N-Propylpiperazine sulfonic acid immobilized on Fe3O4 magnetic silica nanoparticles: An
efficient and heterogeneous catalyst for one-pot synthesis
of
9H-xanthene or
methylenediphenol derivatives under solvent free conditions
Akbar Mobinikhaledi and Alireza Khajeh-Amiri
Department of Chemistry, Faculty of Science, Arak University, Tel: +98 861 4173415; Fax: +98
861 4173406, P.O. Box 38156-8-8349, Arak, Iran
Experimental section
S2-S4
Spectroscopic data
S4-S32
1
Experimental
All chemical including iron (II) chloride tetrahydrate (99%), iron (III) chloride hexahydrate
(98%), xylenol, aldehyde derivatives were purchased from Merck or Fluka Company and were
used without further purification. Water and other solvents were distilled before used. IR spectra
were prepared on a galaxy series FT-IR 5000 spectrophotometer using KBr discs. 1H NMR and
13
C NMR spectra were obtained in DMSO-d6 using Brucker spectrophotometer (300 MHz).
Chemical shifts were expressed in (ppm) downfield from TMS. Nanoparticles were characterized
using a X’Pert Pro MPD X-ray diffraction (XRD) diffractometer (CuK, λ=0.154056) at a
scanning speed 2°/min from 0.6° to 157° (2θ).The particle morphology was examined by
scanning electron microscopy (SEM). The particles size was investigated by a Philip cm 30
transmission electron microscopy (TEM) on an accelerating voltage of 300 kv. The
thermogravimetric analysis (TGA) curves were recorded using Diamond TG/DTA SII Perkin
Elmer Company. The Melting points were determined using an electrothermal digital apparatus
and are uncorrected.
[1] Preparation of Fe3O4 magnetic nanoparticles (MNPs):
First, Fe3O4 magnetic nanoparticles (MNPs) were prepared via improved chemical coprecipitation [56]. FeCl2.4H2O (1.6 mmol, 3.18 g) and FeCl3.6H2O (3.2 mmol, 8.65 g) were
dissolved in deionized water (300 mL). The solution was stirred at 80 °C for 1 h under nitrogen
atmosphere (N2) and then of NH3.H2O (40 mL, 25%) was added rapidly, stirred for another 1h
under N2 and then cooled to room temperature. The precipitated particles were filtered and
washed five times with hot water (100-150 mL) and separated by magnetic decantation. Finally
MNPs were dried under vacuum at 80 °C for 4 h.
[2] Preparation of Fe3O4 magnetic silica nanoparticles (MSNPs):
2
The Fe3O4 coated with SiO2 was prepared through a modified sol-gel method [57]. In a typical
procedure, the prepared Fe3O4 MNPs (0.5 g) were dispersed in a mixture ethanol (50 mL),
deionized water (10 mL) and NH3.H2O (2.5 mL, 25%) by ultrasonication for 1 h. Then, tetraethyl
orthosilicate (TEOS, 1.5 mL) was added dropwise. After stirring at room temperature for 8 h, the
products were collected and washed with deionized water (50-100 mL) for three times and dried
under vacuum at 80 °C for 4 h.
[3] Preparation of chloropropyl-modified silica-coated Fe3O4 MNPs (Fe3O4/SiO2-PropylCl):
Chloropropyl-modified silica-coated magnetic nanoparticles were prepared following the
modified procedure of Zeng et al [58]. To a solution of (3-chloropropyl)trimethoxysilane
(CPTMS) (5 mmol, 1mL) in dried toluene (100 mL) was added Fe3O4/SiO2 (1 g) and the mixture
sonicated for 2 h. The mixture was stirred for 20 h under reflux conditions and the obtained
chloropropyl-functionalized solid (Fe3O4/SiO2-Propyl-Cl) washed with toluene (30-40 mL) three
times, separated using an external magnet and dried under vacuum for 4 h.
[4] Preparation of piperazine-modified silica-coated Fe3O4 MNPs (Fe3O4/SiO2-Propyl-Pip):
To a magnetically stirred mixture of the prepared Fe3O4/SiO2-Propyl-Cl (1 g) and KI (10
mmol, 1.66 g) was added piperazine (10 mmol, 0.86 g) and Et3N (10 mmol, 1.39 mL) in dried
toluene (100 mL) and the mixture was sonicated for 2 h, then stirred for 48 h under reflux
conditions. The obtained solid was magnetically collected from the solution and washed with
water/ethanol (20:10 mL) for three times and dried in vacuum for 4 h.
[5] Preparation of N-propylpiperazine sulfonic acid functionalized Fe3O4 MSNPs
(Fe3O4/SiO2-Propyl-Pip-SO3H):
3
To a mixture of piperazine-modified silica-coated Fe3O4 MNPs (Fe3O4/SiO2-Propyl-Pip) (1 g)
in dried CHCl3 (3 mL), chlorosulfonic acid (ClSO3H, 1 mL) was added dropwise at 0 °C over 2
h and then the mixture was filtered and washed with ethanol (5 mL) and dried at room
temperature to afford the title compound.
[6] Acidity of the Fe3O4/SiO2-Propyl-Pip-SO3H nanocatalyst
Titration was utilized to determine the acid amount on the surface of nanocatalyst. The
Fe3O4/SiO2-Propyl-Pip-SO3H nanocatalyst (0.01 g) was added to an aqueous KCl solution (1M,
10 mL) and the resulting mixture was stirred for 24h, after which the PH of solution decreased to
2 indicating an ion exchange between nanocatalyst protons and potassium ions, the nanocatalyst
was then recovered by an external magnet, and the clear solution was retained for analysis. Two
drops of phenolphthalein indicator were then added to the remaining solution and the resulting
mixture was titrated to neutrality using a 0.1M aqueous KOH solution to determine the acid
amount on the nanocatalyst. The acid amount of the catalyst was determined to be 0.48 mmol.g-1.
[7] General procedure for preparation of xanthene or methylenediphenol derivatives:
To a mixture of aldehyde (1 mmol) and xylenol (2.2 mmol) was added Fe3O4/SiO2-Propyl-PipSO3H (0.05 g) and the reaction mixture stirred magnetically for 30 min at 120 °C. The progress
of the reaction was followed by thin layer chromatography (TLC). After completion of the
reaction, the mixture was cooled to room temperature and then added hot ethanol to it, the
suspension stirred for 15 min and the catalyst separated by an external magnet. Then solvent was
removed by evaporation and for more purification, recrystallization of the obtained precipitate
was carried out by a mixture of EtOH: H2O (4:1).
Spectroscopic data:
1,3,6,8-Tetramethyl-9-phenyl-9H-xanthene (Table 2, entry 1):
4
1
H-NMR (300 MHz, CDCl3): δ 7.21 (d, J = 7.8 Hz, 2H), 7.12 (t, J = 7.4 Hz, 2H), 7.02 (t, J = 7.4
Hz, 1H), 6.80 (s, 2H), 6.61 (s, 2H), 5.08 (s, 1H), 2.25 (s, 6H), 2.22 (s, 6H);
13
CNMR(75 MHz,
CDCl3): δ 151.9, 144.6, 137.4, 136.6, 128.6, 128.5, 126.3, 126.1, 122.3, 115.2, 40.1, 21.1, 19.3;
IR (KBr, cm-1): 3022, 2964, 2918, 1631, 1616, 1564, 1454, 1330, 1294, 1219, 1147, 1055, 841,
752, 702; Anal calcd for C23H22O: C, 87.86; H, 7.05. Found: C, 87.89; H, 7.11.
9-(4-Chlorophenyl)-1,3,6,8-tetramethyl-9H-xanthene (Table 2, entry 2):
1
H-NMR (300 MHz, CDCl3): δ 7.14 (d, J=8.5 Hz, 2H), 7.08 (d, J=8.5 Hz, 2H), 6.79(s, 2H), 6.62
(s, 2H), 5.06(s, 1H), 2.23 (s, 12H),
13
C-NMR (75 MHz, CDCl3): δ 151.7, 143.1, 137.6, 136.3,
131.9, 129.7, 128.6, 126.1, 121.6, 115.1, 39.4, 21.0, 19.2; IR (KBr, cm-1): 3028, 2914, 1632,
1616, 1568, 1485, 1408, 1298, 1221, 1147, 1058, 841, 804; Anal calcd for C23H 21ClO: C, 79.18;
H, 6.07. Found: C, 79.12; H, 6.12.
1,3,6,8-Tetramethyl-9-(4-nitrophenyl)-9H-xanthene (Table 2, entry 3):
1
H-NMR (300 MHz, CDCl3): δ 7.99 (d, J= 8.8 Hz, 2H), 7.37 (d, J= 8.8 Hz, 2H), 6.82 (s, 2H),
6.64 (s, 2H), 5.21 (s, 1H), 2.23 (s, 12H),
13
C-NMR(75 MHz, CDCl3): δ 151.8, 151.6, 146.2,
138.2, 136.3, 129.1, 126.3, 123.8, 120.7, 115.4, 39.9, 21.1, 19.2; IR (KBr, cm-1): 3030, 2953,
2916, 1632, 1614, 1591, 1518, 1450, 1346, 1298, 1221, 1147, 1059, 839, 746; Anal calcd for
C23H 21NO3: C, 76.86; H, 5.89; N, 3.90. Found: C, 76.93; H, 5.94; N, 3.92.
1,3,6,8-Tetramethyl-9-p-tolyl-9H-xanthene (Table 2, entry 4):
1
H-NMR (300 MHz, CDCl3): δ 7.10 (d, J= 8.0 Hz, 2H), 6.92 (d, J = 7.9 Hz, 2H), 6.78 (s, 2H),
6.60 (s, 2H), 5.04 (s, 1H), 2.24 (s, 6H), 2.21 (s, 6H), 2.16 (s, 3H), 13C-NMR(75 MHz, CDCl3): δ
151.8, 141.7, 137.3, 136.5, 135.8, 129.2, 128.4, 126.1, 122.4, 115.1, 39.7, 21.2, 21.1, 19.4; IR
5
(KBr, cm-1 ): 3025, 2918, 1632, 1615, 1568, 1454, 1408, 1298, 1219, 1148, 1057, 843, 797; Anal
calcd for C24H24O: C, 87.76; H, 7.37. Found: C, 87.62; H, 7.42.
6,6'-((4-Chlorophenyl)methylene)bis(2,4-dimethylphenol) (Table 2, entry 5):
1
H-NMR (300 MHz, DMSO-d6): δ 7.93 (s, 2H), 7.22 (d, J= 8.2 Hz, 2H), 6.90 (d, J = 8.3 Hz,
2H), 6.66 (s, 2H), 6.20 (s, 2H), 6.05 (s, 1H), 2.03 (s, 6H), 1.98 (s, 6H);
13
C-NMR(75 MHz,
DMSO-d6): δ 150.7, 144.1, 131.4, 131.3, 130.7, 129.8, 128.3, 128.1, 127.5, 124.6, 43.2, 20.9,
17.2; IR (KBr, cm-1): 3503, 3025, 2917, 1616, 1487, 1406, 1254, 1219, 1184, 1136, 1088, 1014,
847, 725; Anal calcd for C23H23ClO2: C, 75.30; H, 6.32. Found: C, 75.21; H, 6.35.
6,6'-((3-Nitrophenyl)methylene)bis(2,4-dimethylphenol) (Table 2, entry 6):
1
H-NMR (300 MHz, DMSO-d6): δ 8.05 (s, 2H), 7.97 (d, J= 8.1 Hz, 1H), 7.66(s, 1H), 7.49 (t, J=
7.9 Hz, 1H), 7.38 (d, J= 7.4 Hz, 1H), 6.70 (s, 2H), 6.24 (s, 2H), 6.19 (s, 1H), 2.05 (s, 6H), 1.99
(s, 6H);
13
C-NMR (75 MHz, DMSO-d6): δ 150.7, 148.1, 147.6, 136.4, 130.4, 130.1, 129.9,
128.1, 127.8, 124.8, 123.5, 121.4, 43.6, 20.9, 17.2; IR (KBr, cm-1): 3432, 3007, 2912, 1523,
1487, 1348, 1319, 1217, 1165, 862, 739; Anal calcd for C23H 23NO4: C, 73.19; H, 6.14; N, 3.71.
Found: C, 73.28; H, 6.24; N, 3.76.
4,4'-(Phenylmethylene)bis(2,5-dimethylphenol) (Table2, entry 7):
1
H-NMR (300 MHz, DMSO-d6): δ 8.91 (s, 2H), 7.19 (t, J= 7.1 Hz, 2H), 7.10 (t, J= 7.0 Hz, 1H),
6.91 (d, J = 7.4 Hz, 2H), 6.49 (s, 2H), 6.23 (s, 2H), 5.34 (s, 1H), 1.90 (s, 6H), 1.85 (s, 6H);
13
C-
NMR (75 MHz, DMSO-d6): δ 153.7, 144.2, 134.4, 132.9, 131.1, 129.8, 128.6, 126.3, 120.6,
117.1, 48.7, 19.4, 16.4; IR (KBr, cm-1): 3545, 3397, 3020, 2966, 2922, 1622, 1587, 1506, 1462,
6
1410, 1279, 1157, 1068, 991, 900, 739, 700; Anal calcd for C23H 24O2: C, 83.10; H, 7.28. Found:
C, 83.15; H, 7.23.
4,4'-((4-Bromophenyl)methylene)bis(2,5-dimethylphenol) ( Table 2, entry 8):
1
H-NMR (300 MHz, DMSO-d6): δ 8.95 (s, 2H), 7.38 (d, J= 8.1 Hz, 2H), 6.85 (d, J= 8.1 Hz, 2H),
6.49 (s, 2H), 6.20 (s, 2H), 5.33 (s, 1H), 1.89 (s, 6H), 1.86 (s, 6H);
13
C-NMR(75 MHz, DMSO-
d6): δ 153.8, 143.8, 134.5, 132.3, 132.0, 131.5, 131.1, 120.8, 119.4, 117.2, 48.1, 19.3, 16.4; IR
(KBr, cm-1): 3441, 2947, 2920, 1616, 1508, 1458, 1406, 1281, 1153, 1072, 995, 902, 810, 758;
Anal calcd for C23H23BrO2: C, 67.16; H, 5.64. Found: C, 67.23; H, 5.57.
4,4'-((3-Nitrophenyl)methylene)bis(2,5-dimethylphenol) (Table 2, entry 9):
1
H-NMR (300 MHz, DMSO-d6): δ 9.01 (s, 2H), 8.00 (d, J= 7.5 Hz, 1H), 7.74 (s, 1H), 7.51 (t, J=
7.9 Hz, 1H), 7.38 (d, J= 7.7 Hz, 1H), 6.52 (s, 2H), 6.20 (s, 2H), 5.57 (s, 1H), 1.92 (s, 6H), 1.86
(s, 6H); 13C-NMR(75 MHz, DMSO-d6): δ 154.1, 148.3, 146.9, 136.5, 134.7, 131.7, 131.2, 130.0,
123.9, 121.6, 121.1, 117.4, 48.2, 19.3, 16.3; IR (KBr, cm-1): 3441, 3348, 3017, 2914, 1618, 1591,
1529, 1458, 1406, 1357, 1284, 1155, 1074, 993, 904, 804, 735; Anal calcd for C23H23NO4: C,
73.19; H, 6.14; N, 3.71. Found: C, 73.12; H, 6.21; N, 3.75.
6,6'-(Phenylmethylene)bis(3,4-dimethylphenol) (Table 2, entry 10):
1
H-NMR (300 MHz, DMSO-d6): δ 8.77 (s, 2H), 7.13 (t, J= 7.3 Hz, 2H), 7.05 (t, J= 7.0 Hz, 1H),
6.86 (d, J= 7.5 Hz, 2H), 6.47 (s, 2H), 6.31 (s, 2H), 5.81 (s, 1H), 2.00 (s, 6H), 1.89 (s, 6H); 13CNMR (75 MHz, DMSO-d6): δ 151.2, 141.8, 136.5, 131.0, 129.3, 129.0, 128.6, 126.6, 126.1,
117.7, 44.3, 19.5, 19.1; IR (KBr, cm-1): 3555, 3476, 3019, 2918, 1616, 1508, 1456, 1402, 1279,
1194, 1057, 860, 696; Anal calcd for C23H24O2: C, 83.10; H, 7.28. Found: C, 83.17; H, 7.35.
7
6,6'-((4-Chlorophenyl)methylene)bis(3,4-dimethylphenol) (Table 2, entry 11):
1
H-NMR (300 MHz, DMSO-d6): δ 8.82 (s, 2H), 7.19 (d, J= 7.8 Hz, 2H), 6.86 (d, J= 7.9 Hz, 2H),
6.48 (s, 2H), 6.31 (s, 2H), 5.78 (s, 1H), 2.01 (s, 6H), 1.90 (s, 6H); 13C-NMR (75 MHz, DMSOd6): δ 153.0, 144.3, 134.9, 131.2, 131.1, 130.5, 128.2, 127.4, 125.8, 116.9, 42.1, 19.7, 19.2; IR
(KBr, cm-1): 3466, 3412, 3013, 2920, 1616, 1578, 1508, 1489, 1404, 1279, 1192, 1155, 1089,
1012, 860, 812; Anal calcd for C23H23ClO2: C, 75.30; H, 6.32. Found: C, 75.26; H, 6.26.
6,6'-(p-Tolylmethylene)bis(3,4-dimethylphenol) (Table2,entry 12):
1
H-NMR (300 MHz, DMSO-d6): δ 8.71 (s, 2H), 6.93 (d, J= 7.4 Hz, 2H), 6.74 (d, J= 7.7 Hz, 2H),
6.45 (s, 2H), 6.31 (s, 2H), 5.76 (s, 1H), 2.16 (s, 3H), 2.00 (s, 6H), 1.89 (s, 6H);
13
C-NMR (75-
MHz, DMSO-d6): δ 153.0, 142.1, 134.6, 134.5, 131.1, 129.4, 128.9, 128.1, 125.5, 116.8, 42.0,
21.1, 19.7, 19.2; IR (KBr, cm-1): 3470, 3416, 3017, 2918, 1611, 1510, 1456, 1404, 1273, 1186,
1058, 999, 852; Anal calcd for C24H26O2: C, 83.20; H, 7.56. Found: C, 83.30; H, 7.49.
8
HO
Cl
HO
9
HO
Cl
HO
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HO
HO
NO2
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HO
HO
NO2
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HO
HO
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HO
HO
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HO
NO2
HO
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HO
NO2
HO
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HO
Br
HO
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HO
Br
HO
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HO
HO
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HO
HO
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HO
Cl
HO
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HO
Cl
HO
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HO
HO
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HO
HO
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O
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O
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O
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O
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O
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Cl
O
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Cl
O
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NO2
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NO2