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Novel ionic liquid supported on Fe3O4 nanoparticles and its application as a catalyst in Mannich reaction under ultrasonic irradiation
Accepted Manuscript Novel ionic liquid supported on Fe3O4 nanoparticles and its application as a catalyst in Mannich reaction under ultrasonic irradation Javad Safaei Ghomi, Safura Zahedi PII: DOI: Reference:
S1350-4177(16)30273-5 http://dx.doi.org/10.1016/j.ultsonch.2016.08.003 ULTSON 3330
To appear in:
Ultrasonics Sonochemistry
Received Date: Revised Date: Accepted Date:
20 May 2016 1 August 2016 3 August 2016
Please cite this article as: J. Safaei Ghomi, S. Zahedi, Novel ionic liquid supported on Fe3O4 nanoparticles and its application as a catalyst in Mannich reaction under ultrasonic irradation, Ultrasonics Sonochemistry (2016), doi: http://dx.doi.org/10.1016/j.ultsonch.2016.08.003
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Novel ionic liquid supported on Fe3O4 nanoparticles and its application as a catalyst in Mannich reaction under ultrasonic irradation Javad Safaei Ghomi*1 and Safura Zahedi1,2 1
2
Department of Organic Chemistry, Faculty of Chemistry, University of Kashan, Kashan, 51167, I. R. Iran
Young Researchers and Elite Club, Bandar abbas Branch, Islamic Azad University, Bandar abbas, Iran *Corresponding author. E-mail addresses: [email protected], Fax: +98-361-5912397; Tel.: +98-361-5912385
Abstract A family of novel ionic liquid with L-alanine and choline chloride as environmentally benign materials have been synthesized and grafted on Fe3O4 nanoparticles using easy preparation techniques. The structure of ionic liquid supported on Fe3O4 nanoparticles (ILFe3O4 NPs) characterized by various analyses such as FE-SEM, EDX, XRD, NMR, FTIR and VSM. The catalytic activities of this catalyst are examined in the Mannich reaction for synthesis of β-aminocarbonyl compounds under ultrasonic irradiation. The recyclability of catalyst is investigated, and the results have indicated that the catalyst can be recycled six times without obvious activity decreasing.
Keywords: Ultrasonic irradiation; Mannich reaction; Ionic liquid; L-alanine; magnetite nanoparticles.
1
Introduction Molten salts at ambient temperature containing only ions and no solvent are mentioned to as “ionic liquids” [1-3]. Ionic liquids have very different properties from molecular liquids, making them promising substances for use in a diversity of fields. Nowadays, supported ILs containing different metal particles or ions have been used as catalysts in different reactions, such as the Heck reaction [4,5], hydrogenation[6–8]. Though ILs possessed such promising advantages, their extensive practical application was still prevented by numerous drawbacks: high viscosity, which caused in only a minor part of ionic liquids taking part in the catalyzed reaction; homogeneous reaction, which was difficult for product separation and catalyst recovery; consequently, high cost for the use of relatively large amounts of ILs [9,10]. Therefore, in order to resolve these problems mentioned earlier, an immobilized IL catalyst combining the advantageous characteristics of ionic liquids, inorganic acids and solid acids had been proposed [11,12]. A variety of methodologies and mechanisms have recently been developed based on green chemistry or sonochemistry [13]. Sonochemistry as an innovative and powerful technique has attracted increasing interest in accelerating organic reactions [14-17]. This technique can be extremely efficient and is applicable to a wide variety of practical syntheses. Luche and coworkers have conducted a number of studies which provided the basis for using sonochemistry in organic synthesis [18-21]. The remarkable features of the ultrasound approach in organic reactions are improvement of reaction rates, formation of pure products with high yields and easier operation. This technique is also considered as an aid in terms of energy conservation and waste minimization when compared with traditional methods [22,23]. Magnetic separation provides a very convenient approach for removing and recycling particles/composites by applying external magnetic fields [24–26]. Recently, magnetic 2
particles have been extensively employed as alternative catalyst supports, in view of their convenient catalyst recycling, high surface area resulting in high catalyst loading capacity, high dispersion, and outstanding stability [27–29]. A variety of magnetic supports (such as magnetite, barium ferrite, Fe3O4@SiO2 particles and so on) have been reported [30-32]. Also, recently, some multicomponent reactions were catalyzed by magnetic nanoparticles [33-38]. Mannich reaction is one of the most useful methods for the construction of carbon–carbon bonds in organic chemistry [39]. The reaction is especially useful for the synthesis of βamino carbonyl derivatives [40]. Due to the importance of the Mannich products in organic synthesis, various methods for conducting highly diastereoselective and/or enantioselective Mannich reactions have been developed in the past [41]. According to the ways that the reactions are conducted, Mannich reactions may be generally divided into direct Mannich reactions and indirect Mannich reactions. Because direct Mannich reaction does not require the use of preformed enolates or their equivalents as the substrates, it has many advantages over the indirect Mannich reaction, such as better atom economy and operational simplicity [42]. Recently, we have reported organometallic magnetite nanoparticles for the synthesis of βaminocarbonyl compunds via mannich reaction [43]. Here we wish to report the novel ionic liquid-Fe3O4 NPs-catalyzed highly anti-selective three component direct Mannich reaction of aromatic aldehydes, amines and cyclohexanone (Scheme 1). 2. Experimental 2.1. Materials and Apparatus All substrates were purchased from Merck Company (Germany) Sigma---Aldrich and merck. The ultrasonic irradiation was used in reactions by a multiwave ultrasonic 3
generator (Sonicator 3200;
Bandelin, MS
73,
Germany),
equipped
with a
converter/transducer and titanium oscillator (horn), 12.5mm in diameter, operating at 20 kHz with a maximum power output of 200 W. The ultrasonic generator automatically adjusted the power level.1H NMR and 13C NMR spectra were measured respectively at 400 and 100 MHz. The solvent used for NMR spectroscopy was CDCl3, using tetramethylsilane as the internal reference. The IR spectra of all compounds were recorded on FT-IR Magna 550 apparatus using with KBr plates. The elemental analyses (C, H, N) were obtained from a Carlo ERBA Model EA1108 analyzer. Melting points were determined on Electro thermal 9200, and are not corrected. Powder X-ray diffraction (XRD) was carried out on a Philips diffractometer of X’pert company with mono chromatized Cu Ka radiation (k = 1.5406 Å). Microscopic morphology of products was visualized by SEM (LEO 1455VP). Also, the magnetic property of magnetite nanoparticle has been measured with a vibrating sample magnetometer (VSM, PPMS-9T) at 300 K in Iran (Kashan University).
2.2. Preparation of the magnetic Fe3O4 nanoparticles (MNPs) Briefly, MNPs were prepared by the chemical co-precipitation of Fe+3 (FeCl3/0.5 M) and Fe+2 (FeCl2/0.5 M) in a molar ratio of 1.75:1 under nitrogen. The pH of the solution was reached to 9.0 by quickly adding of ammonia aqueous solution under rapid stirring. Black Fe3O4 MNPs were formed and exhibited a strong magnetic response; they were separated by magnetic field and finally washed thoroughly with distilled water and dried o
at 60 C under vacuum.
2.3. Preparation of ionic liquid Sodium l-2-(1-imidazolyl) propanoic acid (I) [44]. Formaldehyde water solution (36%, 16.7 g) and glyoxal water solution (32%, 36.2 g) were added to a 250 mL, three4
necked flask provided with a stirrer and reflux condenser. While the mixture was heated at 50 °C with stirring, a mixture of alanine (17.8 g, 0.2 mol), ammonia solution (28%, 12.1 g), and sodium hydroxide solution (10%, 80 g) was added in small portions during 0.5 h. After the mixture was stirred for an additional 4 h at 50 °C, the water was removed under reduced pressure. The crude product, sodium l-2-(1-imidazolyl) 1
propanoic acid (I), was obtained. H NMR δ 1.59-1.61 (d, J=7.30 Hz, 3H), 4.85-4.90 (q, J=7.29 Hz, 1H), 7.35 (s, 2H), 8.73 (s, 1H) (Fig. 1). Afterwards, sodium l-2-(1-imidazolyl) o
propanoic acid (I) and Choline chloride (25 mL) were refluxed at 80 C for 12 h in the absence of any solvent. At the end, (3-chloro-propyl) trimethoxysilane (31 mL) were o
added to mixture and refluxed at 80 C for 3 days in the absence of any catalyst and solvent under N2 atmosphere. The unreacted materials were washed with diethyl ether (3 * 8 mL). The diethyl ether was removed under reduced pressure at room temperature, and then was heated under high vacuum, to yield a yellowish viscous liquid. The isolated yield was 98%. 1H NMR δ 1.22 (m, 4H), 1.48-1.57 (d, J=7.30 Hz, 3H), 1.69 (m, 2H), 3.70 (m, 22H), 4.85-4.90 (q, J=7.29 Hz, 1H), 6.80 (d, 1H), 7.51 (d, 1H), 8.80 (s, 1H). < Fig. 1>
2.4. Modification of magnetic nanoparticles with ionic liquid (IL---MNPs) Freshly prepared magnetite nanoparticles (2 g) were suspended in ethanol (95%, 250 mL), and sonicated for 60 min. The resulting suspension was mechanically stirred, followed by the addition of a solution of ethanol (95%, 100 mL) containing ionic liquid (6 ml) and concentrated ammonia (28%, 1 mL). Stirring under N2 was continued for 36 h. The modified magnetite nanoparticles were magnetically separated and washed three times with ethanol (95%, 50 mL) and dried under vacuum for 24 h.
2.5. General procedure for Mannich reaction catalyzed by catalyzed by IL---MNPs 5
2.5.1. Typical heating method In a typical mannich reaction, arylaldehyde (2.5 mol), arylamine (2.5 mol) cyclohexanon (3 mol) and EtOH (20 mL) were added to the IL---MNPs (0.001 g) in a 50mL flask equipped with a heating arrangement and a stirrer and the temperature was set at reflux condition. After the reaction was completed, the catalyst was separated by an external magnet. The reaction mixture was purified by flash column chromatography to give the pure β -amino ketone derivatives 2.5.2. Ultrasound irradiation The aromatic aldehyde (1) (2.5 mmol), aromatic amine (2) (2.5 mmol), cyclohexanone (3) (3.0 mmol), IL---MNPs (0.001 g) and EtOH (20 mL) were added into a 25 mL round bottomed flask. The reaction mixture was sonicated under 75 W for the period of time (the reaction was monitored by TLC). The solvent was eliminated under decreased pressure, and the products were puri• ed by silica column chromatography.
2.6. Representative Spectral data for 4d and 4i 2.6.1. 2-(phenyl)(phenylamino)methyl)cyclohexanone (4a). 1
H NMR (400 MHz, CDCl3) δ: 7.65 (d, J=8.0 Hz, 1H, Ar), 7.54 (m, 1H, Ar), 7.21 (m, 1H,
Ar), 7.14–7.08 (m, 4H, Ar), 6.68 (d, J=7.2 Hz, 1H, Ar), 6.56 (d, J=8.0 Hz, 2H, Ar) 4.92 (br s, 1H, NH), 4.85 (d, J=6.4 Hz, 1H, CH), 2.98–2.93 (m, 1H), 2.45–2.33 (m, 2H), 2.15–1.94 (m, 4H), 1.88–1.55 (m, 2H); IR (KBr, ʋ, cm-1): 3395.45, 1696.69, 1602.76, 1501.64, 809.08; 13C NMR (100 MHz, CDCl3) δ: 212.79, 145.69, 140.33, 131.31, 129.08, 128.90, 128.32, 127.44, 123.61, 116.83, 113.11, 58.59, 55.99, 41.80, 32.74, 28.85, 23.80; Calcd for C19H21NO: C, 81.68; H, 7.58; N, 5.01. Found: C, 81.67; H, 7.55; N, 5.06. 2.6.2. 2-(4-Chlorophenylamino)(phenyl)methyl)cyclohexanone (4b).
6
1
H NMR (400 MHz, CDCl3) δ: 7.68 (d, J=8.0 Hz, 1H, Ar), 7.58 (m, 1H, Ar), 7.20(m, 1H,
Ar), 7.18–7.09 (m, 4H, Ar), 6.69 (d, J=7.2 Hz, 1H, Ar), 6.57 (d, J=8.0 Hz, 2H, Ar) 4.90 (br s, 1H, NH), 4.83 (d, J=6.4 Hz, 1H, CH), 2.93–2.89 (m, 1H), 2.48–2.35 (m, 2H), 2.15–1.94 (m, 4H), 1.86–1.53 (m, 2H); IR (KBr, ʋ, cm-1): 3393.45, 1693.69, 1601.76, 1503.64, 809.08; 13C NMR (100 MHz, CDCl3) δ: 212.89, 144.69, 141.23, 130.41, 129.08, 128.90, 128.42, 126.84, 122.91, 117.63, 111.91, 56.59, 54.99, 42.80, 30.74, 28.85, 22.98; Calcd for C19H20ClNO: C, 72.72; H, 6.42; N, 4.46. Found: C, 72.70; H, 6.45; N, 4.47. 2.6.3. 2-(phenyl (m-tolylamino)methyl)cyclohexanone (4c). 1
H NMR (400 MHz, CDCl3) δ: 7.72 (d, J=8.0 Hz, 1H, Ar), 7.68 (m, 1H, Ar), 7.25 (m, 1H,
Ar), 7.19–7.09 (m, 4H, Ar), 6.67 (d, J=7.2 Hz, 1H, Ar), 6.55 (d, J=8.0 Hz, 2H, Ar) 4.91 (br s, 1H, NH), 4.80 (d, J=6.4 Hz, 1H, CH), 2.90–2.84 (m, 1H), 2.52–2.45 (m, 2H), 2.25–2.12 (m, 4H), 2.08 (s, 3H, CH3), 1.96–1.73 (m, 2H); IR (KBr, ʋ, cm-1): 3390.45, 1694.69, 1601.86, 1501.64, 809.08;
13
C NMR (100 MHz, CDCl3) δ: 213.39, 144.69, 140.63, 130.51, 129.28,
128.90, 128.52, 125.84, 121.91, 118.63, 112.91, 58.59, 55.99, 40.80, 32.74, 28.85, 25.34, 23.98; Calcd for C20H23NO: C, 81.87; H, 7.90; N, 4.77. Found: C, 81.85; H, 7.88; N, 4.79. 2.6.4. 2-((2-Chlorophenyl)(phenylamino)methyl)cyclohexanone (4d). 1
H NMR (400 MHz, CDCl3) δ: 7.61 (d, J=8.0 Hz, 1H, Ar), 7.53 (m, 1H, Ar), 7.24 (m, 1H,
Ar), 7.13–7.05 (m, 3H, Ar), 6.66 (d, J=7.2 Hz, 1H, Ar), 6.54 (d, J=8.0 Hz, 2H, Ar) 4.91 (br s, 1H, NH), 4.81 (d, J=6.4 Hz, 1H, CH), 2.99–2.95 (m, 1H), 2.41–2.30 (m, 2H), 2.14–1.95 (m, 4H), 1.85–1.59 (m, 2H); IR (KBr, ʋ, cm-1): 3396.45, 1697.69, 1601.76, 1502.64, 809.08; 13C NMR (100 MHz, CDCl3) δ: 212.89, 146.69, 140.43, 132.31, 129.01, 128.90, 128.28, 127.34, 123.61, 117.23, 113.11, 57.59, 54.99, 42.80, 32.74, 27.85, 24.80; Calcd for C19H20ClNO: C, 72.72; H, 6.42; N, 4.46. Found: C, 72.69; H, 6.35; N, 4.41. 2.6.5. 2-((4-methylphenyl)(phenylamino)methyl)cyclohexanone (4e).
7
1
H NMR (400 MHz, CDCl3) δ: 7.70 (d, J=8.0 Hz, 1H, Ar), 7.65 (m, 1H, Ar), 7.28 (m, 1H,
Ar), 7.22–7.10 (m, 4H, Ar), 6.69 (d, J=7.2 Hz, 1H, Ar), 6.57 (d, J=8.0 Hz, 2H, Ar) 4.92 (br s, 1H, NH), 4.81 (d, J=6.4 Hz, 1H, CH), 2.94–2.88 (m, 1H), 2.53–2.46 (m, 2H), 2.28–2.18 (m, 4H), 2.10 (s, 3H, CH3), 1.96–1.73 (m, 2H); IR (KBr, ʋ, cm-1): 3390.45, 1694.69, 1601.86, 1501.64, 809.08;
13
C NMR (100 MHz, CDCl3) δ: 212.39, 143.89, 141.63, 131.51, 129.58,
128.88, 128.42, 126.84, 122.51, 116.63, 113.91, 57.59, 54.99, 41.80, 31.74, 29.85, 24.34, 22.98; Calcd for C20H23NO: C, 81.87; H, 7.90; N, 4.77. Found: C, 81.91; H, 7.93; N, 4.72. 2.6.6. 2-(4-Chlorophenyl)(phenylamino)methyl)cyclohexanone (4f). 1
H NMR (400 MHz, CDCl3) δ: 7.75 (d, J=8.0 Hz, 1H, Ar), 7.64 (m, 1H, Ar), 7.28 (m, 1H,
Ar), 7.20–7.12 (m, 4H, Ar), 6.71 (d, J=7.2 Hz, 1H, Ar), 6.60 (d, J=8.0 Hz, 2H, Ar) 4.91 (br s, 1H, NH), 4.82 (d, J=6.4 Hz, 1H, CH), 2.98–2.86 (m, 1H), 2.68–2.45 (m, 2H), 2.25–1.99 (m, 4H), 1.88–1.59 (m, 2H); IR (KBr, ʋ, cm-1): 3392.45, 1692.69, 1602.76, 1501.64, 809.08; 13C NMR (100 MHz, CDCl3) δ: 212.89, 143.69, 142.23, 131.01, 129.18, 128.90, 127.82, 126.84, 123.91, 118.63, 112.91, 57.59, 55.99, 41.80, 32.74, 28.85, 21.98; Calcd for C19H20ClNO: C, 72.72; H, 6.42; N, 4.46. Found: C, 72.75; H, 6.43; N, 4.44. 2.6.7. 2-(4-Bromophenyl)(phenylamino)methyl)cyclohexanone (4g). 1
H NMR (400 MHz, CDCl3) δ: 7.73 (d, J=8.0 Hz, 1H, Ar), 7.62 (m, 1H, Ar), 7.29 (m, 1H,
Ar), 7.21–7.15 (m, 4H, Ar), 6.75 (d, J=7.2 Hz, 1H, Ar), 6.63 (d, J=8.0 Hz, 2H, Ar) 4.91 (br s, 1H, NH), 4.81 (d, J=6.4 Hz, 1H, CH), 2.99–2.88 (m, 1H), 2.69–2.49 (m, 2H), 2.35–2.19 (m, 4H), 1.98–1.69 (m, 2H); IR (KBr, ʋ, cm-1): 3392.45, 1691.69, 1603.76, 1502.64, 809.08; 13C NMR (100 MHz, CDCl3) δ: 213.89, 144.69, 141.23, 131.01, 129.18, 128.90, 127.82, 126.84, 124.91, 118.73, 113.91, 58.59, 55.99, 43.80, 31.74, 28.85, 22.98; Calcd for C19H20BrNO: C, 63.70; H, 5.63; N, 3.91. Found: C, 63.72; H, 5.65; N, 3.89. 2.6.8. 2-((4-Chlorophenyl)(p-tolylamino)methyl)cyclohexanone (4h).
8
1
H NMR (400 MHz, CDCl3) δ: 7.79 (d, J=8.0 Hz, 1H, Ar), 7.69 (m, 1H, Ar), 7.38 (m, 1H,
Ar), 7.28–7.15 (m, 2H, Ar), 6.79 (d, J=7.2 Hz, 1H, Ar), 6.67 (d, J=8.0 Hz, 2H, Ar) 4.91 (br s, 1H, NH), 4.81 (d, J=6.4 Hz, 1H, CH), 2.94–2.88 (m, 1H), 2.53–2.46 (m, 2H), 2.28–2.18 (m, 4H), 2.10 (s, 3H, CH3), 1.96–1.73 (m, 2H); IR (KBr, ʋ, cm-1): 3390.45, 1693.69, 1602.86, 1501.64, 809.08;
13
C NMR (100 MHz, CDCl3) δ: 213.39, 144.89, 142.63, 131.51, 129.58,
128.88, 127.82, 126.84, 122.51, 117.63, 113.91, 57.59, 54.99, 41.80, 31.74, 29.85, 23.94, 22.98; Calcd for C20H22ClNO: C, 73.27; H, 6.76; N, 4.27. Found: C, 73.29; H, 6.78; N, 4.24. 2.6.9. 2-((4-Methoxyphenyl)(phenylamino)methyl)cyclohexanone (4i). 1
H NMR (400 MHz, CDCl3) δ: 7.25 (d, J=8.4 Hz, 2H, Ar), 7.14 (d, J=7.6 Hz, 2H, Ar),
7.10-7.07 (m, 2H, Ar), 6.63 (t, J=7.2 Hz, 1H, Ar), 6.66 (d, J=8.4 Hz, 2H, Ar), 4.71 (br s, 1H, NH), 4.62 (d, J=7.2 Hz, 1H, CH), 3.66 (s, 3H, OMe), 2.76–2.72 (m, 1H), 2.38–2.34 (m, 2H), 1.93–1.83 (m, 4H,), 1.75–1.68 (m, 3H); IR (KBr, ʋ, cm-1): 3332.42, 1707.26, 1600.92, 1532.21, 800.33;
13
C NMR (100 MHz, CDCl3) δ: 212.73, 147.01, 138.38, 136.47, 129.21,
128.77, 126.96, 117.16, 113.34, 57.39, 57.30, 41.43, 30.92, 27.92, 23.28, 20.81; Calcd for C20H23NO2: C, 77.64; H, 7.49; N, 4.53. Found: C, 77.43; H, 7.56; N, 4.54. 2.6.10. 2-((phenyl)(p-tolyl)methyl)cyclohexanone (4j). 1
H NMR (400 MHz, CDCl3) δ: 7.72 (d, J=8.0 Hz, 1H, Ar), 7.68 (m, 1H, Ar), 7.24 (m, 1H,
Ar), 7.20–7.08 (m, 4H, Ar), 6.65 (d, J=7.2 Hz, 1H, Ar), 6.53 (d, J=8.0 Hz, 2H, Ar) 4.91 (br s, 1H, NH), 4.82 (d, J=6.4 Hz, 1H, CH), 2.94–2.88 (m, 1H), 2.53–2.46 (m, 2H), 2.28–2.18 (m, 4H), 2.08 (s, 3H, CH3), 1.96–1.73 (m, 2H); IR (KBr, ʋ, cm-1): 3391.45, 1692.69, 16031.86, 1501.64, 809.08;
13
C NMR (100 MHz, CDCl3) δ: 212.39, 144.89, 142.63, 130.81, 129.58,
128.88, 128.42, 126.84, 122.51, 117.63, 112.91, 58.59, 54.99, 41.80, 31.74, 29.85, 25.34, 22.98; Calcd for C20H23NO: C, 81.87; H, 7.90; N, 4.77. Found: C, 81.85; H, 7.893; N, 4.79. 2.6.11. 2-((4-methylphenyl)(4-Chloroamino)methyl)cyclohexanone (4k).
9
1
H NMR (400 MHz, CDCl3) δ: 7.78 (d, J=8.0 Hz, 1H, Ar), 7.69 (m, 1H, Ar), 7.35 (m, 1H,
Ar), 7.29–7.17 (m, 2H, Ar), 6.79 (d, J=7.2 Hz, 1H, Ar), 6.66 (d, J=8.0 Hz, 2H, Ar) 4.91 (br s, 1H, NH), 4.83 (d, J=6.4 Hz, 1H, CH), 2.94–2.88 (m, 1H), 2.53–2.46 (m, 2H), 2.28–2.18 (m, 4H), 2.11 (s, 3H, CH3), 1.96–1.73 (m, 2H); IR (KBr, ʋ, cm-1): 3390.45, 1693.69, 1602.86, 1501.64, 809.08;
13
C NMR (100 MHz, CDCl3) δ: 212.49, 144.59, 141.63, 132.51, 129.58,
128.88, 127.82, 126.84, 123.51, 118.63, 113.91, 57.59, 54.99, 41.80, 32.74, 29.85, 24.94, 22.98; Calcd for C20H22ClNO: C, 73.27; H, 6.76; N, 4.27. Found: C, 73.23; H, 6.74; N, 4.28. 2.6.12. 2-((2-Methoxyphenyl)(phenylamino)methyl)cyclohexanone (4l). 1
H NMR (400 MHz, CDCl3) δ: 7.28 (d, J=8.4 Hz, 2H, Ar), 7.18 (d, J=7.6 Hz, 2H, Ar),
7.10-7.07 (m, 2H, Ar), 6.68 (t, J=7.2 Hz, 1H, Ar), 6.65 (d, J=8.4 Hz, 2H, Ar), 4.81 (br s, 1H, NH), 4.72 (d, J=7.2 Hz, 1H, CH), 3.58 (s, 3H, OMe), 2.76–2.72 (m, 1H), 2.38–2.34 (m, 2H), 1.93–1.83 (m, 4H,), 1.75–1.68 (m, 3H); IR (KBr, ʋ, cm-1): 3331.42, 1706.26, 1601.92, 1532.21, 800.33;
13
C NMR (100 MHz, CDCl3) δ: 212.73, 145.01, 138.38, 136.47, 129.21,
129.77, 126.96, 117.16, 113.34, 57.39, 57.30, 41.43, 30.92, 27.92, 24.28, 20.81; Calcd for C20H23NO2: C, 77.64; H, 7.49; N, 4.53. Found: C, 77.68; H, 7.52; N, 4.50. 2.6.13. 2-(2-Bromophenyl)(phenylamino)methyl)cyclohexanone (4m). 1
H NMR (400 MHz, CDCl3) δ: 7.77 (d, J=8.0 Hz, 1H, Ar), 7.68 (m, 1H, Ar), 7.29 (m, 1H,
Ar), 7.21–7.18 (m, 4H, Ar), 6.74 (d, J=7.2 Hz, 1H, Ar), 6.63 (d, J=8.0 Hz, 2H, Ar) 4.91 (br s, 1H, NH), 4.81 (d, J=6.4 Hz, 1H, CH), 2.99–2.88 (m, 1H), 2.69–2.49 (m, 2H), 2.35–2.19 (m, 4H), 1.98–1.69 (m, 2H); IR (KBr, ʋ, cm-1): 3391.45, 1692.69, 1602.76, 1502.64, 809.08; 13C NMR (100 MHz, CDCl3) δ: 212.89, 143.69, 140.23, 131.01, 129.18, 128.90, 127.82, 126.84, 124.91, 118.73, 113.91, 58.59, 56.99, 43.80, 33.74, 28.85, 22.98; Calcd for C19H20BrNO: C, 63.70; H, 5.63; N, 3.91. Found: C, 63.68; H, 5.60; N, 3.95. 2.6.13. 2-((2,3-dimethoxyphenyl)(phenylamino)methyl)cyclohexanone (4n).
10
1
H NMR (400 MHz, CDCl3) δ: 7.38 (d, J=8.4 Hz, 2H, Ar), 7.21 (d, J=7.6 Hz, 2H, Ar),
7.12-7.07 (m, 1H, Ar), 6.68 (t, J=7.2 Hz, 1H, Ar), 6.65 (d, J=8.4 Hz, 2H, Ar), 4.81 (br s, 1H, NH), 4.78 (d, J=7.2 Hz, 1H, CH), 3.56 (s, 6H, OMe), 2.76–2.72 (m, 1H), 2.38–2.34 (m, 2H), 1.93–1.83 (m, 4H,), 1.75–1.68 (m, 3H); IR (KBr, ʋ, cm-1): 3331.42, 1703.26, 1601.92, 1533.21, 800.33;
13
C NMR (100 MHz, CDCl3) δ: 212.73, 144.01, 137.38, 138.47, 129.21,
129.77, 127.96, 117.16, 114.34, 57.39, 56.30, 48.56, 41.43, 30.92, 27.92, 24.28, 20.81; Calcd for C21H25NO3: C, 74.31; H, 7.42; N, 4.13. Found: C, 74.35; H, 7.46; N, 4.09. 2.6.15. 2-((2,5-dimethoxyphenyl)(phenylamino)methyl)cyclohexanone (4o). 1
H NMR (400 MHz, CDCl3) δ: 7.45 (d, J=8.4 Hz, 2H, Ar), 7.27 (d, J=7.6 Hz, 2H, Ar),
7.15-7.09 (m, 1H, Ar), 6.72 (t, J=7.2 Hz, 1H, Ar), 6.69 (d, J=8.4 Hz, 2H, Ar), 4.81 (br s, 1H, NH), 4.75 (d, J=7.2 Hz, 1H, CH), 3.58 (s, 6H, OMe), 2.76–2.72 (m, 1H), 2.38–2.34 (m, 2H), 1.93–1.83 (m, 4H,), 1.75–1.68 (m, 3H); IR (KBr, ʋ, cm-1): 3331.42, 1703.26, 1601.92, 1533.21, 800.33;
13
C NMR (100 MHz, CDCl3) δ: 212.73, 143.01, 138.38, 137.47, 129.21,
129.77, 127.56, 118.16, 114.44, 57.59, 56.30, 48.96, 40.43, 30.92, 27.92, 24.28, 20.81; Calcd for C21H25NO3: C, 74.31; H, 7.42; N, 4.13. Found: C, 74.34; H, 7.45; N, 4.11. 3. Results and discussion The overall schematic procedure used to synthesize the magnetic catalyst was illustrated in Scheme 2. The nanoparticles of ionic liquid-Fe3O4 were characterized by Xray diffraction spectroscopy (XRD), FTIR, VSM and scanning electron microscopy.
The crystalline structure of ionic liquid-Fe3O4 was also characterized by XRD analysis. As shown in Fig. 2, all of the diffraction peaks can be indexed and assigned to the cubic structure of Fe3O4, which is in good agreement with the literature values (JCPDS Card No. 11
01-1111). In the pattern assigned to magnetite, diffraction peaks at around 30.4°, 35.7°, 43.4°,47.3°, 54.0°, 57.4°, 63.0° and 74.5° correspond to the (111), (220), (311), (222), (400), (311), (422) and (440) reflections, respectively. The large peak widths are ascribed to the formation of nano-sized magnetite particles. In addition, the specific surface area was measured by nitrogen physisorption (the BET method), the specific surface area was approximately 94 m2/g. Also, the theoretical particle size was calculated from the surface area and magnetite density (5.18 g/cm3) from the equation was 12.3 nm.
= (
6000 )
×
Figure 3 also compares the FTIR spectrum of ionic liquid-Fe3O4 (Fig. 3c), ionic liquid (Fig. 3b) and Fe3O4 (Fig. 3a). Some absorption bands are common between the spectra of a and c. For example, the bands at 577 cm-1 and 567 cm-1 arising from stretching vibrations of Fe-O bonds. The strong band at around 3420 cm-1 is due to the O–H stretching vibration. Both the spectra of b and c show the characteristic band at 1620 cm-1 arising from C=O stretching of the carboxylate moiety. The scanning electron microscopy (FE-SEM) image shows that the nanoparticles of ionic liquid-Fe3O4 were produced as uniform particles and the average size of the encapsulated nano-magnetite particles are about 33.5 ± 5.0 nm (Fig. 4a). The EDX analysis verified the core–shell nature of the catalyst by showing the distribution of iron and other elements in the material (Fig. 4b).
12
The magnetic properties of ionic liquid-Fe3O4 nanoparticles were measured via vibrating sample magnetometer (VSM) at room temperature (Fig. 5). It can be seen that the saturation magnetization (Ms) value of the samples are 50.5 emu/g and 30.5 emu/g for Fe3O4 and of ionic liquid-Fe3O4 nanoparticles, respectively. Thus, our catalyst can be recovered by external magnetic field. Malvern Zetasizer Nano Dynamic Light Scattering (DLS) machine was used to measure the hydrodynamic diameter of the magnetite nanoparticles (Fig. 6).
In this study, the catalytic activity and diastereoselectivity of IL–MNPs were tested in the model Mannich reaction of benzaldehyde, aniline and cyclohexanone. This was performed in order to carry out the Mannich reaction in a simple, efficient and inexpensive way. The model reaction was checked in the presence of different amount of IL-MNPs at a range of various temperatures and also under ultrasonic irradiation in various solvents. The results are shown in Table 1. As this Table indicates, the best results were obtained when the reaction was performed using 1mg of the catalyst in EtOH under ultrasonic irradiation.
In order to assess the generality and efficacy of catalyst for the production of βaminocarbonyl, arylaldehydes (with various substituents) were reacted with arylamine and cyclohexanone under the optimal reaction conditions. The results are summarized in Table 2. As the data in this Table show, the catalyst was general and highly efficient for the reaction; all aromatic aldehydes (containing electron-withdrawing substituents, electron-donating The proposed mechanism of Mannich reaction catalyzed by IL-Fe3O4 NPs is depicted in scheme 3. Accordingly, the tautomerism of cyclohexanone (a), the condensation of arylaldehyde and arylamine to give an imine (b), the carbon–carbon bond forming between imine and cyclohexanone in the transition state (c), and then, reaction to give the diastereoselective Mannich product (d). Typically, Mannich products are formed via si-face attack on an imine. Accordingly, in the Mannich transition state we assume that the configuration of imine is in E form [45]. The si-face of the imine is selectively attacked by the re-face of cyclohexanone. Attack of the imine re-face would result in unfavorable steric interactions between the ionic liquid moiety of catalyst and the aromatic ring. The improvement induced by ultrasound can be attributed to the well-established theory of ultrasonic irradiation in which it differs from traditional energy sources (such as heat) in duration, pressure, and etc [46-50]. Therefore, it is reasonable to assume that these effects should accelerate this three-component reaction.
S1350-4177(16)30273-5 http://dx.doi.org/10.1016/j.ultsonch.2016.08.003 ULTSON 3330
To appear in:
Ultrasonics Sonochemistry
Received Date: Revised Date: Accepted Date:
20 May 2016 1 August 2016 3 August 2016
Please cite this article as: J. Safaei Ghomi, S. Zahedi, Novel ionic liquid supported on Fe3O4 nanoparticles and its application as a catalyst in Mannich reaction under ultrasonic irradation, Ultrasonics Sonochemistry (2016), doi: http://dx.doi.org/10.1016/j.ultsonch.2016.08.003
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Novel ionic liquid supported on Fe3O4 nanoparticles and its application as a catalyst in Mannich reaction under ultrasonic irradation Javad Safaei Ghomi*1 and Safura Zahedi1,2 1
2
Department of Organic Chemistry, Faculty of Chemistry, University of Kashan, Kashan, 51167, I. R. Iran
Young Researchers and Elite Club, Bandar abbas Branch, Islamic Azad University, Bandar abbas, Iran *Corresponding author. E-mail addresses: [email protected], Fax: +98-361-5912397; Tel.: +98-361-5912385
Abstract A family of novel ionic liquid with L-alanine and choline chloride as environmentally benign materials have been synthesized and grafted on Fe3O4 nanoparticles using easy preparation techniques. The structure of ionic liquid supported on Fe3O4 nanoparticles (ILFe3O4 NPs) characterized by various analyses such as FE-SEM, EDX, XRD, NMR, FTIR and VSM. The catalytic activities of this catalyst are examined in the Mannich reaction for synthesis of β-aminocarbonyl compounds under ultrasonic irradiation. The recyclability of catalyst is investigated, and the results have indicated that the catalyst can be recycled six times without obvious activity decreasing.
Keywords: Ultrasonic irradiation; Mannich reaction; Ionic liquid; L-alanine; magnetite nanoparticles.
1
Introduction Molten salts at ambient temperature containing only ions and no solvent are mentioned to as “ionic liquids” [1-3]. Ionic liquids have very different properties from molecular liquids, making them promising substances for use in a diversity of fields. Nowadays, supported ILs containing different metal particles or ions have been used as catalysts in different reactions, such as the Heck reaction [4,5], hydrogenation[6–8]. Though ILs possessed such promising advantages, their extensive practical application was still prevented by numerous drawbacks: high viscosity, which caused in only a minor part of ionic liquids taking part in the catalyzed reaction; homogeneous reaction, which was difficult for product separation and catalyst recovery; consequently, high cost for the use of relatively large amounts of ILs [9,10]. Therefore, in order to resolve these problems mentioned earlier, an immobilized IL catalyst combining the advantageous characteristics of ionic liquids, inorganic acids and solid acids had been proposed [11,12]. A variety of methodologies and mechanisms have recently been developed based on green chemistry or sonochemistry [13]. Sonochemistry as an innovative and powerful technique has attracted increasing interest in accelerating organic reactions [14-17]. This technique can be extremely efficient and is applicable to a wide variety of practical syntheses. Luche and coworkers have conducted a number of studies which provided the basis for using sonochemistry in organic synthesis [18-21]. The remarkable features of the ultrasound approach in organic reactions are improvement of reaction rates, formation of pure products with high yields and easier operation. This technique is also considered as an aid in terms of energy conservation and waste minimization when compared with traditional methods [22,23]. Magnetic separation provides a very convenient approach for removing and recycling particles/composites by applying external magnetic fields [24–26]. Recently, magnetic 2
particles have been extensively employed as alternative catalyst supports, in view of their convenient catalyst recycling, high surface area resulting in high catalyst loading capacity, high dispersion, and outstanding stability [27–29]. A variety of magnetic supports (such as magnetite, barium ferrite, Fe3O4@SiO2 particles and so on) have been reported [30-32]. Also, recently, some multicomponent reactions were catalyzed by magnetic nanoparticles [33-38]. Mannich reaction is one of the most useful methods for the construction of carbon–carbon bonds in organic chemistry [39]. The reaction is especially useful for the synthesis of βamino carbonyl derivatives [40]. Due to the importance of the Mannich products in organic synthesis, various methods for conducting highly diastereoselective and/or enantioselective Mannich reactions have been developed in the past [41]. According to the ways that the reactions are conducted, Mannich reactions may be generally divided into direct Mannich reactions and indirect Mannich reactions. Because direct Mannich reaction does not require the use of preformed enolates or their equivalents as the substrates, it has many advantages over the indirect Mannich reaction, such as better atom economy and operational simplicity [42]. Recently, we have reported organometallic magnetite nanoparticles for the synthesis of βaminocarbonyl compunds via mannich reaction [43]. Here we wish to report the novel ionic liquid-Fe3O4 NPs-catalyzed highly anti-selective three component direct Mannich reaction of aromatic aldehydes, amines and cyclohexanone (Scheme 1).
generator (Sonicator 3200;
Bandelin, MS
73,
Germany),
equipped
with a
converter/transducer and titanium oscillator (horn), 12.5mm in diameter, operating at 20 kHz with a maximum power output of 200 W. The ultrasonic generator automatically adjusted the power level.1H NMR and 13C NMR spectra were measured respectively at 400 and 100 MHz. The solvent used for NMR spectroscopy was CDCl3, using tetramethylsilane as the internal reference. The IR spectra of all compounds were recorded on FT-IR Magna 550 apparatus using with KBr plates. The elemental analyses (C, H, N) were obtained from a Carlo ERBA Model EA1108 analyzer. Melting points were determined on Electro thermal 9200, and are not corrected. Powder X-ray diffraction (XRD) was carried out on a Philips diffractometer of X’pert company with mono chromatized Cu Ka radiation (k = 1.5406 Å). Microscopic morphology of products was visualized by SEM (LEO 1455VP). Also, the magnetic property of magnetite nanoparticle has been measured with a vibrating sample magnetometer (VSM, PPMS-9T) at 300 K in Iran (Kashan University).
2.2. Preparation of the magnetic Fe3O4 nanoparticles (MNPs) Briefly, MNPs were prepared by the chemical co-precipitation of Fe+3 (FeCl3/0.5 M) and Fe+2 (FeCl2/0.5 M) in a molar ratio of 1.75:1 under nitrogen. The pH of the solution was reached to 9.0 by quickly adding of ammonia aqueous solution under rapid stirring. Black Fe3O4 MNPs were formed and exhibited a strong magnetic response; they were separated by magnetic field and finally washed thoroughly with distilled water and dried o
at 60 C under vacuum.
2.3. Preparation of ionic liquid Sodium l-2-(1-imidazolyl) propanoic acid (I) [44]. Formaldehyde water solution (36%, 16.7 g) and glyoxal water solution (32%, 36.2 g) were added to a 250 mL, three4
necked flask provided with a stirrer and reflux condenser. While the mixture was heated at 50 °C with stirring, a mixture of alanine (17.8 g, 0.2 mol), ammonia solution (28%, 12.1 g), and sodium hydroxide solution (10%, 80 g) was added in small portions during 0.5 h. After the mixture was stirred for an additional 4 h at 50 °C, the water was removed under reduced pressure. The crude product, sodium l-2-(1-imidazolyl) 1
propanoic acid (I), was obtained. H NMR δ 1.59-1.61 (d, J=7.30 Hz, 3H), 4.85-4.90 (q, J=7.29 Hz, 1H), 7.35 (s, 2H), 8.73 (s, 1H) (Fig. 1). Afterwards, sodium l-2-(1-imidazolyl) o
propanoic acid (I) and Choline chloride (25 mL) were refluxed at 80 C for 12 h in the absence of any solvent. At the end, (3-chloro-propyl) trimethoxysilane (31 mL) were o
added to mixture and refluxed at 80 C for 3 days in the absence of any catalyst and solvent under N2 atmosphere. The unreacted materials were washed with diethyl ether (3 * 8 mL). The diethyl ether was removed under reduced pressure at room temperature, and then was heated under high vacuum, to yield a yellowish viscous liquid. The isolated yield was 98%. 1H NMR δ 1.22 (m, 4H), 1.48-1.57 (d, J=7.30 Hz, 3H), 1.69 (m, 2H), 3.70 (m, 22H), 4.85-4.90 (q, J=7.29 Hz, 1H), 6.80 (d, 1H), 7.51 (d, 1H), 8.80 (s, 1H). < Fig. 1>
2.4. Modification of magnetic nanoparticles with ionic liquid (IL---MNPs) Freshly prepared magnetite nanoparticles (2 g) were suspended in ethanol (95%, 250 mL), and sonicated for 60 min. The resulting suspension was mechanically stirred, followed by the addition of a solution of ethanol (95%, 100 mL) containing ionic liquid (6 ml) and concentrated ammonia (28%, 1 mL). Stirring under N2 was continued for 36 h. The modified magnetite nanoparticles were magnetically separated and washed three times with ethanol (95%, 50 mL) and dried under vacuum for 24 h.
2.5. General procedure for Mannich reaction catalyzed by catalyzed by IL---MNPs 5
2.5.1. Typical heating method In a typical mannich reaction, arylaldehyde (2.5 mol), arylamine (2.5 mol) cyclohexanon (3 mol) and EtOH (20 mL) were added to the IL---MNPs (0.001 g) in a 50mL flask equipped with a heating arrangement and a stirrer and the temperature was set at reflux condition. After the reaction was completed, the catalyst was separated by an external magnet. The reaction mixture was purified by flash column chromatography to give the pure β -amino ketone derivatives 2.5.2. Ultrasound irradiation The aromatic aldehyde (1) (2.5 mmol), aromatic amine (2) (2.5 mmol), cyclohexanone (3) (3.0 mmol), IL---MNPs (0.001 g) and EtOH (20 mL) were added into a 25 mL round bottomed flask. The reaction mixture was sonicated under 75 W for the period of time (the reaction was monitored by TLC). The solvent was eliminated under decreased pressure, and the products were puri• ed by silica column chromatography.
2.6. Representative Spectral data for 4d and 4i 2.6.1. 2-(phenyl)(phenylamino)methyl)cyclohexanone (4a). 1
H NMR (400 MHz, CDCl3) δ: 7.65 (d, J=8.0 Hz, 1H, Ar), 7.54 (m, 1H, Ar), 7.21 (m, 1H,
Ar), 7.14–7.08 (m, 4H, Ar), 6.68 (d, J=7.2 Hz, 1H, Ar), 6.56 (d, J=8.0 Hz, 2H, Ar) 4.92 (br s, 1H, NH), 4.85 (d, J=6.4 Hz, 1H, CH), 2.98–2.93 (m, 1H), 2.45–2.33 (m, 2H), 2.15–1.94 (m, 4H), 1.88–1.55 (m, 2H); IR (KBr, ʋ, cm-1): 3395.45, 1696.69, 1602.76, 1501.64, 809.08; 13C NMR (100 MHz, CDCl3) δ: 212.79, 145.69, 140.33, 131.31, 129.08, 128.90, 128.32, 127.44, 123.61, 116.83, 113.11, 58.59, 55.99, 41.80, 32.74, 28.85, 23.80; Calcd for C19H21NO: C, 81.68; H, 7.58; N, 5.01. Found: C, 81.67; H, 7.55; N, 5.06. 2.6.2. 2-(4-Chlorophenylamino)(phenyl)methyl)cyclohexanone (4b).
6
1
H NMR (400 MHz, CDCl3) δ: 7.68 (d, J=8.0 Hz, 1H, Ar), 7.58 (m, 1H, Ar), 7.20(m, 1H,
Ar), 7.18–7.09 (m, 4H, Ar), 6.69 (d, J=7.2 Hz, 1H, Ar), 6.57 (d, J=8.0 Hz, 2H, Ar) 4.90 (br s, 1H, NH), 4.83 (d, J=6.4 Hz, 1H, CH), 2.93–2.89 (m, 1H), 2.48–2.35 (m, 2H), 2.15–1.94 (m, 4H), 1.86–1.53 (m, 2H); IR (KBr, ʋ, cm-1): 3393.45, 1693.69, 1601.76, 1503.64, 809.08; 13C NMR (100 MHz, CDCl3) δ: 212.89, 144.69, 141.23, 130.41, 129.08, 128.90, 128.42, 126.84, 122.91, 117.63, 111.91, 56.59, 54.99, 42.80, 30.74, 28.85, 22.98; Calcd for C19H20ClNO: C, 72.72; H, 6.42; N, 4.46. Found: C, 72.70; H, 6.45; N, 4.47. 2.6.3. 2-(phenyl (m-tolylamino)methyl)cyclohexanone (4c). 1
H NMR (400 MHz, CDCl3) δ: 7.72 (d, J=8.0 Hz, 1H, Ar), 7.68 (m, 1H, Ar), 7.25 (m, 1H,
Ar), 7.19–7.09 (m, 4H, Ar), 6.67 (d, J=7.2 Hz, 1H, Ar), 6.55 (d, J=8.0 Hz, 2H, Ar) 4.91 (br s, 1H, NH), 4.80 (d, J=6.4 Hz, 1H, CH), 2.90–2.84 (m, 1H), 2.52–2.45 (m, 2H), 2.25–2.12 (m, 4H), 2.08 (s, 3H, CH3), 1.96–1.73 (m, 2H); IR (KBr, ʋ, cm-1): 3390.45, 1694.69, 1601.86, 1501.64, 809.08;
13
C NMR (100 MHz, CDCl3) δ: 213.39, 144.69, 140.63, 130.51, 129.28,
128.90, 128.52, 125.84, 121.91, 118.63, 112.91, 58.59, 55.99, 40.80, 32.74, 28.85, 25.34, 23.98; Calcd for C20H23NO: C, 81.87; H, 7.90; N, 4.77. Found: C, 81.85; H, 7.88; N, 4.79. 2.6.4. 2-((2-Chlorophenyl)(phenylamino)methyl)cyclohexanone (4d). 1
H NMR (400 MHz, CDCl3) δ: 7.61 (d, J=8.0 Hz, 1H, Ar), 7.53 (m, 1H, Ar), 7.24 (m, 1H,
Ar), 7.13–7.05 (m, 3H, Ar), 6.66 (d, J=7.2 Hz, 1H, Ar), 6.54 (d, J=8.0 Hz, 2H, Ar) 4.91 (br s, 1H, NH), 4.81 (d, J=6.4 Hz, 1H, CH), 2.99–2.95 (m, 1H), 2.41–2.30 (m, 2H), 2.14–1.95 (m, 4H), 1.85–1.59 (m, 2H); IR (KBr, ʋ, cm-1): 3396.45, 1697.69, 1601.76, 1502.64, 809.08; 13C NMR (100 MHz, CDCl3) δ: 212.89, 146.69, 140.43, 132.31, 129.01, 128.90, 128.28, 127.34, 123.61, 117.23, 113.11, 57.59, 54.99, 42.80, 32.74, 27.85, 24.80; Calcd for C19H20ClNO: C, 72.72; H, 6.42; N, 4.46. Found: C, 72.69; H, 6.35; N, 4.41. 2.6.5. 2-((4-methylphenyl)(phenylamino)methyl)cyclohexanone (4e).
7
1
H NMR (400 MHz, CDCl3) δ: 7.70 (d, J=8.0 Hz, 1H, Ar), 7.65 (m, 1H, Ar), 7.28 (m, 1H,
Ar), 7.22–7.10 (m, 4H, Ar), 6.69 (d, J=7.2 Hz, 1H, Ar), 6.57 (d, J=8.0 Hz, 2H, Ar) 4.92 (br s, 1H, NH), 4.81 (d, J=6.4 Hz, 1H, CH), 2.94–2.88 (m, 1H), 2.53–2.46 (m, 2H), 2.28–2.18 (m, 4H), 2.10 (s, 3H, CH3), 1.96–1.73 (m, 2H); IR (KBr, ʋ, cm-1): 3390.45, 1694.69, 1601.86, 1501.64, 809.08;
13
C NMR (100 MHz, CDCl3) δ: 212.39, 143.89, 141.63, 131.51, 129.58,
128.88, 128.42, 126.84, 122.51, 116.63, 113.91, 57.59, 54.99, 41.80, 31.74, 29.85, 24.34, 22.98; Calcd for C20H23NO: C, 81.87; H, 7.90; N, 4.77. Found: C, 81.91; H, 7.93; N, 4.72. 2.6.6. 2-(4-Chlorophenyl)(phenylamino)methyl)cyclohexanone (4f). 1
H NMR (400 MHz, CDCl3) δ: 7.75 (d, J=8.0 Hz, 1H, Ar), 7.64 (m, 1H, Ar), 7.28 (m, 1H,
Ar), 7.20–7.12 (m, 4H, Ar), 6.71 (d, J=7.2 Hz, 1H, Ar), 6.60 (d, J=8.0 Hz, 2H, Ar) 4.91 (br s, 1H, NH), 4.82 (d, J=6.4 Hz, 1H, CH), 2.98–2.86 (m, 1H), 2.68–2.45 (m, 2H), 2.25–1.99 (m, 4H), 1.88–1.59 (m, 2H); IR (KBr, ʋ, cm-1): 3392.45, 1692.69, 1602.76, 1501.64, 809.08; 13C NMR (100 MHz, CDCl3) δ: 212.89, 143.69, 142.23, 131.01, 129.18, 128.90, 127.82, 126.84, 123.91, 118.63, 112.91, 57.59, 55.99, 41.80, 32.74, 28.85, 21.98; Calcd for C19H20ClNO: C, 72.72; H, 6.42; N, 4.46. Found: C, 72.75; H, 6.43; N, 4.44. 2.6.7. 2-(4-Bromophenyl)(phenylamino)methyl)cyclohexanone (4g). 1
H NMR (400 MHz, CDCl3) δ: 7.73 (d, J=8.0 Hz, 1H, Ar), 7.62 (m, 1H, Ar), 7.29 (m, 1H,
Ar), 7.21–7.15 (m, 4H, Ar), 6.75 (d, J=7.2 Hz, 1H, Ar), 6.63 (d, J=8.0 Hz, 2H, Ar) 4.91 (br s, 1H, NH), 4.81 (d, J=6.4 Hz, 1H, CH), 2.99–2.88 (m, 1H), 2.69–2.49 (m, 2H), 2.35–2.19 (m, 4H), 1.98–1.69 (m, 2H); IR (KBr, ʋ, cm-1): 3392.45, 1691.69, 1603.76, 1502.64, 809.08; 13C NMR (100 MHz, CDCl3) δ: 213.89, 144.69, 141.23, 131.01, 129.18, 128.90, 127.82, 126.84, 124.91, 118.73, 113.91, 58.59, 55.99, 43.80, 31.74, 28.85, 22.98; Calcd for C19H20BrNO: C, 63.70; H, 5.63; N, 3.91. Found: C, 63.72; H, 5.65; N, 3.89. 2.6.8. 2-((4-Chlorophenyl)(p-tolylamino)methyl)cyclohexanone (4h).
8
1
H NMR (400 MHz, CDCl3) δ: 7.79 (d, J=8.0 Hz, 1H, Ar), 7.69 (m, 1H, Ar), 7.38 (m, 1H,
Ar), 7.28–7.15 (m, 2H, Ar), 6.79 (d, J=7.2 Hz, 1H, Ar), 6.67 (d, J=8.0 Hz, 2H, Ar) 4.91 (br s, 1H, NH), 4.81 (d, J=6.4 Hz, 1H, CH), 2.94–2.88 (m, 1H), 2.53–2.46 (m, 2H), 2.28–2.18 (m, 4H), 2.10 (s, 3H, CH3), 1.96–1.73 (m, 2H); IR (KBr, ʋ, cm-1): 3390.45, 1693.69, 1602.86, 1501.64, 809.08;
13
C NMR (100 MHz, CDCl3) δ: 213.39, 144.89, 142.63, 131.51, 129.58,
128.88, 127.82, 126.84, 122.51, 117.63, 113.91, 57.59, 54.99, 41.80, 31.74, 29.85, 23.94, 22.98; Calcd for C20H22ClNO: C, 73.27; H, 6.76; N, 4.27. Found: C, 73.29; H, 6.78; N, 4.24. 2.6.9. 2-((4-Methoxyphenyl)(phenylamino)methyl)cyclohexanone (4i). 1
H NMR (400 MHz, CDCl3) δ: 7.25 (d, J=8.4 Hz, 2H, Ar), 7.14 (d, J=7.6 Hz, 2H, Ar),
7.10-7.07 (m, 2H, Ar), 6.63 (t, J=7.2 Hz, 1H, Ar), 6.66 (d, J=8.4 Hz, 2H, Ar), 4.71 (br s, 1H, NH), 4.62 (d, J=7.2 Hz, 1H, CH), 3.66 (s, 3H, OMe), 2.76–2.72 (m, 1H), 2.38–2.34 (m, 2H), 1.93–1.83 (m, 4H,), 1.75–1.68 (m, 3H); IR (KBr, ʋ, cm-1): 3332.42, 1707.26, 1600.92, 1532.21, 800.33;
13
C NMR (100 MHz, CDCl3) δ: 212.73, 147.01, 138.38, 136.47, 129.21,
128.77, 126.96, 117.16, 113.34, 57.39, 57.30, 41.43, 30.92, 27.92, 23.28, 20.81; Calcd for C20H23NO2: C, 77.64; H, 7.49; N, 4.53. Found: C, 77.43; H, 7.56; N, 4.54. 2.6.10. 2-((phenyl)(p-tolyl)methyl)cyclohexanone (4j). 1
H NMR (400 MHz, CDCl3) δ: 7.72 (d, J=8.0 Hz, 1H, Ar), 7.68 (m, 1H, Ar), 7.24 (m, 1H,
Ar), 7.20–7.08 (m, 4H, Ar), 6.65 (d, J=7.2 Hz, 1H, Ar), 6.53 (d, J=8.0 Hz, 2H, Ar) 4.91 (br s, 1H, NH), 4.82 (d, J=6.4 Hz, 1H, CH), 2.94–2.88 (m, 1H), 2.53–2.46 (m, 2H), 2.28–2.18 (m, 4H), 2.08 (s, 3H, CH3), 1.96–1.73 (m, 2H); IR (KBr, ʋ, cm-1): 3391.45, 1692.69, 16031.86, 1501.64, 809.08;
13
C NMR (100 MHz, CDCl3) δ: 212.39, 144.89, 142.63, 130.81, 129.58,
128.88, 128.42, 126.84, 122.51, 117.63, 112.91, 58.59, 54.99, 41.80, 31.74, 29.85, 25.34, 22.98; Calcd for C20H23NO: C, 81.87; H, 7.90; N, 4.77. Found: C, 81.85; H, 7.893; N, 4.79. 2.6.11. 2-((4-methylphenyl)(4-Chloroamino)methyl)cyclohexanone (4k).
9
1
H NMR (400 MHz, CDCl3) δ: 7.78 (d, J=8.0 Hz, 1H, Ar), 7.69 (m, 1H, Ar), 7.35 (m, 1H,
Ar), 7.29–7.17 (m, 2H, Ar), 6.79 (d, J=7.2 Hz, 1H, Ar), 6.66 (d, J=8.0 Hz, 2H, Ar) 4.91 (br s, 1H, NH), 4.83 (d, J=6.4 Hz, 1H, CH), 2.94–2.88 (m, 1H), 2.53–2.46 (m, 2H), 2.28–2.18 (m, 4H), 2.11 (s, 3H, CH3), 1.96–1.73 (m, 2H); IR (KBr, ʋ, cm-1): 3390.45, 1693.69, 1602.86, 1501.64, 809.08;
13
C NMR (100 MHz, CDCl3) δ: 212.49, 144.59, 141.63, 132.51, 129.58,
128.88, 127.82, 126.84, 123.51, 118.63, 113.91, 57.59, 54.99, 41.80, 32.74, 29.85, 24.94, 22.98; Calcd for C20H22ClNO: C, 73.27; H, 6.76; N, 4.27. Found: C, 73.23; H, 6.74; N, 4.28. 2.6.12. 2-((2-Methoxyphenyl)(phenylamino)methyl)cyclohexanone (4l). 1
H NMR (400 MHz, CDCl3) δ: 7.28 (d, J=8.4 Hz, 2H, Ar), 7.18 (d, J=7.6 Hz, 2H, Ar),
7.10-7.07 (m, 2H, Ar), 6.68 (t, J=7.2 Hz, 1H, Ar), 6.65 (d, J=8.4 Hz, 2H, Ar), 4.81 (br s, 1H, NH), 4.72 (d, J=7.2 Hz, 1H, CH), 3.58 (s, 3H, OMe), 2.76–2.72 (m, 1H), 2.38–2.34 (m, 2H), 1.93–1.83 (m, 4H,), 1.75–1.68 (m, 3H); IR (KBr, ʋ, cm-1): 3331.42, 1706.26, 1601.92, 1532.21, 800.33;
13
C NMR (100 MHz, CDCl3) δ: 212.73, 145.01, 138.38, 136.47, 129.21,
129.77, 126.96, 117.16, 113.34, 57.39, 57.30, 41.43, 30.92, 27.92, 24.28, 20.81; Calcd for C20H23NO2: C, 77.64; H, 7.49; N, 4.53. Found: C, 77.68; H, 7.52; N, 4.50. 2.6.13. 2-(2-Bromophenyl)(phenylamino)methyl)cyclohexanone (4m). 1
H NMR (400 MHz, CDCl3) δ: 7.77 (d, J=8.0 Hz, 1H, Ar), 7.68 (m, 1H, Ar), 7.29 (m, 1H,
Ar), 7.21–7.18 (m, 4H, Ar), 6.74 (d, J=7.2 Hz, 1H, Ar), 6.63 (d, J=8.0 Hz, 2H, Ar) 4.91 (br s, 1H, NH), 4.81 (d, J=6.4 Hz, 1H, CH), 2.99–2.88 (m, 1H), 2.69–2.49 (m, 2H), 2.35–2.19 (m, 4H), 1.98–1.69 (m, 2H); IR (KBr, ʋ, cm-1): 3391.45, 1692.69, 1602.76, 1502.64, 809.08; 13C NMR (100 MHz, CDCl3) δ: 212.89, 143.69, 140.23, 131.01, 129.18, 128.90, 127.82, 126.84, 124.91, 118.73, 113.91, 58.59, 56.99, 43.80, 33.74, 28.85, 22.98; Calcd for C19H20BrNO: C, 63.70; H, 5.63; N, 3.91. Found: C, 63.68; H, 5.60; N, 3.95. 2.6.13. 2-((2,3-dimethoxyphenyl)(phenylamino)methyl)cyclohexanone (4n).
10
1
H NMR (400 MHz, CDCl3) δ: 7.38 (d, J=8.4 Hz, 2H, Ar), 7.21 (d, J=7.6 Hz, 2H, Ar),
7.12-7.07 (m, 1H, Ar), 6.68 (t, J=7.2 Hz, 1H, Ar), 6.65 (d, J=8.4 Hz, 2H, Ar), 4.81 (br s, 1H, NH), 4.78 (d, J=7.2 Hz, 1H, CH), 3.56 (s, 6H, OMe), 2.76–2.72 (m, 1H), 2.38–2.34 (m, 2H), 1.93–1.83 (m, 4H,), 1.75–1.68 (m, 3H); IR (KBr, ʋ, cm-1): 3331.42, 1703.26, 1601.92, 1533.21, 800.33;
13
C NMR (100 MHz, CDCl3) δ: 212.73, 144.01, 137.38, 138.47, 129.21,
129.77, 127.96, 117.16, 114.34, 57.39, 56.30, 48.56, 41.43, 30.92, 27.92, 24.28, 20.81; Calcd for C21H25NO3: C, 74.31; H, 7.42; N, 4.13. Found: C, 74.35; H, 7.46; N, 4.09. 2.6.15. 2-((2,5-dimethoxyphenyl)(phenylamino)methyl)cyclohexanone (4o). 1
H NMR (400 MHz, CDCl3) δ: 7.45 (d, J=8.4 Hz, 2H, Ar), 7.27 (d, J=7.6 Hz, 2H, Ar),
7.15-7.09 (m, 1H, Ar), 6.72 (t, J=7.2 Hz, 1H, Ar), 6.69 (d, J=8.4 Hz, 2H, Ar), 4.81 (br s, 1H, NH), 4.75 (d, J=7.2 Hz, 1H, CH), 3.58 (s, 6H, OMe), 2.76–2.72 (m, 1H), 2.38–2.34 (m, 2H), 1.93–1.83 (m, 4H,), 1.75–1.68 (m, 3H); IR (KBr, ʋ, cm-1): 3331.42, 1703.26, 1601.92, 1533.21, 800.33;
13
C NMR (100 MHz, CDCl3) δ: 212.73, 143.01, 138.38, 137.47, 129.21,
129.77, 127.56, 118.16, 114.44, 57.59, 56.30, 48.96, 40.43, 30.92, 27.92, 24.28, 20.81; Calcd for C21H25NO3: C, 74.31; H, 7.42; N, 4.13. Found: C, 74.34; H, 7.45; N, 4.11. 3. Results and discussion The overall schematic procedure used to synthesize the magnetic catalyst was illustrated in Scheme 2. The nanoparticles of ionic liquid-Fe3O4 were characterized by Xray diffraction spectroscopy (XRD), FTIR, VSM and scanning electron microscopy.
01-1111). In the pattern assigned to magnetite, diffraction peaks at around 30.4°, 35.7°, 43.4°,47.3°, 54.0°, 57.4°, 63.0° and 74.5° correspond to the (111), (220), (311), (222), (400), (311), (422) and (440) reflections, respectively. The large peak widths are ascribed to the formation of nano-sized magnetite particles.
= (
6000 )
×
Figure 3 also compares the FTIR spectrum of ionic liquid-Fe3O4 (Fig. 3c), ionic liquid (Fig. 3b) and Fe3O4 (Fig. 3a). Some absorption bands are common between the spectra of a and c. For example, the bands at 577 cm-1 and 567 cm-1 arising from stretching vibrations of Fe-O bonds. The strong band at around 3420 cm-1 is due to the O–H stretching vibration. Both the spectra of b and c show the characteristic band at 1620 cm-1 arising from C=O stretching of the carboxylate moiety.
12
The magnetic properties of ionic liquid-Fe3O4 nanoparticles were measured via vibrating sample magnetometer (VSM) at room temperature (Fig. 5). It can be seen that the saturation magnetization (Ms) value of the samples are 50.5 emu/g and 30.5 emu/g for Fe3O4 and of ionic liquid-Fe3O4 nanoparticles, respectively. Thus, our catalyst can be recovered by external magnetic field.