The carbonylation of phenyl bromide and its derivatives under visible light irradiation

Article abstract of DOI:10.1016/j.cclet.2011.09.024

The carbonylation of phenyl bromide catalyzed by Co(OAc)₂ has been investigated with PhCOPh as a sensitizer under visible light in the presence of basic additive. With strong base CH₃ONa, PhCOOCH ₃ is produced in 70% yield with 100% selectivity, the similar results are also obtained with a stronger base (CH₃)₃CONa. However, with another strong base NaOH, the yield of the ester is only 40%. On the other hand, with weak base NaOAc or (n-C₄H₉) ₃N, phenyl bromide cannot be carbonylated. The results of carbonylation of the six substituted phenyl bromides suggest that the activities of o, m, p-BrC₆H₄CH₃ are similar to phenyl bromide, while the activities of o, m, p-BrC₆H₄Cl are higher with the high yields (≥93%) of the corresponding chloro-esters. In addition, the relative position of bromine and chlorine or methyl on phenyl ring has little effect on the activity of the carbonylation.

Full text of DOI:10.1016/j.cclet.2011.09.024

Available online at www.sciencedirect.com
Chinese Chemical Letters 23 (2012) 29–32
www.elsevier.com/locate/cclet
The carbonylation of phenyl bromide and its derivatives
under visible light irradiation
*
Wen Hui Zhong, Ying Na Cui, Shen Min Li, Ying Ping Jia , Jing Mei Yin
*
Liaoning Key Laboratory of Bio-organic Chemistry, Dalian University, Dalian 116622, China
Received 7 June 2011
Available online 8 November 2011
Abstract
The carbonylation of phenyl bromide catalyzed by Co(OAc)
2
has been investigated with PhCOPh as a sensitizer under visible
light in the presence of basic additive. With strong base CH ONa, PhCOOCH is produced in 70% yield with 100% selectivity, the
3
3
similar results are also obtained with a stronger base (CH
is only 40%. On the other hand, with weak base NaOAc or (n-C
carbonylation of the six substituted phenyl bromides suggest that the activities of o, m, p-BrC H CH are similar to phenyl bromide,
3
)
3
CONa. However, with another strong base NaOH, the yield of the ester
4 9 3
H )
N, phenyl bromide cannot be carbonylated. The results of
6
4
3
while the activities of o, m, p-BrC
relative position of bromine and chlorine or methyl on phenyl ring has little effect on the activity of the carbonylation.
2011 Ying Ping Jia. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
6
H
4
Cl are higher with the high yields (ꢀ93%) of the corresponding chloro-esters. In addition, the
#
Keywords: Carbonylation; Phenyl bromide; o, m, p-Bromotoluene; o, m, p-Bromochlorobenzene; Visible light
The carbonylation of aryl halides is an essential reaction to synthesize aryl carboxyl acids and their derivatives,
which are valuable intermediates in the manufacture of pharmaceutical products and chemicals. However, the
traditional carbonylation of the much less reactive aryl halides is difficult to carry out under mild conditions [1], and
only a few systems allow such reactions. In contrast, the photopromoted carbonylation of aryl halides can be easily
achieved [2–5]. Brunet et al. [2] reported the carbonylation of aryl halides with CO (1 atm) catalyzed by Co (CO) at
2
8
65 8C under irradiation by means of a sunlamp (main emissions at 300, 315, 365, 405 and 435 nm) through a Pyrex
flask. Kashimura et al. [3] described the polycarbonylation of polyhalogenated aromatics with CO (0.2 MPa) in the
presence of a catalytic amount of Co (CO) under the irradiation of a high-pressure mercury lamp by a Pyrex filter.
2
8
Cash et al. [4] demonstrated the photochemical carbonylation of phenyl bromide with Co(acac) as catalyst under a
2
low-pressure mercury lamp in a quartz glass reactor. In previous research [5], we have studied on the carbonylation of
PhBr with CO (0.1 MPa) catalyzed by inexpensive stable less toxic Co(OAc) under the irradiation of a high-pressure
2
mercury lamp in a quartz glass reactor, PhCOOCH was achieved with 91% yield by using CH ONa and PhCOCH as
3
3
3
additives in CH OH system. We noted that the photocarbonylation of aryl halides above mentioned occurred mostly
3
under UV light irradiation and with Pyrex glass even quartz glass as reactor. Unsatisfactory, the UV light make the
equipment aged easily due to its strong irradiation; meanwhile, it is dangerous to the operator’s health. Furthermore,
*
Corresponding authors.
E-mail addresses: yingpingjia@163.com (Y.P. Jia), jingmeiyin@163.com (J.M. Yin).
1001-8417/$ – see front matter # 2011 Ying Ping Jia. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
doi:10.1016/j.cclet.2011.09.024

30
W.H. Zhong et al. / Chinese Chemical Letters 23 (2012) 29–32
the high price of the special glass reactor limits the prospects for industrial application. In this paper, we report the first
example of non-precious metal Co(OAc) catalyzed carbonylation of PhBr and its derivatives with 0.1 MPa of CO in
2
an ordinary glass reactor under visible light irradiation. In the study, irradiation was achieved with a 23 W household
warm-white energy-saving lamp placed closely against the ordinary glass reactor, and CH ONa and PhCOPh were
3
used as additives. We focused on the finding of the optimum reaction factors such as the concentration of additives
CH ONa and PhCOPh.
3
1
. Experimental
PhBr, o, m, p-BrC H CH , o, m, p-BrC H Cl (A.R., Shanghai Aladdin Reagent Co.); CO (99.9%, Dalian
6 4
6
4
3
Guangming Institute); Co(OAc) , CH OH, PhCOPh, PhCOCH , NaOH, NaOAc, (n-C H ) N, n-C H (A.R.,
2
3
3
4
9 3
10 22
Beijing Chemical Engineering Co.); CH ONa, (CH ) CONa (prepared in laboratory).
3
3 3
A typical experimental procedure was as follows: first, methanol solution of PhBr or its derivatives (20 mmol/L),
catalyst (2 mmol/L) and additives was placed in an ordinary glass reactor with an interlayer, through which the
circulating water from thermostat water bath was passed to keep constant temperature. Then, the reactions were
carried out under 0.1 MPa of CO pressure with irradiation by a household warm-white energy-saving lamp (Philips
type: Energy Saver 23 W, Chinese type: YPZ 220/23-3U. RD.D., Philips (China) Investment Co., Ltd.). Last, the
products were analyzed by GC (Hitachi GC-3900) and GC–MS (HP 6890/5973) with n-C H as the internal
1
0 22
standard. The emission spectrum of the lamp, provided by Philips (China) Investment Co., Ltd., and reaction device
are shown in Fig. 1.
2
. Results and discussion
The carbonylation reaction is described in Scheme 1. When Co(OAc) , CH ONa and PhCOPh are simultaneously
2
3
added to the reaction system under visible light irradiation, PhBr can be carbonylated, particularly, the selectivity of
the carbonylated product PhCOOCH is 100%. The detailed results are presented in Table 1.
3
It is well known that a certain amount of heat energy produced during the irradiation leads to the increasing of the
temperature of the reaction system, and as a result, to improve the reaction activity in general. However, the solubility
of CO in CH OH decreases as the increasing of the temperature, which is disadvantage to the reaction. Above facts
3
suggest that the optimum temperature is important to the reaction. Four experiments were carried out at 20, 30, 40 and
50 8C. The observed results as shown in Table 1 (entries 1–4) tell us the optimum temperature is 40 8C. But we should
note that even at the optimum temperature, the reaction activity is still low. In order to improve the conversion, we
Fig. 1. (1) The emission spectrum of household warm-white energy-saving lamp and (2) schematic drawing of the reaction device.
Br
+
(
COOCH
+
NaBr
3
hv (λ >380nm)
CO + CH
0.1MPa)
OH
3
Co(OAc) / CH ONa / PhCOPh
2
3
Scheme 1.

W.H. Zhong et al. / Chinese Chemical Letters 23 (2012) 29–32
31
Table 1
The carbonylation of phenyl bromide under visible light.
Entry
Temperature
8C)
Time (h)
Base
Base concentration
(mmol/L)
PhCOPh
Conversion
(%)
Yield (%)
(
(mmol/L)
1
2
3
4
5
6
7
8
9
20
30
40
50
40
40
40
40
40
40
40
40
40
40
40
40
40
40
40
15
15
15
15
12
18
20
24
15
15
15
15
15
15
15
15
15
15
15
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
ONa
ONa
ONa
ONa
ONa
ONa
ONa
ONa
ONa
ONa
ONa
ONa
ONa
ONa
ONa
ONa
40
40
40
40
40
40
40
40
50
60
65
70
65
65
65
65
65
65
100
70
70
70
70
70
70
70
70
70
70
70
70
40
50
60
80
70
70
70
17
33
37
30
19
37
36
36
51
61
70
58
36
49
55
68
72
40
40
17
33
37
30
19
37
36
36
51
61
70
58
36
49
55
68
72
40
40
1
1
1
1
1
1
1
1
1
1
0
1
2
3
4
5
6
7
8
9
3 3
(CH ) CONa
NaOH
NaOH
PhBr 20 mmol/L, Co(OAc)
2
3
2 mmol/L, n-C10H22 5 mmol/L, CH OH 4.5 mL.
tested the effect of reaction time on the reaction (Table 1, entries 3, 5–8). It is found that the conversion has little
change when reaction time is between 15 h and 24 h. One explanation is that the reaction may reach the equilibrium
after 15 h under our experimental conditions.
We also investigated the effects of basic additives on the carbonylation of PhBr under visible light. The three basic
additives such as CH ONa, NaOAc and (n-C H ) N were used as in our previous work [5]. To our surprise, only
CH ONa was effective to the reaction, while there was no PhCOOCH with NaOAc or (n-C H ) N. The results
3
4 9 3
3
3
4 9 3
indicate that strong basicity is necessary for the reaction under visible light, which are remarkably different from those
under UV light. Furthermore, the conversion of PhBr and the yield of PhCOOCH significantly depend on the
3
concentration of CH ONa (Table 1, entries 3, 9–12). With an increase in the concentration of CH ONa, the conversion
3
3
of PhBr and the yield of PhCOOCH increase rapidly, the selectivity of 100% remaining unchanged. The best
3
concentration of CH ONa is 65 mmol/L, and the conversion of PhBr can be reached to 70%. We further tested the
3
effects of other two strong bases, i.e., (CH ) CONa and NaOH, on the reaction (Table 1, entries 17–19). With
3
3
(
PhCOOCH was lower (40%). Meanwhile, considering the weaker basicity of NaOH compared to CH ONa, a high
CH ) CONa, the yield of PhCOOCH was similar to that with CH ONa. However, with NaOH, the yield of
3 3 3 3
3
3
concentration of NaOH was added to the reaction system, there was no increasing of the yield. The reason
why CH ONa and (CH ) CONa have stronger influence on the reaction than NaOH is probably that a large amount
3
3 3
of –OCH provided by CH ONa and (CH ) CONa [(CH ) CONa + CH OH ! CH ONa + (CH ) COH], is favorable
3
3
3 3
3 3
3
3
3 3
to the formation of carboxylic methyl ester [6]. Especially, the existence of –OCH under visible light is more
3
important than that under UV light. One possible explanation is that except as base and nucleophile, –OCH acts as an
3
electron donor in the reaction under visible light. It has been reported [2] that the formation of charge transfer
complexes between PhBr and cobalt compound might be possible under irradiation, and cobalt compound is a poor
electron-donating species, thus the existence of electron donor –OCH is advantage to the reaction.
3
In the further experiments, we examined the influence of PhCOPh on the reaction. The result showed that no any
reaction occurred in the absence of PhCOPh. The effects of PhCOPh are given in Table 1 (entries 11, 13–16). The
optimum concentration of PhCOPh is 70 mmol/L and the yield of PhCOOCH is 70% with 100% selectivity. Contrast
3
to the present results, our previous work also showed that PhCOPh was beneficial to the carbonylation of PhBr under
UV light, i.e., the yield of PhCOOCH was increased from 47% to 80% [5]. It is worthy to note that the selectivity of
3
PhCOOCH (80%) under UV light is lower than that (100%) under visible light. The reason is due to high energy of
3
UV light, resulting in the formation of by-products such as benzene and anisole. Both results suggest that PhCOPh

32
W.H. Zhong et al. / Chinese Chemical Letters 23 (2012) 29–32
Table 2
The carbonylation of some substituted phenyl bromides under visible light.
Entry
Substrate
Product
Conversion (%)
Yield (%)
Selectivity (%)
1
2
3
4
5
6
o-BrC
m-BrC
6
H
4
Cl
o-ClC
m-ClC
p-ClC
6
H
4
COOCH
COOCH
COOCH
COOCH
COOCH
COOCH
3
94
98
95
70
72
71
93
97
94
70
72
71
99
99
6
H
4
Cl
Cl
6
H
4
3
p-BrC
o-BrC
6
H
H
4
4
6
H
4
3
99
6
CH
3
o-CH
m-CH
3
C
6
H
4
3
100
100
100
m-BrC
p-BrC
6
H
4
CH
CH
3
3
C
6
H
4
3
6
H
4
3
3
p-CH C
6
H
4
3
Substrate 20 mmol/L, the other conditions are the same as Table 1, entry 11.
plays different roles in different photochemical reaction. According to the literature [7], the roles of PhCOPh in the
reaction under irradiation are as follows: (1) to abstract hydrogen from hydrogen donor; (2) to be employed as a
sensitizer. Under UV light, the role of PhCOPh is mainly to inhibit the hydrodehalogenation of PhBr to form benzene
via abstracting hydrogen. While under visible light, the role of PhCOPh is just assumed to be a sensitizer, since the
hydrodehalogenation of PhBr does not occur at this condition. Interestingly, our earlier work showed that PhCOCH3
was more effective than PhCOPh in terms of the yield and selectivity of PhCOOCH under UV light. However, with
3
PhCOCH instead of PhCOPh under visible light, PhBr could not be carbonylated, which implied that PhCOCH
3
3
could not be used as a sensitizer under visible light. This result may be related to the triplet excited energy transfer of
PhCOPh and PhCOCH (PhCOPh: 69 kcal/mol, PhCOCH : 74 kcal/mol) [8]. Generally, substrates or related
components can absorb photon is a premise to perform photoreaction. In the present reaction system, the catalyst
3
3
Co(OAc) is the only substance which can absorb visible light, thus, the possible photoprocess is that the catalyst
2
absorbs photon to its excited state or charge transfer complex [2], of which the energy is similar to the energy level of
PhCOPh at its triplet state. As a result, the energy transfer among Co(OAc) , PhCOPh and PhBr is occurred. However,
2
the process cannot happen when PhCOCH is used instead of PhCOPh.
3
In addition, the carbonylation of some substituted phenyl bromides was carried out under visible light, the results
are listed in Table 2. In contrast with PhBr, o, m, p-BrC H Cl are very easily carbonylated and the corresponding
6
4
chloro-esters are obtained in high yields (ꢀ93%) accompanied by a small amount of bicarbonylated products (1%)
Table 2, entries 1–3). Moreover, the activities of o, m, p-BrC H Cl are similar to each other. On the other hand, o, m,
p-BrC H CH can also be carbonylated to give the corresponding methyl esters, and the activities of o, m, p-
(
6
4
6
4
3
BrC H CH are similar to PhBr. These results show that the effect of different substituents on the phenyl ring is
6
4
3
different, i.e., chlorine substituent can evidently improve the activity and methyl has no significant effect on the
reaction, but the substituted position has little effect on the activity of the carbonylation.
In conclusion, the photopromoted carbonylation of PhBr and its derivatives catalyzed by Co(OAc) proceeds
2
smoothly in the presence of a strong base CH ONa or (CH ) CONa and a sensitizer PhCOPh under visible light.
3 3 3
Furthermore, the activities of o, m, p-BrC H CH are similar to PhBr, but lower than those of o, m, p-BrC H Cl.
3
6
4
6 4
References
[
[
[
[
[
[
[
[
1] J. Albaneze-Walker, C. Bazaral, T. Leavey, et al. Org. Lett. 6 (2004) 2097.
2] J.J. Brunet, C. Sidot, P. Caubere, J. Org. Chem. 48 (1983) 1166.
3] T. Kashimura, K. Kudo, S. Mori, et al. Chem. Lett. 15 (1986) 299.
4] D. Cash, A. Combs, V. Dragojlovic, Tetrahedron Lett. 45 (2004) 1143.
5] L.Z. Mu, Y.P. Jia, J.M. Yin, et al. Chin. Chem. Lett. 20 (2009) 531.
6] W.R. Moser, A.W. Wang, N.K. Kildahl, J. Am. Chem. Soc. 110 (1988) 2816.
7] P. Subban, Principles of Photochemistry, Z.G. Lu transl., People’s Education Press, Beijing, 1982, p. 43, p. 51.
8] X.H. Kang, M.Q. Liu, Photochemistry Principles and Applications, Publishing House of Tianjin University, Tianjin, 1995, p. 176.