G Model
CATTOD-9765; No. of Pages6
ARTICLE IN PRESS
Q. Guo et al. / Catalysis Today xxx (2015) xxx–xxx
C H
2
2
5
0
.1eq Cp ZrCl
2 2
+
CH CH CH CHO
+
3
2
2
CH Cl
NH2
2
2
NHC H
4 9
N
C H
3
7
1
eq
4eq
1a
1b
Scheme 1. Cp2ZrCl2-catalyzed reaction of aniline with n-butyraldehyde.
derivatives from aniline and aldehyde using Cp ZrCl2 or Cp ZrCl2
temperature, the catalyst was separated from the liquid product
by filtration. The recovered catalyst was washed with DCM, and
dried at room temperature overnight under aerobic conditions,
and then reused for the next reaction under the same conditions
mentioned above.
2
2
supported on MCM-41 (Cp ZrCl /MCM-41) as catalyst in this paper.
2
2
It is worth noting that the latter catalyst has good catalytic activity,
reusability and simple procedure.
2
. Experimental
3. Results and discussion
2.1. Materials
3
.1. Synthesis of quinoline derivatives catalyzed by Cp ZrCl
2
2
Zeolite Y, ZSM-5, H and MCM-41 were synthesized in our
laboratory according to the methods in the literatures [22–25].
Supported Cp ZrCl catalysts used in this work were prepared
When 1.5 mmol aniline reacted with 6 mmol n-butyraldehyde
2
2
in the presence of 0.15 mmol Cp ZrCl2 (0.1 equiv.) under nitro-
2
by a conventional impregnation method. Typically, at room tem-
perature, 3.75 mmol (1.095 g) Cp ZrCl was dissolved in 20 mL
gen atmosphere, 3-ethyl-2-propylquinoline (1a) was obtained as
a major product in 60% yield (Scheme 1). For the structure of 3-
ethyl-2-propylquinoline was determined by NMR spectrum shown
in supporting information, no other isomer products could be iso-
lated.
2
2
tetrahydrofuran under gentle magnetic stirring. Next, the solution
was dropped into 2.5 g MCM-41 and stirred for 24 h. Then the solu-
◦
tion was dried in a conventional oven with air circulation at 75 C for
2
4 h, after the impregnation pale yellow solids (Cp ZrCl /MCM-41)
2 2
In addition, N-butylbenzenamine (1b) was obtained in 20%
yield as a by-product. Considering the influence of temperature
and solvents, we investigated this double carbon–nitrogen bond
formation under various conditions. The optimal reaction con-
were obtained. THF was purified by distillation under nitrogen from
sodium. Other starting materials were obtained from commercial
supplies and used without further purification.
◦
ditions were 40 C in DCM. Lower yields of 1a were obtained,
2.2. Characterization of the catalyst
◦
when the reaction temperature was decreased to 25 C or raised
◦
to 50 C. A broad number of solvents were tested for the reac-
Power X-ray diffraction (XRD) patterns were recorded on a
tion. Dichloromethane, toluene, acetonitrile, chloroform, dimethyl
sulfoxide and 1,2-dichloroethane gave comparable yields of 1a
whereas lower yields were obtained with tetrahydrofuran.
In the further work, the amount of the reactants and the dosage
of catalysts were varied. As shown in Table 1, an optimal ani-
line/aldehyde ratio of 1/4 is obtained. At lower ratios, the aldehyde
tends to condense and product isolation becomes difficult. Also,
Bruker AXS D8 advance X-ray diffractometer. The texture prop-
◦
erty was determined by measuring the N2 isotherm at −196 C on
a Micromeritics ASAP 2020 automated system. Elemental analysis
was performed on a Rigaku ZSX 100e X-ray fluorescence (XRF) spec-
1
13
trometer. H and C spectra were measured by JEOL JNM-ECA600.
2.3. Synthesis of quinoline derivatives
we obtained good results when 0.1 equiv. of Cp ZrCl2 was used.
2
Treatment of 1 equiv. aniline and 4 equiv. n-butyraldehyde with
The first typical reaction was carried out with 1 mmol aniline
0
.1 equiv. of Cp ZrCl2 afford 60% quinoline and 20% N-butylaniline
2
and 4 mmol n-butyraldehyde added to the solution of 0.1 mmol
Cp ZrCl catalysts dissolved in 8 mL dichloromethane (DCM) in a
(entry 4). It shows essentially same yields compared to 1 equiv. of
2
2
Cp ZrCl2 as the catalyst (entry 7). This indicated that the overall
2
◦
dry Schlenk tube under nitrogen atmosphere at 40 C. Dodecane
was added as an internal standard. The mixture was stirred at 40 C
transformation should be catalytic to Cp ZrCl . The reactions were
2
2
◦
also checked by using 0.05 equiv. catalyst, the yield of quinoline
was 55% (entry 6), but the reaction time of 0.05 equiv. case was
until the reaction was completed. The reaction mixture was then
quenched with 3 M ammonia solution, and extracted with diethyl
ether, then the combined organic layer was washed with water,
brine, dried over sodium sulfate and concentrated to get a crude
product, which was purified by column chromatography over silica
gel using ether/petroleum ether (1/30) as eluent.
3
2 h, as a result, 0.1 equiv. Cp ZrCl2 was the best as the catalytic
2
amount. In this reaction, firstly, the nucleophilic addition reaction
of aniline with aldehyde occurs to give imine after elimination of
Table 1
The second typical reaction was carried out with aniline
a
Cp2ZrCl2 catalyzed of aniline with n-butyraldehyde.
(
(
1.5 mmol), n-butyraldehyde (6 mmol), and Cp ZrCl /MCM-41
2 2
◦
Yield [%]b
0.1 g) in CH Cl (12 mL). The mixture was stirred for 5 h at 40 C
Entry
Aniline:n-
Conditions
2
2
butyraldehyde:
Cp2ZrCl2
in a dry Schlenk tube under nitrogen atmosphere. After cooling the
reaction mixture, the catalyst was separated from the liquid prod-
uct by filtration. It was concentrated and then purified by column
chromatography over silica gel. The reaction was monitored by gas
chromatograph to determine the yield of the product.
Quinoline
N-Butylbenzenamine
◦
◦
1
2
3
4
5
6
7
1:1:0.1
1:2:0.1
1:3:0.1
1:4:0.1
1:5:0.1
1:4:0.05
1:4:1
40 C, 1 h
21
53
47
60
59
55
63
Trace
14
20
20
27
40 C, 18 h
◦
Catalytic activity was determined by the yield of quinoline
derivatives using dodecane as an internal standard. The structures
of the products were identified by 1H, C NMR spectra and HRMS.
The catalytic reaction was carried out with aniline (3 mmol),
n-butyraldehyde (12 mmol), and Cp ZrCl /MCM-41 (0.2 g) in
40 C, 7 h
◦
40 C, 5 h
◦
40 C, 8 h
13
◦
40 C, 32 h
19
37
◦
40 C, 4 h
2
2
a
with dodecane as an internal standard.
◦
CH Cl (24 mL). The mixture was stirred for 7 h at 40 C under
b
2
2
nitrogen atmosphere. After cooling the reaction mixture to room
Please cite this article in press as: Q. Guo, et al., Synthesis of quinoline derivatives from anilines and aldehydes catalyzed by Cp ZrCl2
2
2
2