14
M. Abdollahi-Alibeik, M. Pouriayevali / Catalysis Communications 22 (2012) 13–18
Scheme 1. The Friedlander synthesis of quinolines in the presence of 23% (BSPY)HSO4/MCM-41.
4.02 from the nitrogen adsorption isotherms at −170 °C. All samples
were degassed at 130 °C under flowing nitrogen for 1.5 h. Specific
surface area (SBET) was calculated from adsorption data using BET
equation at P/P°=0.1–0.3, and pore volume (Vpore) was calculated
based on Barret–Joyner–Halenda (BJH) method.
2.84 (s, 3H), 4.11 (q, 2H, J=7.1 Hz), 7.41 (m, 2H), 7.47 (dt, 1H, J=
0.8, 7.2 Hz), 7.53 (m, 3H), 7.62 (d, 1H, J=8.2 Hz), 7.77 (dt, 1H, J=1.3,
7 Hz), 8.13 (d, 1H, J=8.5 Hz). 13C NMR (125.7 MHz, CDCl3):
δ=14.06, 24.15, 61.78, 125.61, 126.9, 126.95, 127.87, 128.66, 128.91,
129.165, 129.80, 130.76, 136. 14, 146.84, 155.05, 168.82.
2.2. Preparation of MCM-41 nanoparticles
3. Results and discussion
The synthesis of nanosized MCM-41 was carried out using tetraethyl
orthosilicate (TEOS) as the Si source, cetyltrimethylammonium bromide
(CTAB) as the template and ammonia as the pH control agent with the
gel composition of SiO2:CTAB:NH4OH:H2O=22.5:2.74:53.5:11.11.
In a typical procedure, to a solution of CTAB (1 g, 2.74 mmol) in
deionized water (200 mL), aqueous ammonia (25 wt.%) was added
until the pH of the solution was adjusted to 10.5. Then TEOS (5 mL)
was added dropwise at 70 °C for 1 h and the mixture was allowed
to cool to room temperature and was stirred for 12 h. The solid was
separated by centrifuge and washed with distilled water (20 mL)
and EtOH (2×10 mL) respectively. The solid was dried in an oven at
120 °C for 1 h and then calcined at 550 °C for 4 h.
3.1. The catalyst preparation
Nanosized MCM-41 was prepared by sol–gel method. The
(BSPY)HSO4/MCM-41 catalysts with various loading amounts of
(BSPY)HSO4 were prepared. For this purpose, suspensions of the MCM-
41 and (BSPY)HSO4 with various molar ratios of (BSPY)HSO4:MCM-41
in a constant amount of acetone were stirred for 12 h. The suspensions
were centrifuged and washed many times with acetone and then dried
in an oven at 120 °C. The details of conditions for catalyst preparation
are listed in Table 1.
As shown in Table 1, loading amounts of (BSPY)HSO4 present in
the MCM-41 were found to be 5, 14, 23 and 28 wt.%.
2.3. Preparation of 23 wt.% (BSPY)HSO4/MCM-41
3.2. Characterization of materials
(BSPY)HSO4 as protic ionic liquid was synthesized according to
reported procedure [18]. To a suspension of the MCM-41 (60 mg) in
acetone (1 mL), (BSPY)HSO4 (0.0626 g) was added and the mixture
was stirred for 12 h. The catalyst was separated by centrifuge, washed
with acetone (4×2 mL) and dried in an oven at 120 °C for 2 h.
The MCM-41 and the prepared catalysts were characterized by
SEM, XRD, FT-IR and BET techniques.
The SEM image of MCM-41 (Fig. 1) shows spherical nanoparticles
with the size of less than 100 nm.
The FT-IR spectra of MCM-41, (BSPY)HSO4 and (BSPY)HSO4/MCM-41
with different loading amounts of (BSPY)HSO4 are shown in Fig. 2. As
shown in Fig. 2a, pure (BSPY)HSO4 exhibited characteristic peaks of
alkyl sulfonate and hydrogensulfate at 1230, 1170, 1058, 1028, 885,
854 and 594 cm−1 and the peaks of pyridine ring at 1489, 1651 and
684 cm−1. FT-IR spectrum of MCM-41 (Fig. 2b) shows typical IR
bands at 1080 and 812 cm−1 corresponding to stretching Si\O and
460 cm−1 corresponding to bending Si\O\Si. In the FT-IR spectra of
5–23% (BSPY)HSO4/MCM-41 (Fig. 2c–f), apart from the main peaks
of MCM-41, additional peaks corresponding to functional group of
2.4. Catalytic activity of (BSPY)HSO4/MCM-41 in Friedlander synthesis
A mixture of o-aminobenzophenone (1 mmol), ketone or β-
diketone (1.2 mmol) and (BSPY)HSO4/MCM-41 (70 mg) was heated
at 100 °C. After completion of the reaction (monitored by TLC, eluent;
n-hexane:EtOAc, 8:2), EtOH (2 mL) was added, the catalyst was
separated and washed with EtOH (3×2 mL). After addition of water,
the product was precipitated with high purity. Further purification
was achieved by recrystallization in EtOH. The pure quinolines were
obtained in 78–95% yields.
2.5. Physical and spectroscopic data for selected compound
2.5.1. Ethyl-2-methyl-4-phenylquinoline-3-carboxylate (3a)
MP: 100–101 °C (Lit. [19], 100–101 °C). IR (KBr): υmax: 2978, 1711,
1561, 1444, 1402, 1297, 1237, 1182, 1130, 1070, 767, 700, 623,
603 cm−1 1H NMR (500 MHz, CDCl3): δ=1.00 (t, 3H, J=7.1 Hz),
.
Table 1
Preparation of (BSPY)HSO4/MCM-41 with various loading amounts of (BSPY)HSO4/
MCM-41.
Entry
Mole ratio of
(BSPY)/HSO4:MCM-41
Amount of (BSPY)/HSO4 on
the MCM-41 (wt.%)
1
2
3
4
1:20
1:10
1:5
5
14
23
28
1:2
Fig. 1. The SEM image of MCM-41.