Isocyanurate-based periodic mesoporous organosilica (PMO-ICS): a highly efficient and recoverable nanocatalyst for the one-pot synthesis of substituted imidazoles and benzimidazoles

Abstract

Isocyanurate bridging periodic mesoporous organosilica (PMO-ICS) was shown to be a highly active and efficient recyclable catalyst for the three-component synthesis of imidazole derivatives from benzoin, different aldehydes and ammonium acetate under mild reaction conditions in short reaction times and good to excellent yields in EtOH. Also, benzimidazole derivatives were efficiently prepared from o-phenylenediamine and different aldehydes in the presence of PMO-ICS. Moreover, the catalyst was also recovered and reused at least four times without a significant decrease in its activity. The PMO-ICS catalyst was characterized by Fourier transformer infrared (FTIR) spectroscopy, thermogravimetry analysis (TGA), powder X-ray diffraction (XRD) and nitrogen adsorption–desorption isotherm (NADI) techniques as well as field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). Compared to the classical methodologies, this method illustrated significant advantages including low loading of the catalyst, avoiding the use of toxic transition metals or reactive reagents for modification of the catalytic activity, short reaction times, high to excellent yields, easy separation and purification of the products, and reusability of the catalyst.

---

Introduction

The use of heterogeneous catalysts has become highly desirable in recent years, because they incorporate many green chemistry principles. In 1999, mesoporous organosilica hybrids were prepared from bridged organosilane precursors ((R′O)₃Si–R–Si(OR′)₃; R: organic bridging group, R′: methyl or ethyl). Such mesoporous hybrids prepared from bridged organosilane precursors have been classified as periodic mesoporous organosilicas (PMOs).^1,2 PMOs are very attractive as supports for heterogeneous catalysts in fine chemicals synthesis among others. The large and tunable pore sizes (between 2 and 30 nm) and pore volumes, well-defined pore morphology, and high surface areas of PMOs allow facile diffusion of bulky reactants and products that are often involved in such reactions. In addition, other unique properties of PMOs such as high loading of uniform distribution of organic functional groups in their framework, superior thermal stability, non-toxicity, reusability, and stability against air and moisture make them an attractive candidate for the widespread applications in catalysis, chromatography, solid-phase extraction, electronic, sensor technology, gas storage, etc.^3,4 On the other hand, multicomponent reactions (MCRs) offer high atom economy and bond-forming efficiency for the synthesis of diverse and complex molecules especially heterocyclic compounds in fast and often experimentally simple procedures.⁵ The imidazole and benzimidazole ring systems are one of the most important heterocyclic moieties found in a large number of natural products and pharmacologically active compounds. Hence, their role in biochemical processes is very significant.^6,7

In the recent years, a few methods have been described for the one-pot multicomponent synthesis of 2,4,5-trisubstituted imidazole derivatives from benzoin in the presence of different catalysts. These include graphene oxide–chitosan composite,⁸ molecular iodine,⁹ p-toluenesulfonic acid (PTSA),¹⁰ N-methyl-2-pyrrolidonium hydrogen sulphate,¹¹ PEG-400 ¹² and 2,6-dimethylpyridinium trinitromethanide {[2,6-DMPyH]C(NO₂)₃}.¹³ However, there are much more catalytic methodologies starting from benzil. For example, catalysts such as KH₂PO₄,¹⁴ p-dodecylbenzenesulfonic acid (PDBSA),¹⁵ glyoxalic acid,¹⁶ L-proline,¹⁷ Zn-proline,¹⁸ InCl₃·3H₂O,¹⁹ KAl(SO₄)₂,²⁰ ZnCl₂,²¹ FeBr₂,²² FeCl₃·6H₂O,²³ nano-In₂O₃,²⁴ NiCl₂·6H₂O/Al₂O₃,²⁵ FeCl₃/SiO₂,²⁶ Wells–Dawson heteropolyacid supported on silica (WD/SiO₂),²⁷ zirconium modified silica gel, ZrO₂-supported-β-cyclodextrin,²⁸ Fe₃O₄–polyethylene glycol–Cu nanocomposite (Fe₃O₄–PEG–Cu),²⁹ Fe₃O₄@SiO₂-imid-PMAⁿ magnetic porous nanosphere,³⁰ silica coated magnetic NiFe₂O₄ nanoparticle supported phosphomolybdic acid,³¹ different fluoroboric acid (HBF₄) derived catalyst systems,³² and ionic liquids.^11,33 However, many of these reported synthetic protocols for the synthesis of imidazoles have limitations in terms of the use of excess amounts of expensive or toxic catalysts, formation of byproducts and unsatisfactory yields, lengthy reaction times, difficult work-up, unavoidable metal pollution, significant amounts of waste materials, and low selectivity. Therefore, development of new methodologies and introducing green catalysts to overcome aforementioned disadvantages is still desirable.

The heteroaromatic isocyanurate ring in the structure of isocyanurate-based periodic mesoporous organosilica (PMO-ICS) contains three nonpolar propyl groups and is well known for its binding ability to transition metals.^2b,34 Furthermore, it is thermally very stable and used to enhance the physical properties of a wide variety of polyurethanes and other coating materials such as polyureas in commercial systems.³⁵ These unique properties as well as other useful properties associated with PMOs make isocyanurate-based periodic mesoporous organosilica (PMO-ICS) a promising support or catalyst depending on the used conditions compared to modified mesoporous silica materials (M41S family) or even other members of PMOs family having two aryl or alkyl groups in their structures. In continuation of our interest to develop mild and efficient catalysts for different MCRs,³⁶ we herein wish to report the catalytic application of an isocyanurate-based periodic mesoporous organosilica (PMO-ICS, 1) nanomaterial without any post-modification with active Bronsted or Lewis acid centres, as an efficient and recoverable catalyst, for the synthesis of 2,4,5-trisubstituted imidazoles (5) and benzoimidazoles (7) in EtOH under reflux conditions (Scheme 1). To the best of our knowledge, there is no report on the use of PMOs for the synthesis of imidazole or benzimidazole derivatives.

Scheme 1 (a) One-pot three-component reaction of benzoin (2) and different aldehydes 3 with NH₄OAc (4); (b) condensation of different aldehydes 3 with 1,2-phenylenediamine (6).

Results and discussion

PMO-ICS (1) was prepared through a known procedure described by Jaroniec and his co-workers.³⁴ The catalyst was then characterized using techniques including Fourier transform infrared (FTIR) spectroscopy, X-ray powder diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and thermal gravimetric analysis (TGA). The IR spectrum of PMO-ICS (1) shows the presence of organic functional groups in the material framework (see ESI†). Indeed, the bands observed at 2935 and 2850 cm⁻¹ are assigned to C–H stretching of aliphatic moieties. Moreover, the signals appeared at 1689 and 1471 cm⁻¹ are attributed to the stretching vibrations of the isocyanurate ring. On the other hand, PMO-ICS (1) showed bands at 1120, 1070 and 935 cm⁻¹ corresponding to asymmetric and symmetric vibrations of Si–O–Si (siloxane) bonds, respectively. The strong and broad signal appeared about 3334 cm⁻¹ is attributed to O–H bonds of silanol groups.

The transmission electron microscopy (TEM) images demonstrated that the mesostructure PMO-ICS (1) exhibits ordered hexagonal structure (Fig. 1).

Fig. 1 TEM image of PMO-ICS (1) nanocatalyst.

Furthermore, BET analysis of PMO-ICS (1) showed specific surface area close to 570 m² g⁻¹, pore size ≈ 4.1 and volume pore ≈ 5 nm (Fig. 2). On the other hand, thermogravimetric analysis (TGA) of PMO-ICS (1) showed the thermal stability about 470 °C for the isocyanurate bridging containing organics which have been incorporated into the silica framework (Fig. 3).

Fig. 2 BET analysis of the PMO-ICS (1) nanocatalyst.

Fig. 3 Thermal gravimetric analysis (TGA) of the fresh PMO-ICS (1) (■) and recycled PMO-ICS (1) (▲) nanocatalyst.

To show the efficiency of periodic mesoporous organosilica (PMO-ICS, 1) for the synthesis of 2,4,5-trisubstituted imidazoles (5), the reaction of benzoin (2, 1 mmol), 4-chlorobenzaldehyde (3a, 1 mmol) and ammonium acetate (4, 2.5 mmol) was investigated as the model reaction. The reaction conditions were optimized with regard to the best catalyst loading, different solvents and temperature for the synthesis of desired product of 2-(4-chlorophenyl)-4,5-diphenyl-1H-imidazole (5a). The results are summarized in Table 1. It is noteworthy that only a trace amount of the desired product 5a was obtained in the absence of PMO-ICS (1) at room temperature after 4 h in EtOH (Table 1, entry 1). On the other hand, the yield of trisubstituted imidazole 5a was improved to 40% under similar reaction conditions in refluxing EtOH (Table 1, entry 2). The effect of catalyst loading on the completion of the reaction was examined in next experiments (Table 1, entries 3–5). Interestingly, after addition of 15 mg of the catalyst (1) the yield of the desired product 5a was increased significantly under similar reaction conditions in refluxing EtOH compared to catalyst-free conditions. Furthermore, 20 mg loading of PMO-ICS (1) afforded higher yield of the desired product 5a in shorter reaction time in refluxing EtOH (Table 1, entry 4). In the next step, the effect of other solvents such as H₂O and THF on the model reaction was investigated. Both of solvents afforded lower yield of the desired product 5a (Table 1, entries 6–7). Furthermore, product 5a was obtained in the presence 20 mg loading of PMO-ICS (1) in lower yield at room temperature after 3 h (Table 1, entry 8). Finally, the desired product 5a was obtained in lower yield and longer reaction time at 100 °C under solvent-free conditions compared to reflux conditions in EtOH (Table 1, entries 4 and 9). On the other hand, when MCM-41, as pure silica, or trisubstituted isocyanurates were used under same catalyst loadings, the desired product 5a was obtained in lower yields and longer reaction times (entries 4 and 10–12). These findings clearly show the synergic effects of both silica and isocyanurate moieties on the catalytic activity of PMO-ICS (1). Consequently, 20 mg PMO-ICS (1) loading in EtOH under reflux conditions was selected as the optimized conditions in the next experiments.

Table 1 Optimization of conditions in the reaction of benzoin (2), 4-chlorobenzaldehyde (3a) and NH₄OAc under different conditions^a

Entry	Catalyst 1 loading (mg)	Solvent	Temp. (°C)	Time (min)	Yield^b (%)
a Reaction conditions: benzoin (2, 1 mmol), 4-chlorobenzaldehyde (3a, 1 mmol), and NH4OAc (4, 2.5 mmol) in the presence of 20 mg PMO-ICS (1).b Isolated yields.c MCM-41 was used as catalyst.d 1,3,5-Tripropyl isocuanurate was used as catalyst.e 1,3,5-Triphenyl isocuanurate was used as catalyst.
1	—	EtOH	r.t	240	Trace
2	—	EtOH	Reflux	240	40
3	15	EtOH	Reflux	35	88
4	20	EtOH	Reflux	25	97
5	25	EtOH	Reflux	25	93
6	20	H2O	Reflux	120	45
7	20	THF	Reflux	100	80
8	20	EtOH	r.t	180	70
9	20	—	100	55	84
10^c	20	EtOH	Reflux	360	85
11^d	20	EtOH	Reflux	360	58
11^e	20	EtOH	Reflux	360	44

---

In order to demonstrate the scope of this protocol, the optimized reaction conditions were developed to other aromatic, heterocyclic or aliphatic aldehydes 3a–t. The results are summarized in Table 2. After completion of the reaction (monitored by TLC), EtOH was added and the catalyst was easily isolated from the reaction mixture by simple filtration during recrystallization of the products. As it can be seen, high to quantitative yields were obtained under the optimized conditions in short reaction times for the desired products 5a–t. Both aromatic carbocyclic and heterocyclic aldehydes containing electron-withdrawing and electron-donating groups involved in the optimized conditions to afford corresponding trisubstituted imidazoles 5a–t. In general, the nature of the substituents on the phenyl ring has a significant influence on the reaction rate. Indeed, aromatic aldehydes with electron-withdrawing groups often afforded the desired imidazole derivatives 5a–t in higher yields and shorter reaction times compared to electron-donating groups (Table 2). In the next stage, the reaction between 1,2-phenylenediamine (6) and various aldehydes 3a–u was investigated. The results are summarized in Table 3. In all studied cases, the reactions proceeded efficiently under the optimized conditions to afford corresponding products 7a–s in high to excellent yields within very short reaction times.

Table 2 Isocyanurate bridging periodic mesoporous organosilica (PMO-ICS, 1) catalyzed one-pot three-component synthesis of 2,4,5-trisubstituted imidazoles 5 from benzoin (2), different aldehydes 3 with NH₄OAc (4) under the optimized conditions^a

Entry	Aldehyde 3	Product 5	Time (min)	Yield^b^,^c (%)
a Reaction conditions: benzoin (2, 1 mmol), 4-chlorobenzaldehyde (3a, 1 mmol), and NH4OAc (4, 2.5 mmol) in the presence of 20 mg PMO-ICS (1) and EtOH (2 mL).b Isolated yields.c All compounds are known compounds and were identified by comparison of their physical and spectroscopic data with authentic samples.^7b,11,13,37,38,39,40,41
1	4-Chlorobenzaldehyde (3a)	5a	25	97
2	2-Chlorobenzaldehyde (3b)	5b	35	81
3	2-Nitrobenzaldehyde (3c)	5c	30	85
4	4-Nitrobenzaldehyde (3d)	5d	35	94
5	3-Nitrobenzaldehyde (3e)	5e	45	92
6	4-Cyanobenzaldehyde (3f)	5f	55	98
7	2,4-Dichlorobenzaldehyde (3g)	5g	45	95
8	4-Boromobenzaldehyde (3h)	5h	42	98
9	Benzaldehyde (3i)	5i	60	81
10	4-Methylbenzaldehyde (3j)	5j	75	80
11	4-Methoxybenzaldehyde (3k)	5k	60	74
12	4-Hydroxybenzaldehyde (3l)	5l	70	84
13	2-Hydroxybenzaldehyde (3m)	5m	60	78
14	Vanillin (3n)	5n	60	90
15	4-Dimethylaminobenzaldehyde (3o)	5o	55	75
16	Furfural (3p)	5p	50	93
17	Thiophene-2-carbaldehyde (3q)	5q	45	97
18	4-Pyridincarbaldehyde (3r)	5r	55	96
19	Formaldehyde (3s)	5s	60	90
20	3-Phenylpropionaldehyde (3t)	5t	60	94

---

Table 3 Isocyanurate bridging periodic mesoporous organosilica (PMO-ICS, 1) catalyzed condensation of 1,2-phenylenediamine (6) with diverse aldehydes 3 under the optimized conditions^a

Entry	Aldehyde 3	Product 7	Time (min)	Yield^b^,^c (%)
a Reaction conditions: 4-chlorobenzaldehyde (3a, 1 mmol) with 1,2-phenylenediamine (6, 1 mmol) in the presence of 20 mg PMO-ICS (1) and EtOH (2 mL).b Isolated yields.c All compounds are known compounds and were identified by comparison of their physical and spectroscopic data with authentic samples.^16,37,40b,42,43
1	4-Chlorobenzaldehyde (3a)	7a	30	93
2	2-Chlorobenzaldehyde (3b)	7b	30	90
3	2-Nitrobenzaldehyde (3c)	7c	45	99
4	4-Nitrobenzaldehyde (3d)	7d	50	87
5	3-Nitrobenzaldehyde (3e)	7e	35	88
6	4-Cyanobenzaldehyde (3f)	7f	45	95
7	4-Boromobenzaldehyde (3h)	7g	45	96
8	Benzaldehyde (3i)	7h	40	92
9	4-Methylbenzaldehyde (3j)	7i	65	88
10	4-Methoxybenzaldehyde (3k)	7j	60	90
11	4-Hydroxybenzaldehyde (3l)	7k	65	85
12	2-Hydroxybenzaldehyde (3m)	7l	70	88
13	4-Dimethylaminobenzaldehyde (3o)	7m	67	93
14	Furfural (3p)	7n	65	90
15	Thiophene-2-carbaldehyde (3q)	7o	65	97
16	4-Pyridincarbaldehyde (3r)	7p	65	98
17	2-Pyridincarbaldehyde (3u)	7q	60	92
18	Formaldehyde (3s)	7r	60	92
19	3-Phenylpropionaldehyde (3t)	7s	50	83

---

A probable mechanistic pathway for the formation of 2,4,5-trisubstituted imidazoles (5) and benzimidazoles analogues (7) is outlined in Scheme 2. According to the mechanism, it can be proposed that the enormous hydroxyl groups on the surface of PMO-ICS (1) are responsible for the initial activation of the carbonyl group of aldehydes 3 to facilitate nucleophilic addition of ammonia or 1,2-phenylenediamine (6) on the intermediate I to afford aminal intermediates II or III′, respectively. It is noteworthy that ammonia itself is produced in situ by decomposition of ammonium acetate (4) in the presence of catalyst 1. In the case of 2,4,5-trisubstituted imidazoles (5), aminal intermediates II is condensed with benzoin (2) to produce corresponding 4,5-dihydroimidazole intermediate IV through intermediate III. Air oxidation of the intermediates IV or IV′ and subsequent [1,5]-sigmatropic hydrogen shift of the intermediate V affords desired products 5 or 7, respectively. It is noteworthy that the byproducts of this tandem MCR reaction are mainly water molecules which can be sorbed on the surface of PMO-ICS (1) physically by the silanols or chemically by siloxane functional groups. Higher catalytic activity of PMO-ICS (1) compared to MCM-41 can be attributed to both fine-tuning of the polarity of inorganic silica moiety by the organic 1,3,5-tripropyl isocuanurate functionality and size-exclusion (sieve) effect.^3a

Scheme 2 Plausible mechanism for the one-pot synthesis of 2,4,5-trisubstituted imidazoles (5 or 7) catalyzed by PMO-ICS (1) through three component reaction.

Another important aspect of this active, efficient, non-toxic, and eco-friendly heterogeneous nanocatalyst is its high degree of recyclability. In this part of our study, it has been shown that the PMO-ICS (1) could be recovered and reused at least four times in the subsequent runs for the model reaction using the same recovered catalyst without a considerable loss of its catalytic activity (Fig. 4).

Fig. 4 Reusability of PMO-ICS (1) nanocatalyst for the synthesis of 2-(4-chlorophenyl)-4,5-diphenyl-1H-imidazole (5a).

To demonstrate the efficiency and capability of the present protocol for the synthesis of substituted imidazole and benzimidazole derivatives, it has been compared with some of the previously reported and published procedures. Results are summarized in Table 4. Obviously, the present protocol is indeed superior to several of the others in terms of catalyst loading, avoiding the use of toxic transition metals or reactive reagents for modification of the catalytic activity, product yield, reaction time and using a green solvent.

Table 4 Comparison of the catalytic efficiency of PMO-ICS (1) with other heterogeneous or homogeneous catalysts^a,b

Entry	Catalyst	Catalyst loading	Solvent	Temp (°C)	Time (min)	Yield (%)	Ref.
a For the synthesis of 5a.b 7a.
1^a	[EMIM]OAc	170 mg	EtOH	r.t	90	96	33^b
2^a	Poly(AMPS-co-AA)	30 mg	Solvent-free	110	25	95	37^a
3^a	Ceric(IV) ammonium nitrate	55 mg	EtOH–water (1 : 1)	Reflux	70	98	38
4^a	MoO3/SiO2	20 mol%	CH3CN	80	120	92	39^a
5^a	ZrCl4	47 mg	CH3CN	r.t	240	84	40
6^a	Benzotriazole	5 mol%	n-Butanol	80	720	88	41
7^a	NH4VO3	10 mol%	EtOH	Reflux	45	91	37^b
8^a	AlN/Al	20 wt%	EtOH	Reflux	45	94	39^b
9^a	PMO-ICS	20 mg	EtOH	Reflux	35	97	This work
10^b	L-Proline	10 mol%	EtOH	Reflux	125	93	17
11^b	Yb(OPf)3	67 mg	Perfluorodecalin	90	360	98	42
12^b	[pmim]BF4	178 mg	Solvent-free	r.t	340	92	43
13^b	PMO-ICS	20 mg	EtOH	Reflux	30	96	This work

---

Conclusions

In summary, the catalytic application of isocyanurate bridging periodic mesoporous organosilica (PMO-ICS) for the synthesis of a wide range of trisubstituted imidazole and benzimidazole derivatives has been demonstrated. The progress of reaction was significantly affected by catalyst loading, reaction temperature and solvent. The catalyst illustrated high efficiency for the one-pot three-component synthesis of substituted imidazole derivatives using a variety of aldehydes and 1,2-phenylenediamine or benzoin and ammonium acetate in EtOH under reflux conditions. In addition, the catalyst could be recovered and reused at least four times with no significant decrease in its activity and selectivity. Therefore, the attractive features of this procedure are low catalyst loading, avoiding the use of toxic transition metals or reactive reagents for modification of the catalytic activity, short reaction times, high yields, elimination of toxic organic solvents, reusability and re-activity of the catalyst and simple procedure.

Experimental

General

All chemicals were purchased from Merck or Aldrich and used as received except for benzaldehyde which a fresh distilled sample was used. Field emission scanning electron microscopy (FESEM) images was obtained using Sigma instrument of Zeiss company, Germany. The BET specific surface area of the catalyst was obtained using an equipment ASAP 2020™ micromeritics. Thermal gravimetric analysis (TGA) was performed by means of Bahr company STA 504 instrument. Transmission electron microscopy (TEM) images were recorded using EM10C-100 kV of Zeiss company, Germany. XRD analysis was performed using STOE-Thata-Thata. FTIR spectra were recorded as KBr pellets on a Shimadzu FT IR-8400S spectrometer. Melting points were determined using an Electrothermal 9100 apparatus and are uncorrected. ¹H NMR (500 MHz) spectra were obtained using a Bruker DRX-500 AVANCE spectrometer in CDCl₃ at ambient temperature. Analytical TLC was carried out using Merck 0.2 mm silica gel 60 F-254 Al-plates. All the products are known compounds and were identified by comparison of their physical and spectroscopic and analytical data with authentic samples.

General procedure for the synthesis of PMO-ICS (1)

The synthesis of PMO-ICS (1) was achieved using known procedure described by Jaroniec and his co-workers.³⁴ In a typical experiment, 2.0 g of Pluronic P123 (Aldrich, average M_w ≅ 5800 dalton) was dissolved in a mixture of 15 mL of deionized water and 60 g of 2 M HCl solution. Then, 0.01 mol (3.08 g) of tris[3-(trimethoxysilyl)propyl]isocyanurate (ICS, Aldrich) and 0.03 mol tetraethoxysilane (TEOS, 3.12 g) was added dropwise into that solution. The obtained mixture was stirred at the constant rate and room temperature for 20 h. The mixture was aged at 100 °C for 48 h without stirring. The solid was filtered off and washed thoroughly with hot EtOH/H₂O (60 mL of EtOH 96% and 2 mL of 12 M HCl) using a soxhelet apparatus for 72 h to remove the surfactant molecules. The obtained white powder was dried in air at 100 °C overnight.

General procedure for synthesis of 2,4,5-trisubstituted imidazole derivatives (5a–t)

In a 5 mL round-bottomed flask, benzoin (2, 1 mmol), aldehyde 3 (1 mmol), ammonium acetate (4, 2.5 mmol) and 20 mg PMO-ICS (1) were added to EtOH 96% (2 mL). The obtained mixture was stirred at reflux conditions for times indicated in Table 2. After completion of the reaction monitored by TLC (eluent: EtOAc : n-hexane), EtOH (3 mL) was added and the obtained mixture was heated and filtered off to separate the solid catalyst 1. Water was added dropwise to the filtrate at 50 °C to give pure crystals of the desired products 5a–t in 74–98% yields based on the starting aldehyde. The separated catalyst was suspended in EtOAc (1 mL) for 30 min and then filtered. The obtained white powder was heated in an oven at 70 °C for 1 h and reused for successive runs.

General procedure for synthesis of benzimidazole derivatives (7a–s)

In a 5 mL round-bottomed flask, 1,2-phenylenediamine (6, 1 mmol), aldehyde 3 (1 mmol), and PMO-ICS (1, 20 mg) were added to EtOH 96% (2 mL). The obtained mixture was stirred at reflux conditions for times indicated in Table 3. After completion of the reaction, monitored by TLC (eluent: EtOAc : n-hexane) EtOH (3 mL) was added and the obtained mixture was heated and filtered off to separate the solid catalyst 1. Water was added dropwise to the filtrate at 50 °C to give pure crystals of the desired products 7a–s in 83–99% yields based on the starting aldehyde. The separated catalyst was suspended in EtOAc (1 mL) for 30 min and then filtered. The obtained white powder was heated in an oven at 70 °C for 1 h and reused for successive runs.

Acknowledgements

We are grateful for the financial support from The Research Council of Iran University of Science and Technology (IUST), Tehran, Iran (Grant No. 160/347). We would also like to acknowledge the support of Iran Nanotechnology Initiative Council (INIC), Iran.

Notes and references

1. (a) P. V. D. Voort, D. Esquivel, E. D. Canck, F. Goethals, I. V. Driessche and F. J. Romero-Salguero, Chem. Soc. Rev., 2013, 42, 3913–3955; (b) N. Mizoshita, T. Tani and S. Inagaki, Chem. Soc. Rev., 2011, 40, 789–800; (c) R. J. White, R. Luque, V. L. Budarin, J. H. Clark and D. J. Macquarrie, Chem. Soc. Rev., 2009, 38, 481–494.
2. (a) B. Hatton, K. Landskron, W. Whitnall, D. Perovic and G. A. Ozin, Acc. Chem. Res., 2005, 38, 305–312; (b) W. J. Hunks and G. A. Ozin, J. Mater. Chem., 2005, 15, 3716–3724; (c) K. Nakajima, I. Tomita, M. Hara, S. Hayashi, K. Domen and J. N. Kondo, Adv. Mater., 2005, 17, 1839–1842.
3. (a) F. Hoffmann and M. Fröba, Chem. Soc. Rev., 2011, 40, 608–620; (b) W. Whitnall, L. Cademartiri and G. A. Ozin, J. Am. Chem. Soc., 2007, 129, 15644; (c) S. Abedi, B. Karimi, F. Kazemi, M. Bostina and H. Vali, Org. Biomol. Chem., 2013, 11, 416–419; (d) M. N. Esfahani, D. Elhamifar, T. Amadeha and B. Karimi, RSC Adv., 2015, 5, 13087–13094.
4. J. A. Melero, R. V. Grieken and G. Morales, Chem. Rev., 2006, 106, 3790–3812.
5. (a) V. Estevez, M. Villacampa and J. C. Menendez, Chem. Soc. Rev., 2014, 43, 4633–4657; (b) K. R. Reddy, K. Rajgopal, C. U. Maheswari and M. L. Kantam, New J. Chem., 2006, 30, 1549–1552.
6. (a) S. S. K. Boominathan, C. Y. Chen, R. J. Hou, P. J. Huang and J. J. Wang, New J. Chem., 2015, 39, 6914–6918; (b) E. Gopi, T. Kumar, R. F. S. Menna-Barreto, W. O. Valenca, E. N. da Silva Junior and I. N. N. Namboothiri, Org. Biomol. Chem., 2015, 13, 9862–9871.
7. (a) A. Patel, S. Y. Sharp, K. Hall, W. Lewis, M. F. G. Stevens, P. Workman and C. J. Moody, Org. Biomol. Chem., 2016, 14, 3889–3905; (b) H. Naeimi and D. Aghaseyedkarimi, New J. Chem., 2015, 39, 9415–9421.
8. A. Maleki and R. Paydar, RSC Adv., 2015, 5, 33177–33184.
9. M. Kidwai, P. Mothsra, V. Bansal, R. K. Somvanshi, A. S. Ethayathulla, S. Dey and T. P. Singh, J. Mol. Catal. A: Chem., 2007, 265, 177–182.
10. M. Afzal Pasha and A. Nizam, J. Saudi Chem. Soc., 2011, 15, 55–58.
11. H. R. Shaterian and M. Ranjbar, J. Mol. Liq., 2011, 160, 40–49.
12. (a) X. C. Wang, H. P. Gong, Z. J. Quan, L. Li and H. L. Ye, Chin. Chem. Lett., 2009, 20, 44; (b) B. Das, C. Sudhakar and Y. Srinivas, Synth. Commun., 2010, 40, 2667–2675.
13. M. A. Zolfigol, S. Baghery, A. R. Moosavi-Zare and S. M. Vahdat, RSC Adv., 2015, 5, 32933–32940.
14. R. G. Jacob, L. G. Dutra, C. S. Radatz, S. R. Mendes, G. Perin and E. J. Lenardao, Tetrahedron Lett., 2009, 50, 1495–1497.
15. H. H. Kung and M. C. Kung, Catal. Today, 2004, 97, 219–224.
16. S. S. Pawar, D. V. Dekhane, M. S. Shingare and S. N. Thore, Chin. Chem. Lett., 2008, 19, 1055–1058.
17. R. Varala, A. Nasreen, R. Enugala and S. R. Adapa, Tetrahedron Lett., 2007, 48, 69–72.
18. R. Varala, R. Enugala, V. Kotra and S. R. Adapa, Chem. Pharm. Bull., 2007, 55, 1254–1257.
19. S. D. Sharma, P. Hazarika and D. Konwar, Tetrahedron Lett., 2008, 49, 2216–2220.
20. M. M. Heravi, F. Derikvand and F. Bamoharram, J. Mol. Catal., 2007, 263, 112–114.
21. R. G. Jacob, L. G. Dutra, C. S. Radatz, S. R. Mendes, G. Perin and E. J. Lenardao, Tetrahedron Lett., 2009, 50, 1495–1497.
22. M. Shen and T. G. Driver, Org. Lett., 2008, 10, 3367–3370.
23. M. M. Heravi, F. Derikvand and M. Haghighi, Monatsh. Chem., 2008, 139(1), 31–33.
24. S. Santra, A. Majee and A. Hajra, Tetrahedron Lett., 2012, 53, 1974–1977.
25. M. M. Heravi, K. Bakhtiari, H. A. Oskooie and S. Taheri, J. Mol. Catal. A: Chem., 2007, 263, 279–281.
26. Q. Dang, B. S. Brown and M. D. Erion, Tetrahedron Lett., 2000, 41, 6559–6562.
27. A. R. Karimi, Z. Alimohammadi and M. M. Amini, Mol. Diversity, 2010, 14, 635–641.
28. (a) S. Balalaie and A. Arabanian, Green Chem., 2002, 2, 274–277; (b) Y. R. Girish, K. S. Sharath Kumar, K. N. Thimmaiah, K. S. Rangappa and S. Shashikanth, RSC Adv., 2015, 5, 75533–75546.
29. Z. Zarnegar and J. Safari, New J. Chem., 2014, 38, 4555–4565.
30. M. Esmaeilpour, J. Javidi and M. Zandi, New J. Chem., 2015, 39, 3388–3398.
31. B. Maleki, H. Eshghi, A. Khojastehnezhad, R. Tayebee, S. Sedigh Ashrafi, G. Esmailian Kahoo and F. Moeinpour, RSC Adv., 2015, 5, 64850–64857.
32. D. Kumar, D. N. Kommi, N. Bollineni, A. R. Patel and A. K. Chakraborti, Green Chem., 2012, 14, 2038–2049.
33. (a) S. A. Siddiqui, U. C. Narkhede, S. S. Palimkar, T. Daniel, R. J. Lahoti and K. V. Srinivasan, Tetrahedron Lett., 2005, 61, 3539–3546; (b) H. Zang, Q. Su, Y. Mo, B. W. Cheng and S. Jun, Ultrason. Sonochem., 2010, 17, 749–751.
34. O. Olkhovyk and M. Jaroniec, J. Am. Chem. Soc., 2005, 127(1), 60–61.
35. (a) M. F. Sonnenschein, Polyurethanes: Science, Technology, Markets, and Trends, Wiley, 1st edn, 2014; (b) M. G. Dekamin, M. Ghanbari, M. R. Moghbeli, M. Barikani and S. Javanshir, Polym.-Plast. Technol. Eng., 2013, 52, 1127–1132; (c) M. G. Dekamin, K. Varmira, M. Farahmand, S. Sagheb-Asl and Z. Karimi, Catal. Commun., 2010, 12, 226–230; (d) M. G. Dekamin, M. F. Moghaddam, H. Saeidian and S. Mallakpour, Monatsh. Chem., 2006, 137, 1591–1595.
36. (a) M. G. Dekamin, M. Azimoshan and L. Ramezani, Green Chem., 2013, 15, 811–820; (b) M. G. Dekamin and M. Eslami, Green Chem., 2014, 16, 4914–4921; (c) M. G. Dekamin, S. Ilkhanizadeh, Z. Latifidoost, H. Daemi, Z. Karimi and M. Barikani, RSC Adv., 2014, 4, 56658–56664; (d) M. G. Dekamin, S. Z. Peyman, Z. Karimi, S. Javanshir, M. R. Naimi-Jamal and M. Barikani, Int. J. Biol. Macromol., 2016, 87, 172–179; (e) M. G. Dekamin, M. Eslami and A. Maleki, Tetrahedron, 2013, 69, 1074–1085; (f) M. G. Dekamin, M. Alikhani and S. Javanshir, Green Chem. Lett. Rev., 2016, 9, 96–105; (g) M. G. Dekamin and S. Z. Peyman, Monatsh. Chem., 2016, 147, 445–450; (h) A. Alinasab Amiri, S. Javanshir, Z. Dolatkhah and M. G. Dekamin, New J. Chem., 2015, 39, 9665–9671.
37. (a) A. Mohammdi, H. Keshvari, R. Sandaroos, H. Rouhi and Z. Sepehr, J. Chem. Sci., 2012, 124, 717–722; (b) K. S. Niralwad, B. B. Shingate and M. S. Shingare, J. Heterocycl. Chem., 2011, 48, 742–745.
38. J. N. Sangshetti, N. D. Kokare, S. A. Kotharkara and D. B. Shinde, J. Chem. Sci., 2008, 120, 463–467.
39. (a) S. V. Bhosale, M. B. Kalyankar, S. V. Nalage, D. S. Bhosale, S. L. Pandhare, T. V. Kotbagi, S. B. Umbarkar and M. K. Dongare, Synth. Commun., 2011, 41, 762–769; (b) N. S. Kanhe, S. U. Tekale, N. V. Kulkarni, A. B. Nawale, A. K. Das, S. V. Bhoraskar, R. D. Ingle and R. P. Pawar, J. Iran. Chem. Soc., 2013, 10, 243–249.
40. G. V. M. Sharma, Y. Jyothi and P. S. Lakshmi, Synth. Commun., 2006, 36, 2991–3000.
41. F. Xu, N. Wang, Y. Tian and G. Li, J. Heterocycl. Chem., 2013, 50, 668–670.
42. (a) M. G. Shen and C. Cai, J. Fluorine Chem., 2007, 128, 232–235; (b) H. Sharghi, O. Asemani and R. Khalifeh, Synth. Commun., 2008, 38, 1128–1136.
43. P. Ghosh and A. Mandal, Tetrahedron Lett., 2012, 53, 6483–6488.

---

Footnote

† Electronic supplementary information (ESI) available. See DOI: 10.1039/c6ra14550g

---