English

• 1.   Introduction

  Magnetic nanoparticles (MNPs) that have been studied extensively for various biological and medical applications, such as magnetic resonance imaging [1], drug delivery [2, 3], bioseparations [4, 5], biomolecular sensors [6, 7], and magneto-thermal therapy [8, 9]. Moreover, other advantages of magnetic nanoparticles as heterogeneous catalyst include their ease of preparation, a large surface area ratio, and ease of recovery from the reaction mixture using an external magnet. In recent decades, magnetic nanoparticles, as efficient and ecofriendly catalysts, have been used in various organic reactions, such as synthesis of a-amino nitriles [10], nucleophilic substitution reactions of benzyl halides [11], 14-aryl-14H-dibenzo[a, j]xanthene derivatives [12], Friedländer quinoline reaction [13], oxidation of sulfides and oxidative coupling of thiols [14], suzuki coupling reactions [15], dihydropyrimidinones derivatives [16, 17], esterifications [18], regioselective azidolysis of epoxides [19], knoevenagel reaction [20], hydrogenation of alkynes [21], biginelli synthesis of 3, 4-dihydropyrimidin-2(1H)-ones/thiones [22], epoxidation of alkenes [23], CO₂ cycloaddition reactions [24], and three-component condensations [25].

  2H-Chromen-2-ones (coumarins) are an important class of compounds that have been studied extensively for various biological and pharmaceutical applications. Biological and pharmaceutical properties, such as anticancer [26], inhibitory of HIV-1 protease [27], and antibacterial [28]. They are also present or used in additives in food, perfumes, cosmetics [29], alcoholic beverages [30], optical brighteners [31], and dispersed fluorescent and laser dyes [32]. Also, these compounds are well documented as therapeutic agents and have been utilized as medicines in ancient Egypt and in aboriginal cultures [33, 34]. 2H-Chromen-2-ones (coumarins) have been prepared by various procedures, including Knoevenagel condensation, Perkin, Pechmann condensation, Reformatsky reaction, Wittig and Claisen rearrangement [35], of which the Pechmann reaction is the most common procedure. The one-pot condensation reaction of various phenols with ethyl acetoacetate has been used as the best procedure for the preparation of coumarin derivatives. Some acidic catalysts have been reported to promote this reaction, including strong mineral acids like sulfuric acid [36], trifluoroacetic acid [37], phosphorous pentachloride [38], and many others of the same type including expensive metal halides of indium [39], and palladium [40] and recently Bi₂(NO₃)₃ [41]. Furthermore, the Pechmann condensation has been used in the presence of different acids, such as Fe₃O₄@SiO₂@EtSO₃H [42], CMK-5 supported sulfonic acid [43], sulfated zirconia [44], molecular iodine [45], Wells-Dawson heteropolyacid [46], and mesoporous zirconium phosphate [47]. However, some of these procedures suffer from at least one of the following disadvantages: unsatisfactory yields, harsh reaction conditions, use of toxic catalysts, longer reaction times, tedious work-up procedures, strongly acidic wastes, and non-recyclable reagents.

  In continuing our work on catalyzed reactions using green catalyst [48], we have synthesized Ag supported on hydroxyapatite-core-shell magnetic γ-Fe₂O₃ nanoparticles as a novel, efficient, and magnetically recyclable catalyst (γ-Fe₂O₃@HAp-Ag NPs) (Scheme 1).

  Scheme 1

  

  图 Scheme 1  The synthesis of γ-Fe₂O₃@HAp-Ag NPs.

  Scheme 1.  The synthesis of γ-Fe₂O₃@HAp-Ag NPs.

  下载: 全尺寸图片 幻灯片

  The γ-Fe₂O₃@HAp-Ag NPs were characterized by FT-IR, TEM, SEM, XRD, and VSM techniques, and applied as a novel, magnetically recyclable, and heterogeneous nanocatalyst for the synthesis of coumarin derivatives by the one-pot condensation of various phenols with ethyl acetoacetate under solvent-and halogen-free conditions (Scheme 2).

  Scheme 2

  

  图 Scheme 2  Synthesis of coumarin derivatives catalyzed by γ-Fe₂O₃@HAp-Ag NPs.

  Scheme 2.  Synthesis of coumarin derivatives catalyzed by γ-Fe₂O₃@HAp-Ag NPs.

  下载: 全尺寸图片 幻灯片

  2.   Experimental

  Reagents and solvents were purchased from Merck, Fluka or Aldrich companies. Melting points were determined in capillary tubes in an electro-thermal C14500 apparatus. The progress of the reaction and the purity of compounds were monitored by TLC using analytical silica gel plates (Merck 60 F250). All known compounds were identified by comparison of their melting points and ¹H NMR and ¹³C NMR data with those of authentic samples. The ¹H NMR (250 MHz) and ¹³C NMR (62.9 MHz) spectra were acquired on a Bruker Avance DPX-250, FT-NMR spectrometer. IR spectra were recorded on a Frontier FT-IR (Perkin Elmer) spectrometer using KBr disks. The phases present in the magnetic materials were analyzed using powder XRD on a Philips (Holland) spectrometer, model X0 Pert with X'Pert with CuKα radiation (λ=1.5401 Å), with the X-ray generator operated at 40 kV and 30 mA. Diffraction patterns were collected from 2θ=20-80°.

  2.1   Preparation of Ag supported on hydroxyapatite-core-shell magnetic γ-Fe₂O₃

  In this study, hydroxyapatite-core-shell γ-Fe₂O₃ NPs were prepared according to the literature procedure [49]. Then the hydroxyapatite-core-shell γ-Fe₂O₃ NPs (0.6 g) was introduced into 150 mL aqueous solution of silver nitrate (6.7 × 10^-3 mol/L) and stirred at r.t. for 6 h. The resulting slurry was filtered, washed, and dried at r.t. under vacuum. Next, the γ-Fe₂O₃@HAp NPs containing Ag was treated with an aqueous solution of KBH₄ (5.0 × 10^-2 mol/L) for 1 h at r.t. Again, the slurry was filtered, washed, and dried at r.t. under vacuum, giving Ag supported on Fe₂O₃@HAp NPs (Scheme 1). The mean size and the surface morphology of the Ag supported on hydroxyapatite-core-shell magnetic γ-Fe₂O₃ were characterized by TEM, SEM, VSM, XRD and FT-IR techniques.

  2.2   General procedure for the Pechmann condensation

  In a round bottom flask, γ-Fe₂O₃@HAp-Ag NPs (10 mg) were added to the mixture of the phenolic compound (1 mmol) and ethyl acetoacetate (1 mmol) at 80 ℃ and the reaction mixture stirred for the appropriate time (Table 3). The progress of the reaction was monitored by TLC (eluent, n-hexane:ethyl acetate, 4:1) analysis. Upon completion of the reaction, EtOH was added to the reaction mixture and the γ-Fe₂O₃@HAp-Ag NPs were separated with an external magnet. The solvent was then removed under reduced pressure and the resulting product was purified by recrystallization using ethanol. The coumarin derivatives were obtained in good to excellent isolated yields (83%-96%). The spectral data (¹H NMR and ¹³C NMR) of some representative compounds are given below:

  7-Hydroxy-4-methyl-2H-chromen-2-one (Table 3, entry 1): ¹H NMR (250 MHz; CDCl₃): δ 10.50 (brs, 1H), 7.54-7.50 (d, 1H, J=9 Hz), 6.76-6.73 (d, 1H, J=8 Hz), 6.65 (s, 1H), 6.072 (brs, 1H), 2.30 (brs, 3H); ¹³C NMR (62.9 MHz, CDCl₃): δ 161.5, 160.7, 155.2, 153.8, 126.9, 113.2, 112.4, 110.6, 102.5, 18.4.

  4, 7-Dimethyl-2H-chromen-2-one (Table 3, entry 4): ¹H NMR (250 MHz; CDCl₃): δ 7.64-7.61 (d, 1H, J=8.25 Hz), 7.19 (brs, 1H), 7.16 (s, 1H), 6.29 (s, 1H), 2.391 (br, 6H); ¹³C NMR (62.9 MHz, CDCl₃): δ 160.3, 153.6, 153.4, 143.2, 125.8, 125.5, 117.6, 116.9, 113.7, 21.4, 18.4.

  7-Methoxy-4-methyl-2H-chromen-2-one (Table 3, entry 5): ¹H NMR (250 MHz; CDCl₃): δ 7.67-7.64 (d, 1H, J=8.5 Hz), 6.95 (s, 1H), 6.92-6.91 (d, 1H, J=2.5 Hz), 6.18 (s, 1H), 3.8 (s, 3H), 2.3 (s, 3H); ¹³C NMR (62.9 MHz, CDCl₃): δ 162.8, 160.5, 155.2, 153.8, 126.8, 113.5, 112.5, 111.5, 101.1, 56.3, 18.5.

  7-Hydroxy-4, 8-dimethyl-2H-chromen-2-one (Table 3, entry 17): ¹H NMR (250 MHz; CDCl₃): δ 10.33 (s, 1H), 7.39-7.35 (d, 1H, J=8.75 Hz), 6.83-6.79 (d, 1H, J=8.5 Hz), 6.05 (s, 1H), 2.30 (s, 3H), 2.11 (s, 3H); ¹³C NMR (62.9 MHz, CDCl₃): δ 160.8, 159.3, 154.0, 153.2, 123.4, 112.3, 112.0, 111.0, 110.3, 18.5, 11.1.

  3.   Results and discussion

  3.1   Characterization of catalyst

  Herein, we present an efficient and simple procedure for the Pechmann reaction using Ag supported on hydroxyapatite-core-shell magnetic γ-Fe₂O₃ nanoparticles as a novel, efficient, and magnetically recyclable catalyst under solvent-and halogen-free conditions at 80 ℃ (Scheme 2). This procedure provides an easy access to a variety of coumarin derivatives. In this study, the structure of the γ-Fe₂O₃@HAp-Ag NPs was characterized by TEM, SEM, VSM, XRD and FT-IR techniques. The scanning electronic microscopy (SEM) image of Ag supported on hydroxyapatite-core-shell magnetic γ-Fe₂O₃ nanoparticles is given in Fig. 1. As can be clearly seen, the SEM of the γ-Fe₂O₃@HAp-Ag NPs showed that the particles of the catalyst were nanosize.

  图 1

  

  图 1  SEM images of γ-Fe₂O₃@HAp-Ag NPs.

  Figure 1.  SEM images of γ-Fe₂O₃@HAp-Ag NPs.

  下载: 全尺寸图片 幻灯片

  The transmission electronic microscopy (TEM) image of Ag supported on hydroxyapatite-core-shell magnetic γ-Fe₂O₃ nanoparticles (MNPs) is given in Fig. 2. As can be clearly seen, the TEM micrograph of the γ-Fe₂O₃@HAp-Ag NPs clearly proved that the particles are nanosize. These nanoparticles consist of relatively small, nearly spherical particles, which is nicely consistent with the value obtained from XRD measurements with diameters of approximately 30 nm for the catalyst.

  图 2

  

  图 2  TEM images of γ-Fe₂O₃@HAp-Ag NPs.

  Figure 2.  TEM images of γ-Fe₂O₃@HAp-Ag NPs.

  下载: 全尺寸图片 幻灯片

  As shown in Fig. 3, X-ray diffraction (XRD) patterns of the synthesized Ag supported on hydroxyapatite-core-shell γ-Fe₂O₃ MNPs display several relatively strong reflection peaks in the 2θ region of 20-70°. Fig. 3B shows the XRD for Ag supported on hydroxyapatite-core-shell magnetic γ-Fe₂O₃ nanoparticles. The crystallinity of the prepared γ-Fe₂O₃@HAp NPs (A) was confirmed by the reflections observed at 2θ values of 31.2, 32.3, 33.1, 34.3, 45.9 and 49.2. It also identified the metallic Ag phase at 2θ of 32.2° and 45.3° attributed to Ag doped catalysts.

  图 3

  

  图 3  XRD pattern of (A) γ-Fe₂O₃@HAp and (B) γ-Fe₂O₃@HAp-Ag NPs.

  Figure 3.  XRD pattern of (A) γ-Fe₂O₃@HAp and (B) γ-Fe₂O₃@HAp-Ag NPs.

  下载: 全尺寸图片 幻灯片

  In another investigation, magnetic measurements of Ag supported on hydroxyapatite-core-shell γ-Fe₂O₃ MNPs were performed at r.t. using a vibrating sample magnetometer (VSM). The magnetization curve in Fig. 4 gives a saturation magnetization value of 13.21 emu/g.

  图 4

  

  图 4  Magnetization curve of γ-Fe₂O₃@HAp-Ag NPs.

  Figure 4.  Magnetization curve of γ-Fe₂O₃@HAp-Ag NPs.

  下载: 全尺寸图片 幻灯片

  The structural properties of synthesized γ-Fe₂O₃@HAp-Ag MNPs (trace A), HAp supported with Fe₃O₄ MNPs (B) [48], and HAp (C) [48] are analyzed by FT-IR (Fig. 5). The band at 3570 cm^-1 corresponds to O-H stretching in the hydroxyapatite structure. The bands at 1095 cm^-1, 1025, and 958 correspond to asymmetric and symmetric stretching vibrations of the phosphate group (PO₄^-3). The peak observed at~2344 cm^-1 is due to asymmetric stretching C-H. The stretching modes of C-O and C=O are observed at~1388 cm^-1 and 1521 cm^-1, respectively. On doping, stronger and wider absorption bands are observed in the region~1170-698 cm^-1 due to the organic capping of silver.

  图 5

  

  图 5  FT-IR spectra of (A) γ-Fe₂O₃@HAp-Ag NPs, (B) γ-Fe₂O₃@HAp, and (C) HAp.

  Figure 5.  FT-IR spectra of (A) γ-Fe₂O₃@HAp-Ag NPs, (B) γ-Fe₂O₃@HAp, and (C) HAp.

  下载: 全尺寸图片 幻灯片

  3.2   Optimization the reaction condition

  After full characterization of γ-Fe₂O₃@HAp-Ag NPs by TEM, SEM, VSM, XRD and FT-IR techniques, its catalytic activity was examined by the Pechmann condensation of various phenols with ethyl acetoacetate to provide coumarin derivatives (Scheme 2). In the first step, as a model reaction, the condensation of ethyl acetoacetate (1 mmol) with resorcinol (1 mmol) under solventfree conditions at r.t. afforded the corresponding 7-hydroxy-4-methyl-2H-chromen-2-one which was conducted using different amounts of γ-Fe₂O₃@HAp-Ag NPs (Table 1). As evident in Table 1, after 90 min, no product was obtained in the absence of the γ-Fe₂O₃@HAp-Ag NPs (Table 1, entry 1). We found that the best results were obtained with 10 mg of the γ-Fe₂O₃@HAp-Ag NPs which was sufficient to promote the reaction efficiently under solvent-free conditions at r.t., and provides the product in 80% yield and in 30 min (Table 1, entry 6). Furthermore, Table 1 indicates that the higher temperature is necessary for the reaction conditions.

  表 1

  

  表 1  The Pechmann reaction between resorcinol and ethyl acetoacetate with different amounts of γ-Fe₂O₃@HAp-Ag NPs.

  Table 1.  The Pechmann reaction between resorcinol and ethyl acetoacetate with different amounts of γ-Fe₂O₃@HAp-Ag NPs.

  下载: 导出CSV

  In the second step, the various temperature effects on the condensation of ethyl acetoacetate (1 mmol) with resorcinol (1 mmol) in the presence of γ-Fe₂O₃@HAp-Ag NPs (10 mg) under solvent-free conditions afforded the corresponding 7-hydroxy-4-methyl-2H-chromen-2-one as a model are studied (Table 2). The best results were obtained when the reaction was performed at 80 ℃ after 20 min in excellent yield (95%). After optimizing the conditions, this reaction was developed with other phenolic compounds under solvent-free conditions at 80 ℃, and the results are summarized in Table 3.

  表 2

  

  表 2  Effect of temperature on the reaction of resorcinol (1 mmol) with ethyl acetoacetate (1 mmol), in the presence of γ-Fe₂O₃@HAp-Ag NPs (10 mg).

  Table 2.  Effect of temperature on the reaction of resorcinol (1 mmol) with ethyl acetoacetate (1 mmol), in the presence of γ-Fe₂O₃@HAp-Ag NPs (10 mg).

  下载: 导出CSV

  表 3

  

  表 3  Syntheses of coumarins via Pechmann condensation of phenols with ethyl acetoacetate in γ-Fe₂O₃@HAp-Ag NPs.

  Table 3.  Syntheses of coumarins via Pechmann condensation of phenols with ethyl acetoacetate in γ-Fe₂O₃@HAp-Ag NPs.

  下载: 导出CSV

  3.3   Using the optimal conditions for the reaction

  Resorcinol (Table 3, entries 1, 2, 3 and 10), 3-methoxyphenol (Table 3, entry 6), 4-methoxyphenol (Table 3, entry 8), 3-aminophenol (Table 3, entry 9), phloroglucinol (Table 3, entries 11, 12 and 13), 3, 5-dihydroxy toluene (Table 3, entry 16), 2, 6-dihydroxy toluene (Table 3, entry 17) reacted with a variety of β-ketoesters in the short reaction time and excellent yield of the corresponding coumarin derivatives were obtained. 3-Methylphenol (Table 3, entry 4), 3-methoxylphenol (Table 3, entry 5), 3, 5-dihydroxy toluene (Table 3, entry 15) reacted with a variety of β-ketoesters in good yields with slightly longer reaction times. The reaction of 1-naphthol, however, requires a longer reaction time to obtain the corresponding coumarin derivative due to presence of another phenyl ring (Table 2, entries 19 and 20). In the case of phenol, one of the interesting feature of this procedure over most of the previous heterogeneous and homogeneous systems, is the formation of 4-methylcoumarin in good yield which required a longer reaction time vs. the reaction of unsubstituted phenol (Table 2, entry 21). Finally, in all cases, the reactions successfully proceeded to give the corresponding coumarin derivatives in good to excellent yield and in short and acceptable reaction time.

  The reusability of the catalysts is an important advantage in green chemistry and heterogeneous catalysis; and also important from an industrial point of view in the large scale operations and commercial applications. In the next stage, recyclability of γ-Fe₂O₃@HAp-Ag NPs was investigated (Fig. 6). For this purpose, the condensation of ethyl acetoacetate (1 mmol) with resorcinol (1 mmol) under solvent-free conditions at 80 ℃ in the presence of 10 mg of γ-Fe₂O₃@HAp-Ag NPs afforded the corresponding 7-hydroxy-4-methyl-2H-chromen-2-one and was selected as the model reaction. After the reaction was carried out under the optimized reaction conditions, the catalyst was separated using an external magnetic field, washed with methanol dried in air and reused for the next reaction. The recovered catalyst was reused for ten consecutive cycles without any significant loss in catalytic activity (Fig. 6).

  图 6

  

  图 6  Reusability of the nanocatalyst.

  Figure 6.  Reusability of the nanocatalyst.

  下载: 全尺寸图片 幻灯片

  In order to investigate the efficiency of this new procedure in comparison with some recently reported protocols, we provide the results of the synthesis of 7-hydroxy-4-methyl-2H-chromen-2-one with various catalysts, such as PVPP-BF₃, CMK-5-SO₃H, sulfated zirconia, I₂, H₆P₂W₁₈O₆₂·24H₂O, and m-ZrP with respect to the amounts of catalyst, reusability of catalyst, and reaction times and yields of the products (Table 4). As presented in Table 4, some of these methods suffer from at least one of the following disadvantages: use of toxic or harmful solvents like toluene [45, 46], reflux conditions [42, 46], very long reaction time for completion of the reaction [42, 44-47], low yield of product [45, 46], high temperature [43, 46, 47], tedious work-up procedures, and non-recyclable reagents [42, 44-46]. As we have determined, γ-Fe₂O₃@HAp-Ag NPs remarkably improves the synthesis of coumarin derivatives; affords excellent yields of product, results in shorter reaction time, requires low (or lower) temperatures, uses recyclable or no reagents and an external magnetic field to reduce purification requirements. These results show that γ-Fe₂O₃@HAp-Ag NPs is a powerful catalyst for the synthesis of coumarin derivatives.

  表 4

  

  表 4  Comparison of various procedures for the synthesis of 7-hydroxy-4-methyl-2H-chromen-2-one with different catalysts.1.

  Table 4.  Comparison of various procedures for the synthesis of 7-hydroxy-4-methyl-2H-chromen-2-one with different catalysts.1.

  下载: 导出CSV

  A proposed mechanism for preparation of 7-hydroxy-4-methyl-2H-chromen-2-one from the reaction of ethyl acetoacetate with resorcinol is shown in Scheme 3. The mechanism for the reaction is assumed to be the same as proposed by Rezaee Nezhad et al. [12, 17] using γ-Fe₂O₃@HAp-Fe²⁺ NPs as a Lewis acid.

  Scheme 3

  

  图 Scheme 3  Proposed reaction mechanism for one-pot synthesis of 7-hydroxy-4-methyl-2H-chromen-2-one promoted by γ-Fe₂O₃@HAp-Ag NPs.

  Scheme 3.  Proposed reaction mechanism for one-pot synthesis of 7-hydroxy-4-methyl-2H-chromen-2-one promoted by γ-Fe₂O₃@HAp-Ag NPs.

  下载: 全尺寸图片 幻灯片

  4.   Conclusion

  In summary, we prepared γ-Fe₂O₃@HAp-Ag NPs as a novel, efficient, and magnetically recyclable catalyst and characterized the material by SEM, TEM, FT-IR, XRD, and VSM spectroscopy. In this study, we have developed an efficient, green, and simple procedure for the synthesis coumarin derivatives by the Pechmann condensation reaction under solvent-and halogen-free conditions at 80 ℃. The significant advantages of the present method include the non-chromatographic purification of the products, a simple experimental procedure, short reaction times and green content of the procedure, high yields of products, and ease of recovery of the reusable catalyst from the reaction mixture using an external magnet.

  Acknowledgment

  We gratefully acknowledge funding from the National Elites Foundation of Iran for this research.

  Appendix A. Supplementary data

  Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.cclet.2016.06.022.

• 1. [1]

     Pankhurst Q.A., Connolly J., Jones S.K., Dobson J.. Applications of magnetic nanoparticles in biomedicine[J]. J. Phys. D. Appl. Phys., 2003, 36:  R167-R181. doi: 10.1088/0022-3727/36/13/201

  2. [2]

     Gupta A.K., Curtis A.S.G.. Surface modified superparamagnetic nanoparticles for drug delivery:interaction studies with human fibroblasts in culture[J]. J. Mater. Sci. Mater. Med., 2004, 15:  493-496. doi: 10.1023/B:JMSM.0000021126.32934.20

  3. [3]

     Neuberger T., Schöpf B., Hofmann H., Hofmann M., von Rechenberg B.. Superparamagnetic nanoparticles for biomedical applications:possibilities and limitations of a new drug delivery system[J]. J. Magn. Magn. Mater., 2005, 293:  483-496. doi: 10.1016/j.jmmm.2005.01.064

  4. [4]

     Wang D.S., He J.B., Rosenzweig N., Rosenzweig Z.. Superparamagnetic Fe₂O₃ beads-CdSe/ZnS quantum dots core-shell nanocomposite particles for cell separation[J]. Nano Lett., 2004, 4:  409-413. doi: 10.1021/nl035010n

  5. [5]

     Xu C.J., Xu K.M., Gu H.W.. Dopamine as a robust anchor to immobilize functional molecules on the iron oxide shell of magnetic nanoparticles[J]. J. Am. Chem. Soc., 2004, 126:  9938-9939. doi: 10.1021/ja0464802

  6. [6]

     Perez J.M., Simeone F.J., Saeki Y., Josephson L., Weissleder R.. Viral-induced selfassembly of magnetic nanoparticles allows the detection of viral particles in biological media[J]. J. Am. Chem. Soc., 2003, 125:  10192-10193. doi: 10.1021/ja036409g

  7. [7]

     Graham D.L., Ferreira H.A., Freitas P.P.. Magnetoresistive-based biosensors and biochips[J]. Trends Biotechnol., 2004, 22:  455-462. doi: 10.1016/j.tibtech.2004.06.006

  8. [8]

     Hiergeist R., Andr W., Buske N.. Application of magnetite ferrofluids for hyperthermia[J]. J. Magn. Magn. Mater., 1999, 201:  420-422. doi: 10.1016/S0304-8853(99)00145-6

  9. [9]

     Jordan A., Scholz R., Wust P., Fähling H., Felix R.. Magnetic fluid hyperthermia (MFH):cancer treatment with AC magnetic field induced excitation of biocompatible superparamagnetic nanoparticles[J]. J. Magn. Magn. Mater., 1999, 201:  413-419. doi: 10.1016/S0304-8853(99)00088-8

  10. [10]

      Kassaee M.Z., Masrouri H., Movahedi F.. Sulfamic acid-functionalized magnetic Fe₃O₄ nanoparticles as an efficient and reusable catalyst for one-pot synthesis of α-amino nitriles in water[J]. Appl. Catal. A Gen., 2011, 395:  28-33. doi: 10.1016/j.apcata.2011.01.018

  11. [11]

      Kiasat A.R., Nazari S.. Magnetic nanoparticles grafted with β-cyclodextrin-polyurethane polymer as a novel nanomagnetic polymer brush catalyst for nucleophilic substitution reactions of benzyl halides in water[J]. J. Mol. Catal. A:Chem., 2012, 365:  80-86. doi: 10.1016/j.molcata.2012.08.012

  12. [12]

      Haeri H.S., Rezayati S., Nezhad E.R., Darvishi H.. Fe²⁺ supported on hydroxyapatite-core-shell-γ-Fe₂O₃ nanoparticles:efficient and recyclable green catalyst for the synthesis of 14-aryl-14H-dibenzo[a, j]xanthene derivatives[J]. Res. Chem. Intermed., 2016, 42:  4773-4784. doi: 10.1007/s11164-015-2318-5

  13. [13]

      Rezayati S., Jafroudi M.T., Nezhad E.R., Hajinasiri R., Abbaspour S.. Imidazolefunctionalized magnetic Fe₃O₄ nanoparticles:an efficient, green, recyclable catalyst for one-pot Friedländer quinoline synthesis[J]. Res. Chem. Intermed., 2016, 42:  5887-5898. doi: 10.1007/s11164-015-2411-9

  14. [14]

      Ghorbani A., Choghamarani -, Ghasemi B., Safari Z., Azadi G.. Schiff base complex coated Fe₃O₄ nanoparticles:a highly reusable nanocatalyst for the selective oxidation of sulfides and oxidative coupling of thiols[J]. Catal. Commun., 2015, 60:  70-75. doi: 10.1016/j.catcom.2014.11.007

  15. [15]

      Taher A., Kim J.B., Jung J.Y., Ahn W.S., Jin M.J.. Highly active and magnetically recoverable Pd-NHC catalyst immobilized on Fe₃O₄ nanoparticle-ionic liquid matrix for Suzuki reaction in water[J]. Synlett, 2009, 15:  2477-2482.

  16. [16]

      Nazari S., Saadat Sh., Fard P.K.. Imidazole functionalized magnetic Fe₃O₄ nanoparticles as a novel heterogeneous and efficient catalyst for synthesis of dihydropyrimidinones by Biginelli reaction[J]. Monatsh. Chem Chem. Mon., 2013, 144:  1877-1882. doi: 10.1007/s00706-013-1085-5

  17. [17]

      Nezhad E.R., Abbasi Z., Sajjadifar S.. Fe²⁺ supported on hydroxyapatite-core-shell-γ-Fe₂O₃ nanoparticles:as a novel, efficient and magnetically-recoverable catalyst for the synthesis of dihydropyrimidinones derivatives[J]. Sci. Iran. C., 2015, 22:  903-910.

  18. [18]

      Jiang Y.Y., Guo C., Xia H.S.. Magnetic nanoparticles supported ionic liquids for lipase immobilization:enzyme activity in catalyzing esterification[J]. J. Mol. Catal. B:Enzym., 2009, 58:  103-109. doi: 10.1016/j.molcatb.2008.12.001

  19. [19]

      Sajjadifar S., Abbasi Z., Nezhad E.R.. Ni²⁺ supported on hydroxyapatite-coreshell γ-Fe₂O₃ nanoparticles:a novel, highly efficient and reusable Lewis acid catalyst for the regioselective azidolysis of epoxides in water[J]. J. Iran. Chem. Soc., 2014, 11:  335-340. doi: 10.1007/s13738-013-0304-7

  20. [20]

      Zhang Y., Xia C.G.. Magnetic hydroxyapatite-encapsulated γ-Fe₂O₃ nanoparticles functionalized with basic ionic liquids for aqueous Knoevenagel condensation[J]. Appl. Catal. A:Gen., 2009, 366:  141-147. doi: 10.1016/j.apcata.2009.06.041

  21. [21]

      Abu R., Reziq -, Wang D.S., Post M., Alper H.. Platinum nanoparticles supported on ionic liquid-modified magnetic nanoparticles:selective hydrogenation catalysts[J]. Adv. Synth. Catal., 2007, 349:  2145-2150. doi: 10.1002/(ISSN)1615-4169

  22. [22]

      Safari J., Zarnegar Z.. Brønsted acidic ionic liquid based magnetic nanoparticles:a new promoter for the Biginelli synthesis of 3, 4-dihydropyrimidin-2(1H)-ones/thiones[J]. New J. Chem., 2014, 38:  358-365. doi: 10.1039/C3NJ01065A

  23. [23]

      Kooti M., Afshari M.. Phosphotungstic acid supported on magnetic nanoparticles as an efficient reusable catalyst for epoxidation of alkenes[J]. Mater. Res. Bull., 2012, 47:  3473-3478. doi: 10.1016/j.materresbull.2012.07.001

  24. [24]

      Zheng X.X., Luo S.Z., Zhang L., Cheng J.P.. Magnetic nanoparticle supported ionic liquid catalysts for CO₂ cycloaddition reactions[J]. Green Chem., 2009, 11:  455-458. doi: 10.1039/b823123k

  25. [25]

      Zhang Q., Su H., Luo J., Wei Y.Y.. A magnetic nanoparticle supported dual acidic ionic liquid:a "quasi-homogeneous" catalyst for the one-pot synthesis of benzoxanthenes[J]. Green Chem., 2012, 14:  201-208. doi: 10.1039/C1GC16031A

  26. [26]

      Wang C.J., Hsieh Y.J., Chu C.Y., Lin Y.L., Tseng T.H.. Inhibition of cell cycle progression in human leukemia HL-60 cells by esculetin[J]. Cancer Lett., 2002, 183:  163-168. doi: 10.1016/S0304-3835(02)00031-9

  27. [27]

      Spino C., Dodier M., Sotheeswaran S.. Anti-HIV coumarins from calophyllum seed oil[J]. Bioorg. Med. Chem. Lett., 1998, 8:  3475-3487. doi: 10.1016/S0960-894X(98)00628-3

  28. [28]

      Fan G.J., Mar W., Park M.K.. A novel class of inhibitors for steroid 5areductase:synthesis and evaluation of umbelliferone derivatives[J]. Bioorg. Med. Chem. Lett., 2001, 11:  2361-2363. doi: 10.1016/S0960-894X(01)00429-2

  29. [29]

      Ghodke S., Chudasama U.. Solvent free synthesis of coumarins using environment friendly solid acid catalysts[J]. Appl. Catal. A, 2013, 453:  219-226. doi: 10.1016/j.apcata.2012.12.024

  30. [30]

      Izquierdo M.E.F., Granados J.Q., Mir M.V., Martinez M.C.L.. Comparison of methods for determining coumarins in distilled beverages[J]. Food. Chem., 2000, 70:  251-258. doi: 10.1016/S0308-8146(00)00071-6

  31. [31]

      Mokhtary M., Najafizadeh F.. Polyvinylpolypyrrolidone-bound boron trifluoride (PVPP-BF3); a mild and efficient catalyst for synthesis of 4-metyl coumarins via the Pechmann reaction[J]. C.R. Chim., 2012, 15:  530-532. doi: 10.1016/j.crci.2012.03.004

  32. [32]

      Ahmed A.I., El-Hakam S.A., Khder A.S., El W.S.A., Yazeed -. Nanostructure sulfated tin oxide as an efficient catalyst for the preparation of 7-hydroxy-4-methyl coumarin by Pechmann condensation reaction[J]. J. Mol. Catal. A Chem., 2013, 366:  99-108. doi: 10.1016/j.molcata.2012.09.012

  33. [33]

      Killard A.J., O'kennedy R., Bogan D.P.. Analysis of the glucuronidation of 7-hydroxycoumarin by HPLC[J]. J. Pharm. Biomed. Anal., 1996, 14:  1585-1590. doi: 10.1016/0731-7085(96)01801-8

  34. [34]

      Semple S.J., Nobbs S.F., Pyke S.M., Reynolds G.D., Flower R.L.P.. Antiviral flavonoid from Pterocaulon sphacelatum, an Australian Aboriginal medicine[J]. J. Ethnopharmacol., 1999, 68:  283-288. doi: 10.1016/S0378-8741(99)00050-1

  35. [35]

      Rajitha B., Kumar V.N., Someshwar P.. Dipyridine copper chloride catalyzed coumarin synthesis via Pechmann condensation under conventional heating and microwave irradiation[J]. Arkivoc., 2006, 2006:  23-27.

  36. [36]

      Patil A.D., Freyer A.J., Eggleston D.S.. The inophyllums, novel inhibitors of HIV-1 reverse transcriptase isolated from the Malaysian tree, Calophyllum inophyllum Linn[J]. J. Med. Chem., 1993, 36:  4131-4138. doi: 10.1021/jm00078a001

  37. [37]

      Woods L.L., Sapp J.. A new one-step synthesis of substituted coumarins[J]. J. Org. Chem., 1962, 27:  3703-3705. doi: 10.1021/jo01057a519

  38. [38]

      Robertson A., Sandrock W.F., Hendry C.B.. CCCXX.X.-Hydroxy-carbonyl compounds. Part V. The preparation of coumarins and 1:4-pyrones from phenol, pcresol, quinol, and α-naphthol[J]. J. Chem. Soc., 1931, :  2426-2432.

  39. [39]

      Bose D.S., Rudradas A.P., Babu M.H.. The indium (Ⅲ) chloride-catalyzed von Pechmann reaction:a simple and effective procedure for the synthesis of 4-substituted coumarins[J]. Tetrahedron Lett., 2002, 43:  9195-9197. doi: 10.1016/S0040-4039(02)02266-9

  40. [40]

      Kadnikov D.V., Larock R.C.. Synthesis of coumarins via palladium-catalyzed carbonylative annulation of internal alkynes by o-Iodophenols[J]. Org. Lett., 2000, 2:  3643-3646. doi: 10.1021/ol0065569

  41. [41]

      Alexander V.M., Bhat R.P., Samant S.D.. Bismuth (Ⅲ) nitrate pentahydrate-a mild and inexpensive reagent for synthesis of coumarins under mild conditions[J]. Tetrahedron Lett., 2005, 46:  6957-6959. doi: 10.1016/j.tetlet.2005.07.117

  42. [42]

      Samadizadeh M., Nouri S., Kiani Moghadam F.. Magnetic nanoparticles functionalized ethane sulfonic acid (MNESA):as an efficient catalyst in the synthesis of coumarin derivatives using Pechmann condensation under mild condition[J]. Res. Chem. Intermed., 2016, 42:  6089-6103. doi: 10.1007/s11164-016-2447-5

  43. [43]

      Zareyee D., Serehneh M.. Recyclable CMK-5 supported sulfonic acid as an environmentally benign catalyst for solvent-free one-pot construction of coumarin through Pechmann condensation[J]. J. Mol. Catal. A:Chem., 2014, 391:  88-91. doi: 10.1016/j.molcata.2014.04.013

  44. [44]

      Rodríguez-Domínguez J.C., Kirsch G.. Sulfated zirconia, a mild alternative to mineral acids in the synthesis of hydroxycoumarins[J]. Tetrahedron Lett., 2006, 47:  3279-3281. doi: 10.1016/j.tetlet.2006.03.030

  45. [45]

      DeGrote J., Tyndall S., Wong K.F., VanAlstine M., Parris -. Synthesis of 7-alkoxy-4-trifluoromethylcoumarins via the von Pechmann reaction catalyzed by molecular iodine[J]. Tetrahedron Lett., 2014, 55:  6715-6717. doi: 10.1016/j.tetlet.2014.10.025

  46. [46]

      Romanelli G.P., Bennardi D., Ruiz D.M.. A solvent-free synthesis of coumarins using a Wells-Dawson heteropolyacid as catalyst[J]. Tetrahedron Lett., 2004, 45:  8935-8939. doi: 10.1016/j.tetlet.2004.09.183

  47. [47]

      Sinhamahapatra A., Sutradhar N., Pahari S., Bajaj H.C., Panda A.B.. Mesoporous zirconium phosphate:an efficient catalyst for the synthesis of coumarin derivatives through Pechmann condensation reaction[J]. Appl. Catal. A, 2011, 394:  93-100. doi: 10.1016/j.apcata.2010.12.027

  48. [48]

      Rezayati S., Nezhad E.R., Hajinasiri R.. 1-(1-Alkylsulfonic)-3-methylimidazolium chloride as a reusable Brønsted acid catalyst for the regioselective azidolysis of epoxides under solvent-free conditions[J]. Chin. Chem. Lett., 2016, 27:  974-978. doi: 10.1016/j.cclet.2016.02.015

  49. [49]

      Donadel K., Felisberto M.D.V., Laranjeira M.C.M.. Preparation and characterization of hydroxyapatite-coated iron oxide particles by spray-drying technique[J]. An. Acad. Bras. Ciênc., 2009, 81:  179-186. doi: 10.1590/S0001-37652009000200004

  50. [50]

      Rahmatpour A., Mohammadian S.. An environmentally friendly, chemoselective, and efficient protocol for the preparation of coumarin derivatives by Pechman condensation reaction using new and reusable heterogeneous Lewis acid catalyst polystyrene-supported GaCl₃[J]. C.R. Chimie, 2013, 16:  271-278. doi: 10.1016/j.crci.2013.01.006

  51. [51]

      Karami B., Kiani M., Hoseini M.A.. In (OTf)₃ as a powerful and recyclable catalyst for Pechmann condensation without solvent[J]. Chin. J. Catal., 2014, 35:  1206-1211. doi: 10.1016/S1872-2067(14)60090-5

• 

  Scheme 1  The synthesis of γ-Fe₂O₃@HAp-Ag NPs.

  下载: 全尺寸图片 幻灯片
  

  Scheme 2  Synthesis of coumarin derivatives catalyzed by γ-Fe₂O₃@HAp-Ag NPs.

  下载: 全尺寸图片 幻灯片
  

  Figure 1  SEM images of γ-Fe₂O₃@HAp-Ag NPs.

  下载: 全尺寸图片 幻灯片
  

  Figure 2  TEM images of γ-Fe₂O₃@HAp-Ag NPs.

  下载: 全尺寸图片 幻灯片
  

  Figure 3  XRD pattern of (A) γ-Fe₂O₃@HAp and (B) γ-Fe₂O₃@HAp-Ag NPs.

  下载: 全尺寸图片 幻灯片
  

  Figure 4  Magnetization curve of γ-Fe₂O₃@HAp-Ag NPs.

  下载: 全尺寸图片 幻灯片
  

  Figure 5  FT-IR spectra of (A) γ-Fe₂O₃@HAp-Ag NPs, (B) γ-Fe₂O₃@HAp, and (C) HAp.

  下载: 全尺寸图片 幻灯片
  

  Figure 6  Reusability of the nanocatalyst.

  下载: 全尺寸图片 幻灯片
  

  Scheme 3  Proposed reaction mechanism for one-pot synthesis of 7-hydroxy-4-methyl-2H-chromen-2-one promoted by γ-Fe₂O₃@HAp-Ag NPs.

  下载: 全尺寸图片 幻灯片

  Table 1.  The Pechmann reaction between resorcinol and ethyl acetoacetate with different amounts of γ-Fe₂O₃@HAp-Ag NPs.

  下载: 导出CSV

  Table 2.  Effect of temperature on the reaction of resorcinol (1 mmol) with ethyl acetoacetate (1 mmol), in the presence of γ-Fe₂O₃@HAp-Ag NPs (10 mg).

  下载: 导出CSV

  Table 3.  Syntheses of coumarins via Pechmann condensation of phenols with ethyl acetoacetate in γ-Fe₂O₃@HAp-Ag NPs.

  下载: 导出CSV

  Table 4.  Comparison of various procedures for the synthesis of 7-hydroxy-4-methyl-2H-chromen-2-one with different catalysts.1.

  下载: 导出CSV
•