Home Physical Sciences Fe3O4@urea/HITh-SO3H as an efficient and reusable catalyst for the solvent-free synthesis of 7-aryl-8H-benzo[h]indeno[1,2-b]quinoline-8-one and indeno[2′,1′:5,6]pyrido[2,3-d]pyrimidine derivatives
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Fe3O4@urea/HITh-SO3H as an efficient and reusable catalyst for the solvent-free synthesis of 7-aryl-8H-benzo[h]indeno[1,2-b]quinoline-8-one and indeno[2′,1′:5,6]pyrido[2,3-d]pyrimidine derivatives

  • Shenghao Jiang EMAIL logo , Macheng Shen and Fatima Rashid Sheykhahmad
Published/Copyright: June 18, 2020

Abstract

In this study, Fe3O4@urea/HITh-SO3H MNPs as a new, efficient, and recyclable solid acid magnetic nanocatalyst was synthesized and characterized using various methods including Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, transmission electron microscopy, vibrating sample magnetometry, energy-dispersive X-ray spectroscopy, and X-ray powder diffraction. After the characterization of this new magnetic nanocatalyst, it was efficiently utilized for the promotion of the one-pot synthesis of 7-aryl-8H-benzo[h]indeno[1,2-b]quinoline-8-one and indeno[2′,1′:5,6]pyrido[2,3-d]pyrimidine derivatives via three-component reaction of the 1,3-indanedione, aldehyde, and 1-naphthylamine/1,3-dimethyl-6-aminouracil under solvent-free conditions at 80°C. The procedure gave the desired heterocyclic structures in high-to-excellent yields and short reaction times. Also because of the magnetic nature of the nanocatalyst, it can be separated with an external magnetic field and reused at least six runs without any considerable decrease in the catalytic behavior.

1 Introduction

The use of magnetic nanoparticles (Fe3O4 MNPs) as a core to support the catalyst in organic transformation has become quite popular in chemistry. Because they include unique features such as high dispersion and reactivity, easy separation under external permanent magnetic fields and reusability, pairing with two or multidentate ligands or inorganic structures [16]. The use of magnetic nanoparticles may be restricted for reasons such as deformation and aggregation during the chemical process [7]. To remove this restriction and reclaim their features for the specific application, these particles need to be modified by functionalizing their surface via organic or inorganic groups.

Pyrimidine cores are important classes of bioactive and heterocyclic molecules that have received significant importance in the pharmaceutical studies over recent years due to their wide range of therapeutic and pharmacological features such as anticancer [8], anti-inflammatory [9], antimicrobial [10], or antihistaminic activity [11]. Among these compounds, pyrido[2,3-d]pyrimidine is one of the main groups of heterocyclic compounds annulated uracil; due to their wide range of medicinal activities such as antibacterial, anticonvulsants, antiaggressive activity, antifolate, antileishmanial, antimicrobial, anti-inflammatory, and inhibitors of cyclin-dependent kinases [12,13]. Thus it is important to prepare the pyrido[2,3-d]pyrimidine derivatives. For the one-pot multicomponent preparation, the most common types of compounds are as follow: the reaction of 1,3-indanedione (1 mmol), aryl aldehyde (1 mmol) and 1,3-dimethyl-6-aminouracil (1 mmol) for preparing indeno[2′,1′:5,6]pyrido[2,3-d]pyrimidine.

The indenoquinoline derivatives, such as ubiquitous nitrogen-containing heterocycles, play important roles in medicinal chemistry by possessing a diverse spectrum of pharmacological activities such as steroid reductase inhibitors [14], acetylcholinesterase inhibitors [15], antitumor [16,17], and antimalarial activities [18]. Therefore, the synthesis of these heterocyclic compounds is significant for both organic and medicinal chemists. Several applications of quinoline-fused frameworks have already been highlighted in the literature as scaffolds of biological substances, such as ligands for preparing OLED phosphorescent complexes and intermediates in the dyestuffs industry [19,20,21,22,23,24,25]. The most common process for synthesizing indeno [1,2-b]quinoline diones have been reported via the condensation of 1-naphthylamine (1 mmol), aldehyde (1 mmol), and 2H-indene-1,3-dione (1 mmol).

2 Experimental

2.1 General

The chemicals used in this work were obtained from Merck, Fluka, and Aldrich chemical companies and were utilized with any further purification. All melting points were achieved on an Electrothermal 9100 instrument. Fourier transform infrared spectroscopy (FTIR) spectroscopy was done as KBr discs with a Shimadzu spectrometer. Thermogravimetric analysis (TGA) spectra were recorded using a TGA thermoanalyzer (PerkinElmer) instrument. Scanning electron microscopy (SEM) images were obtained using a Tescanvega II XMU Digital Scanning Microscope. Vibrating sample magnetometry (VSM) analyses were performed in a Lakeshore 7407 at ambient temperature. Energy dispersive X-ray spectroscopy (EDX) measurement was performed using ESEM, Philips, and XL30. X-ray powder diffraction (XRD) patterns of samples were obtained using a Siemens D-5000 X-ray diffractometer. Transmission electron microscope (TEM) images were recorded with a TEM Philips EM 208S instrument.

2.1.1 Catalyst synthesis

2.1.1.1 Preparation of the magnetite nanoparticles (Fe3O4 MNPs)

About 4.8 g of FeCl3·6H2O and 1.7 g of FeCl2·4H2O were dispersed in 100 ml of deionized water by ultrasonication. Then, 10 ml of aqueous ammonia (25%) was added dropwise to the reaction solution under Ar atmosphere by stirring about 30 min with a magnetic stirrer. After the time taken to advance the reaction, the black magnetite precipitate (Fe3O4) was rinsed three times with deionized water and dried in vacuum at 60°C.

2.2 Preparation of silica-coated magnetic nanoparticles (Fe3O4@SiO2 MNPs)

One gram of Fe3O4 MNPs was added to a mixture including 10 ml deionized water, 45 ml ethanol, and 7 ml of aqueous ammonia solution (25 wt%) and agitated at ambient temperature for about 30 min. After the time required, 6 ml of tetraethylorthosilicate (TEOS) was added dropwise to the reaction vessel and stirred for 24 h under mechanical agitation to afford silica-coated magnetic nanoparticles (Fe3O4@SiO2). Finally, the resulting solid material was isolated using a permanent magnetic field, washed thoroughly with ethanol, and then dried in vacuum at 50°C for 24 h.

2.2.1 Preparation of chloropropyl-functionalized magnetic nanoparticles (Fe3O4@CPTES MNPs)

Three grams of the above-synthesized Fe3O4@SiO2 was modified with 6 ml of 3-chloropropyltriethoxysilane (CPTES) in dry toluene (80 ml), and the reaction solution was refluxed under nitrogen atmosphere for 12 h. The obtained Fe3O4@CPTES MNPs were filtered with the help of a permanent magnetic field, rinsed thoroughly with dry toluene and diethyl ether, and then dried in vacuum at 80°C for 8 h.

2.2.2 Preparation of urea-functionalized magnetic nanoparticles (Fe3O4@CPTES/urea MNPs)

About 2.5 g of Fe3O4@CPTES and 10 mmol of urea were added to 50 ml dry toluene and refluxed for 12 h. The resulting black sediment (Fe3O4@CPTES/urea MNPs) was filtered with the help of a permanent magnetic field, washed three times with 30 ml of ethanol to remove the unreacted chemicals and dried in vacuum at 50°C for 24 h.

2.2.3 Preparation of Fe3O4@urea/HITh MNPs

Two grams of Fe3O4@CPTES/urea MNPs was dispersed in 25 ml dry toluene by ultrasonication for half an hour. Subsequently, 0.65 g of 4,5-dihydroxyimidazolidine-2-thione (HITh) and 0.1 ml of trifluoroacetic acid (TFA) were added into the reaction flask, and the mixture was agitated for 1 h at ambient temperature. Then, the resulting solid product was separated by magnetic decantation, washed twice with distilled water (20 ml) and acetone (10 ml) to eliminate the unreacted chemicals, and dried in vacuum at 70°C for 18 h.

2.2.4 Preparation of Fe3O4@urea/HITh-SO3H MNPs

At the end of work, 1 g of Fe3O4@urea/HPITh MNPs was dispersed in 25 ml dry dichloromethane by ultrasonication for 30 min and then 10 mmol of 1,4-butane sulfonate was added to the reaction vessel. The reaction mixture was refluxed for 8 h; after this, the resulting solid product was isolated using magnetic decantation. The obtained solid catalyst was rinsed three times with 30 ml of distilled water and dried overnight in vacuum oven at 60°C. This synthesis is exhibited in Scheme 1.

Scheme 1 Synthesis of Fe3O4@urea/HITh-SO3H MNPs.
Scheme 1

Synthesis of Fe3O4@urea/HITh-SO3H MNPs.

2.2.5 General process for the preparation of 7-aryl-8H-benzo[h]indeno[1,2-b]quinoline-8-one derivatives 4

A mixture containing 1,3-indanedione (1 mmol), aldehyde (1 mmol), 1-naphthylamine (1 mmol), and Fe3O4@urea/HITh-SO3H MNPs magnetic nanocatalyst (10 mg) reacted with each other in a one-pot condensation at 80 °C under solvent-free conditions. To ensure the completion of the reaction, thin layer chromatography (TLC) was used to monitor the reaction mixture. After viewing a single spot on the TLC for the final product, the catalyst was isolated using an external magnet, and the desired pure products were attained from the reaction container by recrystallization from the hot ethanol.

2.2.6 General process for the preparation of indeno[2′,1′:5,6]pyrido[2,3-d]pyrimidine derivatives 6

A mixture containing 1,3-indanedione (1 mmol), aldehyde (1 mmol), 1,3-dimethyl-6-aminouracil (1 mmol), and Fe3O4@urea/HITh-SO3H MNPs magnetic nanocatalyst (15 mg) reacted with each other in a one-pot condensation at 80°C under solvent-free conditions. To ensure the completion of the reaction, the reaction mixture was monitored using TLC. After viewing a single spot on the TLC for the desired product, the catalyst was separated by a permanent magnetic field, and the desired pure products were achieved from the reaction container by recrystallization from the hot ethanol.

  1. Ethical approval: The conducted research is not related to human or animal use.

3 Results and discussion

3.1 Catalyst characterization

3.1.1 FTIR analysis of Fe3O4@urea/HITh-SO3H MNPs

Figure 1 exhibits FTIR spectra for Fe3O4@CPTES MNPs, Fe3O4@urea/HITh MNPs, Fe3O4@urea/HITh-SO3H MNPs, and recovered Fe3O4@urea/HPITh-SO3H MNPs. The FTIR spectrum for the Fe3O4@CPTES MNPs shows a broad peak at 3,436 cm−1 that can be attributed to the stretching vibration of the O–H bands, which are linked to the surface of Fe3O4 nanoparticles. Two typical absorption peaks at 578 and 465 cm−1 can be attributed to the stretching vibration of the Fe–O band of the Fe3O4 lattice, while the characteristic peak at 1,087 cm−1 corresponds to the Si–O–Si stretching vibration. The existence of a weak peak at 1,621 cm−1 comes from vibrations of O–H stretching and twisting bonds of Si–O–H and H–O–H in the silica shell, respectively. The absorption band at 2,968 cm−1 is associated with the C–H stretching vibration of 3-chloropropyltriethoxysilane (CPTES) group. The weak absorption peak at 1,633 cm−1 is attributable to the C═O stretching vibrations of the amidic group in Fe3O4@CPTES/urea MNPs. Moreover, the absorption correlated to C═S peak vibration appears at 2,325 cm−1. The existence of SO3H groups in the Fe3O4@urea/HITh-SO3H MNPs are claimed with 3,405 and 1,239 cm−1 peaks relating to the O–H and O–SO2 stretching vibration, respectively. It is worth explaining that the FTIR spectra for recovered Fe3O4@urea/HITh-SO3H MNPs after the third recovery and reuse do not show any significant change.

Figure 1 FTIR spectra of Fe3O4@CPTES MNPs, Fe3O4@urea/HITh MNPs, Fe3O4@urea/HITh-SO3H MNPs, and recovered Fe3O4@urea/HITh-SO3H MNPs.
Figure 1

FTIR spectra of Fe3O4@CPTES MNPs, Fe3O4@urea/HITh MNPs, Fe3O4@urea/HITh-SO3H MNPs, and recovered Fe3O4@urea/HITh-SO3H MNPs.

3.1.2 Thermal analysis of Fe3O4@urea/HITh-SO3H MNPs

The TGA corresponding to the Fe3O4@CPTES MNPs, Fe3O4@urea/HPITh MNPs, and Fe3O4@urea/HITh-SO3H MNPs exhibited information about functional organic groups bonded on the magnetic nanoparticles’ surface and the thermal stability through the primary loss of mass (Figure 2). TGA data for all cases showed about 4% loss of mass below 150°C because of the loss of the surface O–H groups as well as desorption of a small quantity of adsorbed solvents. From the TGA curve of Fe3O4@CPTES MNPs, it can be inferred that the loss of mass was about 7%, which can be chiefly attributed to the CPTES organic functional group on the core–shell structure surface. With further increase in temperature, the TGA curve corresponding to Fe3O4@urea/HITh MNPs indicated a more remarkable loss of mass compared with that found in Fe3O4@CPTES MNPs. This change in the slope of the curve can be attributed to the decomposition of propyl groups, urea, and HITh on the surface of core–shell structure. Besides the similar loss of mass for all three samples, Fe3O4@urea/HITh-SO3H MNPs have two weight loss steps that are associated with the decomposition of organic functional groups and SO3H molecules.

Figure 2 TGA curves of Fe3O4@CPTES MNPs, Fe3O4@urea/HITh MNPs, and Fe3O4@urea/HITh-SO3H MNPs.
Figure 2

TGA curves of Fe3O4@CPTES MNPs, Fe3O4@urea/HITh MNPs, and Fe3O4@urea/HITh-SO3H MNPs.

3.1.3 SEM analysis of Fe3O4@urea/HITh-SO3H MNPs

Figure 3 shows the morphology and structure of Fe3O4@CPTES MNPs and Fe3O4@urea/HITh-SO3H using SEM. Fe3O4@CPTES MNPs have a mean particle dimension of about 40 nm (Figure 3a). The SEM micrograph shown in Figure 3b demonstrates clear and vivid changes in the morphology of the Fe3O4@urea/HITh-SO3H, which can be mainly associated with the bonding of acidic groups to the catalyst surface. The particle dimension of Fe3O4@urea/HITh-SO3H MNPs was about 50 nm.

Figure 3 SEM image of (a) Fe3O4@CPTES MNPs and (b) Fe3O4@urea/HITh-SO3H MNPs.
Figure 3

SEM image of (a) Fe3O4@CPTES MNPs and (b) Fe3O4@urea/HITh-SO3H MNPs.

3.1.4 TEM analysis of Fe3O4@urea/HITh-SO3H MNPs

TEM image of Fe3O4@urea/HITh-SO3H MNPs is depicted in Figure 4. According to this image, the particle size of the synthesized heterogeneous magnetic nanocatalyst is found to be approximately 17 nm.

Figure 4 TEM image of Fe3O4@urea/HITh-SO3H MNPs.
Figure 4

TEM image of Fe3O4@urea/HITh-SO3H MNPs.

3.1.5 VSM analysis of Fe3O4@urea/HITh-SO3H MNPs

To study the magnetic feature of Fe3O4 MNPs and Fe3O4@urea/HITh-SO3H MNPs, magnetic measurements were carried out by a room temperature VSM under applied magnetic field (Figure 5). The obtained values for the saturation magnetizations of Fe3O4 MNPs and Fe3O4@urea/HITh-SO3H MNPs were 60.29 and 29.35 emu/g, respectively. These values indicate that the magnetic saturation of the catalyst has been reduced. Despite this decline in the magnetic saturation, the heterogeneous magnetic nanocatalyst can still be efficiently isolated from the reaction mixture using a powerful magnet.

Figure 5 Magnetic curves of Fe3O4 MNPs and Fe3O4@urea/HITh-SO3H MNPs.
Figure 5

Magnetic curves of Fe3O4 MNPs and Fe3O4@urea/HITh-SO3H MNPs.

3.1.6 EDX analysis of Fe3O4@urea/HITh-SO3H MNPs

The elemental composition of Fe3O4@urea/HITh-SO3H MNPs was obtained using EDX (Figure 6). The EDX spectrum exhibits the characteristic peaks (Fe, O, N, Si, and S) of the catalyst.

Figure 6 EDX of Fe3O4@urea/HITh-SO3H MNPs.
Figure 6

EDX of Fe3O4@urea/HITh-SO3H MNPs.

3.1.7 XRD analysis of Fe3O4@urea/HITh-SO3H MNPs

The structure of Fe3O4 (a) and Fe3O4@urea/HITh-SO3H MNPs (b) was analyzed using the XRD spectroscopy in the 2θ range of 10°–80°. As shown in Figure 7, XRD of the Fe3O4 MNPs displayed six reflections at 2θ values: 30.08, 35.91, 43.96, 53.78, 57.84, and 63.05, which were marked by the diffractions of (220), (311), (400), (422), (511), and (440), respectively. The same sets of reflections were also obtained for Fe3O4@urea/HITh-SO3H MNPs, indicating the retention of the crystalline structure of Fe3O4 MNPs during surface modification.

Figure 7 XRD for Fe3O4 MNPs (a) and Fe3O4@urea/HITh-SO3H MNPs (b).
Figure 7

XRD for Fe3O4 MNPs (a) and Fe3O4@urea/HITh-SO3H MNPs (b).

This study aimed to publish the rapid and effective preparation of 7-aryl-8H-benzo[h]indeno[1,2-b]quinoline-8-one and indeno[2′,1′:5,6]pyrido[2,3-d]pyrimidine derivatives with lower loading of the new, efficient, and recyclable solid acid magnetic nanocatalyst (e.g., Fe3O4@urea/HITh-SO3H MNPs) under solvent-free conditions (Scheme 2).

Scheme 2 Production of 7-aryl-8H-benzo[h]indeno[1,2-b]quinoline-8-one 4 and indeno[2′,1′:5,6]pyrido[2,3-d]pyrimidine 6 derivatives using Fe3O4@urea/HITh-SO3H MNPs.
Scheme 2

Production of 7-aryl-8H-benzo[h]indeno[1,2-b]quinoline-8-one 4 and indeno[2′,1′:5,6]pyrido[2,3-d]pyrimidine 6 derivatives using Fe3O4@urea/HITh-SO3H MNPs.

To screen the reaction conditions to produce 7-aryl-8H-benzo[h]indeno[1,2-b]quinoline-8-one derivatives, the effect of the solvents, the concentrations of catalyst, and the reaction temperature were explored via the three-component reaction of 1,3-indanedione 1 (1 mmol), 4-chlorobenzaldehyde 2d (1 mmol), and 1-naphthylamine 3 (1 mmol). The results are listed in Table 1. To attain the optimum reaction solvent, different solvents (e.g., water, ethanol, and solvent-free conditions) were examined in the presence of a certain concentration of catalyst (Table 1, entries 1–3). The reaction gave lower yields when water was utilized as the solvent (Table 1, entry 1). According to the results, the highest reaction yield was obtained when using ethanol as the solvent (Table 1, entry 2). However, the optimal rate and yield were achieved in the absence of solvent for the reaction (Table 1, entry 3). Moreover, the conditions regarding the concentration of catalyst were evaluated on the reaction yield. After numerous screening experiments with different levels of the nanocatalyst, it was observed that using 10 mg of the Fe3O4@urea/HITh-SO3H MNPs was applicable to complete the reaction at the short reaction time (Table 1, entry 3). Enhancing the concentration of catalyst beyond 10–15 mg did not increase the yield (Table 1, entry 5). A low amount of the catalyst required for the reaction from 10 to 5 mg resulted in a decreased yield (Table 1, entry 6). Moreover, when the reaction was conducted in the absence of a catalyst, the product yields decreased remarkably and only a trace level of the desired product was found on TLC, even after the reaction time was prolonged to 60 min (Table 1, entry 4). Also, the effect of temperature was checked on the reaction yield (Table 1, entries 3 and 7–12). It is clear that a low yield of the product was achieved without heating (Table 1, entry 7). The yield of the product was increased at higher temperatures (entries 3 and 8–10). However, a further increase in temperature did not improve the yield of reaction (Table 1, entries 11 and 12).

Table 1

Optimizing the three-component reaction of 1,3-indanedione (1), 4-chlorobenzaldehyde (2d), and 1-naphthylamine (3) under different conditionsa

EntrySolventCatalyst (mg)Temp. (°C)Time (min)Yieldb (%)
1H2O10Reflux6035
2EtOH10Reflux3585
3Solvent free1080498
4Solvent free8060Trace
5Solvent free1580495
6Solvent free580483
7Solvent free10256045
8Solvent free10501578
9Solvent free10601085
10Solvent free1070891
11Solvent free1090496
12Solvent free10100493
  1. a

    Reaction conditions: 1,3-indanedione (1 mmol), 4-chlorobenzaldehyde (1 mmol), 1-naphthylamine (1 mmol), and needed concentration of the catalysts.

  2. b

    The yields refer to the isolated product.

After optimizing the reaction conditions, the generality of these conditions was studied via multifarious aromatic aldehydes, the outcomes of which are listed in Table 2. It was observed that aromatic aldehydes carrying both different electron-donating and electron-withdrawing groups were subjected to the condensation and in all cases, the relating 7-aryl-8H-benzo[h]indeno[1,2-b]quinoline-8-one derivatives (4a–p) were obtained in high-to-excellent yields after the appropriate reaction times.

Table 2

Fe3O4@urea/HITh-SO3H MNPs-catalyzed synthesis of 7-aryl-8H-benzo[h]indeno[1,2-b]quinoline-8-one derivativesa

EntryRCHO (2)ProductYield (%)/time (min)M.P. (obsd) (°C)M.P. (°C) [lit.]
1
94/6201–203202–204 [26]
2
96/4290–292289–291 [27]
3
95/5229–231230–232 [26]
4
98/4253–256259–261 [27]
5
95/7209–212212–214 [26]
6
91/8218–221220–222 [26]
7
96/6233–235236–238 [26]
8
97/5216–219218–220 [26]
9
96/6225–227222–224 [26]
10
97/5225–227210–212 [26]
11
98/6238–240231–235 [27]
12
98/8243–245240–241 [28]
13
89/12230–232228–229 [27]
14
93/10251–253256–260 [27]
15
91/10231–234233–235 [26]
16
89/12231–234233–235 [26]
  1. a

    Reaction conditions: 1,3-indanedione (1 mmol), aldehyde (1 mmol), 1-naphthylamine (1 mmol), and Fe3O4@urea/HITh-SO3H MNPs (10 mg).

Also, we reported a fast and effective one-pot three-component production of indeno[2′,1′:5,6]pyrido[2,3-d]pyrimidine derivatives through the reaction of 1,3-indanedione, aldehyde, 1,3-dimethyl-6-aminouracil in the existence of Fe3O4@urea/HITh-SO3H MNPs (Table 3). To determine the best optimal conditions, we performed the reaction between 1,3-indanedione 1 (1 mmol), 4-nitrobenzaldehyde 2j (1 mmol), and 1,3-dimethyl-6-aminouracil 5 (1 mmol), in the existence of 15 mg of Fe3O4@urea/HITh-SO3H MNPs at 80°C under solvent-free conditions. The final product 6j was achieved with an excellent yield (96%) within 15 min (Table 3, entry 3).

Table 3

Optimization of the three-component reaction of 1,3-indanedione (1), 4-nitrobenzaldehyde (2), and 1,3-dimethyl-6-aminouracil (5) under different conditionsa

EntrySolventCatalyst (mg)Temp. (°C)Time (min)Yieldb (%)
1H2O15Reflux6035
2EtOH15Reflux3585
3Solvent free15801596
4Solvent free8060Trace
5Solvent free20801593
6Solvent free10801585
7Solvent free15256042
8Solvent free15502575
9Solvent free15602083
10Solvent free15702090
11Solvent free15901594
12Solvent free151001592
  1. a

    Reaction conditions: 1,3-indanedione (1 mmol), 4-nitrobenzaldehyde (1 mmol), 1,3-dimethyl-6-aminouracil (1 mmol), and needed concentration of the catalysts.

  2. b

    The yields refer to the isolated product.

Under optimum conditions, the scope and generality of this procedure were explored. To synthesize indeno[2′,1′:5,6]pyrido[2,3-d]pyrimidine derivatives, a variety of aromatic aldehydes comprising electron-withdrawing and electron-donating groups in the existence of 15 mg of Fe3O4@urea/HITh-SO3H MNPs were investigated to react with 1,3-indanedione and 1,3-dimethyl-6-aminouracil, and the outcomes are listed in Table 4. It was observed that the above-mentioned aromatic aldehydes produced a high percentage of products in reaction with two other components.

Table 4

Fe3O4@urea/HITh-SO3H MNPs-catalyzed synthesis of indeno[2′,1′:5,6]pyrido[2,3-d]pyrimidine derivativesa

EntryRCHO (2)ProductYield (%)/time (min)M.P. (obsd) (°C)M.P. (°C) [lit.]
1
91/15>300>300 [34]
2
94/15>300>300 [33]
3
93/18>300>300 [35]
4
96/15>300>300 [32]
5
96/18295–297297–298 [35]
6
95/20252–255253–256 [35]
7
92/15>300>300 [33]
8
95/12>300>300 [35]
9
93/15>300>300 [32]
10
96/15256–259258–260 [34]
11
94/12291–295294–297 [35]
12
93/10>300>300 [33]
13
92/20>300>300 [33]
14
92/22>300>300 [35]
  1. a

    Reaction conditions: 1,3-indanedione (1 mmol), aldehyde (1 mmol), 1,3-dimethyl-6-aminouracil (1 mmol), and Fe3O4@urea/HITh-SO3H MNPs (15 mg).

Scheme 3 presents a reasonable pathway for the one-pot three-component condensation of 1,3-indanedione 1, various aldehyde 2, 1-naphthylamine 3/1,3-dimethyl-6-aminouracil 5, and Fe3O4@urea/HITh-SO3H MNPs. Initially, 1,3-indanedione 1 and carbonyl group of activated aldehyde 2 as the reactant materials react with each other through a Knoevenagel condensation reaction to obtain intermediate 7. Then, the polar transition state 8 is obtained by adding 1-naphthylamine 3/1,3-dimethyl-6-aminouracil 5, as the C–H-activated acid, via Michael addition to the intermediate 7. This material is not stable and is converted through cyclization, dehydration, and oxidation to desired products 4, 6.

Scheme 3 A probable mechanism corresponding to the one-pot three-component reaction of 1,3-indanedione, aldehyde, and 1-naphthylamine/1,3-dimethyl-6-aminouracil, catalyzed by Fe3O4@urea/HITh-SO3H MNPs under solvent-free conditions.
Scheme 3

A probable mechanism corresponding to the one-pot three-component reaction of 1,3-indanedione, aldehyde, and 1-naphthylamine/1,3-dimethyl-6-aminouracil, catalyzed by Fe3O4@urea/HITh-SO3H MNPs under solvent-free conditions.

Recyclability is an important merit of any catalysts, therefore, studying the recyclability of the Fe3O4@urea/HITh-SO3H MNPs was necessary (Figure 8). To this end, the reaction was performed using the three-component condensation of 1,3-indanedione (1 mmol), 4-chlorobenzaldehyde (1 mmol), and 1-naphthylamine/1,3-dimethyl-6-aminouracil (1 mmol) in the existence of the catalytic level of Fe3O4@urea/HITh-SO3H MNPs at 80°C. At the end of the reaction, the catalyst was isolated from the reaction solution using an external magnet and rinsed with ethanol several times, dried under reduced pressure, and reused in subsequent reactions at least 6 runs without any considerable reduction in the yield of the products.

Figure 8 The recycling of Fe3O4@urea/HITh-SO3H MNPs in the preparation of 7-(4-chlorophenyl)-8H-benzo[h]indeno[1,2-b]quinolin-8-one 4d (a) and 5-(4-chlorophenyl)-1,3-dimethyl-1H-indeno[2′,1′:5,6]pyrido[2,3-d]pyrimidine-2,4,6(3H)-trione 6d (b) derivatives.
Figure 8

The recycling of Fe3O4@urea/HITh-SO3H MNPs in the preparation of 7-(4-chlorophenyl)-8H-benzo[h]indeno[1,2-b]quinolin-8-one 4d (a) and 5-(4-chlorophenyl)-1,3-dimethyl-1H-indeno[2′,1′:5,6]pyrido[2,3-d]pyrimidine-2,4,6(3H)-trione 6d (b) derivatives.

Efficiency and usability of the catalyst for synthesizing 7-aryl-8H-benzo[h]indeno[1,2-b]quinoline-8-one and indeno[2′,1′:5,6]pyrido[2,3-d]pyrimidine derivatives were compared with that of some previously reported catalysts. As presented in Table 5, Fe3O4@urea/HITh-SO3H MNPs is better than previously reported catalysts in saving time, energy, and excellent yields of the products (Table 5).

Table 5

Comparison of the outcomes of the production of 7-aryl-8H-benzo[h]indeno[1,2-b]quinoline-8-one and indeno[2′,1′:5,6]pyrido[2,3-d]pyrimidine derivatives by means of different catalysts

EntryCatalyst and conditionsReaction time (min)Yield (%)Ref.
1Fe3O4@cellulose-OSO3H/solvent‐free/40°C54028
2[Fe(HSO4)3]/DMSO/90°C2109030
3P(4-VPH)HSO4/EtOH/reflux1208629
4H6P2W18O62 18H2O/acetic acid/reflux3609631
5TBM/solvent‐free/80°C459426
7Fe3O4@urea/HITh-SO3H MNPs/solvent‐free/80°C498This work
1InCl3/H2O/reflux609032
2Co3O4-CS-HPA/EtOH/ultrasound309233
3Nano-Fe3O4@SiO2-SO3H/H2O/70°C259434
4[bmim]Br/solvent‐free/95°C2109135
5Nano-Fe3O4@cellulose-SO3H/H2O/80°C309536
7Fe3O4@urea/HITh-SO3H MNPs/solvent‐free/80°C1596This work

4 Conclusion

In conclusion, a convenient and effective technique has been designed to synthesize 7-aryl-8H-benzo[h]indeno[1,2-b]quinoline-8-one and indeno[2′,1′:5,6]pyrido[2,3-d]pyrimidine derivatives through a one-pot three-component condensation of 1,3-indanedione, aldehyde, and 1-naphthylamine/1,3-dimethyl-6-aminouracil, respectively, using Fe3O4@urea/HITh-SO3H MNPs as a novel heterogeneous magnetic nanocatalyst under solvent-free conditions. Applying an efficient and eco-friendly catalyst, lower loading of the catalyst, magnetical recyclability of the catalyst, omitting organic solvent, simple operation, and high yields of the final products are some benefits of the described protocol. This nanocatalyst was isolated via a permanent magnetic field and recovered efficiently for the six runs without any significant reduction in the catalytic behavior.

  1. Conflict of interest: Authors declare no conflict of interest.

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Received: 2019-10-21
Revised: 2020-03-12
Accepted: 2020-03-18
Published Online: 2020-06-18

© 2020 Shenghao Jiang et al., published by De Gruyter

This work is licensed under the Creative Commons Attribution 4.0 International License.

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