Research Article Cite This: ACS Comb. Sci. 2018, 20, 19−25
pubs.acs.org/acscombsci
Novel Multicomponent Synthesis of Pyridine−Pyrimidines and Their Bis-Derivatives Catalyzed by Triazine Diphosphonium Hydrogen Sulfate Ionic Liquid Supported on Functionalized Nanosilica Fahime Rahmani,† Iraj Mohammadpoor-Baltork,*,† Ahmad Reza Khosropour,*,† Majid Moghadam,† Shahram Tangestaninejad,† and Valiollah Mirkhani† †
Catalysis Division, Department of Chemistry, University of Isfahan, Isfahan 81746-73441, Iran S Supporting Information *
ABSTRACT: In this Research Article, we report an efficient synthesis of 1,3-dimethyl-5-aryl-7-(pyridine-3(2)(4)-yl)pyrimidine2,4(1H,3H)-diones via a three-component reaction of aryl aldehydes, 1,3-dimethyl-6-aminouracil and carbonitriles in the presences of triazine diphosphonium hydrogen sulfate ionic liquid supported on functionalized nanosilica (APTADPHS-nSiO2) as a reusable catalyst under microwave irradiation and solvent-free conditions. The bis-derivatives of pyridine−pyrimidines were also efficiently prepared from dialdehydes and dinitriles. In addition, 3-methyl-1H-pyrazole-5-amine was used successfully instead of 1,3-dimethyl-6-aminouracil under the same conditions to afford the corresponding products in high yields. The catalyst can be reused at least five times without any significant loss of its activity. The easy recovery, reusability and excellent activity of the catalyst as well as easy workup are other noteworthy advantages of this method. KEYWORDS: one-pot synthesis, pyrimidine derivatives, multicomponent reactions, acidic ionic liquid, microwave irradiation
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INTRODUCTION
synthesis of pyridine−pyrimidine derivatives is of practical importance and is highly desirable. Recently, several useful organic transformations using supported nanocatalysts have been reported by our research group.19 In continuation of our research in the development of new applications of APTADPHS-nSiO2 catalyst,20 we disclose herein for the first time a novel one-pot multicomponent synthesis of pyridine-pyrimidines and their bis-derivatives via APTADPHSnSiO2 catalyzed reaction between aldehydes/dialdehydes, 1,3-dimethyl-6-aminouracil or 3-methyl-1H-pyrazol-5-amine and carbonitriles/dinitriles under microwave irradiation and solvent-free conditions (Scheme 1).
During the past years, multicomponent reactions (MCRs) have attracted great attention in many useful organic transformations because of their widespread applications for the production of biologically active compounds and complex heterocyclic molecules as well as in the total synthesis of natural products. Compared to conventional multistep synthetic approaches, the MCRs provide outstanding benefits, such as straightforward experimental procedures, high atom economy, high yields, less formation of byproducts, short reaction times, and avoidance of complex isolation and purification of intermediates.1−4 Pyrimidines have emerged as promising and valuable functional components of the very important heterocycles in organic and medicinal chemistry.5−8 Heterocycles containing pyrimidine nucleus possess a variety of useful biological properties including antibacterial, anti-inflammatory, anti-HIV, antimalarial, antihypertensive, antihistaminic, antifungal, antioxidant, antiplasmodial, antitumor, anticancer, antiviral, and analgesia activities.9−18 Because of their wide range of interesting properties and applications, the development of an efficient and novel methodology for the © 2017 American Chemical Society
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RESULTS AND DISCUSSION Initially, to find the optimum conditions, the reaction between 4-nitrobenzaldehyde 1{1} (1 mmol), 1,3-dimethyl-6-aminouracil 2{1}(1 mmol), and pyridine-2-carbonitrile 3{1}(1 mmol) was Received: May 14, 2017 Revised: December 1, 2017 Published: December 7, 2017 19
DOI: 10.1021/acscombsci.7b00079 ACS Comb. Sci. 2018, 20, 19−25
Research Article
ACS Combinatorial Science Scheme 1. Synthesis of Pyridine−Pyrimidines and Their Bis-Derivatives Catalyzed by APTADPHS-nSiO2
Table 1. continued d
Reaction was performed with an applied power of 300 W. eReaction was performed with an applied power of 400 W. fReaction was performed under conventional heating conditions.
Table 1. Optimization of the Reaction Conditions for the Synthesis of 4{1,1,1}a
Figure 1. Diversity of reagents.
entry
catalyst (mol %)
solvent
T (°C)
time (min)
yieldb (%)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20c 21d 22e 23f
none FeCl3 (3) ZnCl2 (3) AlCl3 (3) BiCl3 (3) H3PW12O40H20 (3) P-TSA (3) [Hmim]HSO4 (3) APTADPHS-nSiO2 (3) APTADPHS-nSiO2 (3) APTADPHS-nSiO2 (3) APTADPHS-nSiO2 (3) APTADPHS-nSiO2 (3) APTADPHS-nSiO2 (2) APTADPHS-nSiO2 (2.5) APTADPHS-nSiO2 (4) APTADPHS-nSiO2 (3) APTADPHS-nSiO2 (3) APTADPHS-nSiO2 (3) APTADPHS-nSiO2 (3) APTADPHS-nSiO2 (3) APTADPHS-nSiO2 (3) APTADPHS-nSiO2 (3)
none none none none none none none none none H2O CHCl3 EtOH toluene none none none None None None none none none none
90 90 90 90 90 90 90 90 90 90 60 75 90 90 90 90 70 80 100 90 90 90 90
30 15 15 15 15 15 15 15 15 20 20 20 20 15 15 15 15 15 15 15 15 15 240
0 10 10 25 35 64 60 65 95 0 0 20 10 55 77 95 60 72 95 58 85 95 5
carried out as a model under microwave irradiation solvent-free conditions. In the absence of catalyst, the reaction did not proceed and the starting materials remained intact in the reaction mixture (Table 1, entry 1). The model reaction was then performed in the presence of different catalysts under microwave irradiation (350 W, 90 °C) and solvent-free conditions (entries 2−9). Among the screened catalysts, APTADPHSnSiO2 was found to be the most efficient catalyst and gave the desired product 4{1,1,1} in 95% yield (entry 9). The same reaction was also carried out in various solvents at different temperatures in the presence of 3 mol % APTADPHS-nSiO2 (entries 10−13). As can be seen, the reaction did not proceed in H2O and CHCl3, and very low yields of the desired product was obtained in EtOH and toluene solvents. Thus, solvent-free conditions is essential for this reaction. Next, the effect of the catalyst amount, temperature, and MW power on the yield of the product was investigated. The amount of the catalyst ranging from 2 to 4 mol % were evaluated and the highest yield of the desired product was obtained in the presence of 3 mol % catalyst (entries 9, 14−16). The effect of temperature was examined in the range of 70−100 °C under microwave irradiation (350 W) and solvent free conditions (entries 9, 17−19). When the temperature was increased from 70 to 90 °C, the yield of product 4{1,1,1} was improved from 58% to 95%. Further increase in temperature to 100 °C had no significant effect on the product yield. Consequently, 90 °C was selected as optimum temperature for all the reactions. Finally, the MW power was optimized by carrying out the model reaction at 250, 300, 350, and 400 W (entries 9, 20−22), under solvent-free conditions at 90 °C. The results indicated that MW irradiation at 350 W gave the highest yield.
a
Reaction was performed with an applied power of 350 W. bIsolated yield. cReaction was performed with an applied power of 250 W. 20
DOI: 10.1021/acscombsci.7b00079 ACS Comb. Sci. 2018, 20, 19−25
Research Article
ACS Combinatorial Science Table 2. Synthesis of 1,3-Dimethyl-5-aryl-7-(pyridine-3(2)(4)-yl)pyrimidine-2,4(1H,3H)-diones Catalyzed by APTADPHS-nSiO2a
a Reaction conditions: Aldehyde (1 mmol), aminouracil (1 mmol), pyridine carbonitrile (1 mmol), APTADPHS-nSiO2 (3 mol %) under microwave irradiation (350 W, 90 °C) and solvent-free conditions. bIsolated yield.
yield of the products and the reaction times. It is noteworthy that, while aldehydes containing electron-withdrawing groups are converted to their corresponding pyridine−pyrimidine derivatives by the present protocol under the optimum reaction conditions, those with electron-donating groups (such as 4-methylbenzaldehyde and 4-methoxybenzaldehyde) remain intact. In this respect, the reaction of an equimolar mixture of 4-nitrobenzaldehyde and 4-methylbenzaldehyde with 1,3-dimethyl6-aminouracil and pyridine-2-carbonitrile was investigated under MW irradiation and solvent-free conditions. As shown in Scheme 2, 4-nitrobenzaldehyde is selectively transformed to the corresponding pyridine-pyrimidine derivative, whereas 4-methylbenzaldehyde remains intact in the reaction mixture. Next, we investigated the versatility of this method using dialdehydes under the optimized conditions. In this respect, treatment of terephthaldialdehyde or isophthaldialdehyde with 6-amino-1,3-dimethyluracil and pyridine carbonitriles provided
To clarify the effect of MW, the synthesis of 4{1,1,1} was performed under conventional heating (90 °C) and only 5% of the desired product was produced even after 4 h (entry 23). On the basis of the obtained results, the optimal conditions were 1:1:1:0.03 molar ratio of aldehyde, 1,3-dimethyl-6-aminouracil, pyridine-2-carbonitrile, and APTADPHS-nSiO2 using MW power of 350 W at temperature of 90 °C under solvent-free conditions. Under these optimized conditions, the scope of this reaction was investigated using a series of aldehydes, amines and carbonitriles (Figure 1). As illustrated in Table 2, a variety of pyridine-pyrimidine derivatives were successfully synthesized in high to excellent yields by the reaction of electron deficient aldehydes, 6-amino-1,3-dimethyluracil and carbonitriles in the presence of APTADPHS-nSiO2 catalyst (Table 2). The results showed that the electronic properties of the substituents on the aromatic aldehydes significantly affect the 21
DOI: 10.1021/acscombsci.7b00079 ACS Comb. Sci. 2018, 20, 19−25
Research Article
ACS Combinatorial Science Scheme 2. Selective Conversion of 4-Nitrobenzaldehyde into the Corresponding Pyridine−Pyrimidine in the Presence of 4-Methylbenzaldehyde Catalyzed by APTADPHS-nSiO2
Table 3. Synthesis of Bis-Pyridine−Pyrimidines from Dialdehydes Catalyzed by APTADPHS-nSiO2a
the desired bis-derivatives in high yields within short reaction times (Table 3). In an alternative route, benzene-1,4-dicarbonitrile was used instead of pyridine carbonitriles. Unlike the previous reactions, in this case, solvent-free condition was not appropriate (Table S1). For this purpose, the reaction was carried out in different solvents and acetic acid was found to be the most suitable solvent for this reaction. It is also noteworthy that even in acetic acid solvent, the yield of the product was higher in the presence of catalyst, indicating the efficiency of the catalyst. Under these conditions, 4-nitro- and 3-nitrobenzaldehyde reacted efficiently with benzene-1,4-dicarbonitrile and 1,3-dimethyl-6aminouracil in the presence of APTADPHS-nSiO2 and the desired bis-products were obtained in 80% and 75% yields, respectively (Scheme 3). To further investigate the substrate scope, 1,3-dimethyl-6aminouracil 2{1} was replaced with 3-methyl-1H-pyrazole-5amine 2{2}. As depicted in Table 4, 3-methyl-1H-pyrazole-5amine 2{2} was treated with various aldehydes and pyridine carbonitriles in the presence of APTADPHS-nSiO2 catalyst under the same conditions to afford the desired products in 75−95% yields. It is worth mentioning that, to the best of our knowledge, the synthesis of pyridine-pyrimidines and their bis-derivatives via such a one-pot multicomponent reaction is reported here for the first time. The structures of all products were elucidated by FT-IR, 1 H NMR, and 13C NMR spectra and by elemental analysis. As a representative example, the 1H NMR (400 MHz) spectrum of the product 4{3,1,2} displayed signals at δ 9.52 (d, J = 2.2 Hz, 1H), 8.96 (d, J = 2.2 Hz, 1H), 8.77−8.81 (m, 2H), 8.40−8.43 (m, 2H), 8.07 (d, J = 8.0 Hz, 1H), and 7.29 (d, J = 5.0 Hz, 1H) for eight aromatic protons of pyridine rings. In addition, the signals due to methyl groups were observed at δ 3.69 (s, 3H) and 3.68 (s 3H). In the FT-IR spectrum of the product, the characteristic absorption bands at around 3115 (CH-aromatic), 2988 (CH-aliphatic), 1694 (CO), 1640 (CN), 1468 (CC), 1081 and 1012 (C−N), 772 and 734 cm−1 (CH-bending) were observed. The 13C NMR (100 MHz) spectrum exhibited signals at δ 158.9 and 150.5 for the carbonyl carbons and at δ 167.0, 162.0, 155.1, 149.5, 146.4, 137.0, 131.8, 130.3, 123.7, and 105.4 for the aromatic carbons. Furthermore, the methyl carbons showed their signals at δ 30.8 and 28.3.
a
Reaction conditions: Dialdehyde (1 mmol), aminouracil (2 mmol), pyridine carbonitrile (2 mmol), catalyst (6 mol %) under microwave irradiation (350 W, 90 °C) and solvent-free conditions. bIsolated yield.
A plausible mechanism for the APTADPHS-nSiO2 catalyzed synthesis of 1,3-dimethyl-5-aryl-7-(pyridine-3(2)(4)-yl)pyrimidine-2,4(1H,3H)-diones is suggested in Scheme 4. Initially, the aldehyde 1 is activated by the catalyst to give A. Aminouracil 2 then attacks A to furnish B, which undergoes a heteroDiels−Alder reaction with carbonitrile 3 in the presence of the catalyst to produce intermediate C. Ultimately, oxidative aromatization of C under air and in the presence of the catalyst, 22
DOI: 10.1021/acscombsci.7b00079 ACS Comb. Sci. 2018, 20, 19−25
Research Article
ACS Combinatorial Science Scheme 3. Synthesis of Bis-Pyrimidines from Benzene-1,4dicarbonitrile Catalyzed by APTADPHS-nSiO2
Table 4. Synthesis of 4-Aryl-3-methyl-6-(pyridin-2(3)(4)-yl)1H-pyrazolo[3,4-d]pyrimidines Catalyzed by APTADPHSnSiO2
affords the desired product and releases the catalyst for the next run. Catalyst Recovery and Reuse. The reusability and recycling of catalyst is one of the valuable advantages of green and efficient catalysts. Hence, the reusability of the catalyst was investigated in the reaction of 4-nitrobenzaldehyde (3 mmol) with 1,3-dimethyl-6-aminouracil (3 mmol) and pyridine-2-carbonitrile (3 mmol) in the presence of APTADPHS-nSiO2 (0.09 mmol, 135 mg) under MW irradiation (350 W, 90 °C) and solventfree conditions. After completion of the reaction, EtOH was added, the catalyst was separated by centrifugation and washed several times with EtOH. It was then dried, weighted, and reused in the next run without any reactivation or regeneration. As shown in Table 5, the catalyst could be reused for five consecutive times without significant loss of its activity or lowering the yield of the product. The recovery rate of the catalyst was about 97−98% for each run.
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CONCLUSIONS In summary, we have disclosed a novel, simple, efficient and new route for the synthesis of a variety of pyridine-pyrimidine derivatives via a one-pot multicomponent reaction of aldehydes, 1,3-dimethyl-6-aminouracil or 3-methyl-1H-pyrazole-5-amine and carbonitriles using APTADPHS-nSiO2 as a reusable catalyst under microwave irradiation and solvent-free conditions. In addition, the attractive synthesis of bis-derivatives of pyridinepyrimidines from dialdehydes and dinitrile in the presence of this catalytic system has been developed. Friendly experimental conditions, short reaction times, high yield of the products, easy
a
Isolated yield.
recovery and reuse of the catalyst and prevention of toxic solvent, make this method valuable for the synthesis of pyridinepyrimidine derivatives.
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EXPERIMENTAL PROCEDURES General Information. Melting points were determined using a Stuart Scientific SMP2 apparatus. FT-IR spectra were 23
DOI: 10.1021/acscombsci.7b00079 ACS Comb. Sci. 2018, 20, 19−25
Research Article
ACS Combinatorial Science
product was filtered and washed with EtOH (2 × 5 mL) to afford the pure product 4{1,1,1} in 95% yield. mp: 290− 292 °C. IR (KBr): νmax = 3123 (CH-aromatic), 2976 (CHaliphatic), 1678 (CO), 1665 (CN), 1556 (NO), 1503 (CC), 1450 (CC), 1352 (NO), 1012 (C−N), 830 (CH-bending), 734 (CH-bending) cm−1. 1H NMR (400 MHz, DMSO-d6): δ = 8.73 (d, J = 8.4 Hz, 1H, ArH), 8.42 (d, J = 8.4 Hz, 1H, ArH), 8.35 (d, J = 8.0 Hz, 1H, ArH), 8.20 (d, J = 8.8 Hz, 2H, ArH), 7.88 (d, J = 8.4 Hz, 1H, ArH), 7.56 (d, J = 8.4 Hz, 1H, ArH), 7.48 (d, J = 8.4 Hz, 1H, ArH), 3.75 (s, 3H, CH3), 3.28 (s, 3H, CH3). 13C NMR (100 MHz, DMSO-d6): δ = 170.0 (Ar−C), 166.8 (CN), 162.0 (CN), 159.1 (CO), 150.7 (CN), 150.0 (CO), 147.8 (Ar−CH), 145.0 (Ar−C), 131.8 (Ar−C), 129.9 (Ar−CH), 124.2 (Ar−CH), 123.7 (Ar−CH), 122.6 (Ar−CH), 120.5 (Ar−CH), 109.3 (Ar−C), 30.8 (CH3), 28.1 (CH3). Anal. Calcd for C19H14N6O4: C, 58.46; H, 3.61; N, 21.53. Found: C, 58.40; H, 3.59; N, 21.49.
Scheme 4. Plausible Mechanism for the Synthesis of Pyridine−Pyrimidines Catalyzed by APTADPHS-nSiO2
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ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acscombsci.7b00079. Experimental procedure, 1H and 13C NMR spectra, and elemental analysis data for all products (PDF)
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Table 5. Reusability of the APTADPHS-nSiO2 Catalyst in the Synthesis of 4 {1,1,1}a run
yielda (%)
recovery rate of the catalyst (mg) (%)
1 2 3 4 5 6
95 93 91 89 86 85
135 (−) 132 (98) 129 (98) 127 (98) 123 (97) 121 (98)
AUTHOR INFORMATION
Corresponding Authors
*Phone: 98 313 7934927. Fax: 98 313 6689732. E-mail:
[email protected]. *E-mail:
[email protected]. ORCID
Iraj Mohammadpoor-Baltork: 0000-0001-7998-5401 Majid Moghadam: 0000-0001-8984-1225 Notes
a
Reaction conditions: 4-nitrobenzaldehyde (3 mmol), 6-amino-1,3dimethyluracil (3 mmol), pyridine-2-carbonitrile (3 mmol), and catalyst (0.09 mmol, 135 mg) under microwave irradiation (350 W, 90 °C) and solvent-free conditions. bIsolated yield.
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS The authors are grateful to the Research Council of the University of Isfahan for financial support of this work.
recorded on a Nicolet-Impact 400D instrument in the range of 400−4000 cm−1. The 1H and 13C NMR (400 and 100 MHz) spectra were recorded in a DMSO-d6 solution on a Bruker-Avance 400 spectrometer. Elemental analysis was done on LECO, CHNS932 analyzer. The microwave system used in these experiments includes the following items: Micro-SYNTH Labstation, equipped with a glass door, a dual magnetron system with a pyramid-shaped diffuser, 1000 W delivered power, exhaust system, magnetic stirrer, ‘‘quality pressure” sensor for flammable organic solvents, and a ATCFO fiber optic system for automatic temperature control. Typical Procedure for the Synthesis of 1,3-Dimethyl5-(4-nitrophenyl)-7-(pyridin-2-yl)pyrimido[4,5-d]pyrimidine-2,4(1H,3H)-dione 4a{1,1,1} in the Presence of APTADPHS-nSiO2 Catalyst. A mixture of 4-nitrobenzaldehyde (1.0 mmol), 1,3-dimethyl-6-aminouracil (1.0 mmol), pyridine-2carbonitrile (1.0 mmol), and APTADPHS-nSiO2 (3 mol %, 45 mg) was subjected to microwave irradiation (350 W, 90 °C) under solvent-free conditions. The progress of the reaction was monitored by TLC (eluent: petroleum ether/EtOAc, 2:5). After completion of the reaction, the mixture was stirred with 10 mL EtOH in a few minutes and the catalyst was filtered. The reaction mixture was cooled to room temperature, the precipitated
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