Transit Met Chem
significant research area, and this approach to the synthesis
of organic molecules has attracted much attention [16].
Hence, in continuation of our interest in the development
of greener and sustainable processes for organic synthesis
and nanocatalysis [17–21], we here report on the immo-
bilization of L-Histidine on silica-coated magnetic
nanoparticles followed by incorporation of Cu(II) to give
immobilized on Fe O @SiO @L-Histidine as a new
General procedure for the synthesis of 5-substituted
1H-tetrazoles derivatives
A mixture of the required nitrile (1 mmol), sodium azide
(1 mmol) and the catalyst MNP (0.05 g) was stirred at
120 °C in PEG (1 mL) as solvent. After completion of the
reaction, as indicated by TLC, the mixture was cooled to
room temperature and diluted with 1:1 H O:Ethylacetate
2
3
4
2
heterogeneous nanocatalyst for the synthesis of 5-substi-
(10 mL) and then stirred at ambient temperature (10 min).
The catalyst was removed by applying a magnetic field,
and the decantate was treated with HCl (4 N, 10 mL). The
organic layer was separated, washed with water, dried over
sodium sulfate and concentrated to precipitate the crude
crystalline solid. The pure tetrazoles were characterized by
their spectroscopic data and melting points.
tuted 1H-tetrazoles.
Experimental
Materials and methods
All reagents and solvents were purchased from Sigma-
Aldrich, Fluka or Merck and used without further purifi-
cation. Particle size and morphology were investigated
with a JEOL JEM-2010 scanning electron microscope
Representative data
2-(1H-tetrazol-5-yl) phenol (Table 2, Entry 2): white solid,
-
1
m.p. 225 °C, FTIR (KBr): mmax/cm : 3253 (S), 3059 (S),
2933 (S), 2709 (S), 2566 (M), 2359 (M), 1610 (S), 1545 (S),
1475 (S), 1395 (S), 1358 (S), 1296 (M), 1230 (S), 1115 (W),
(
SEM), using an accelerating voltage of 200 kV. Ther-
mogravimetric analysis (TGA) curves were recorded using
a PL-STA 1500 device manufactured by Thermal Sciences.
IR spectra were recorded as KBr pellets on a VRTEX 70
model BRUKER FTIR spectrophotometer. Powder XRD
patterns were collected with a Rigaku-Dmax 2500
1
1067 (S), 946 (W), 808 (S), 746 (S), 680 (S), 541 (W). H
NMR (400 MHz, DMSO, ppm) d = 8.00–8.02 (m, 1H),
7.40–7.44 (m, 1H), 7.08–7.11 (m, 1H), 6.99–7.03 (m, 1H),
1
11.10 (br, 1H), 15.72 (br, 1H); C NMR (100 MHz, DMSO,
3
diffractometer with nickel-filtered Cu Ka radiation
ppm) d = 155.7, 153, 133.1, 129.4, 120.2, 116.7, 110.9.
˚
(
k = 1.5418 A, 40 kV).
4
-(1H-tetrazol-5-yl)benzonitrile (Table 2, entry 7): white
-
1
solid, m.p. 192.193 °C, FTIR (KBr):mmax/cm : 3475 (S),
150 (S), 3090 (M), 3019 (M), 2923 (M), 2859 (M), 2726
S), 2624 (M), 2565 (M), 2485 (M), 2232 (S), 1620 (S),
566 (S), 1494 (S), 1430 (S), 1364 (M), 1275 (M), 1153
Preparation of Fe O @SiO @L-Histidine
3
4
2
3
nanoparticles
(
1
Fe O was synthesized by a chemical co-precipitating
3 4
(
(
M), 1067 (M), 1028 (S), 848 (S), 749 (S), 695 (M), 552
1
method similar to that previously reported [22], followed
W). H NMR (400 MHz, DMSO, ppm) d = 8.22–8.24 (m,
by a SiO -coating procedure. The resulting MNP powder
2
13
H), 8.09–8.14 (m, 2H); C NMR (100 MHz, DMSO,
2
(
1.00 g) was dispersed in deionized water (100 mL) fol-
lowed by sonication for 30 min, and then L-Histidine (2 g,
2 mmol) was added and the mixture was stirred at 90 °C
ppm) d = 155.7, 133.9, 129.2, 128.2, 1118.8, 113.9.
1
1-(4-(1H-tetrazol-5-yl)phenyl)ethanone (Table 2, entry
for 15 h. The resulting product was separated by magnetic
decantation, washed with distilled water several times and
dried at room temperature overnight.
10): white solid, m.p. 176–178 °C, FTIR (KBr): mmax
cm : 3432 (S), 3144 (M), 3079 (M), 3012 (M), 2969 (M),
2921 (M), 2858 (M), 2719 (M), 2625 (M), 2472 (M), 1680
/
-
1
(
(
(
(
S), 1566 (S), 1431 (S), 1365 (S), 1274 (S), 1156 (W), 1120
W), 1081 (M), 1058 (M), 998 (M), 982 (M), 969 (W), 841
1
S), 752 (M), 705 (M), 589 (M), 491 (M). H NMR
Preparation of immobilized Cu(II) nanoparticles
400 MHz, DMSO, ppm) d = 8.13–8.20 (m, 4H), 2.67 (s,
The as-synthesized Fe O @SiO @L-Histidine nanoparti-
3
4
2
13
3
H); C NMR (100 MHz, DMSO, ppm d = 198, 156.3,
cles (1.00 g) were dispersed in absolute ethanol (30 mL)
1
38.5, 129.7, 129.5, 127.5, 27.4.
for 20 min. Cu(NO ) Á3H O (0.5 g) was then added, and
3
2
2
the mixture was boiled under reflux for 24 h and then
cooled to room temperature. The product was collected by
an external magnetic field, washed several times with
ethanol and dried under vacuum at room temperature
5-(4-methoxyphenyl)-1H-tetrazole (Table 2, entry 11): white
-
1
solid, m.p. 231–232 °C, FTIR (KBr): mmax/cm : 3431 (S),
3155 (S), 3082 (S), 2927 (S), 2855 (S), 2726 (S), 2625 (M),
2555 (M), 2477 (M), 1618 (S), 1503 (S), 1450 (M), 1404 (M),
1302 (M), 1266 (S), 1174 (M), 1119 (M), 1053 (S), 1022 (S),
(
Scheme 1).
1
23