Room temperature N-alkylation of amines with alcohols under UV irradiation catalyzed by Cu-Mo/TiO2

Article abstract of DOI:10.1039/c5cy00316d

It is highly desirable to develop efficient heterogeneous photocatalysts for organic reactions. Here, we show the preparation and catalytic performance of a novel TiO₂ (P25) supported Cu and Mo photocatalyst (Cu-Mo/TiO₂) for N-alkylation of amines with alcohols under UV irradiation at room temperature. A variety of aromatic and aliphatic amines were selectively converted into the corresponding secondary amines or tertiary amines in moderate to excellent yields without the addition of any co-catalysts such as bases and organic ligands. Noteworthy, this catalytic system is feasible in the alkylation of anilines containing halogen substituents with alcohols and the yields of the desired products are up to 95%.

Full text of DOI:10.1039/c5cy00316d

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Room Temperature N-Alkylation of Amines with
Alcohols under UV Irradiation Catalyzed by
Cu-Mo/TiO2
Cite this: DOI: 10.1039/x0xx00000x
Lina Zhangab, Yan Zhanga, Youquan Denga, Feng Shi*a
Received 00th January 2012,
Accepted 00th January 2012
It is highly desirable to develop efficient heterogeneous photocatalysts for organic reactions.
Here, we show the preparation and catalytic performance of a novel TiO2 (P25) supported
Cu and Mo photocatalyst (CuꢀMo/TiO2) for Nꢀalkylation of amines with alcohols under UV
irradiation at room temperature. A variety of aromatic and aliphatic amines were selectively
converted into the corresponding secondary amines or tertiary amines in moderate to
excellent yields without the addition of any coꢀcatalysts such as bases and organic ligands.
Noteworthy, this catalytic system is feasible in the alkylation of anilines containing halogen
substituents with alcohols and the yields of the desired products are up to 95%.
DOI: 10.1039/x0xx00000x
www.rsc.org/
have often been considered as highly unselective processes,
especially in water35. We have been particularly interested in
Introduction
using semiconductor photocatalysts as a new way to drive
chemical reactions for organic synthetic transformations with
high activity and selectivity, such as the reaction of Nꢀ
alkylation of amines with alcohols. So far, several
semiconductor photocatalysts have been reported, inclusive of
Nitrogenꢀcontaining compounds, particularly amines and their
derivatives are important intermediates and products for
pharmaceuticals,
agrochemicals,
polymers,
bioactive
compounds, and dyes1ꢀ5. There are several methods to produce
them, including amination of aryl/alkyl halides2,
, and
6
36,
38
39,
Pt/TiO2 37, Au/TiO2 and Pd/TiO2 40, which use noble
metal catalysts. However, there is no report of active and
general nonꢀnoble metal catalyst for this transformation. The
development of nonꢀnoble metal semiconductor photocatalyst is
highly desirable.
reductive amination of carbonyl compounds 7, 8. However, these
methods suffer from the drawbacks of the use of
a
stoichiometric amount of detrimental and/or expensive reagents
and the formation of a large amount of noxious side products.
In recent years, much attention has been focused on
development of catalytic methods for the production of Nꢀ
alkylated amines applying alcohols as alkylating agents because
alcohols are nontoxic, plentiful, inexpensive and renewable
feedstock regents.
Herein, we report our results about CuꢀMo/TiO2 catalyzed
reaction of amine with alcohol under UV irradiation at room
temperature. To the best of our knowledge, this is the first nonꢀ
noble metal supported semiconductor photocatalyst for the Nꢀ
alkylation of amines with alcohols. Notably, our catalytic
system is also suitable for the alkylation of anilines with
halogen group and the dehalogenation reaction can be inhibited
efficiently under UV light irradiation.
Initially, the Nꢀalkylation of amines with alcohols was
carried out in the presence of various kinds of homogeneous
transitionꢀmetal catalysts including ruthenium9ꢀ11, platinum12,
iridium13ꢀ18, silver19 and palladium20, 21 complexes with which
good results were obtained. Later on, some heterogeneous
catalysts such as Pd/MgO22, Ag/Mo23 or Ag/Al2O324, Cuꢀ
Results and Discussion
28
Ag/Al2O325, Au/TiO226, Cu(OH)2/Al2O327, Ni/Al2O3
，Cu/Niꢀ
based29, NiꢀCu/Al2O3 and Fe3O431, were developed for the Nꢀ
alkylation of amines. However, it is still extremely challenging
to require harsh reaction conditions such as high temperature
and strong base or using noble metal.
30
Catalyst characterization. The catalysts used in this work
were prepared by the precipitationꢀdeposition method and
followed by reduction with NaBH4 solution. The textual
property of the catalysts was characterized by N2 adsorptionꢀ
desorption method. The results of BET surface area, pore
volume and pore size of TiO2 and Metal/TiO2 (M/TiO2)
samples were given in Table 1. The BET surface area of
M/TiO2 samples was slight larger than TiO2. The pore volume
and pore size for M/TiO2 samples were similar, but twice as
much as TiO2. According to the ICPꢀAES analysis, the copper
loadings in Cu/TiO2 and Cu1ꢀMo1/TiO2 were 0.853 wt% and
0.854 wt%, respectively. However, only 0.002ꢀ0.003 wt%
molybdenum existed in Mo/TiO2 and Cu1ꢀMo1/TiO2.
The development of more green and economic processes for
the Nꢀalkylation of amines with alcohols is crucial subject
imposed on organic chemistry. Semiconductor photocatalysis
has attracted much attention in the past decades owing to its
application in environmental purification32, water splitting for
the generation of hydrogen as a fuel33, and conversion of solar
energy into electrical energy34, etc. However, the application of
semiconductor photocatalysts as a synthetic methodology is
less common because semiconductor photocatalytic reactions
This journal is © The Royal Society of Chemistry 2013
J. Name., 2013, 00, 1-3 | 1

Catalysis Science & Technology
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VJieowuArrtnicalelONnlainme e
DOI: 10.1039/C5CY00316D
Table 1. BET surface area, pore volume, pore size and metal loadings of
typical catalysts
Pore
volume
(cm3/g)
0.103
0.228
0.224
Cu
content
(wt%)
ꢀ
Mo
content
(wt%)
ꢀ
0.003
ꢀ
SBET
Pore
size(nm)
Catalysts
(m2/g)
TiO2
Mo/TiO2
Cu/TiO2
49
56
51
55
8.45
16.39
17.54
15.51
ꢀ
0.853
0.854
Cu1ꢀMo1/TiO2
0.214
0.002
The crystal structures of all samples in our study were
characterized by XRD measurement, as show in Figure 1. The
peaks marked “A” and “R” refer to anatase and rutile phases,
respectively. All catalysts showed identical mixed phases of
anatase and rutile TiO2 without appearance of metal oxide or
metal particles, which might be ascribed to the low metal
loadings and the good dispersion of metal species on the
surface of TiO2. The morphology of the Cu1ꢀMo1/TiO2 and
Cu1ꢀMo3/TiO2 samples was examined by TEM and high
resolution TEM (HRꢀTEM) in Figure 2. It is clear that the
photocatalysts were almost composed of TiO2 which have
different shapes and sizes because of including two phases
(anatase and rutile). No obvious Cu species particles were
observed on the two samples. The possible reason for the
observation was that at the low loading, the small Cu particles
highly dispersed on the surface. This was in good agreement
with the results of the XRD analysis shown in Figure 1.
Figure 2. TEM and HR-TEM images of Cu1-Mo1/TiO2 (a and b) and Cu1-Mo3/TiO2
(c and d).
Figure 3b is the Cu2p XPS spectra for Cu1ꢀMo1/TiO2 and
Cu/TiO2. The XPS spectra of Cu1ꢀMo1/TiO2 displays two main
peaks at 932.7 and 952.4 eV, that can be attributed to the
Cu2p3/2 and Cu2p1/2 binding energies45, respectively. The XPS
spectra indicate the possible presence of Cu0 or Cu+45, 46. In
order to verify the chemical state of copper species, CuLMM
peaks were collected and were shown in Figure S1. A peak at
921.7eV, which should be assigned to Cu0, and a smaller peak
XPS was used to analyze the chemical state and composition
of surface elements in the catalysts. Figure 3a shows the Ti2p
XPS profiles for TiO2, Cu1ꢀMo1/TiO2, Mo/TiO2 and Cu/TiO2.
The peaks of Ti2p1/2 and Ti2p3/2 for all samples were observed
at ~458.8 and ~464.3 eV. This indicated the presence of TiO2 in
the form of Ti4+ ions41ꢀ43. The positions of Ti2p peaks for other
catalysts don’t show significant difference compared to the bare
TiO2, but a decrease in intensity of Ti2p peaks is observed for
Cu1ꢀMo1/TiO2 and Cu/TiO2, implying that Ti4+ is partially
transformed into Ti3+, which is widely accepted as having
at 914.8 eV, which can be attributed to Cu+, are observed47ꢀ49
.
Therefore, both Cu+ and Cu0 were contained in the catalyst. In
addition, a peak (Cu2p1/2 at 954.1 eV) and a satellite peak (at
942.0 eV) for characteristic Cu2+ are also observed50, 51. The
appearance of metallic Cu is due to the reduction of Cu2+ to Cu0
during catalyst preparation (reduction with NaBH4 solution).
The Cu2+ exists in Cu1ꢀMo1/TiO2 on account of the generation
of Cu copper oxide in the air. In contrast, the Cu2p peaks for
Cu0 are observed in Cu/TiO2, but the Cu2p peaks related to
copper oxide are very weak. Figure 3c presents the O1s spectra
of the samples. The O1s spectra are composed by two peaks
whose binding energies are 530 eV (TiꢀO) and 532.2 eV (Tiꢀ
OH)43, 46. The peaks of the O1s spectra in Mo/TiO2 move to
remarkably lower bindingꢀenergy levels if compared to the
values of TiO2. The positions of the O1s peaks of Cu1ꢀ
Mo1/TiO2 show slight shifts toward lower bindingꢀenergy and a
decrease in intensity is also observed. In sample Cu/TiO2, the
intensity of the O1s peaks at 532.2 eV becomes stronger and
the other peak at 530 eV is weaker compared with TiO2. The
Mo3d spectra of Mo/TiO2 and Cu1ꢀMo1/TiO2 samples are
shown in Figure 3d. No Mo3d peaks were observed in the two
catalysts due to the low concentration of Mo on the surface.
As a sensitive technique, Raman spectroscopy has been used
to investigate the phase composition and surface homogeneity.
Figure 4 shows the Raman spectra of different catalysts. There
are five Raman peaks at 142, 196, 395, 515 and 636cmꢀ1 for all
the samples, corresponding to Eg, Eg, B1g, A1g and Eg modes of
anatase phase of TiO252, 53, respectively. It indicates that anatase
TiO2 nanoparticles are the predominant species. Furthermore,
there are no characteristic peaks corresponding to Cu or Mo
species were found in the samples, which is consistent with the
results of XRD diffraction patterns. The Raman peaks at Eg of
142 cmꢀ1 and those at B1g of 395 cmꢀ1 are OꢀTiꢀO bendingꢀtype
higher photocatalytic activity43, 44
.
A:anatase
R:rutile
Cu -Mo /TiO
1
3
2
Cu -Mo /TiO
3
1
2
Cu -Mo /TiO
1
1
2
2
Mo/TiO
Cu/TiO
TiO
2
2
20
40
60
80
2 theta
Figure 1. XRD diffraction patterns of the catalyst samples
2 | J. Name., 2012, 00, 1-3
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DOI: 10.1039/C5CY00316D
vibrations, and the peaks at Eg of 636 cmꢀ1 and those at A1g of
515 cmꢀ1 are the TiꢀO bond stretchingꢀtype vibrations54.
As shown in Fig. 4, the peaks of Mo/TiO2, compared to the
peaks of bare TiO2, have stronger intensity. It is also found that
the peaks of Cu1ꢀMo1/TiO2 are stronger than Mo/TiO2.
However, some peaks of Cu/TiO2 almost disappear.
E
g
d
c
E
g
b
a
A
1g
B
1g
E
g
300
600
-1
Raman Shift/cm
Figure 4. Raman spectra of (a) Cu/TiO2 ,(b) TiO2, (c) Mo/TiO2 and (d) Cu1-
Mo1/TiO2
To compare the optical responses of the synthesized
photocatalysts, their diffuse reflectance UVꢀvis absorption
spectra are determined and are shown in Figure 5. All samples
exhibit a wide optical absorption in the range below 400 nm. It
is apparent that the diffuse reflectance spectra of Mo/TiO2 and
Cu/TiO2 have a red shift in comparison with TiO2. However,
the absorption edge of Cu1ꢀMo1/TiO2 is observed to be blueꢀ
shifted, which may be attributed to the quantumꢀsize effect55, 56
.
Coꢀmodifying with Cu and trace Mo is shown to induce the
band gap of TiO2 broadening. This result suggests that Cu and
trace Mo have a synergistic effect on the photoꢀcatalytic
52
.
activity of TiO2
d
b,c
a
320
360
400
Wavelength/nm
Figure 3. Ti2p (a), Cu2p (b), O1s (c) and Mo3d (d) XPS spectra of the catalyst
samples
Figure 5. UV-visible absorbance spectra of (a) TiO2, (b) Cu/TiO2, (c) Mo/TiO2 and
(d) Cu1-Mo1/TiO2
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ARTICLE
DOI: 10.1039/C5CY00316D
Catalytic N-alkylation reactions. Following, we continued to including morpholine and piperidine as substrates gave good
test the activity of the catalysts in Nꢀalkylation of amines with yields of the desired products, from 82 to 85% (Entries 8ꢀ9).
alcohols at room temperature under UV irradiation. In the case,
Table 3. Nꢀmethylation of amines with methanola
p
ꢀClꢀaniline and methanol were used as model substrates. The
corresponding results were summarized in Table 2. First, TiO2
without any modification was used as catalyst and no desired
product was obtained (Entry 1). Then, the reaction was carried
out in presence of Mo/TiO2, unfortunately, there was also no
desired product formed (Entry 2). Following, when the reaction
was conducted using Cu/TiO2 as catalyst, only 19% yield was
obtained (Entry 3). These results indicated that the TiO2 itself
and Mo/TiO2 are inactive for the Nꢀalkylation reaction of amine
under our reaction conditions. Although the yield is not high,
Cu/TiO2 as the catalyst was efficient for this transformation. In
order to get a more effective catalyst, we tried to apply Cu and
Mo together to modify TiO2. By adjusting the Cu/Mo molar
ratio, three catalysts were obtained and used in the Nꢀalkylation
reaction and the highest yield, i.e., 95%, was obtained when the
Cu/Mo molar ratio was 1 : 1. If the Cu/Mo molar ratios were
varied to 3 : 1 and 1 : 3, the yields were 29% and 13%,
respectively (Entries 4ꢀ6). The light intensity also remarkably
influences the reaction. An excellent yield, i.e. 95%, was
obtained if using Cu1ꢀMo1/TiO2 as catalyst under irradiation of
100% light intensity (245 mW/cm2, entry 5). The yield was
only 5% when the light intensity was decreased to 60%, and no
desired product was observable if the light intensity was further
decreased to 30% (Entries 7 and 8). In addition, a selfꢀprepared
TiO2 was used as the support for catalyst preparation but lower
activity was obtained (Entry 9).
Entry
1
Amines
Products
Yield%b
46
2
3
70
95c
4
80c
5
6
85
94
7
94c
Table 2. Catalyst screening and reaction conditions optimization using N,Nꢀ
dimethylation of pꢀchloroaniline reactiona
8
9
82
85
aReaction condition: amine (0.2 mmol), methanol (5 mL), Cu1ꢀMo1/TiO2 (20
b
mg), argon, UV (365 nm LED, 245 mW/cm2), r.t., 21 h. The yields were
Entry
Catalyst
TiO2
Mo/TiO2
Conversion%
100
Yield%b
c
obtained by GCꢀFID using biphenyl as external standard material. Isolated
1
2
3
4
5
6
7
8
9
0
0
yields.
100
100
100
100
100
100
100
100
Cu/TiO2
19
29
95c
13
5d
0e
Cu3ꢀMo1/TiO2
Cu1ꢀMo1/TiO2
Cu1ꢀMo3/TiO2
Cu1ꢀMo1/TiO2
Cu1ꢀMo1/TiO2
Cu1ꢀMo1/TiO2ꢀSP
Subsequently, Nꢀalkylation reactions of amines with
different alcohols were investigated. As shown in Table 4, a
variety of primary amines were smoothly alkylated with various
aliphatic alcohols affording the corresponding Nꢀalkylated
secondary or tertiary amines with good to excellent yields.
Interestingly, the chain length of alcohol had significant
influence on the reaction (Entries 1ꢀ4). When ethanol and 1ꢀ
propanol were used, the N,Nꢀdialkylation occurred and the
yields of products were 80ꢀ83% (Entries 1ꢀ2). When the
reactions were carried out in 1ꢀbutanol and 1ꢀhexylalcohol, the
Nꢀmonoalkylation products were obtained in high yields
4f
aReaction condition: amine (0.2 mmol), methanol (5 mL), catalyst (20 mg),
argon, UV (365 nm LED, 245 mW/cm2), r.t., 21 h. bThe yields were obtained
by GCꢀFID using biphenyl as external standard material. cIsolated yield.
d
60% light intensity. e30% light intensity. fTiO2 was prepared in our laboratory.
With this optimized reaction condition in hand, we next
proceeded to examine the scope of the Cu1ꢀMo1/TiO2 catalyst
in the Nꢀalkylation reaction of amines with alcohols. First, the
catalytic protocol was extended to the Nꢀalkylation reaction of
amines with methanol and the results were listed in Table 3.
(Entries 3ꢀ4). The transformation of
pꢀbromoaniline with
different alcohols afforded the similar results. The
corresponding products were obtained in 95 and 65% yield
(Entries 5ꢀ6), respectively. 4ꢀToluidine and 4ꢀanisidine reacted
with 1ꢀpropanol to give alkylated products in moderate yields
under the same conditions (Entries 7ꢀ8). The catalyst also
showed good activity towards the alkylation of aniline with two
substituted groups. 3,5ꢀDimethylaniline was alkylated by using
1ꢀpropanol and 1ꢀbutanol to give secondary amines in good to
excellent yields (Entries 9ꢀ10). We found that 5ꢀaminoindan
was also transformed into the corresponding Nꢀalkylated
secondary or tertiary amines in moderate to excellent yields
(Entries 11ꢀ13). The reactions of aniline with longer alkyl chain
Aromatic amines, including aniline,
pꢀmethylaniline, pꢀ
chloroaniline and ꢀbromoaniline, could be transformed into the
p
corresponding Nꢀmethyl tertiary amines with 46 to 95% yields
(Entries 1ꢀ4). Aliphatic amines, such as benzylamine,
cyclohexylamine and dodecanamine, could be used as starting
materials for the Nꢀmethylation reaction, too, and excellent
yields of the corresponding tertiary amines were achieved
(Entries 5ꢀ7). The use of cyclic aliphatic secondary amines
4 | J. Name., 2012, 00, 1-3
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Table 4. Nꢀalkylation of amines with alcoholsa
group, such as 4ꢀhexylaniline and 4ꢀbutylaniline, and ethanol
were investigated. To our delight, Nꢀalkylated products were
afforded in 83 and 95% yield (Entries 14ꢀ15). 3ꢀ
Isopropylaniline and 4ꢀtertꢀbutylaniline could also react
smoothly to generate the corresponding amines in good yields
(Entries 16ꢀ17). In addition, our catalytic system was also
suitable for alkylation of aliphatic amines. For example, the
reaction of dodecanamine with ethanol and 1ꢀpropanol gave the
corresponding products in 90 and 81% yields (Entries 18ꢀ19),
respectively. Finally, almost no Nꢀalkylation product was
observed if benzyl alcohol was used in the Nꢀalkylation
reaction of pꢀchloroꢀaniline. Therefore, this catalyst is active for
the Nꢀalkylation of amines with aliphatic alcohols but not
active for the amination reaction of aromatic alcohols.
The proposed reaction mechanism. After the successful
alkylation of amines with different alcohols, we were further
interested in the reaction mechanism. Therefore, the reactions
Entry
1
Amines
alcohols
Products
Yield%b
80
2
3
4
83
90
93
N
Cl
of pꢀchloroaniline with methanol and ethanol were traced by
GCꢀMS to check the possible reaction intermediates,
respectively. Interestingly, the two reactions have similar
intermediates, i.e., imines, in the process of secondary amines
generation,
however,
completely
different
reaction
intermediates are formed during the production of tertiary
amines. Methoxy hemiaminals as intermediates are formed
during the generation of trimethyl amine in the Nꢀmethylation
reaction via the addition of methanol to iminium ion. This
intermediate is not observed in the Nꢀethylation reactions of
amines. (Figure 6(A)). The timeꢀdependent change in quantity
variations of the intermediates were shown in Figure 6. In
5
6
95
65
Figure 6 (B), almost all the
the initial stage and the possible product was
ethylideneaniline via condensation of ꢀchloroaniline with
acetaldehyde, which was produced by the dehydrogenation of
ethanol. As the amount of ꢀchloroꢀNꢀethylideneaniline and
chloroꢀNꢀethylaniline reduced fast, we supposed that ꢀchloroꢀ
Nꢀethylideneaniline was hydrogenated to ꢀchloroꢀNꢀ
ethylaniline and ꢀchloroꢀNꢀethylaniline will react with ethanol
again, and
ꢀchloroꢀN,Nꢀdiethylaniline was produced57.
p
ꢀchloroaniline was consumed at
p
ꢀchloroꢀNꢀ
p
7
8
60
70
p
pꢀ
p
p
p
p
Similar results were obtained if the addition reaction of
methanol and iminium ion could not proceed.
On the basis of the above results, two main pathways can be
proposed for the alkylation of amines with alcohols in our
catalytic system, and they are illustrated in Figure 7. (1) As
pathway A showed, the photocatalytic activity is improved in 10
the UVꢀlight region. During the Nꢀmethylation reaction, the
electron and hole pairs formed in TiO2, by UVꢀlight irradiation,
9
94
91
80
78
migrate to catalyst surface to react with absorbed substrates.
11
The hole oxidizes methanol to formaldehyde and H+ in presence
of CuOx. H+ is reduced on the surface of Cu0 by the electron
transferred from the TiO2 conduction band and produces the
12
Cuꢀhydride species (CuꢀH)58. Parts of the H atoms are removed
from the surface Cu0 by coalescence as H2 gas39. The imine is
generated by condensation of the formed formaldehyde with pꢀ
chloroaniline by the Lewis acid site on the TiO2 surface59. Next,
the imine is hydrogenated by CuꢀH species and is transformed
13
14
87
95
to
p
ꢀchloroꢀNꢀmethylaniline. Then, iminium ion is generated by
condensation of
p
ꢀchloroꢀNꢀmethylaniline with formaldehyde60.
There are two stages to transform the iminium ion. At the initial
stage, iminium ion preferentially reacts with methanol to
generate methoxy hemiaminals, which are thermodynamically
less stable and serves as a resting state for iminium ion61, 62. In
the second stage, the iminium ion is immediately reduced by
15
83
CuꢀH species and pꢀchloroꢀN,Nꢀdimethylaniline is generated.
(2) A conventional reductive reaction of iminium ion with
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88
CuꢀH species is smoothly performed in ethanol and pꢀchloroꢀ
N,Nꢀdiethylaniline is gained. Excepting for methanol,
hemiaminal intermediates were not detected during the
investigation of
pꢀchloroaniline with ethanol (Figure 6 (B)).
17
85
Therefore, the pathway B is suitable for the alkylation of
amines with other alcohols under the present reaction condition.
Noteworthy, although different catalytic activities were
observed when catalysts with different Cu/Mo ratios were
applied, they should take the same reaction pathways due to the
similar reaction intermediates observed by GCꢀMS.
18
19
90
81
Conclusions
aReaction condition: amine (0.2 mmol), alcohol (5 mL), Cu1ꢀMo1/TiO2, (20
mg), argon, UV (365 nm LED, 245 mW/cm2), r.t., 21 h. bIsolated yield.
In summary, we have developed
a convenient and
straightforward photocatalytic system for the Nꢀalkylation of
amines using alcohols as solvent and reactant. A series of
photocatalysts, which are TiO2 decorated with nonꢀnoble metal
copper and molybdenum (CuꢀMo/TiO2), were prepared through
a simple procedure using commercially available TiO2. By
applying this catalyst, various secondary and tertiary amines are
successfully synthesized with high yields at room temperature
under UV irradiation. This photocatalytic system offers
significant advantages including broad substrate scope, no
harmful byproduct formation, simple procedure and
environmentally benign, which make it an attractive method for
Nꢀalkyl amine synthesis.
100
(A)
80
60
40
20
0
a
d
c
b
e
Acknowledgements
f
This work was financially supported by the National Natural
Science Foundation of China (21203219) and the Chinese
Academy of Sciences. Thanks are also due to Professor Yingpu
Bi for his kind assistance on theory and UvꢀVis measurement.
0
3
6
9
12
15
18
21
Time/h
100
80
60
40
20
0
(B)
Experimental Section
Typical procedure for catalyst preparation: MoO3 (12 mg)
was dissolved with stirring in 1 M NaOH (1 mL) at room
temperature until the complete dissolution of MoO3, then
deionized water (30 mL) was added. Following, TiO2 (0.5 g,
P25, J&K Scientific, anatase/rutile =80/20, BET surface, 35ꢀ65
m2/g) was dispersed in the solution and CuCl2 aqueous solution
(14 mg/5 mL deionized water) were added into the solution
under vigorous stirring. After the addition of CuCl2 was
completed, the solution was stirred for another 3 h at room
temperature. Then NaBH4 (20 mg/3 mL deionized water) was
added to the solution in ice water bath and stirred for 2 h. The
solid sample was recovered by centrifugation and washed with
deionized water (40 mL × 2). The obtained solid was dried at
a
h
i
g
0
2
4
6
8
10 12 14 16
Time/h
o
80 C, and was denoted as Cu1ꢀMo1/TiO2. Cu1ꢀMo3/TiO2 and
Cu3ꢀMo1/TiO2 were prepared with the same procedure but 7 mg
CuCl2/18 mg MoO3 or 21 mg CuCl2/6 mg MoO3 were used.
Typical reaction procedure: amine (0.2 mmol), catalyst (20
mg) and alcohol (5 mL) were added into a glass tube (35 mL).
Argon was bubbled through the solution for 5 min. Then the
tube was sealed with a rubber cap and photoirradiated by a
LED light (365 nm, 245 mW/cm2) with magnetic stirring at
room temperature for 21 h. Subsequently, 10 mg biphenyl and 5
mL ethanol were added for quantitative analysis by GCꢀFID
Figure 6. Time-dependent variation of substrates and products during
photoreaction of p-chloroaniline with (A) methanol and (B) ethanol catalyzed by
Cu1-Mo1/TiO2. Reaction conditions: see Table 3 and Table 4.
6 | J. Name., 2012, 00, 1-3
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DOI: 10.1039/C5CY00316D
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ARTICLE
Figure 7. Proposed reaction mechanism for light promoted N-alkylation of p-chloroaniline over Cu-Mo/TiO2
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Notes and references
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a State Key Laboratory for Oxo Synthesis and Selective Oxidation, Centre
for Green Chemistry and Catalysis, Lanzhou Institute of Chemical
Physics, Chinese Academy of Sciences, No.18, Tianshui Middle Road,
Lanzhou, 730000, China Fax: +86ꢀ931ꢀ8277088; Tel: +86ꢀ931ꢀ4968142;
Eꢀmail: fshi@licp.cas.cn
b University of Chinese Academy of Sciences, Beijing, 100049, China
† Electronic
Supplementary
Information
(ESI)
available:
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8 | J. Name., 2012, 00, 1-3
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DOI: 10.1039/C5CY00316D
Room Temperature N-Alkylation of Amines with Alcohols under
UV Irradiation Catalyzed by Cu-Mo/TiO2
Lina Zhangab, Yan Zhanga, Youquan Denga, Feng Shi*a
Cu-Mo/TiO2 can be an activephotocatalyst for N-alkylation of amines with alcohols under UV
irradiation at room temperature without the addition of noble metals.