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RSC Advances
reaction progress and determination of purity of the mol), dry chloroform (40 mL), one argon inlet, and a gas outlet
compounds were accomplished using TLC performed with tube for conducting HCl gas over an adsorbing solution (10%
silica gel SIL G/UV254 plates. Melting points were determined NaOH). Then, Fe3O4@SiO2–OB(OH)2 (7.5 g) was charged into
by an electrothermal KSB1N apparatus and are uncorrected. the ask. Chlorosulfonic acid was added drop-wise over
The NMR spectra of 1H in DMSO were recorded on a Bruker a period of 60 min at 0 C. HCl gas immediately evolved from
ꢀ
Avance Ultra Shield 400 MHz spectrometer, and 13C NMR the reaction vessel. When the addition was completed, the
spectra were recorded at 100 MHz using TMS as an internal mixture was sonicated for 1 h. The functionalized magnetic
standard. Infrared (IR) spectra were obtained with a JASCO nanoparticles were collected by a magnet. The supernatant was
Fourier transform-infrared (FT-IR)/680 spectrometer using KBr decanted, and the nanoparticles were washed with dry chloro-
pellets. X-ray powder diffraction (XRD) patterns were recorded form (3 ꢂ 5 mL) and then dried in high vacuum overnight.
using a Bruker AXS (D8 Advance) X-ray diffractometer with Cu
Ka radiation (l ¼ 0.15418 nm). The measurement was made in
General procedure for the synthesis of pyrano coumarins 4
and 6
2q ranging from 10ꢀ to 80ꢀ at the speed of 0.05ꢀ minꢁ1. Energy
dispersive spectroscopy (EDS) was performed using a TESCAN
Vega model instrument. The morphology of the particles was Fe3O4@SiO2–BSA (0.005 g) was added to
a mixture of
observed by scanning electron microscopy (SEM) under an malononitrile/ethyl cyanoacetate, aryl aldehyde, and 5,7-
ꢀ
acceleration voltage of 26 kV. The magnetic measurement was dihydroxy-4-substituted coumarin/4-hydroxycoumarin at 80 C
carried out in a vibrating sample magnetometer (VSM; Kashan under solvent-free conditions. The reaction progress was
University, Kashan, Iran) at room temperature.
monitored by TLC (n-hexane/EtOAc, 3 : 2). Aer completion of
the reaction, boiling EtOAc (10 mL) was added, and the catalyst
was separated by ltration. To further purify the product, the
obtained powder was recrystallized from EtOH.
Preparation of Fe3O4
To synthesize Fe3O4 magnetic nanoparticles through a chemical
coprecipitation method, a solution of FeCl3$6H2O (2.7 g, 10
mmol) and FeCl2$4H2O (1 g, 5 mmol) in 45 mL double distilled
water was mechanically stirred under an argon atmosphere at
80 ꢀC for 30 min. In the next step, a sodium hydroxide solution
(5 mL, 10 M) ꢀwas gradually added dropwise. Aer continuous
stirring at 80 C for 1 h under an argon atmosphere, the black
precipitate of Fe3O4 magnetic nanoparticles was decanted using
an external magnetic eld. The product was washed with double
distilled water until pH 9 was obtained and then dried at 60 ꢀC
under a vacuum.32
Compound 4e. FT-IR (KBr): nmax 3477, 3423, 3315, 1702,
1681 cmꢁ1. 1H NMR (DMSO-d6, 400 MHz) d ¼ 10.88 (s, 1H), 7.61
(s, 2H), 7.25–7.05 (m, 5H), 6.39 (s, 1H), 6.04 (s, 1H), 3.50 (s, 2H),
3.44 (s, 1H), 2.66 (s, 3H), 1.02–1.11 (m, 3H) ppm. 13C NMR
(DMSO-d6, 100 MHz) d ¼ 168.47, 168.18, 159.97, 159.92, 159.45,
158.12, 158.12, 158.05, 154.23, 153.41, 147.54, 143.85, 143.69,
132.54, 131.78, 111.30, 110.01, 101.57, 98.09, 56.06, 24.11,
18.56, 14.27 ppm. Anal. calcd for C22H18ClNO6: C, 61.76; H,
4.24; N, 3.27. Found: C, 61.70; H, 4.26; N, 3.31. MS (m/z): 427
[M]+.
Compound 4h. FT-IR (KBr): nmax 3413, 3311, 1687,
1625 cmꢁ1. 1H NMR (DMSO-d6, 400 MHz) d ¼ 10.81 (s, 1H), 7.58
(s, 2H), 7.22–7.84 (m, 7H), 6.36 (s, 1H), 6.11 (s, 1H), 5.87 (s, 1H),
2.74 (m, 5H), 1.06 (t, J ¼ 5.22 Hz, 3H) ppm. 13C NMR (DMSO-d6,
Procedure for the synthesis of Fe3O4-silica-coated
nanoparticles
According to the current method in the literature, a suspension 100 MHz) d ¼ 168.41, 160.07, 160.02, 159.44, 157.86, 153.89,
containing Fe3O4 magnetic nanoparticles (1 g) was sufficiently 153.39, 147.61, 144.95, 132.86, 130.67, 127.87, 126.31, 126.23,
dispersed in a mixture of ethanol (80 mL), distilled water 125.61, 125.16, 125.08, 124.93, 112.66, 111.32, 101.88, 98.08,
(20 mL), concentrated ammonia aqueous solution (3 mL, 28%), 78.46, 50.23, 24.04, 18.52 ppm. Anal. calcd for C26H21NO6: C,
and tetraethyl orthosilicate (0.5 mL). The reaction mixture was 70.42; H, 4.77; N, 3.16. Found: C, 70.38; H, 4.80; N, 3.21.
heated under reux for 12 h. The Fe3O4-silica-coated (Fe3O4@-
1
Compound 4r. FT-IR (KBr): nmax 3402, 1728, 1663 cmꢁ1. H
SiO2) was separated by a magnet, washed several times with NMR (DMSO-d6, 400 MHz) d ¼ 11.10 (s, 1H), 8.18 (d, J ¼ 8.8 Hz,
ethanol, and dried at 60 C in air.33
2H), 7.44 (d, J ¼ 8.4 Hz, 2H), 7.17 (s, 2H), 6.51 (s, 1H), 6.12 (s,
1H), 4.82 (s, 1H), 2.63 (s, 3H) ppm. 13C NMR (DMSO-d6, 100
MHz) d ¼ 160.02, 159.76, 157.97, 155.17, 153.76, 153.10, 147.99,
146.72, 128.92, 124.29, 120.17, 112.12, 107.55, 102.46, 99.11,
56.64, 36.81, 24.49 ppm.
Compound 6c. FT-IR (KBr): nmax 3380, 3311, 3189, 1714,
1675 cmꢁ1. 1H NMR (DMSO-d6, 400 MHz) d ¼ 7.92 (d, J ¼ 8 Hz,
1H), 7.82 (s, 1H), 7.80 (d, J ¼ 1.6 Hz, 1H), 7.76 (d, J ¼ 1.6 Hz, 1H),
7.74 (s, 1H), 7.72 (d, J ¼ 1.6 Hz, 1H), 7.54 (s, 1H), 7.52 (s, 1H),
7.49 (t, J ¼ 3.6 Hz, 2H), 7.47 (s, 1H) ppm. 13C NMR (DMSO-d6,
100 MHz) d ¼ 160.0, 158.5, 154.4, 152.7, 149.2, 133.5, 132.9,
129.3, 125.1, 123.0, 119.4, 119.2, 117.0, 113.4, 110.4, 103.3, 57.3,
ꢀ
Procedure for Fe3O4@SiO2–OB(OH)2
A saturated solution of boric acid was added to a slurry con-
taining Fe3O4@SiO2 nanoparticles (8 g) in dry toluene (45 mL).
The mixture was reuxed for 24 h. The resultant suspension was
collected using an external magnet and washed several times
with distilled water and then methanol. It was dried at 80 ꢀC to
obtain the brown solid named nano Fe3O4@SiO2–OB(OH)2.34
Procedure for the preparation of Fe3O4@SiO2–OB(OSO3H)2
In the nal stage, a 100 mL suction ask was equipped with 37.5 ppm. Anal. calcd for C20H11N3O3: C, 70.38; H, 3.25; N,
a dropping funnel containing chlorosulfonic acid (7.64 g, 0.066 12.31. Found: C, 70.42; H, 3.20; N, 12.25.
This journal is © The Royal Society of Chemistry 2017
RSC Adv., 2017, 7, 46644–46650 | 46645