One step C-N bond formation from alkylbenzene and ammonia over Cu-modified TS-1 zeolite catalyst

Article abstract of DOI:10.1039/c4cy00472h

A Cu doped TS-1 zeolite sample was applied to catalyze the formation of C-N bonds on both the ring and the side chain of toluene, as well as other alkylbenzenes. A yield of 3.4% of toluidine was obtained for the amination of toluene, with a 1.0% yield of nitrobenzene. Cyanobenzene was also obtained as the C-N bond product on the side chain with a yield of 1.0%. The selectivity for C-N bond formation was 52.4%. The catalyst promoted the formation of a hydroxylamine intermediate from ammonia and hydrogen peroxide, and then the instantaneously generated amino cation reacted with the substrate to form C-N bonds on both the ring and side chain. Cyanobenzene was produced from the dehydration of benzylamine, formed via the reaction of ammonia and toluene. The formation of C-N bonds on the ring had an ortho-orientation advantage for mono-substituted-benzenes. With the increase in the number of methyl substituents, the yield of the ring products decreased, which might be caused by steric hindrance. the Partner Organisations 2014.

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One step C–N bond formation from alkylbenzene and ammonia over
Cu-modified TS-1 zeolite catalyst†
Sheng Xia, Tianhua Yu, Huihui Liu, Guiying Li*, Changwei Hu*
5
Received (in XXX, XXX) Xth XXXXXXXXX 200X, Accepted Xth XXXXXXXXX 200X
DOI: 10.1039/b000000x
Cu doped TSꢀ1 zeolite sample was applied to catalyze the formation of C–N bonds on both the
ring and the side chain of toluene as well as other alkylbenzenes. A yield of 3.4% to toluidine was
10 obtained for the amination of toluene, with 1.0% yield to nitrobenzene. Cyanobenzene was also
obtained as the C–N bond product on the side chain with a yield of 1.0%. The selectivity to C–N
bond formation was 52.4%. The catalyst promoted the formation of hydroxylamine intermediate
from ammonia and hydrogen peroxide, and then the instantaneously generated amino cation react
with the substrate to form C–N bonds on both the ring and side chain. The cyanobenzene was
15 produced from the dehydration of benzylamine formed via the reaction of ammonia and toluene.
The formation of C–N bonds on the ring had orthoꢀorientation advantage for monoꢀsubstitutedꢀ
benzene. With the increase of the number of methyl substituent, the yield of ring products
decreased, which might be caused by steric hindrance.
activity for the amination process of benzene9. In the present
work the catalyst was employed to catalyze the reaction of
55 toluene with aqueous ammonia and hydrogen peroxide to
investigate the functionalization of C–H bonds both on the ring
and side chain.
1 Introduction
20 The C–N bond formation reaction has been known to contribute
to the ideality of biosynthesis in nature1ꢀ8. Arylamines are
abundant in biologically active natural products and medicinally
important compounds, and widely used in materials with useful
electrical and mechanical properties. The selective activation and
25 functionalization of C–H bonds, especially those of aromatics
under mild conditions, remain one of the most significant
2. Experimental
challenges in both synthetic and green chemistry9ꢀ19. Previous 60 2.1. Preperation of TS-1 and Cu/TS-1 zeolite samples
ways for the formation of C–N bonds include transferring an
amino group from one moleculer to another20ꢀ24. The promoted
30 investigation of the direct amination of aromatics with ammonia
and hydrogen peroxide is mostly concerned with the preparation
of aniline directly from benzene9,10, while that for other aromatic
A hydrothermal synthesis method similar to our previous work9
was used to prepare TSꢀ1 zeolite. 96.0 g of tetrapropylammonium
hydroxide (TPAOH) (25.0 wt.%) was firstly added to a 1L
beaker, and then 91.0 g of tetraethyl orthosilicate (TEOS) was
compounds is rarely studied. The photocatalytic aromatic ring 65 added dropwise. The mixture was stirred by magnetic stirring
amination was also studied with less than 1% aniline yield
35 obtained25.Toluidine acts as important aromatic amine, which can
be used in the production of dyes, pharmaceutical and rubber
chemicals. The traditional methods for preparation of toludine
apparatus at 298 K in water bath, followed by adding 40.0 g
isopropanol and 40.0 g water. After being stirred for 10 minutes,
5.0 g aqueous solution of titanium trichloride (15.0 wt.%) diluted
by 20 mL water was added into the mixture dropwise. The
were multistep, high cost and environmentally unfriendly. In the 70 resultant solution was heated to 333 K with stirring and kept for 1
previous work, the direct amination of toluene to toludine has
40 been come true with acceptable yield using hydroxylamine
h, then to 358 K and kept for 6 h with stirring. During the heating
process, water was added to keep the total volume of 400 mL.
Then the resultant solution was cooled down to room
temperature, and finally crystallized in autoclave at 448 K for 7
hydrochloride26ꢀ28
.
The TSꢀ1 zeolite is a kind of molecular sieve which is
crystalline with MFI topology structure and widely used as 75 days. The solid product was obtained through filtrating, washing,
catalysts29ꢀ32. Since the discovery of the synthesis method of TSꢀ1
45 zeolite in 1983 at Enichem33, the properties of the TSꢀ1 zeolite
continue to attract attention by researchers. It is an active and
highly selective catalyst in a number of organic reactions such as
crushing and drying. Then the obtained sample was calcined at
823 K in air atmosphere for 8 h. Thus the TSꢀ1 zeolite catalyst
was obtained.
The Cu doped TSꢀ1 catalyst was prepared by wet impregnation
epoxidation of alkenes, oxidation of alkanes and alcohols34ꢀ39, and 80 method. The above obtained TSꢀ1 of 3 g was mixed with
hydroxylation of aromatics40ꢀ44 under mild conditions with
50 hydrogen peroxide as oxidant.
After screening of different metal (Cu, Ni, V, etc) doped TSꢀ1,
it was found that Cu modified TSꢀ1catalyst exhibited acceptable
equivalentꢀvolume aqueous solution containing 0.1798 g or
0.2265 g or 0.2831 g or 0.3398 g of Cu(NO3)2ꢁ3H2O at 343 K.
Then the mixture was impregnated at room temperature for 24 h.
After dried at about 373 K for 12h, the sample was calcined at
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Table 1 The BET surface area of the samples.
823 K in air atmosphere for 8 h to obtain the Cu/TSꢀ1 catalyst.
Thus, Cu species were introduced to TSꢀ1 zeolite. According to
the controlled amount of Cu(NO3)2ꢁ3H2O, the Cu/TSꢀ1 samples
were named as 1.5Cu/TSꢀ1 (1.5 wt.%), 2.0Cu/TSꢀ1 (2.0 wt.%),
2.5Cu/TSꢀ1 (2.5 wt.%) and 3.0Cu/TSꢀ1 (3.0 wt.%).
Samples
SBET (m2/g)
Vmic (cm3/g)
Davg (Å)
5
TSꢀ1
400
387
374
365
353
0.096
0.095
0.093
0.076
0.075
17.55
17.54
17.54
17.51
17.51
1.5Cu/TSꢀ1
2.0Cu/TSꢀ1
2.5Cu/TSꢀ1
3.0Cu/TSꢀ1
2.2 Characterization of the TS-1 and Cu/TS-1 samples
BET surface area of the samples was detected on Micromeritics
Tristar 3020 analyser by N2 adsorption/desorption measurement.
10 The surface area of these samples was calculated with multipoint
by BrunauerꢀEmmettꢀTeller method. The BET equation was
applied to the N2 adsorption isotherms. The pore size distribution
and the average pore diameters were determined by the BJH
method. Before measurement, the samples were activated at 373
15 K for 1 h and then at 573 K for 4 h under vacuum.
a SBET, Vmic and Davg represented specific surface area, micropore volume and
average pore diameter, respectively.
65
After that, the reaction product was cooled down to room
temperature. The liquid phase of the above process was separated
from the catalyst by filtration. Acetonitrile was added to avoid
stratifying and keep the total volume of the mixture at 50 mL.
70 GCꢀMS (coupled gas chromatograph and mass spectroscopy,
Agilent, 5973 Network 6890N) was used for qualitative analyze
and GC chromatography (FILI, GCꢀ9790) with an Innowax
capillary column (30 m 0.25 mm) was used for quantitative
analysis. The products with CꢀN bond formed obtained were
75 toluidine, nitrotoluene and cyanobenzene, while oxidation
products with C–O bond formed were cresols, benzaldehyde, and
benzylalcohol.
The yield of products and the selectivity to C–N bondꢀcontaining
products were calculated by the following formulas:
80 Yield (%)
= Mole amount of product (toluidine, etc.)
/(Mole amount of initial toluene)×100;
Selectivity of CꢀN bonds on the ring (%)
= (Mole amount of toluidine + Mole amount of nitrotoluene)
85 /(Mole amount of all products) ×100.
Selectivity of products containing CꢀN bonds (%)
= (Mole amount of toluidine + Mole amount of nitrotoluene
+ Mole amount of cyanobenzene)
/(Mole amount of all products) ×100.
90 Selectivity of products on the ring (%)
= (Mole amount of toluidine + Mole amount of nitrotoluene
+ Mole amount of cresols)
/(Mole amount of all products) ×100.
Xꢀray diffraction patterns (XRD) of the TSꢀ1 and Cu/TSꢀ1
samples were obtained by DXꢀ1000 CSC diffraction instrument
using Cu Kα (λ=1.54056 Å) radiation operated at 25 mA and 40
kV. The 2θ value range was from 2.7° to 80°, and the data were
20 collected with a step of 0.0544° under continuous scanning mode.
Fourier transform infrared (FTꢀIR) spectra of TSꢀ1 and Cu/TSꢀ
1 samples were acquired on a Nicolet Nexus NEXUS670 FTꢀIR
instrument by film method with an MCT detector. The samples
were firstly mixed with KBr by the mass ratio of 1:100 and
25 pressed. The FTꢀIR spectra were collected in the range of 4000ꢀ
400 cmꢀ1 with a resolution of 2 cmꢀ1.
Ultraviolet visible diffuse reflectance (UVꢀVIS) spectra of
these samples were collected on a TUꢀ1901 spectrophotometer
equipped with a reflectance attachment using the mitering of Abs
30 at intermediate speed. The spectral bandwidth was 5 nm with a
sample interval of 1.000 nm. Before measurement, the samples
were dried at 373 K overnight and packed with a BaSO4 plate as
the reference.
The surface morphology and composition of different samples
35 were characterized by scanning electron microscopy (SEM) with
energy dispersive spectrum (EDS) (JSMꢀ7500F, JEOL, Tokyo,
Japan). The instrument was set at 5 kV. Gold was applied to coat
on the surface of the samples with a vacuum sputterꢀcoater to
enhance the conductivity of the samples and the quality of the
40 SEM images.
Inductively coupled plasmaꢀatomic emission spectrometry
(ICPꢀAES) was used to analyze the actual Cu content of the
samples. The analysis was performed on thermoelemental: IRIS
Advantage. The pump rate was 110 rpm (2,035 mL / min), and
45 the nebulizer pressure (PSI) was 27 with low auxiliary gas rate.
The RF power was 1150 W. 0.05 g sample was dissolved in aqua
regia of 100 mL at 333K in water bath.
TON
95 = (Mole amount of toluidine + Mole amount of nitrotoluene
+ Mole amount of cyanobenzene + Mole amount of cresols
+ Mole amount of benzaldehyde +Mole amount of benzylalcohol)
/(Mole amount of copper contained)
TOF
100 = (Mole amount of toluidine + Mole amount of nitrotoluene
+ Mole amount of cyanobenzene + Mole amount of cresols
+ Mole amount of benzaldehyde +Mole amount of benzylalcohol)
/(Mole amount of copper contained × Reaction time)
2.3. Activity test
50 The reaction was carried out in a oneꢀnecked roundꢀbottom flask
(50 mL) at atmospheric pressure in open air. The TSꢀ1 and
Cu/TSꢀ1 samples were used to catalyze the reaction. Firstly, 0.5
mL substrate toluene and certain amount of catalyst were
introduced into the reaction flask connected with a condenser.
55 The flask was heated in oil bath with stirring. The mixture of
NH3ꢁH2O and H2O2 were diluted by water and kept at 273 K
under the protection of ice water mixture, and then added into the
reaction system dropwise using peristaltic pump with 0.1 mL/min
from the top of the condenser in the whole reaction process10. The
60 reaction time was generally 365 min, and the variation of reaction
time was also shown in the optimization of reaction conditions.
3 Results and Discussion
105 3.1 Nitrogen adsorption/desorption
The BET surface area of TSꢀ1 and Cu/TSꢀ1 samples were shown
in Table 1. The N2 adsorption/desorption isotherms and the pore
size distribution of the TSꢀ1 and 2.5Cu/TSꢀ1 were shown in
110 Fig.1. As shown in Fig.1 (a), the N2 adsorption/desorption
2
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isotherms were corresponded to TSꢀ1 zeolite in the literatures38, 30 species on the Cu/TSꢀ1 samples, no crystalline phase related to
40, 45, 46. The
Cu species was observed on these samples. The relative
(a)
5
(b)
Fig. 1 N2 adsorption/desorption isotherms of different samples (a)
and the pore size distribution (b).
10 isotherm of the samples showed typically Type character, for
which the flat part of the isotherm indicates the complete filling
of the micropores by condensed nitrogen, and the hysteresis loops
in the nitrogen isotherm represented the existence of some
mesoporosity in minority. The pore size distribution Fig.1 (b) of
15 different samples confirmed the presence of micropores in these
samples. As the results shown in Table 1, the BET surface area of
TSꢀ1 was about 400 m2/g with the micropore volume of 0.096
cm3/g. The surface area showed decreasing tendency with the
increase of Cu content. It was considered that the impregnation of
20 Cu species blocked some of the micropores of TSꢀ1, thus the
surface area and micropore volume of these samples decreased
with the increase of Cu content.
3.2 XRD characterization
25
The TSꢀ1 and Cu/TSꢀ1 zeolite samples were characterized by Xꢀ
Ray Diffraction. As shown in Fig. 2, the characteristic diffraction
peaks of crystal MFI structure were observed at 2θ of 7.9°, 8.8°,
23.1°, 23.9° and 24.4°32, 41, 46, 47 . Due to the high dispersion of Cu
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Fig. 2 XRD patterns of TSꢀ1 and Cu/TSꢀ1 samples.
35
Fig. 4 UVꢀvis of TSꢀ1 and Cu/TSꢀ1.
3.4 UV-vis characterization
The UVꢀvis spectra of the TSꢀ1 and Cu/TSꢀ1 were shown in Fig.
40 4. Based on the literature38,41,51,52, the strong absorption band
around 210 nm was the characteristic peak of Ti species in the
framework of silicalite, indicating the formation of framework Ti
species in these samples. The band around 260ꢀ280 nm and 330
nm were corresponded to the Ti species extraꢀframework wherein
45 the former was assigned to the titanium species and the latter was
deemed to be caused by the anatase phase of TiO2. The results
revealed that the Ti species were almost in the framework with
few out of the framework for TSꢀ1 and Cu/TSꢀ1 samples. The
weak absorption band around 600ꢀ800 nm of the Cu/TSꢀ1
50 samples was assigned to the dꢀd transitions of Cu2+ ions53. With
the increase of the Cu content, the intensity of the band around
600ꢀ800 nm got stronger, indicating the formation of CuO species
which was in accord with the tendency reported in our previous
work10,53. It was indicated that the Ti species entered into the
55 framework of the skeleton structure for TSꢀ1, and the
impregnation of Cu (NO3)2ꢁ3H2O to TSꢀ1 zeolite samples had not
led to the appearance of Ti at extraꢀframework.
5
Fig. 3 FTꢀIR of TSꢀ1 and Cu/TSꢀ1 samples.
crystallinity (RC) of the samples were calculated based on the
10 ratio of the total intensity of the characteristic diffraction peaks,
using TSꢀ1 sample (RC=100%) as standard. It could be seen that
the RC of the Cu/TSꢀ1 sample was almost the same as TSꢀ1.
Thus both the TSꢀ1 and Cu/TSꢀ1 zeolite samples had typical MFI
crystal structure. The loaded Cu species did not affect the crystal
15 structure of TSꢀ1, and the Cu species was considered to be low9.
It was indicated that the existence of Cu species on Cu/TSꢀ1
samples prepared by impregnation was similar to that on TSꢀ1
prepared by MH method47.
3.5 The SEM-EDS and ICP-AES characterization
60 The scanning electron microscopy images of the samples were
collected. TSꢀ1 and 2.5Cu/TSꢀ1 were chosen and analyzed as the
typical samples, and the images were shown in Fig. 5 (a) and (b).
These samples were obviously crystalline, and the sizes of them
were around 0.4 ꢂm. The results indicated that TSꢀ1sample was
65 irregular spherical crystal. It was found in our previous work that
only the CuꢀTSꢀ1 samples which were prepared by adding Cu
species in the period of hydrothermal synthesis step had the
polygonal structure47. But in the present work, the Cu/TSꢀ1
sample that prepared by impregnation after hydrothermal process
70 also showed the similar tendency of forming polygonal crystal. It
was deemed that in our previous work, the Ti species at extra
framework had effect on the morphology of TSꢀ1 resulting in the
fact that no polygonal structure of Cu/TSꢀ1 was observed by
impregnation method47. But in the present work, there were
75 almost no Ti species at extraꢀframework of these samples, thus
the loading Cu species also promoted the formation of polygonal
structure. The data of EDS in Table 2 showed the surface
composition of TSꢀ1 and Cu/TSꢀ1 samples. With the increase of
Cu content loaded on TSꢀ1, the content of Ti species on the
80 surface decreased from 2.12% to 0.74%, and the surface content
of Cu increased from 1.19% to 1.86%. It implied that the loaded
20 3.3 FT-IR characterization
Fig. 3 showed the FTꢀIR spectra of TSꢀ1 and Cu/TSꢀ1 samples.
The bonds around 445 cmꢀ1, 545 cmꢀ1, 796 cmꢀ1, 965 cmꢀ1, 1100
cmꢀ1 and 1220 cmꢀ1 were corresponded to the characteristic bands
25 of the TSꢀ1 sieve47. The two bands located at 545 and 1220 cmꢀ1
were considered to be the characteristic bands of MFI structure46.
The peaks at 445, 796 and 1100 cmꢀ1 were assigned to the
internal linkages in SiO4 tetrahedral49. The peak at 965 cmꢀ1 was
assigned to the vibration of SiꢀOꢀTi bond in framework50.
30 However, there were no bands related to Cu species shown in
these spectra. Thus, we could assume that TSꢀ1 and Cu/TSꢀ1
samples had the MFI structure, which was consistent with the
result of XRD characterization.
4
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(a)
5
(b)
Fig. 5 SEM micrographs of TSꢀ1(a) and 2.5Cu/TSꢀ1(b).
10 Table 2 Surface composition of TSꢀ1 and Cu/TSꢀ1 and the actual Cu contents
of the samples from ICPꢀAES
The actual
Samples
O %
Si %
Ti % Cu (CuO) %
Cu content
(ICPꢀAES)
TSꢀ1
60.30
59.42
58.39
58.67
57.75
37.58
38.54
39.47
38.81
39.23
2.12
0.85
0.78
0.75
0.74
ꢀꢀ
ꢀꢀ
1.5Cu/TSꢀ1
2.0Cu/TSꢀ1
2.5Cu/TSꢀ1
3.0Cu/TSꢀ1
1.19
1.36
1.77
1.86
1.47
1.95
2.43
2.91
Cu species might cover the Ti species on the surface. What’s
more, the Cu species on the surface was detected in the state of
15 CuO. The ICPꢀAES was also applied in the analysis of Cu
contents of the samples. The data indicated that the contents of
1.5TSꢀ1, 2.0TSꢀ1, 2.5TSꢀ1 and 3.0TSꢀ1 were 1.47wt.%,
1.95wt.%, 2.43wt.% and 2.91wt.% respectively, and the data
were very close to the controlled values. The results of surface
20 copper lower than that of total values indicated that the surface
was less concentrated in Cu than the total values of ICPꢀAES for
the reason that part of Cu species might enter into the pores of the
TSꢀ1 support54, which was in accordance with the decrease of
micropore volume. The lesser copper species on the surface
25 might also be caused by the selfꢀcoverage of Cu species as well.
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Table 3 The effect of Cu content on the catalytic reaction of toluene.a
Molar Yield （%）
Selectivity (%)
The theoretical
content of
Cu loading
(wt%)
TON
TOF
Products
(mol
containing
C–N bonds
Samples
(hꢀ1)
C–N bonds
on the ring
Products
on the ring
TDb
CSb
NTb
BAb
CBb
BMb
/mol)
TSꢀ1
0.0
1.5
2.0
2.5
3.0
1.9
2.6
2.9
3.4
3.1
1.5
1.3
2.6
3.3
2.7
0.5
0.2
0.9
1.0
0.8
0.6
0.5
0.6
0.6
0.6
0.8
0.9
1.0
1.0
0.9
0.8
0.7
0.7
1.0
0.7
39.3
45.2
43.7
42.7
44.3
52.5
59.7
55.2
52.4
54.5
63.9
66.1
73.6
74.8
75.0
ꢀꢀ ꢀꢀ
1.5Cu/TSꢀ1
2.0Cu/TSꢀ1
2.5Cu/TSꢀ1
3.0Cu/TSꢀ1
7.8 1.3
8.9 1.5
8.4 1.4
6.0 1.0
a Reaction conditions：Catalyst 0.15 g; Toluene 4.7 mmol; NH3ꢁH2O 87.4 mmol; H2O2 14.7 mmol; H2O 25 mL; 353 K, 365min.
b TD, CS, NT, BA, CB and BM represented toluidine, cresols, nitrotoluene, benzaldehyde, cyanobenzene and benzylalcohol, respectively.
5
Table 4 Effect of the amount of catalyst.a
Molar Yield （%）
Selectivity (%)
TON
(mol
/mol)
C–N
bonds
on
the ring
2.5Cu/TSꢀ1
Catalyst (g)
TOF
(hꢀ1)
Products
containing
C–N bonds
Products
on the ring
TDb CSb NTb BAb CBb BMb
0.05
0.10
0.15
0.20
0.25
0.4 0.3 0.1 0.2 0.3 0.1
1.6 1.5 0.2 0.4 0.7 0.5
3.4 3.3 1.0 0.6 1.0 1.0
3.2 3.0 0.8 0.6 1.1 0.9
3.0 2.8 0.9 0.7 0.9 0.9
35.7
36.7
42.7
41.7
42.4
57.1
51.0
52.4
53.1
52.2
57.1
67.3
74.8
72.9
72.8
3.4
6.0
8.4
5.9
4.5
0.6
1.0
1.4
1.0
0.7
a Reaction conditions：2.5Cu/TSꢀ1; Toluene 4.7 mmol; NH3ꢁH2O 87.4 mmol; H2O2 14.7 mmol; H2O 25 mL; 353 K,365min.
b TD, CS, NT, BA, CB and BM represented toluidine, cresols, nitrotoluene, benzaldehyde, cyanobenzene and benzylalcohol, respectively.
Table 5 Effect of temperature on the catalytic reaction of toluene.a
Molar Yield （%）
Selectivity(%)
TON
(mol
/mol)
Temperature
(K)
TOF
(hꢀ1)
C–N
bonds on
the ring
11.1
35.1
39.3
42.7
41.5
28.8
22.7
Products
containing
C–N bonds
33.3
47.4
50.0
52.4
52.8
44.0
41.2
Products
on the ring
TDb
CSb
NTb
BAb
CBb
BMb
333
343
348
353
358
363
373
0.1
1.8
2.5
3.4
3.3
2.2
1.1
0.3
1.7
2.8
3.2
3.2
3.8
4.3
ꢀꢀ
0.1
0.6
0.5
0.6
0.7
1.7
0.9
0.2
0.7
0.9
1.0
1.2
1.9
2.2
0.2
0.7
0.9
1.0
1.1
1.5
1.8
44.4
64.9
72.6
74.8
71.7
59.2
58.8
0.7
4.7
6.9
8.4
8.7
10.2
9.8
0.1
0.8
1.1
1.4
1.4
1.7
1.6
0.2
0.8
1.0
1.1
1.4
1.6
10
a Reaction conditions：Catalyst Cu/TSꢀ1 0.15 g；Toluene 4.7 mmol ; NH3ꢁH2O 87.4 mmol ; H2O2 14.7 mmol ; H2O 25 mL, 365min.
b TD, CS, NT, BA, CB and BM represented toluidine, cresols, nitrotoluene, benzaldehyde, cyanobenzene and benzylalcohol, respectively.
35 Benzylamine was not stable in TSꢀ1/H2O2 system and was easily
converted to cyanobenzene by the oxidative dehydrogenation.
Thus, there was no benzylamine detected by GCꢀMS. In the
products containing C–N bonds, toluidine and nitrotoluene were
the ring C–H oxidation products with the selectivity of 81.5%
3.6. Catalytic performance of Cu/TS-1
15 We used the TSꢀ1 and Cu/TSꢀ1 catalysts to activate the C–H
bonds of toluene for the direct formation of C–N bonds. As
shown in Table 3, toluidine was obtained and the highest yield of
toluidine was 3.4%, with the yields of 1.0% to nitrotoluene and 40 while cyanobenzene was the side chain C–H oxidation product
1.0% to cyanobenzene (based on benzene introduced), over the
20 2.5Cu/TSꢀ1 catalyst (Scheme 1). The existence of the electronꢀ
donating group (methyl) promoted the yield of amination
products compared with the amination of benzene9. Nitrotoluene
with the selectivity of 18.5%. Meanwhile, cresols and the side
chain oxidation products such as benzaldehyde and benzylalcohol
were also obtained. The selectivity to the ring was higher than
that to the side chain, while the selectivity to the formation of C–
could be considered to be the deep oxidation product of the 45 N bonds (52.4%ꢀ59.7%) was higher than that of C–O bonds
initially formed toludine based on the resluts observed in the
25 amination of benzene9. Cyanobenzene was the C–N bond product
obtained on the side chain, which could be formed from
benzylamine or formamide. To verify the origin of cyanobenzene,
(40.3%ꢀ47.6%).
With the increase of the Cu loading on TSꢀ1, the yield of
toluidine and cyanobenzene increased. The optimal Cu content
was 2.5 wt.%, that is, the dependence of the catalytic
control experiments using benzylamine and formamide as 50 performance on Cu loading was the same as that in benzene
substrates were proceeded under the same reaction conditions.
30 The result revealed that the product of benzylamine partial
oxidation was cyanobenzene with the yield of 85.3%. No
cyanobenzene was obtained using formamide as substrate, and
amination9,10. Then the 2.5Cu/TSꢀ1 was chosen for further study.
The effect of the amount of 2.5Cu/TSꢀ1 catalyst on the reaction
process was investigated, and the results were shown in Table 4.
The yield of toluidine and selectivity to C–N bonds on the ring
the product was benzaldehyde oxime. Thus it was considered that 55 increased with the amount of catalyst up to 0.15 g, and then
the intermediate from toluene to cyanobenzene was benzylamine.
tended to be stable with the amount of 0.20 g or 0.30 g.
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Table 6 Effect of H2O2 dosage on the catalytic reaction of toluene.a
Molar Yield （%）
Selectivity(%)
H2O2
Dosage
(mL)
TON
(mol
/mol)
TOF
(hꢀ1)
C–N
bonds on
the ring
Products
containing
C–N bonds
Products
on the ring
TDb
CSb
NTb
BAb
CBb
BMb
0.5c
1.0c
1.5c
2.0c
2.5c
3.0c
1.1
2.3
3.4
3.3
2.9
2.1
1.2
2.8
3.2
3.8
4.0
4.4
0.6
1.0
1.0
1.1
1.6
2.0
0.6
0.6
0.6
0.7
0.9
1.2
0.8
1.0
1.0
1.2
1.4
1.5
0.6
0.9
1.0
1.1
1.8
1.9
34.7
54.3
50.0
52.4
50.0
46.8
40.3
59.2
70.9
74.8
73.2
67.5
64.9
4.0
7.0
8.4
9.2
10.3
10.7
0.7
1.2
1.4
1.5
1.7
1.8
38.4
42.7
39.3
35.7
31.3
a Reaction conditions：Catalyst 2.5Cu/TSꢀ1 0.15 g；Toluene 4.7 mmol; NH3ꢁH2O 87.4 mmol; H2O2 (4.9 mmol , 9.8 mmol , 14.7 mmol , 19.6 mmol , 24.5
mmol , 29.4 mmol) ; H2O 25 mL; 353 K.
5
b TD, CS, NT, BA, CB and BM represented toluidine, cresols, nitrotoluene, benzaldehyde, anobenzene and benzylalcohol, respectively.
c The reaction time were 355min, 360min, 365min, 370min, 375min and 380min, respectively.
Table 7 Effect of NH3ꢁH2O dosage on catalytic reaction of toluene.a
Molar Yield （%）
Selectivity(%)
NH3ꢁH2O
Dosage
(mL)
TON
(mol
/mol)
TOF
(hꢀ1)
C–N
bonds on
the ring
36.7
42.7
47.1
Products
containing
C–N bonds
46.8
52.4
56.5
Products
on the ring
TDb
CSb
NTb
BAb
CBb
BMb
5c
2.5
3.4
3.1
2.6
2.7
3.2
2.6
2.1
0.4
1.0
0.9
0.3
0.7
0.6
0.6
0.4
0.8
1.0
0.8
0.8
0.8
1.0
0.5
0.5
70.9
74.8
77.6
74.6
6.5
8.4
7.0
5.5
1.2
1.4
1.0
0.7
10c
15c
20c
41.4
55.2
a Reaction conditions：Catalyst 2.5Cu/TSꢀ1 0.15 g; Toluene 4.7 mmol ; NH3ꢁH2O (43.71 mmol , 87.4 mmol ,131.1 mmol , 174.8 mmol) ;
H2O2 14.7 mmol ; H2O 25 mL ; 353 K.
10
b TD, CS, NT, BA, CB and BM represented toluidine, cresols, nitrotoluene, benzaldehyde, cyanobenzene and benzylalcohol, respectively.
c The reaction time were 315min, 365min, 415min and 465min, respectively.
Table 8 Effect of H2O dosage on catalytic reaction of toluene.a
Molar Yield （%）
Selectivity(%)
H2O
Dosage
(mL)c
TON
(mol
/mol)
TOF
(hꢀ1)
C–N
bonds on
the ring
24.7
29.2
36.7
Products
containing
C–N bonds
38.7
Products
on the ring
TDb
CSb
NTb
BAb
CBb
BMb
10d
15d
20d
25d
30d
0.5
1.2
2.7
3.4
3.3
2.1
2.5
3.1
3.2
3.0
1.8
1.4
1.2
1.0
1.0
1.7
1.4
0.8
0.6
0.8
1.3
1.3
1.1
1.0
0.9
1.9
1.8
0.9
1.0
0.9
47.3
53.1
71.4
74.8
73.7
4.8
7.9
8.0
8.4
8.1
1.4
1.8
1.5
1.4
1.2
40.6
51.0
52.4
52.5
42.7
44.4
15
20
a Reaction conditions：Catalyst 2.5Cu/TSꢀ1 0.15 g；Toluene 4.7 mmol ; NH3ꢁH2O 87.4 mmol ; H2O2 14.7 mmol ; 353 K.
b TD, CS, NT, BA, CB and BM represented toluidine, cresols, nitrotoluene, benzaldehyde, cyanobenzene and benzylalcohol, respectively.
c The molar concentrations of NH3ꢁH2O were 4.1 mol/L, 3.3 mol/L, 2.8 mol/L, 2.4 mol/L and 2.1 mol/L, successively. The molar concentrations of
H2O2 were 0.7 mol/L, 0.6 mol/L, 0.5 mol/L, 0.4 mol/L and 0.4 mol/L, successively. The pH values of these mixtures containing NH3ꢁH2O, H2O2 and
H2O were 10.65, 10.27, 9.72, 9.24 and 8.87, successively.
d The reaction time were 215min, 265min, 315min, 365min and 415min, respectively.
slightly higher than that for benzene amination (343K)9. While
the highest yield of toluidine obtained was 3.4%, which was
higher than that for benzene amination.
40
The influence of the amount of hydrogen peroxide (30 wt. %)
on the yield and selectivity of the C–N bond products was
investigated. The results were shown in Table 6. With the
increase of the dosage of hydrogen peroxide, the yield of
toluidine rose at first and then decreased. The highest yield of
Scheme 1 The products containing C–N bonds obtained
in the reaction process
25 3.7 Optimization of reaction conditions
The influence of reaction temperature on the yield and selectivity
of the C–N bond products was also investigated. The results were
shown in Table 5. At 333 K, there were only trace amount of
30 products containing C–N bond or C–O bond products. It
indicated that the activation of the C–H bond of toluene and N–H
bond of ammonia needed higher temperature. When the
temperature rose to above 358 K, the selfꢀdecomposition of
hydrogen peroxide and volatilizing of ammonia were serious,
35 resulting in low utilization of aqueous ammonia and hydrogen
peroxide10. The optimal temperature was 353 K, which was
45 toluidine was 3.4% when the amount of hydrogen peroxide was
1.5 mL (14.7 mmol). There was apparently no advantage for the
yield to toluidine and selectivity to products containing C–N
bond on the ring with excessive amount of H2O2. The yield of
nitrotoluene increased with increasing amount of H2O2 and the
50 increasing yields of other byꢀproducts containing C–O bonds
exhibited the same trends as that of nitrotoluene. It was indicated
that increased dosage of H2O2 aggravated the deep oxidation of
toluidine to nitrotoluene, and promoted the oxidation of toluene
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Table 9 The distribution of the products from different substrates over 2.5Cu/TSꢀ1.a
Products
C–O bonds
Aromatic substrates
C–N bonds
On the side chain
On the ring
On the side chain
On the ring
Benzene
ꢀꢀ
ꢀꢀ
Toluene
Ethylbenzene
Cumene
oꢀxylene
ꢀꢀ
ꢀꢀ
ꢀꢀ
ꢀꢀ
mꢀxylene
pꢀxylene
Mesitylene
a Reaction conditions：Catalyst 0.15 g；Substrate 0.5 mL; NH3ꢁH2O 87.4 mmol; H2O2 14.7 mmol; H2O 25 mL; 353 K 365min.
5
both on the ring and on the side chain. The yield of cyanobenzene 30 oxidation of toluidine and the volatilization of ammonia. Then
was also increased with increasing amount of H2O2, indicating
that the excess amount of H2O2 could promote the formation of
CꢀN bonds on the side chain and the oxidative dehydrogenation
of benzylamine. The results of the influence of the amount of
the nitroꢀproduct was relatively high. The low ratio of ammonia
would decrease the formation of C–N bonds, which resulted in
low selectivity to products containing C–N bonds. When 30 mL
water (NH3ꢁH2O 2.1mol/L, H2O2 0.4mol/L) was introduced, the
10 ammonia (28 wt.%) on the reaction were shown in Table 7. The 35 yield of toluidine slightly decreased compared with the reaction
increased amount of ammonia diluted hydrogen peroxide,
decreased intimate contact between hydrogen peroxide and other
species among reactants and catalyst, and then led to lower yield.
Meanwhile, toluene could escape from the system with ammonia
15 which made the catalytic process less effective, because the
reaction system was not completely sealed. The optimal amount
of ammonia for the highest yield of toluidine was 10mL.
with 25 mL water (NH3ꢁH2O 2.4mol/L, H2O2 0.4mol/L). It was
considered that the pH value of the mixture also had effect on the
catalytic reaction of toluene. The yield of toluidine was higher
with lower pH, while the yield of cyanobenzene decreased.
It should be noted that the reaction time varied also with the
amount of the mixture containing ammonia, hydrogen peroxide
and water. Thus, the variation of the amount of ammonia,
hydrogen peroxide and water was accompanied by the variation
of reaction time to some extent. The actual reaction times were
40
Water was added into the NH3ꢁH2O and H2O2 mixture for
diluting. The amount of water affected the concentration of
20 hydrogen peroxide and ammonia as well as the pH value of the 45 shown at footnotes of Table 6, Table 7 and Table 8, respectively.
mixture. As shown in Table 8, with increasing dosage of water,
the molar concentration of NH3ꢁH2O decreased from 4.1 mol/L to
2.1 mol/L, and that of H2O2 decreased from 0.7 mol/L to 0.4 mol
/L. The mixtures were alkaline with the pH values ranged from
25 8.87 to 10.65. With the increase of the amount of water, the
concentrations of NH3ꢁH2O and H2O2 decreased. It resulted in the
increase of toluidine yield and the decrease of nitrotoluene yield.
When the dosage of water was few, the relatively high
concentration of hydrogen peroxide would aggravate the deep
As a comparison, the reaction was kept for another 100 min after
the mixture was added completely, to make the reaction time to
be in accordance with the longest reaction time (465min), and the
other reaction conditions were the same as that of the optimal
50 ones, but the yield of toluidine (2.9%) was decreased. Toluidine
was converted to nitrotoluene (1.4%), and the yield of
cyanobenzene (1.1%) was almost the same as that obtained for
365 min reaction. The extra reaction time led to deep oxidation of
toluidine to nitrobenzene with no promotion to the formation of
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Table 10 Activation of ethylbenzene over 2.5Cu/TSꢀ1.a
Entry
Quantity(mg)
Molar yield(%)
Selectivity(%)
47.3
Acetyl benzene
1ꢀphenyl ethanol
2ꢀethyl aniline
4ꢀethyl aniline
3ꢀethyl aniline
2ꢀethyl phenol
4ꢀethyl phenol
3ꢀethyl phenol
4.6
8.3
9.6
0.8
0.3
2.6
0.5
0.1
0.9
1.7
1.5
0.4
0.3
0.4
0.2
0.1
40.0
12.7
a Reaction conditions：Catalyst 2.5Cu/TSꢀ1 0.15 g；Ethylbenzene 0.5 mL; NH3ꢁH2O 87.4 mmol; H2O2 14.7 mmol;
H2O 25 mL; 353 K,365min.
5
Table 11 Activation of pꢀxylene over 2.5Cu/TSꢀ1.a
Entry
Quantity(mg)
Molar yield(%)
Selectivity(%)
20.0
4ꢀmetylbenzaldehyde
4ꢀmetylcyanobenzene
4ꢀmetylbenzylalcohol
2,5ꢀdimethylaniline
2,5ꢀdimethylphenol
2.7
2.7
1.8
2.0
3.0
0.5
0.6
0.4
0.4
0.6
24.0
16.0
16.0
24.0
a Reaction conditions：Catalyst 0.15 g；pꢀxylene 0.5 mL; NH3ꢁH2O 87.4 mmol; H2O2 14.7 mmol; H2O 25 mL; 353 K, 365min.
Table 12 The activity of mesitylene over 2.5Cu/TSꢀ1.a
Entry
Quantity(mg)
Selectivity(%)
28.6
3,5ꢀdimethylbenzaldehyde
3,5ꢀdimethylcyanobenzene
2,4,6ꢀtrimethylaniline
3,5ꢀdimethylbenzylalcohol
2,4,6ꢀtrimethylphenol
0.2
0.2
0.1
0.1
0.1
28.6
14.3
14.3
14.3
a Reaction conditions：Catalyst 0.15 g；mesitylene 0.5 mL; NH3ꢁH2O 87.4 mmol; H2O2 14.7 mmol;
10
H2O 25 mL; 353 K,365min.
C–N bonds. Thus, the reaction time was stopped when the adding
of the mixture (ammonia, hydrogen peroxide and water) was
15 over. It was shown that the optimal condition of the catalytic
position on the ring. No nitroꢀproducts were detected from these
substrates except benzene and toluene, which implied that the
relatively low activities from these alkylbenzene to amino
reaction of toluene on the Cu doped TSꢀ1 was the following: the 50 products made the deep oxidation of amination products difficult.
amount of 2.5Cu/TSꢀ1 0.15 g; the molar ratio of toluene,
NH3•H2O and H2O2, 1 (4.7 mmol): 18.6 (14.7 mmol):3.1 (87.4
mmol); 25mL water for the diluting of nitrogen source and
20 oxidant; the feeding rate of the mixture of ammonia and
We only quantified the products from catalytic results of pꢀ
xylene, ethylbenzene and mesitylene in Table 10, Table 11 and
Table 12 due to the lack of the standard samples of the products
that obtained from other substrates. The quantitive results of
hydrogen peroxide 0.1 mL/min (365 min); the reaction 55 mesitylene were only expressed in terms of the quantity and
temperature 353 K. The effects of the reaction conditions were
selectivities to the products, because the molar yields of the
products from mesitylene were calculated less than 0.1%.
similar to those in our previous work9,10.
The results shown in Table 10 indicated that the yields of
amination products from ethylbenzene were lower than that of
60 toluene. The yields of acetyl benzene and 1ꢀphenyl ethanol were
relatively higher than other products. It might be caused by the
fact that the bond energy of C–H at α location of the side chain
was lower than that at other carbon. Trace amount of
cyanobenzene and benzaldehyde could also be detected, but the
25 3.8 The extension of substrate to alkyl-substituted-benzenes
The reaction for the formation of C–N bonds was carried out with
other alkylꢀsubstituted aromatic hydrocarbons such as
ethylbenzene, pꢀxylene, oꢀxylene, mꢀxylene, cumene and
30 mesitylene under the same optimal conditions. The results of
qualitative analyses by GCꢀMS were shown in Table 9. The Cu 65 yields of these two products were less than 0.1%, then we did not
doped TSꢀ1 zeolite samples could also activate the ring C–H
bond of other aromatic compounds to form C–N bond with the
participation of aqueous ammonia and hydrogen peroxide except
35 cumene and oꢀxylene. However, the byproducts of side chain C–
give them out in Table 10.
The quantitative data of pꢀxylene in Table 11 and mesitylene in
Table 12 showed that the yields of products containing C–N
bonds on the ring were lower than that on the side chain. With the
N bond products and oxidation products could also be obtained. 70 number of methyl substituent increasing, the yield of ring
There were no amination products detected using cumene and oꢀ
xylene as substrates. The products from benzene were mainly
aniline, nitrobenzene and phenol as reported in our previous
40 work9. The corresponding amination products were obtained
products decreased which might be the effect of steric hindrance
that influenced the interaction between catalyst and the aromatic
ring. With the number of methyl substituent increasing, the
exclusion effect might prevent the access of the larger molecules
from ehtylbenzene, mꢀxylene, pꢀxylene and mesitylene, and the 75 to zeolite framework pores, and the effect can also prevent the
product distribution of these alkylbenzene was almost in
accordance with the rule of electrophilic substitution reaction.
Methyl was a chargeꢀdonating group, and the ortho and para
45 positions were chargeꢀrich, thus the formations of C–N and C–O
bonds should be theoretically much easier at oꢀposition and pꢀ
formation of some larger precursors within the TSꢀ1 pores, which
might leads to the lower yields of ring products.
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Table 13 The distribution of C–N and C–O bondsꢀproducts on the ring from
toluene and ethylbenzene.a
Selectivity/%
Ortho products
of C–N bonds/
C–O bonds
Meta products
of C–N bonds/
C–O bonds
Para products
of C–N bonds/
C–O bonds
Substrates
Toluene
68.3/64.5
21.5/23.2
10.2/12.3
Ethylbenzene
71.0/68.6
17.0/20.9
12.0/10.5
a Reaction conditions：Catalyst 0.15 g；toluene 4.7 mmol; NH3ꢁH2O 87.4
mmol; H2O2 14.7 mmol; H2O 25 mL; 353 K,365min.
5
3.9 Discussion
The selectivity of the products containing C–N bonds on the
aromatic ring kept stable with the loading of the Cu species on
10 the TSꢀ1 catalyst. With the increase of the Cu content, the
selectivity to products on the ring (C–N and C–O) increased from
63.9% to 75.0%, but the yield and selectivity to products on the
side chain became lower on the Cu doped catalysts, indicating
that the Cu species could probably promote the selectivity of the
15 ring products to some extent and inhibit the activation of C–H
bonds on the side chain. We also used CuO and Cu (NO3)2 as
catalyst for C–H bond activation of toluene. The results revealed
that the products obtained over CuO were the same as those on
Cu/TSꢀ1 with much lower activity, where the yield to toluidine
20 was only 0.25%. However, no products were obtained when Cu
(NO3)2 was used as catalyst. It was considered that the catalytic
activity was related to the Cu–O, and the higher catalytic yield to
toluidine over Cu/TSꢀ1 might be related to Cu–O–Ti bond as
reported in our previous work9.
60
Scheme 2 The proposed reaction mechanism
However, the present reaction proceeded in alkali system, thus
we deemed that hydroxylamine reduced to protonated amino
65 cation (ꢁNH3 ) and hydroxamino (NHOHꢀ) instantaneously. The
instantaneously generated ꢁNH3+ reacted with the aromatic ring to
produce an amino intermediate, followed by producing toludine,
and then a fraction of toluidine turned to nitrobenzene by deep
oxidation. The data shown in Table 8 indicated that the yield of
70 toluidine was higher at a relatively lower pH value which was in
accordance with our previous work26ꢀ28 in acidic system.
Meanwhile, the protonated amino cation attacked the C–H bonds
of the side chain to form benzylamine, and then be oxidized
further to cyanobenzene. The instantaneously generated
+
25
The distribution of the products containing C–N bonds on the
ring under the optimal conditions in the activation of toluene was
shown in Table 13. It should be noted that the calculation of the
selectivity of C–N bond products was confined to those on the
ring. The results showed obvious selectivity to ortho toludine and
75 hydroxylamine and ꢁNH3 was unstable in alkaline system
+
resulting in the fact that the yield of toluidine was not as high as
that when using hydroxylamine hydrochloride as aminating
reagent in acidic system26ꢀ28. We also used methylcyclohexane as
substrate to proceed the catalytic reaction in a control experiment,
80 but no amination products were obtained, indicating that the
activity of amination process in the present reaction system was
related to the benzene ring structure. Further deep study is
needed.
30 ortho nitrotoluene. The distribution of the products from
ethylbenzene (Table 10, Table 13) bought out the similar trend.
What`s more, the hydroxylation products on the ring both from
toluene and ethylbenzene gave also the similar trend. Although
methyl and ethyl were chargeꢀdonating substituent, the ring
35 products only showed the ortho advantage. Thus, the high
selectivity on the orthoꢀposition was not only due to the effect of
chargeꢀdonating substituent (methyl and ethyl), the interaction of
the substrate with Cu/TSꢀ1 catalyst might also gave an orthoꢀ
orientation of the products. The yields of oꢀ, mꢀ and pꢀ
40 substitution ring products from toluene were shown in Table S1ꢀ
Table S6.
85
4. Conclusion
In summary, the Cu/TSꢀ1 catalyst exhibited obvious activity for
the formation of C–N bonds from toluene, ammonia and
90 hydrogen peroxide. The yield of 3.4% to toluidine was obtained
with 1.0% to nitrobenzene. Cyanobenzene was also obtained as
the C–N bond product on the side chain with the yield of 1.0%.
Nitrotoluene was considered to be the deep oxidation product of
the initially formed toludine, and benzylamine was considered to
95 be the intermediate from toluene to cyanobenzene. The
selectivity to the ring was higher than that to the side chain while
the selectivity to the formation of C–N bonds was higher than
that of C–O bonds. The formation of C–N bonds on the ring had
ortho orientation advantage. With the increase of the number of
100 methyl substituent, the yield of ring products decreased which
might be caused by steric hindrance and exclusion effect of the
pore structure of zeolite. The Cu doped TSꢀ1 catalyst catalyzed
The formation of C–N bonds and C–O bonds were competing
with each other. The molar ratio of the C–N bond products on the
ring and the C–O bond products on the ring ranged from 1.2:1 to
45 1.4:1. The data revealed that the formation of C–N bonds on the
ring had a slight advantage than the formation of C–O bonds on
the ring in the reaction system. The inhibiting effect of Cu
species to the formation of hydroxylation products on the ring of
toluene was not obvious as that on the benzene ring9 because of
50 the charge donating effect of methyl.
Based on the above data, a tentative proposition of the reaction
mechanism for the direct formation of C–N bond from toluene
over the Cu doped TSꢀ1 catalyst was given in Scheme 2. The Cu
doped TSꢀ1 catalyst catalyzed the partial oxidation of ammonia
55 by hydrogen peroxide to produce hydroxylamine10, while the
catalyst activated also the C–H bonds of toluene simultaneously.
In the amination of benzene with hydroxylamine55, the active
the partial oxidation of ammonia by hydrogen peroxide to
+
produce hydroxylamine,
and
then
generated
ꢁNH3
ꢁ
+
species formed was considered to be NH3 in acidic system.
105 instantaneously. It is illustrated that C–N bond could be
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Catal. Lett., 2008, 123, 135.
constructed from extended aromatic hydrocarbons and the lowꢀ
cost nitrogen source (aqueous ammonia) via oneꢀstep process on
the basis of our previous work.
5
Acknowledgements
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Notes and references
Key Laboratory of Green Chemistry and Technology, Ministry of
Education, College of Chemistry, Sichuan University, Chengdu, Sichuan,
610064, China. Tel: +86-28-85411105; Fax: +86-28-85411105; E-mail:
15 G. Y. Li: gchem@scu.edu.cn, C. W. Hu: changweihu@scu.edu.cn
* The two authors both are corresponding authors.
† Electronic Supplementary Information (ESI) available: activity data.
See DOI:10.1039/c0xx000x/
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DOI: 10.1039/C4CY00472H
One step C–N bond formation from alkylbenzene and
ammonia over Cu-modified TS-1 zeolite catalyst
†
Sheng Xia, Tianhua Yu, Huihui Liu, Guiying Li*, Changwei Hu*
Key Laboratory of Green Chemistry and Technology, Ministry of Education, College of
Chemistry, Sichuan University, Chengdu, Sichuan, 610064, China
The formation of C–N bonds from toluene and ammonia both on the ring and the side
chain was realized on Cu-modified TS-1 catalyst, and the ring products had
ortho-orientation advantage.