterized based on the following procedure (Scheme 2) (see the ESI†).

Scheme 2 Preparation of chitosan supported magnetic ionic liquid (CSMIL); (i) 1,2-dichloro ethane, acetone, 25 °C, (ii) chitosan, isopropanol, 25 °C.

Optimization of the reaction

In our initial studies, the effect of different catalysts on the outcome of the reaction was considered. For this reason, the conversion of p-bromobenzaldehyde to the p-bromobenzonitrile was used as a standard model. The reaction was performed using a mixture containing 1 mmol of p-bromobenzaldehyde, 1.2 mmol of hydroxylamine hydrochloride, 1.2 mmol of mesyl chloride, and different amounts of the various catalysts (Table 1). The results confirmed that no product is obtained when the reaction is carried out without a catalyst (Table 1, entry 1). When FeCl₃ was used as a solid catalyst, the reaction time and the yield of the product were unsatisfactory (Table 1, entry 2). By using a typical IL such as butyl methyl imidazolium chloride [BMIm][Cl] as the solvent system for the FeCl₃ catalyst, 70% yield of the product was obtained after 6 h (Table 1, entry 3). In comparison with [BMIm][Cl], butyl methyl imidazolium tetrachloro ferrate [BMIm]FeCl₄ as the solvent–catalyst increased the yield up to 73% in a shorter reaction time (Table 1, entry 4). But unfortunately, the separation and reuse of the [BMIm]FeCl₄ from the product was not as satisfactory. Therefore, with the new catalyst at hand, we decided to use chitosan supported magnetic ionic liquid (CSMIL) as a heterogeneous catalyst. The use of 8 mg of CSMIL under solvent free conditions afforded 84% of the desired nitrile. Optimization of the reaction conditions was undertaken to increase the yield of the product using different amounts of CSMIL. The yield was increased to 96% using 15 mg of CSMIL under solvent-free conditions.

Table 1 Effect of different solvents on the conversion of 4-nitrobenzaldehyde into 4-nitrobenzonitrile^a

Entry	Catalyst/mg	Solvent	Time (h)	Temp (°C)	Yield^b (%)
a Reaction conditions: 4-nitrobenzaldehyde (1 mmol), NH2OH·HCl (1.2 mmol), MsCl (1.2 mmol).b Isolated yield.
1	No catalyst	DMF	24	120	Trace
2	FeCl3/15	DMF	24	120	42
3	FeCl3/15	(BMIm)Cl	6	120	70
4	—	(BMIm)FeCl4	4	120	73
5	Dry-CSMIL/8	EtOH	3	120	77
6	Dry-CSMIL/8	MeCN	3	120	77
7	Dry-CSMIL/8	DMSO	4	120	80
8	Dry-CSMIL/8	DMF	4	120	80
9	Dry-CSMIL/8	Neat	2	120	84
10	Dry-CSMIL/8	Neat	2	70	87
11	Dry-CSMIL/10	Neat	1.5	70	90
12	Dry-CSMIL/15	Neat	1.0	70	96

---

Moreover, we screened a variety of solvents and examined their effect on the reaction time and yield (Table 1). The use of EtOH, DMF, DMSO and MeCN (Table 1, entries 5–8) led to moderate yields of 4-nitrobenzonitrile, whereas in the absence of solvent the reaction still proceeded and the best yields of the nitrile were attained. Therefore, solvent-free (entry 9) was found to be the most appropriate condition and was used for all subsequent reactions. Additionally, we also evaluated the effect of temperature on the progress of the model reaction (entries 9 and 10). The best result was obtained at 70 °C. Further increases in temperature caused no distinguishable improvement in the progress of the reaction, because of the gelification of chitosan in the structure of the catalyst at a high temperature.

Many methods of obtaining this goal have been developed; the present methodology was compared to some reported oxidizing conditions, as summarized in Table 2. This method has the distinction of providing a green biopolymer-supported catalyst. It has attracted much interest in relation to the available methods catalyzed by different catalysts, because this method was undertaken at 70 °C, with high yields in short reaction time. It can be seen that 96% yield of product is obtained at 70 °C in the presence of 15 mg CSMIL after 1–2 h, whereas 82–97% yield is obtained at 90–120 °C in the presence of other catalysts such as DMSO,³⁴ Al₂O₃/MeSO₂Cl,³⁵ KF/Al₂O₃,³⁶ grafit/MeSO₂Cl,³⁷ and DBU/EtOPOCl₂.³⁸

Table 2 Comparison of various catalysts with CSMIL for the synthesis of nitriles from aldehydes

Entry	Conditions	Solvent	Time (h)	Temp (°C)	Yield^a (%)
a Isolated yield.
1	NH2OH·HCl, DMSO	DMSO	2	90	97
2	NH2OH·HCl, dry-Al2O3/MeSO2Cl	Neat	0.5	100	95
3	NH2OH·HCl, KF/Al2O3	DMF	4.5	100	82
4	NH2OH·HCl, DBU, EtOPOCl2	CH2Cl2	15	25	90
5	NH2OH·HCl, MsCl, grafite	Neat	1	100	91
6	NH2OH·HCl, MsCl, dry-CSMIL	Neat	2	70	96

---

This heterogeneous system offers an easy work-up that involves simply mixing with a suitable solvent, using a simple magnet to remove the magnetic catalyst, extraction with water and evaporation of the solvent. Therefore, we report here a very simple procedure for the transformation of a wide range of aldehydes into nitriles by treatment with NH₂OH·HCl and MsCl in solvent-free conditions at 70 °C (Scheme 3).

Scheme 3

The present system was further examined for use in the direct conversion of aldehydes into nitriles, and the results are summarized in Table 3. The results showed that an electron donating group, or an electron withdrawing group, on benzaldehyde does not have a significant effect, and that the system gives a good yield irrespective of the electronic nature of the aldehyde.

Table 3 Synthesis of nitriles from aldehydes in the presence of dry-CSMIL^a

Entry^ref	Product	Time (h)	Yield^b (%)	IR (cm^−1)
a Reaction conditions: aldehyde (1 mmol), hydroxylamine hydrochloride (1.2 mmol), mesyl chloride (1.2 mmol) and dry chitosan supported (EMIm)FeCl4 (15 mg).b Isolated yield.
3a^39		1.5	93	2218
3b^40		1.0	96	2223
3c^41		1.0	96	2224
3d^39		2	92	2227
3e^40		2	92	2224
3f^40		2	90	2223
3g^39		0.75	97	2230
3h^40		1.5	91	2237
3i^40		1	95	2235
3j^42		1	95	2228
3k^40		1	91	2233
3l^43		1.5	90	2213
3m^40		0.75	93	2233
3n^40		2	91	2218
3o^44		1.5	93	2214
3p^40		2	90	2232
3q^40		2	91	2227

---

We found that, by using wet-CSMIL under the same reaction conditions, amides were obtained instead of nitriles, in high yields. Therefore, we report a very efficient method for the preparation of amides from aldehydes in wet conditions (Scheme 4). The results demonstrated that this methodology gives good yields of aryl, alkyl and heterocyclic amides from aldehydes, when reacted with a mixture of NH₂OH·HCl/wet-CSMIL/MeSO₂Cl at 70 °C, without the use of any solvents. The work-up of the reaction mixture was very simple with a quick processing time, and the yields of the products were high.

Scheme 4

We next examined a wide variety of aldehydes to establish the scope of this transformation. Aldehydes with electron-withdrawing groups, as well as electron-donating substituents, underwent the one-pot conversion to give the corresponding amides in good yields (Table 4).

Table 4 Synthesized amides from aldehydes in the presence of wet-CSMIL^a

Entry^ref	Product	Time (h)	Yield^b (%)	MP (°C) (literature value)
a Reaction conditions: aldehyde (1 mmol), hydroxylamine hydrochloride (1.2 mmol), mesyl chloride (1.2 mmol) and wet-CSMIL (15 mg).b Isolated yield.
4a^45		4	87	129 (127)
4b^40		3	88	183 (183)
4c^45		4	90	161 (163)
4d^40		3.5	91	161 (162)
4e^40		3	92	199 (201)
4g^40		3.5	88	171 (170.5)
4h^40		3	90	141 (141)
4i^45		4	89	94 (95)
4j^40		3.5	90	125 (125)
4k^40		3	90	203 (204)
4l^40		3	91	176 (176.6)
4m^40		3.5	91	141 (142)
4n^40		3	93	142 (142.4)
4o^40	MeCONH2	4	88	80 (81)
4p^40		4	87	114 (114.8)

---

A plausible reaction pathway for the conversion of aldehydes to the corresponding nitriles is shown in Scheme 5. At first, the aldehyde reacts with hydroxylamine hydrochloride to form an aldoxime I. Then, the aldoxime reacts with mesyl chloride in the presence of CSMIL to form an O-mesyloaldoxime II, followed by the elimination of MsOH to generate the corresponding nitrile (Scheme 5). On the other hand, when wet-CSMIL is used, the nitrile undergoes rapid hydration to produce an amide.

Scheme 5 A plausible reaction pathway for the conversion of aldehydes to the corresponding nitriles and amides.

The CSMIL catalyst was characterized using different microscopic and spectroscopic techniques such as transmission electron microscopy (TEM), scanning electron microscopy (SEM), FT-IR and Raman spectroscopies (see the ESI, Fig. 1–5†).³³

The possibility of recycling the catalyst was tested using the reaction of 4-nitrobenzaldehyde, hydroxylamine hydrochloride and mesyl chloride under optimized conditions. This catalyst can be successfully recycled by different methods such as adsorption by using strong magnetic field (1 T), a centrifuge method, and filtration. Therefore, the use of a magnet to recover the catalyst from reaction mixtures will be very useful and has great potential. When the reaction was completed, the reaction mixture was cooled to room temperature and diluted with ethyl acetate; the CSMIL was then separated from the reaction mixture using a magnet over 5–6 minutes. The recycled catalyst was washed with ether three times and could then be used for another cycle. The catalyst was recycled and reused five times, which was accompanied by a reduction in its catalytic activity. The results are shown in Table 5.

Table 5 Recycling of CSMIL

Run	1	2	3	4	5
Time to completion of the reaction/h	0.75	0.75	1.0	1.5	1.5

---

Experimental

General considerations

Chitosan was purchased from Zhejiang Jinke (Golden Shell). The degree of deacetylation was 90% and the average molecular weight was 5 × 10⁴. Other chemicals were purchased from Fluka, Merck and Aldrich chemical companies. For recording ¹H NMR spectra we used a Bruker (250 MHz) Avance DRX in pure deuterated DMSO-d₆ and CDCl₃ solvents, with tetramethyl silane (TMS) as the internal standard. Mass spectra were recorded on a FINNIGAN-MAT 8430 mass spectrometer operating at 70 eV. FT-IR spectroscopy (on a Shimadzu FT-IR 8300 spectrophotometer) was employed for the characterization of the compounds. The scanning electron micrograph for the CSMIL catalyst was obtained by SEM instrumentation (SEM, XL-30 FEG SEM, Philips, at 20 kV). Melting points were determined in open capillary tubes in a Barnstead Electrothermal 9100 BZ circulating oil melting point apparatus. Reaction monitoring was accomplished via TLC on silica gel PolyGram SILG/UV254 plates.

General procedure for the synthesis of nitriles or amides

A mixture of aldehyde (1 mmol), hydroxyl amine hydrochloride (1.2 mmol), and mesyl chloride (1.2 mmol), in the presence of 15 mg of CSMIL, was stirred at 70 °C. When TLC monitoring indicated no further improvement in the reaction, the reaction mixture was cooled to room temperature and diluted with CH₂Cl₂ (3 × 20 ml). The catalyst was removed using either a magnetic field or filtration, then the resulting solution was washed with H₂O and the combined CH₂Cl₂ fractions were evaporated. The crude products thus obtained were purified by column chromatography (silica gel, 200–300 mesh; ethyl acetate–petroleum ether). All products were characterized by ¹H, ¹³C NMR and FT-IR, and the melting points were determined; the results were in agreement with the literature.

Conclusions

In summary, a convenient and facile method has been established for the conversion of aldehydes into nitriles and amides using a recyclable wet and dry biopolymer-supported ionic liquid as an efficient, inexpensive and non-corrosive catalyst under solvent-free conditions. The operationally simple procedure, mild reaction conditions, short reaction time, and versatility are the advantages of this method.

Acknowledgements

We acknowledge Shiraz University for partial support of this work.

Notes and references

1. E. Guibal, Prog. Polym. Sci., 2005, 30, 71; A. Primo, M. Liebel and F. Quignard, Chem. Mater., 2009, 21, 621; R. R. N. Patil, F. Castillo and J. L. W. Truitt, Macromolecules, 2009, 42, 7772.
2. (a) H. Sashiwa and S. Aiba, Prog. Polym. Sci., 2004, 29, 887; (b) M. N. V. Ravi Kumar, React. Funct. Polym., 2000, 46, 1.
3. I. Aranaz, M. Menǵıbar, R. Harris, I. Pãnos, B. Miralles, N. Acosta, G. Galed and Á. Heras, Curr. Chem. Biol., 2009, 3, 203.
4. (a) D. J. Macquarrie and J. J. E. Hardy, Ind. Eng. Chem. Res., 2005, 44, 8499.
5. (a) L. F. Xiao, F. W. Li and C. G. Xia, Appl. Catal., A, 2005, 279, 125; (b) G. Huai-min and C. Xian-su, Polym. Adv. Technol., 2004, 15, 89; (c) F. Quignard, A. Choplin and A. Domard, Langmuir, 2000, 16, 9106; (d) J. J. E. Hardy, S. Hubert, D. J. Macquarrie and A. J. Wilson, Green Chem., 2004, 6, 53.
6. (a) O. C. Agboh and Y. Qin, Polym. Adv. Technol., 1996, 8, 355; S. Hirano, Polym. Int., 1999, 48, 732; (b) D. J. Macquarrie and J. J. E. Hardy, Ind. Eng. Chem. Res., 2005, 44, 23; (c) J. J. E. Hardy, S. Hubert, D. J. Macquarrie and A. J. Wilson, Green Chem., 6, 53; L. B. Moskvin, A. V. Bulatov, G. L. Griogorjev and G. I. Koldobkij, J. Flow Injection Anal., 2003, 20, 53.
7. J. Sun, J. Wang, W. Cheng, J. Zhang, X. Li, S. Zhang and Y. Sheb, Green Chem., 2012, 14, 654.
8. M. J. Earle, S. P. Katdare and K. R. Seddon, Org. Lett., 2004, 6, 707.
9. (a) M. J. Earle, P. B. McCormac and K. R. Seddon, Green Chem., 1999, 1, 23; (b) R. Vijayaraghavan and D. R. MacFarlane, Aust. J. Chem., 2004, 57, 129; (c) J. N. Rosa, C. A. M. Afonso and A. G. Santos, Tetrahedron, 2001, 57, 4189.
10. Y. Chauvin, L. Mussmann and H. Olivier, Angew. Chem., Int. Ed. Engl., 1995, 34, 2698.
11. (a) M. A. Klingshirn, R. D. Rogers and K. H. Shaughnessy, J. Organomet. Chem., 2005, 690, 3620; (b) E. Mizushima, T. Hayashi and M. Tanaka, Green Chem., 2001, 3, 76.
12. (a) J. S. Yadav, B. V. S. Reddy, G. Baishya, K. V. Reddy and A. V. Narsaiah, Tetrahedron, 2005, 61, 9541; (b) M. Johansson, A. Linden and A. J.-E. Baeckvall, J. Organomet. Chem., 2005, 690, 3614; (c) A. Serbanovic, L. C. Branco, M. Nunes da Ponte and C. A. M. Afonso, J. Organomet. Chem., 2005, 690, 3600.
13. (a) M. Picquet, S. Stutzmann, I. Tkatchenko, I. Tommasi, J. Zimmermann and P. Wasserscheid, Green Chem., 2003, 5, 153.
14. (a) S. A. Forsyth, H. Q. N. Gunaratne, C. Hardacre, A. McKeown, D. W. Rooney and K. R. Seddon, J. Mol. Catal. A: Chem., 2005, 231, 61; (b) M. T. Reetz, W. Wiesenh€oefer, G. Francio and W. Leitner, Chem. Commun., 2002, 992.
15. J. March, Advanced Organic Chemistry, John Wiley & Sons (Asia) Ltd, Singapore, 4th edn, 2005; R. C. Larock, Comprehensive Organic Transformations, Wiley, New York, 2nd edn, 1999.
16. (a) K. Friedrich and K. Wallenfels, in The Chemistry of the Cyano Group, ed. Z. Rappaport, Interscience, New York, 1970, pp. 92–93; (b) A. J. Fatiadi, in Preparation and Synthetic Applications of Cyano Compounds, ed. S. Patai and Z. Rappaport, Wiley, New York, 1983; (c) N. Anand, N. A. Owston, A. J. Parker, P. A. Slatford and J. M. J. Williams, Tetrahedron Lett., 2007, 48, 7761; (d) A. F. Hegarty and P. J. Tuohey, J. Chem. Soc., Perkin Trans. 2, 1980, 1313.
17. H. S. Kim, S. H. Kim and J. N. Kim, Tetrahedron Lett., 2009, 50, 1717.
18. M. N. S. Rad, A. Khalafi-Nezhad, S. Behrouz, Z. Amini and M. Behrouz, Synth. Commun., 2010, 40, 2429.
19. S. H. Yang and S. Chang, Org. Lett., 2001, 3, 4209.
20. K. Lee, S. B. Han, E. M. Yoo, S. R. Chung, H. Oh and S. Hong, Synth. Commun., 2004, 34, 1775.
21. G. A. Olah and Y. D. Vankar, Synthesis, 1978, 702.
22. J. N. Kim, K. H. Chung and E. K. Ryu, Synth. Commun., 1990, 20, 2785.
23. S. Gabriel and R. Meyer, Ber. Dtsch. Chem. Ges., 1881, 14, 2332.
24. J.-P. Dulcere, Tetrahedron Lett., 1981, 22, 1599.
25. C. P. Miller and D. H. Kaufman, Synlett, 2000, 1169.
26. J. K. Chakrabarti and T. M. Hotten, J. Chem. Soc., Chem. Commun., 1972, 1226.
27. S. Kim and K. Y. Yi, Tetrahedron Lett., 1986, 27, 1925.
28. D. Konwar, R. C. Boruah and J. S. Sandhu, Tetrahedron Lett., 1990, 31, 1063.
29. N. Iranpoor and B. Zeynizadeh, Synth. Commun., 1999, 29, 2747.
30. M. Boruah and D. Konwar, J. Org. Chem., 2002, 67, 7138.
31. D. Li, F. Shi, S. Guo and Y. Deng, Tetrahedron Lett., 2005, 46, 671.
32. T. A. Khan, S. Peruncheralathan, H. Ila and H. junjappa, Synlett, 2004, 2019.
33. A. khalafi-Nezhad and S. Mohammadi, RSC Adv., 2013, 3, 4362.
34. A. Augustine, A. Bombrun and R. N. Attaa, Synlett, 2011, 15, 2223.
35. H. Sharghi and M. H. Sarvari, Tetrahedron, 2002, 58, 10323.
36. B. Movassagha and S. Shokria, Tetrahedron Lett., 2005, 46, 6923.
37. H. Shargi and M. H. Sarvari, Synthesis, 2003, 243.
38. J.-L. Zhu, F.-Y. Lee, J.-D. Wu, C.-W. Kuo and K.-S. Shia, Synlett, 2007, 1317.
39. K. H. M. Sampath, B. V. Subba Reddy, R. P. Tirupathi and J. S. Yadav, Synthesis, 1999, 4, 586.
40. B. Movassagh and A. Fazeli, Synthetic Commun., 2007, 37, 623.
41. N. D. Arote, D. S. Bhalerao and K. G. Akamanchi, Tetrahedron Lett., 2007, 48, 3651.
42. S. Cacchi and D. Misiti, Synthesis, 1980, 243.
43. H. M. Sampath Kumar, P. K. Mohanty, M. Suresh Kumar and J. S. Yadav, Synth. Commun., 1997, 27, 1327.
44. S. L. Ali, M. D. Nikalje, G. K. Dewkar, A. S. Paraskar, H. S. Jagtap and A. Sudalai, J. Chem. Res., 2000, 1, 30.
45. S. Cacchi and D. Misiti, Synthesis, 1980, 243.

---

Footnote

† Electronic supplementary information (ESI) available: The ¹H NMR and ¹³C NMR for some of the synthesized compounds, and the preparation and characterization of the catalyst. See DOI: 10.1039/c3ra43440k

---