Fabrication of HPA-ZSM-5 and their successful application to the recyclable heterogeneous catalyst for the smooth synthesis of spiro-pyrido-pyrimidine indoline derivatives
Javad SafaeiGhomi
1
(
Department of Organic Chemistry, Faculty of Chemistry,University of Kashan, Iran
)
Mohammaed Mutashar
2
(
Department of Inorganic Chemistry, Faculty of Chemistry, University of Kashan, Kashan, I. R, Iran.
)
Raheleh Teymuri
3
(
Department of Organic Chemistry, Faculty of Chemistry, University of Kashan, Kashan, P.O. Box 87317-51167, I. R. Iran
)
Keywords:
Abstract :
Fabrication of HPA-ZSM-5 and their successful application to the recyclable heterogeneous catalyst for the smooth synthesis of spiro-pyrido-pyrimidine indoline derivatives
Abstract
A beneficial and efficient one-pot three-component approach for the synthesis of spiro cyclic 2-oxindole derivatives has been described by the reaction of isatins, cyclic-1,3-diketones and 6-amino-1,3-dimethyluracil in presence of highly active HPA-ZSM-5 microporous catalyst. The zeolite catalyst has been synthesized and the catalyst has been thoroughly characterized by X-ray diffraction (XRD), field emission scanning electronic microscopy (FE-SEM), Fourier transform infrared (FT-IR), energy dispersive spectroscopy (EDS) and N2-adsorption analysis. HPA-ZSM-5 catalyst exhibited exceptional recyclability at least for 6 times and the surface acidity was not significantly changed. The best results were gained in H2O and we found the convincing results for the synthesis of spiro-pyrido-pyrimidine in the presence of HPA-ZSM-5 (10 mg) under ultrasound irradiation (40W). Experimental simplicity, wide range of products, excellent yields in short reaction times and low catalyst loading are some of the substantial features of this procedure. The present catalytic method is extensible to a wide diversity of substrates for the synthesis of a variety-oriented library of spiro-pyrido-pyrimidine indoline derivatives.
Keywords : Zeolite, Heterogeneous catalysts, Hetero polyacids, Phosphomolybdic acid, Spiro cyclic 2-oxindole
Introduction
Nowadays, solid acid catalysts, which are recyclable and readily separable from the reaction system, offer the opportunity to reduce the impact on the environment and increase industrial interest for the liquid phase acid catalytic process [1-3]. Heteropolyacids (HPAs) have polyoxometalate inorganic cage structures, which may adopt the Keggin form with the general formula H3MX12O40, where M is the central atom and X the heteroatom. Typically M can be either P or Si, and X = W or Mo [4]. Heteropolyacids have proved to be the alternative of traditional acid catalysts, such as sulfuric acid and aluminum chloride, due to their strong acidity and harmless for environmental. The low surface area (~5 m2/g), high solubility in polar reaction systems, which thus results in separation problems and the low thermal stability of pure HPA, has severely hindered its applications [5, 6]. It is necessary to have a support in which they can be structurally incorporated with uniform shapes, sizes and specific surface area. Immobilization of HPAs on a silica support gives more stability and enhanced catalytic activity [7, 8]. Among the common known Keggin-type HPAs, we selected Phosphomolybdic acid (H3PMo12O40; PMA), in anhydrous acid form. Its effectiveness as a catalyst has been explored in various organic transformations including aza-Diels–Alder reactions [9]. deprotection of ethers [10], Hydrolysis of Acetonides [11], Acetylation of Alcohols, Phenols, and Amines [12], Ferrier rearrangement [13], polymerization reaction [14] and aza-Piancatelli rearrangement [15]. There is various carrier such as amorphous silica [16] or a porous supports including zeolite Y and ZSM-5 [17, 18] ordered mesoporous silica [19, 20] (e.g. SBA-15 or MCM-41). In this context, among different solid supports, nanocrystalline ZSM-5 zeolite is most preferred because of its many advantageous properties such as high surface area with different active sites, small pore sizes, a short diffusion path, excellent chemical and thermal stability, and good accessibility [21]. ZSM-5 zeolites are used in a variety of applications in industry, environment and medicine [22, 23]. In general, the surface of ZSM-5 zeolites has two types of active sites, Bronsted acid sites and Lewis acid sites. The Bronsted acid sites include the terminal silanol groups on the external surface and the bridging hydroxyl groups (Si-OH-Al), which are located at the channel intersections, while the Lewis acid sites, which are electron acceptors, refer to extra-framework aluminum species [24-26].
These days, there has been considerable growth of interest in the synthesis of spirooxindole derivatives (Figure 1) because of the wide-ranging biological activity associated with them such as antibacterial, antifungal, anti-inflammatory, and antipyretic activities [27, 28].
Figure 1. Reported biologically active spirooxindole-based molecules.
As well as, a large number of pyrimidine derivatives consist of barbituric acid and 2-aminouracil have attracted great interest for their biological activities and applications in medicine and therapeutics [29, 30]. In this context, the synthesis of this important ring system fused with spirooxindole remains a topic of current interest. Various methods for the preparation of spirooxindole derivatives have been reported [30-35]. However, some of these methods suffer from tedious synthetic routes, long reaction time, drastic reaction conditions, toxicity, corrosiveness, cost, as well as unrecoverable of catalyst. Thus, we want to develop an alternative protocol for the preparation of these spiro-pyrido-pyrimidine indoline derivatives with enhanced synthetic scope and better reaction profiles, thereby satisfying several green chemistry aspects. Ideally, utilizing environmental and green catalysts which can be easily recycled at the end of reactions has obtained great attention in recent years [36-39]. Accordingly, we herein report an ultrasound-promoted expedient and green practical method to access functionalized spiro-pyrido-pyrimidine indoline derivatives from the one-pot multicomponent reaction between 6-amino-1,3-dimethyluracil (1), isatin (2) and 1,3-diketone (3,4,5,6) using HPA-ZSM-5 catalysis in aqueous system (Scheme 1). The notable advantages of this present protocol compared to the earlier method are broader substrate scope, reduced reaction time in minutes, energy-efficiency occurring at ambient temperature, use of H2O as solvent, reusability of reaction media and large-scale synthetic applicability.
Scheme 1.Synthesis of spiro-pyrido-pyrimidine indoline derivatives
Newly, ultrasound irradiation has been in broad use as a green tool in organic
synthesis due to its several interest for instance energy savings, enhancement of reaction rates, and the enhancement in the mass transfer and product selectivity [40, 41]. The use of aqueous system as green solvent, effective application of ultrasonication in expediting reaction rate, employing reusable catalyst for the smooth synthesis, beneficial application of one-pot multicomponent reaction (MCR) strategy, and ambient reaction conditions are, thus, the steps forward to the cause of green and sustainable chemistry.
Experimental section
Materials
NMR spectra were recorded on Bruker Avance-400 MHz spectrometers in the presence of tetramethylsilane as internal standard. The IR spectra were recorded on FT-IR Magna 550 apparatus using KBr discs. Melting points were determined on Electro thermal 9200 and are not corrected. The elemental analyses (C, H, N) were obtained using a Carlo ERBA Model EA 1108 analyzer. The XRD patterns were recorded on an X-ray diffractometer (PHILIPS, PW 1510, Netherland) using Cu-Kα radiation (λ = 0.154056 nm) in the range 2θ = 0.8–10°. Field Emission Scanning electron microscope (FE-SEM) of nanocatalyst was visualized by SEM (MIRA3). Energy-Dispersive X-ray Spectroscopy (EDS) measurement was carried out with the SAMX analyser. The N2 adsorption/desorption analysis (BET) was performed using an automated gas adsorption analyzer (BEL SORP mini II).
Methods
Preparation of ZSM-5:
Zeolite precursor was prepared by adding tetrapropylammonium hydroxide (TPAOH), tetraethyl orthosilicate (TEOS) to a mixed aqueous solution of aluminium isopropoxide [Al(ίPro)3] and NaOH with stirring. The mixture was converted to gel. The gel was stirred for 20 h. The mole composition of the gel was 1Al2O3:46SiO2:4TPA:5Na2O:2500H2O. The resulting gel was sealed in Teflon-lined autoclaves and heated at 165 ºC for 72h. The solid product was recovered by filtration, washed by deionized water for several times, dried in an oven at 100 ºC overnight. The as-synthesized material was then calcined at 550 ºC for 8h to remove the templates.
Preparation of HPA-ZSM-5:
ZSM-5 Zeolites (1 g) was added to the solution of 0.3 g of phosphomolybdic acid (HPA) in ethanol (25 mL) and the reaction mixture was stirred for 24 h. The mixture was filtrated, washed by deionized water for several times, dried in an oven at 100 ºC overnight. The as-synthesized material was subjected at 400 ºC for 2h to product HPA-ZSM-5.
General procedure for the preparation of spiro-pyrido-pyrimidine indoline derivatives:
A mixture of isatins (1 mmol), 6-amino-1,3-dimethyluracil (1 mmol), cyclic-1,3-diketones (1 mmol) and water (10 ml) in presence of highly active HPA-ZSM-5 microporous catalyst (10 mg) was sonicated at 40 W. After completion of the reaction, progress of reaction was monitored using TLC (eluent EtOAc/n-hexane, 1:3), the formed precipitate was isolated by filtration. The product was dissolved in hot CH3OH and the catalyst was filtered. After cooling, the crude products were precipitated. The precipitate was washed with EtOH to afford the pure product and then dried well under vacuum pump.
Spectra data:
1',3',8',8'-Tetramethyl-8',9'-dihydro-1'H-spiro[indoline-3,5'-pyrimido[4,5-b]quinoline] 2,2',4',6'(3'H,7'H,10'H)-tetraone (7a): Yellow crystals, mp: 320-322 °C. IR (KBr): v =3280, 3210, 3090, 2959, 1690, 1644, 1499 cm-1. 1H NMR (400 MHz, DMSO-d6): δ=0.91 (3H, s, CH3), 1.02 (3H, s, CH3), 1.90-2.13 (2H, m, CH2), 2.50-2.55 (2H, m, CH2), 2.97 (3H, s, CH3), 3.45 (3H, s, CH3), 6.61-7.01 (4H, m, ArH), 8.94, 10.07 (2H, br s, 2NH, exchangeable with D2O) ppm. Anal. Calcd. for C22H22N4O4: C, 65.01; H, 5.46; N, 13.78. Found: C, 64.98; H, 5.36; N, 13.68.
1′,3′,7′,9′-Tetramethyl-1′H-spiro[indoline-3,5′-pyrido[2,3-d:6,5-d′]dipyrimidine]-2,2′,4′,6′,8′ (3′H,7′H, 9′H,10′H)-pentaone (8a): Yellow crystals, mp: 320-322 °C. IR (KBr): v = 3442, 3291, 3146, 1700, 1536 cm-1. 1H NMR (400 MHz, DMSO-d6): δ= 2.99 (3H, s, CH3), 3.07 (3H, s, CH3), 3.34 (3H, s, CH3), 3.39 (3H, s, CH3), 6.88-7.56 (4H, m, ArH), 9.35, 11.57 (2H, br s, 2NH, exchangeable with D2O) ppm. Anal. Calcd. for C20H18N6O5: C, 56.87; H, 4.30; N, 19.90. Found: C, 56.78; H, 4.25; N, 19.89.
1',3'-Dimethyl-1'H-spiro[indoline-3,5'-pyrido[2,3d:6,5d']dipyrimidine]2,2',4',6',8' (3'H,
7'H, 9'H,10'H)-pentaone (9a): White crystals, m.p. >300 oC. IR (KBr): 3264, 3286, 1685, 1617, 1536, 1495 cm-1. 1H NMR (400 MHz, DMSO-d6): δ 3.10 (s, 3H, CH3), 3.37 (s, 3H, CH3), 6.87-7.16 (4H, m, ArH), 9.09 (s, NH, D2O exchangeable), 10.44 (s, NH, D2O exchangeable), 10.60 (s, NH, D2O exchangeable), 11.56 (s, NH, D2O exchangeable).13C NMR (100 MHz, DMSO-d6): δ 26.2, 32.6, 56.7, 117.4, 121.5, 123.4, 126.8, 128.8, 134.2, 145.5, 150.1, 150.8, 152.5, 155.9, 159.6, 173.7, 180.4; Anal. Calcd. for C18H14N6O5: C, 54.82; H, 3.58; N, 21.31; Found: C, 54.72; H, 3.48; N, 21.14.
1,3-dimethyl-1H-spiro[indeno[1,2-b]pyrido[2,3-d]pyrimidine-5,3'-indoline]-2,2',4,6 (3'H,10'H)-tetraone (10 a): Orange powder, mp 290-292 °C. IR (KBr): 3237, 3200, 1759, 1697, 1633, 1615 cm-1. 1H NMR (400 MHz, DMSO-d6): δ (ppm) 3.02 (3H, s, CH3), 3.44 (3H, s, CH3), 7.01-7.65 (8H, m, H-Ar), 10.95 (1H, s, NH), 11.65 (1H, s, NH). 13C NMR (100 MHz, DMSO-d6): δ (ppm) 27.4, 31.6, 50.2, 97.4, 100.4, 118.2, 119.6, 120.6, 123.7, 124.9, 128.3, 129.1, 131.2, 131.2, 135.1, 136.4, 136.9, 151.7, 152.8, 156.4, 157.3, 180.6, 188.8. Anal. Calcd for C23H16N4O4 C, 66.99; H, 3.91; N, 13.59. Found: C, 66.90; H, 3.82; N, 13.48.
Results and discussion
The prepared catalyst was characterized by spectral techniques including FT-IR, XRD, FE-SEM, EDX, BET analyses.
FT-IR studies on zeolite ZSM-5 and its immobilized catalysts were carried out (Figure 2). Unmodified product has bands at the following wavenumbers (cm-1): 548 (δSi-O-Si), 796
(νsSi-O-Si), 1096 (νasSi-O-Si), 1630 (adsorbed H2O) and 3448 (νOH). The 796 band was shifted
in PMA-modified sample to 787 cm-1 that is the result of overlapping with bands δ Mo-O-Mo
(754 cm-1) [42]. The band of silanol groups shifted in the case of PMA-containing sample only. In addition, new strong band at 962 cm-1 appeared in the spectra of modified ZSM-5. This band is typical for Keggin’s structure of heteropolyacids and corresponds to νasMo-O-Mo or νasW-O-W vibrations [43].
Figure 2. Fourier transform infrared spectroscopy spectra of ZSM-5, HPA-ZSM-5
FE-SEM images of ZSM-5 and its immobilized catalyst are provided in Figure 3. After the immobilization, the surfaces of the catalyst (b) were covered with a white translucent substance, and the surfaces became smoother. The particles became larger in size and their profiles became clearer, indicating that HPA was immobilized on the surface of ZSM-5. The evaluation of the used catalyst structure by FE-SEM evidences that the morphology of the catalyst remained unchanged after the 5th cycle (Fig. 5e, 5f).
Figure 3. FE-SEM images of (a ZSM-5, (b) HPA-ZSM-5, (c) the used HPA-ZSM-5
EDX analysis (Figure 4) of the catalyst showed the presence of Al, P, O, Si, and Mo elements confirming the formation of the catalytic system as visualized. Elemental mapping images (Figure 4) of the catalyst showed uniform distribution of the elements P and Mo in the desired catalytic system.
Figure 4. EDS of HPA-ZSM-5
The XRD patterns of ZSM-5 and its immobilized catalyst are shown in Figure 4. In pattern (a),
the peaks of high intensity at 23.4°, 24.1°, and 24.6° are the characteristic diffraction peaks of ZSM-5, indicating good crystallinity of our synthesized ZSM-5. Compared with ZSM-5 pattern, HPA-ZSM-5 pattern exhibit all the diffraction peaks of ZSM-5, and the shape and intensity of the diffraction peaks have negligible changes, indicating that the prepared catalysts maintained the good crystallinity of ZSM-5 after immobilization of the HPA onto ZSM-5.
Figure 5. XRD of ZSM-5 and HPA-ZSM-5
N2-sorption isotherms at 77 K of ZSM-5 and HPA-ZSM-5 were indicated in figure 6. As shown in Figure 4, all the isotherms exhibited a typical type IV isotherm with an H1 hysteresis loop starting from P/P0 = 0.5. The results presented that the BET specific surface area of ZSM-5 was increased from 170 to 240 m2/g after modification with HPA.
Figure 6. N2 adsorption–desorption isotherms of ZSM-5 and HPA-ZSM-5
The optimum reaction conditions were obtained by using a model reaction (Scheme 2) to show the effect of various parameters such as the effect of different catalysts and solvents, HPA-ZSM-5 loading, amount of HPA-ZSM-5, and different temperatures.
Scheme 2. Synthesis of 7a
First, the model reaction was employed on 1a, 2a and 3a to give 4a without any catalyst, and a small quantity (89%) of the product was formed after prolonged heating [32] (Table 1, entry 1).
The model reaction was then examined with different catalysts such as MA Ionic Liquid, PTSA, SBA-15-PhSO3H and SBA-Oxime-Zn. It was observed that MA Ionic Liquid, PTSA, SBA-15-PhSO3H and SBA-Oxime-Zn afforded a moderate yield of the
product after a longer time period (Table 1, entries 2, 3, 4, 5)
Entry | Catalyst | amount | Solvent/ Condition | Time (min) | Yield (%) | Ref |
1 | Free-Catalyst |
| EtOH | 180 | 89 | 32 |
2 | MA Ionic Liquid | (10 mol%) | H2O | 300 | 89 | 30 |
3 | PTSA | (5 mol%) | H2O | 300 | 90 | 34 |
4 | SBA-15-PhSO3H | 15 mg | H2O:EtOH | 300 | 95 | 33 |
5 | SBA-Oxime-Zn | 15 mg | H2O | 30 | 91 | 35 |
6 | AlCl3 | 20 mg | H2O | 300 | 65 | - |
7 | CH3COOH | 10 mol% | H2O | 300 | 70 | - |
8 | H3PMo12O40 | 10 mol% | H2O | 300 | 80 | - |
9 | ZSM-5 | 15 mg | H2O | 300 | 60 | - |
10 | HPA-ZSM-5 | 15 mg | H2O | 180 | 90 | - |
11 | HPA-ZSM-5 | 15 mg | EtOH | 300 | 87 |
|
12 | HPA-ZSM-5 | 10 mg | H2O/US (30 W) | 20 | 85 |
|
13 | HPA-ZSM-5 | 10 mg | H2O/US (40 W) | 15 | 92 | - |
14 | HPA-ZSM-5 | 10 mg | H2O/US (50 W) | 15 | 92 |
|
15 | HPA-ZSM-5 | 8 mg | H2O/US (40 W) | 15 | 90 |
|
16 | HPA-ZSM-5 | 15 mg | H2O/US (40 W) | 15 | 92 |
|
With Lewis acid and Brønsted–Lowry acid (Table 1, entries 6, 7) small amounts of the product were obtained. However, the reaction with heteropoly acid such as H3PMo12O40 afforded an improved yield of the product (Table 1, entry 8). When the reaction was conducted with HPA–doped ZSM-5 the rate of reaction was enhanced and time period reduced
giving good yield of the product (Table 1, entries 10 and 11). However, using
HPA supported on ZSM-5 (HPA-ZSM-5), the reaction completed in a relatively shorter reaction time (180 min) affording an excellent yield of the product (90%; Table 1, entry 10) showing the effect of doped HPA on the catalytic activity of the catalyst, whereas, for the model reaction carried out with ZSM-5 alone as catalyst, small amounts of the product were obtained (Table 1, entry 9).
For a demonstration of the superiority of ultrasound-assisted method the model reaction was carried out in H2O as solvent and the result are shown in entry 13. As observed, when the reaction was carried out under ultrasound irradiation (40 W), the maximum yield of the product was obtained in the minimum time period (Table 1, entry 13).
A mixture of 6-Amino-1,3-dimethyluracil (1a), isatin (2a) and 1,3-diketone (3a) in presence of HPA-ZSM-5 as catalyst in H2O for about 15 min, afforded 1',3',8',8'-tetramethyl-8',9'-dihydro-1'H-spiro[indoline-3,5'-pyrimido[4,5-b]quinoline]-2,2',4',6'(3'H,7'H,10'H)-tetraone (7a) in good yields (Scheme 2). The scope of the present methodology was investigated by synthesizing structurally different spiro-pyrido-pyrimidine indoline derivatives using the optimized reaction conditions. Various spiro-pyrido-pyrimidine indoline derivatives were obtained in high yields by MCRs of 2-6-Amino-1,3-dimethyluracil (1a), isatin (2a-d) and 1,3-diketone (3a-d) under the optimal reaction conditions, and the results are presented in Table 2. To the best of our knowledge, this new procedure provides the first example of use of H2O green solvent and ultrasound-assisted method of spirooxindole. Overall, this efficient method is applicable for the synthesis of different types of spiro-pyrido-pyrimidine indolines. In addition, the workup of these very clean reactions involves only a filtration and simple washing step with water.
Time/yield% m.p | Time/yield% m.p |
|
|
15 min/ 92 320-322°C | 15 min/ 94 mp>300°C |
|
|
15 min/ 94 mp>300°C | 20 min/ 90 320-322 °C |
|
|
15 min/ 92 301-303°C | 20 min/ 91 296-298 °C |
|
|
20 min/ 88 m.p. >300 oC | 20 min/ 90 m.p. >300 oC |
|
|
20 min/ 90 296-298 oC | 15 min/ 90 290-292 oC |
|
|
15 min/ 92 m.p. >300 oC | 15 min/94 294-296 oC |
On the basis of the point mentioned above, a reasonable mechanism for the preparation of 1',3'-dimethyl-1'H-spiro[indoline-3,5'-pyrido[2,3-d:6,5-d']dipyrimidine]-2,2',4',6',8'(3'H,7'H,9'H,10'H) -pentaone by the HPA-ZSM-5 is suggested in Scheme 3.
Scheme 3. Plausible Mechanism for the Catalytic Synthesis
of spiro-pyrido-pyrimidine indoline derivatives
Conclusions
In conclusion, we have designed a facile method for the synthesis of novel HPA-ZSM-5. The zeolite catalyst has been characterized by XRD, FE-SEM, FT-IR, EDS and N2-adsorption analysis. The catalyst has been applied for the synthesis of spiro-pyrido-pyrimidine indolines by the reaction of isatins, cyclic-1,3-diketones and 6-amino-1,3-dimethyluracil in presence of highly active HPA-ZSM-5 microporous catalyst (10 mg) under ultrasound irradiation (40 W) in water. This method is applicable for the synthesis of different types of spiro-pyrido-pyrimidine indolines. The catalyst could be recycled for five runs during the course of the reaction. The widespread scope, reusability of the catalyst, clean reaction profile, improved rate of reaction, and product yield are the advantages of the present protocol.
Acknowledgment
The authors are grateful to University of Kashan for supporting this work.
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