L. Ma’mani et al. / Applied Catalysis A: General 384 (2010) 122–127
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silica-supported Fe(ClO4)3 [26], MeSO3H/Al2O3 [27], Nafion-H [28],
CoCl2/Ac2O [29], Fe3+-K10 montmorillonite [30], heteropolyacids
[31], PMA/SiO2 [32], zeolites [33], triflic anhydride [34], P2O5–SiO2
[35] and using tertiary esters [36] or trimethylsilyl cyanide [37]
instead of alcohols or nitriles, respectively. However aforemen-
tioned developed methods suffer from the following disadvantages
such as: expensive or unavailability or toxicity of the reagent,
extended reaction times, additionally the main drawback of almost
existing methods is that the catalysts are decomposed under aque-
ous work-up conditions and their recoveries are often impossible.
Therefore the importance of overcoming these drawbacks is grow-
ing that as attention and many efforts are directed to develop an
efficient, catalytic system for synthesis of amides, we described
a green protocol recoverable and cost-effective catalyst for this
purpose. In an effort we introduce a convenient and recoverable
procedure for the preparation of amides from alcohols and nitriles
by employing a catalytic amount of ␥-Fe2O3@SiO2-HClO4.
under neat condition at room temperature, until complete dis-
appearance of starting alcohols (as monitored by TLC). After
completion, the mixture reaction diluted by 5 mL diethyl ether,
then the catalytic system removed by an external magnet then mix-
10% NaHCO3 and water, dried with Na2SO4 and concentrated to
give the products. All isolated products gave satisfactory spectral
data (IR, 1H NMR and 13C NMR) and compared with those reported
in literature.
Spectral data:
1. 1H NMR (500 MHz, CDCl3): ı = 5.43 (brs, NH), 1.93 (s, 3H), 1.36
(s, 9H). 13C NMR (125.7 MHz, CDCl3): ı = 51.5, 29.1, 24.9.
2. 1H NMR (500 MHz, CDCl3): ı = 7.27–7.38 (m, 5H), 5.97 (brs, NH),
4.88–4.93 (q, 1H), 2.01 (s, 3H), 1.81–1.91 (m, 2H), 0.90–0.93 (t,
3H). 13C NMR (125.7 MHz, CDCl3): ı = 169.7, 142.5, 129, 127.7,
127, 55.3, 23.8, 11.1.
3. 1H NMR (500 MHz, CDCl3): ı = 7.35–7.38 (m, 4H), 7.29–7.32 (m,
2H), 7.26–7.27 (m, 4H), 6.27–6.30 (brs, 2H), 2.07 (s, 3H). 13C
NMR (125.7 MHz, CDCl3): ı = 169.5, 141.9, 129, 127.89, 127.87,
57.4, 23.7.
4. 1H NMR (500 MHz, CDCl3): ı = 7.28–7.30 (m, 1H), 7.19–7.20 (m,
2H), 7.11–7.13 (m, 1H), 5.93–5.95 (brs, 1H), 5.18–5.19 (brs, 1H),
2.78–2.83 (m, 2H), 2.04–2.06 (m, 1H), 2.02 (s, 3H), 1.82–1.88 (m,
3H). 13C NMR (125.7 MHz, CDCl3): ı = 169.7, 137.9, 137.1, 129.5,
129.1, 127.6, 126.6, 47.8, 30.5, 29.6, 23.8, 20.3.
2. Experimental
2.1. Synthesis of HClO4-functionalized silica-coated magnetic
nanoparticles ꢀ-Fe2O3@SiO2-HClO4
5. 1H NMR (500 MHz, CDCl3): ı = 7.20–7.32 (m, 5H), 6.23 (brs, NH),
5.05–5.11 (m, 1H), 1.92 (s, 3H), 1.44–1.45 (d, J = 6.9 Hz, 3H). 13
C
The maghemite (␥-Fe2O3) nanoparticle was synthesized by a
chemical co-precipitation technique of ferric and ferrous ions in
alkali solution. ␥-Fe2O3 nanoparticles were synthesized based on
a reported method with minor modifications. FeCl2·4H2O (1.99 g)
and anhydrous FeCl3 (3.25 g) were dissolved in water (20 mL) sep-
arately, followed by the two iron salt solutions being mixed under
vigorous stirring (800 rpm). A NH4OH solution (0.6 M, 200 mL) was
then added to the stirring mixture at room temperature, immedi-
ately followed by the addition of a concentrated NH4OH solution
(25%, w/w, 30 mL) to maintain the reaction pH between 11 and
12. The resulting black dispersion was continuously stirred for 1 h
at room temperature and then heated to reflux for 1 h to yield a
brown dispersion. The magnetic nanoparticles were then purified
by a repeated centrifugation (3000–6000 rpm, 20 min), decanta-
tion, and redispersion cycle 3 times, until a stable brown magnetic
dispersion (pH 9.4) was obtained.
Coating of a layer of silica on the surface of the ␥-Fe2O3 nanopar-
ticles was achieved by premixing (ultrasonic) a dispersion of the
purified nanoparticles (8.5%, w/w, 20 mL) obtained previously with
methanol (80 mL) for 1 h at 40 ◦C. Concentrated ammonia solution
as added, and the resulting mixture was stirred at 40 ◦C for 30 min.
Subsequently, tetraethyl orthosilicate (TEOS, 1.0 mL) was charged
to the reaction vessel, and the mixture was continuously stirred at
40 ◦C for 24 h. The silica-coated nanoparticles were collected by a
permanent magnet, followed by washing three times with EtOH,
diethyl ether and drying at 100 ◦C in vacuum for 24 h.
NMR (125.7 MHz, CDCl3): ı = 169.8, 143.8, 129, 128.9, 127.6,
126.7, 126.6, 49.2, 32.7, 22.2.
6. 1H NMR (500 MHz, CDCl3): ı = 7.76 (d, J = 8.03 Hz, 2H),
7.43–7.52 (m, 3H), 5.98 (brs, NH), 1.51 (s, 9H). 13C NMR
(125.7 MHz, CDCl3): ı = 167.3, 136.3, 131.5, 129.0, 128.9, 127.1,
52.0, 29.3.
7. 1H NMR (500 MHz, CDCl3): ı = 7.81–7.82 (d, J = 7.2 Hz, 2H),
7.30–7.55 (m, 8H), 6.44 (brs, NH), 5.37–5.40 (m, 1H), 1.64–1.66
(d, J = 6.9 Hz, 3H). 13C NMR (125.7 MHz, CDCl3): ı = 167, 143.5,
135, 131.9, 129.1, 128.9, 127.9, 127.3, 126.7, 49.6, 22.1.
8. 1H NMR (500 MHz, CDCl3): ı = 7.86–7.87 (d, J = 7.93 Hz, 2H),
7.52–7.57 (q, 1H), 7.46–7.50 (m, 2H), 7.38–7.41 (m, 4H),
7.30–7.38 (m, 6H), 6.78–6.80 (brs, 1H), 6.50–6.51 (d, J = 7.8 Hz,
1H). 13C NMR (125.7 MHz, CDCl3): ı = 166.9, 141.9, 134.6, 132.1,
129.1, 129, 128, 127.9, 127.5, 57.8.
9. 1H NMR (500 MHz, CDCl3): ı = 6.23–6.26 (d, J = 16.86 Hz, 1H),
6.04–6.09 (q, 1H), 5.57–5.59 (d, J = 10.19 Hz, 1H), 5.54 (brs,
NH), 1.42 (s, 9H). 13C NMR (125.7 MHz, CDCl3): ı = 165.2, 132.4,
125.8, 51.7, 29.1.
10. 1H NMR (500 MHz, CDCl3): ı = 7.27–7.38 (m, 5H), 6.29–6.32 (d,
J = 16.9 Hz, 1H), 6.13–6.18 (m, 2H), 5.64–5.66 (d, J = 10.2 Hz, 1H),
4.97–5.02 (q, 1H), 1.86–1.93 (m, 2H), 0.92–0.95 (t, 3H). 13C NMR
(125.7 MHz, CDCl3): ı = 165.2, 142.4, 131.3, 129, 127.7, 127.1,
126.9, 55.4, 29.4, 11.2.
11. 1H NMR (500 MHz, CDCl3): ı = 7.38–7.35 (m, 4H), 7.32–7.26 (m,
6H), 6.45–6.46 (d, J = 7.31 Hz, 1H), 6.33–6.37 (m, 2H), 6.18–6.24
(q, 1H), 5.68–5.70 (d, J = 10.21 Hz, 1H). 13C NMR (125.7 MHz,
CDCl3): ı = 165, 141.7, 130.9, 129.1, 127.9, 127.8, 127.6, 57.4.
12. 1H NMR (500 MHz, CDCl3): ı = 7.30–7.32 (d, J = 7.45 Hz, 1H),
7.20–7.24 (m, 2H), 7.13–7.15 (d, J = 7.24 Hz, 1H), 6.33–6.37 (d,
J = 16.93 Hz, 1H), 6.10–6.16 (q, 1H), 5.91 (brs, NH), 5.68–5.70
(d, J = 10.28 Hz, 1H), 5.28–5.31 (m, 1H), 2.79–2.89 (m, 2H),
2.08–2.14 (m, 1H), 1.89–1.93 (m, 3H). 13C NMR (125.7 MHz,
CDCl3): ı = 165.1, 138, 136.9, 131.4, 129.6, 129.2, 127.7, 126.9,
126.7, 47.9, 30.4, 29.6, 20.3.
HClO4 (0.3 mmol, as a 70% aq. solution) was added to a sus-
pension of 1 g ␥-Fe2O3@SiO2 in Et2O (50 mL) while dispersed by
sonication. The mixture was concentrated and the residue was
heated at 70 ◦C for 72 h under vacuum, while being mechan-
ically stirred, to obtain [␥-Fe2O3@SiO2-HClO4] (0.25 mmol/g,
10 mg = 0.0025 mmol of HClO4).
2.2. Typical experimental protocol for the synthesis of amides
from alcohols and nitriles
13. 1H NMR (500 MHz, CDCl3): ı = 7.27–7.35 (m, 5H), 6.78 (brs,
1H), 6.26–6.30 (dd, J = 16.97, 1.74 Hz, 1H), 6.17–6.22 (m, 1H),
5.59–5.62 (dd, J = 16.94, 1.73 Hz, 1H), 5.19–5.22 (m, 1H),
Alcohol (2 mmol) and nitrile (2.2 mmol) were mixed with [␥-
Fe2O3@SiO2-HClO4] (100 mg, 0.025 mmol, and 2.5 mol% of HClO4)