Electrocatalytic carboxylation of arylic bromides at silver cathode in the presence of carbon dioxide

Article abstract of DOI:10.1080/00397911.2010.520399

A simple and efficient electrocatalytic carboxylation of arylic bromides has been developed using silver as cathode and magnesium as anode in N,N-dimethylformamide (DMF) under mild conditions. The influences of some key factors (such as the nature of cathode material, current density, and temperature) on this reaction were investigated. The investigations were extended to other arylic bromides under the optimized conditions, and the corresponding carboxylic acids were obtained in moderate to good yields (30- 78%). The electrochemical behavior was studied at different electrodes (Ag, Cu, Ni, and Ti) by cyclic voltammetry, which showed significant electrocatalytic effect of the silver electrode toward the reductive carboxylation of arylic bromides. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/00397911.2010.520399

This article was downloaded by: [University of Otago]
On: 05 October 2014, At: 08:51
Publisher: Taylor & Francis
Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered
office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK
Synthetic Communications: An
International Journal for Rapid
Communication of Synthetic Organic
Chemistry
Publication details, including instructions for authors and
subscription information:
http://www.tandfonline.com/loi/lsyc20
Electrocatalytic Carboxylation of Arylic
Bromides at Silver Cathode in the
Presence of Carbon Dioxide
Jingbo Zhang a , Dongfang Niu a b , Yangchun Lan a , Huan Wang a
Guirong Zhang a & Jiaxing Lu a
,
a Shanghai Key Laboratory of Green Chemistry and Chemical
Processes, Department of Chemistry , East China Normal University ,
Shanghai , China
b State Key Laboratory of Chemical Engineering , East China
University of Science and Technology , Shanghai , China
Accepted author version posted online: 30 Jun 2011.Published
online: 16 Jun 2011.
To cite this article: Jingbo Zhang , Dongfang Niu , Yangchun Lan , Huan Wang , Guirong Zhang &
Jiaxing Lu (2011) Electrocatalytic Carboxylation of Arylic Bromides at Silver Cathode in the Presence
of Carbon Dioxide, Synthetic Communications: An International Journal for Rapid Communication of
Synthetic Organic Chemistry, 41:24, 3720-3727, DOI: 10.1080/00397911.2010.520399
To link to this article: http://dx.doi.org/10.1080/00397911.2010.520399
PLEASE SCROLL DOWN FOR ARTICLE
Taylor & Francis makes every effort to ensure the accuracy of all the information (the
“Content”) contained in the publications on our platform. However, Taylor & Francis,
our agents, and our licensors make no representations or warranties whatsoever as to
the accuracy, completeness, or suitability for any purpose of the Content. Any opinions
and views expressed in this publication are the opinions and views of the authors,
and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content
should not be relied upon and should be independently verified with primary sources
of information. Taylor and Francis shall not be liable for any losses, actions, claims,
proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or
howsoever caused arising directly or indirectly in connection with, in relation to or arising
out of the use of the Content.

This article may be used for research, teaching, and private study purposes. Any
substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing,
systematic supply, or distribution in any form to anyone is expressly forbidden. Terms &
Conditions of access and use can be found at http://www.tandfonline.com/page/terms-
and-conditions

Synthetic Communications1, 41: 3720–3727, 2011
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397911.2010.520399
ELECTROCATALYTIC CARBOXYLATION OF ARYLIC
BROMIDES AT SILVER CATHODE IN THE PRESENCE
OF CARBON DIOXIDE
Jingbo Zhang,1 Dongfang Niu,1,2 Yangchun Lan,1
Huan Wang,1 Guirong Zhang,1 and Jiaxing Lu1
1Shanghai Key Laboratory of Green Chemistry and Chemical Processes,
Department of Chemistry, East China Normal University, Shanghai, China
2State Key Laboratory of Chemical Engineering, East China University of
Science and Technology, Shanghai, China
GRAPHICAL ABSTRACT
Abstract A simple and efficient electrocatalytic carboxylation of arylic bromides has been
developed using silver as cathode and magnesium as anode in N,N-dimethylformamide
(DMF) under mild conditions. The influences of some key factors (such as the nature of
cathode material, current density, and temperature) on this reaction were investigated.
The investigations were extended to other arylic bromides under the optimized conditions,
and the corresponding carboxylic acids were obtained in moderate to good yields (30–
78%). The electrochemical behavior was studied at different electrodes (Ag, Cu, Ni, and
Ti) by cyclic voltammetry, which showed significant electrocatalytic effect of the silver
electrode toward the reductive carboxylation of arylic bromides.
Keywords Arylic bromides; CO2; electrocatalytic; silver cathode
INTRODUCTION
Carbon dioxide (CO2) is the most abundant waste produced by human
activities and one of the greenhouse gases.[1] However, CO2 is recognized to be a nat-
urally abundant, cheap, recyclable, and nontoxic carbon source that can sometimes
replace toxic chemicals such as phosgene, isocyanates, or carbon monoxide.[2] As a
result, CO2 fixation has become an active area of research in green chemistry.
Electrochemical carboxylation is one of the most useful methods for CO2 fixation
Received December 10, 2009.
Address correspondence to Jiaxing Lu, Shanghai Key Laboratory of Green Chemistry and
Chemical Processes, Department of Chemistry, East China Normal University, Shanghai 200062,
China. E-mail: jxlu@chem.ecnu.edu.cn
3720

ELECTROCATALYTIC CARBOXYLATION OF ARYLIC BROMIDES
3721
to organic molecules because it is a mild and easy-to-handle process. Carbanions
can easily be genenrated by the electrochemical reduction of organic halides,[3]
aromatic ketones,[4] and activated olefins,[5] and then carbon dioxide can work as
an electrophile in the reaction of anion species to give carboxylic acids with one
carbon elongation.
Benzoic acids are important intermediates in many natural and medicinally
important compounds.[6] In recent years, metal-catalyzed carboxylation of aryl
halides has become a powerful alternative to the classical synthetic approaches for
these compounds.[7] Correa and Martin[8] used palladium complex as catalyst for
the carboxylation of aryl bromides under 10 atmospheres of CO2. In an electro-
chemical field, several metal complexes[9] (such as nickel and palladium complexes)
have also been used as homogeneous catalysts for the electrochemical carboxylation
of aryl halides, or else poisonous Hg was used as the electrode.[10] Although good
current efficiencies were obtained with many of these catalytic systems, the presence
of additive catalysts made the reaction system and the separation complicated, and
it is also expensive and not friendly to the environment.
In the past years, a series of studies dealing with the reduction of organic halides
at an Ag electrode have been reported.[11] It has been shown that such an electrode
material exhibits extraordinary electrocatalytic activities toward the reduction pro-
cess, especially in the case of bromides and iodides. In this work, we have investigated
in detail the influences of operative parameters on the electrocarboxylation of arylic
bromides in CO2–saturated dimethylformamide (DMF) solution at the Ag cathode,
aiming to optimize the process and exploit an applicable methodology. This method
occurs under mild temperature and atmospheric pressure, avoiding the use of catalyst.
EXPERIMENTAL
Cyclic voltammograms were measured with a CHI660 electrochemical analyzer
(CHI, USA). Silver (Ag), copper (Cu), nickel (Ni), and titanium (Ti) electrodes
(d ¼ 2 mm) were used as working electrodes, respectively. The counterelectrode
and the reference electrode were a platinum wire and Ag–AgI–0.1 M n-Bu4NI in
˚
DMF, respectively. DMF was kept over 4-A molecular sieves. Tetraethylammonium
tetrafluoroborate (TEABF4), tetrabutylammonium iodide (TBAI), and methyl
p-(methoxycarbonyl) benzoate were used as received.
General Procedure for Electrochemical Carboxylation
of Arylic Bromides
The galvanostatic electrolysis was carried out in a mixture of arylic bromides
(0.1 M) and TBAI (0.1 M) in DMF (10 mL) under a slow stream of CO2 in an undiv-
ided electrochemical cell equipped with a metallic ring cathode and a sacrificial Mg
anode. The electrochemical carboxylation of arylic bromides and CO2 followed the
principle shown in Scheme 1.
After electrolysis, the residue was esterified by adding anhydrous K2CO3 (0.3 g)
and CH3I (0.6 mL) and stirring the mixture at 50 ꢀC for 5 h. For the quantitative
determination of benzoic acids by gas chromatography (GC), we converted the acids
into their corresponding methyl esters. The solution was quenched by water and

3722
J. ZHANG ET AL.
Scheme 1. Electrocatalytic carboxylation of arylic bromides at Ag cathode in DMF-TBAI.
extracted with Et2O, and the organic layers were dried over MgSO4 and evaporated.
The methyl esters corresponding to acids were isolated by column chromatography
with petroleum ether=ethyl acetate mixtures as eluent. After isolation and identifi-
cation of the products, working curves with n-decane as the internal standard were
used for analysis of the electrochemical carboxylation. The methyl esters correspond-
ing to acids were confirmed with 1H NMR and GC-MS spectra. The spectral data of
the products are given.
Methyl Benzoate
1
GC-MS (m=z, %): 136 (Mþ, 11), 105 (29), 77 (16), 51 (5), 28 (100); H NMR
(500 MHz, CDCl3): d 8.03–7.41 (5H, m), 3.89 (3H, s).
Methyl p-Methoxybenzoate
1
GC-MS (m=z, %): 166 (Mþ, 33), 135 (100), 107 (9), 77 (18), 64 (7); H NMR
(500 MHz, CDCl3): d 8.00–6.92 (4H, m), 3.89 (3H, s), 3.86 (3H, s).
Methyl p-Methyl Benzoate
1
GC-MS (m=z, %): 150 (Mþ, 39), 119 (100), 91 (41), 65 (12), 39 (5); H NMR
(300 MHz, CDCl3): d 7.93–7.17 (4H, m), 3.86 (3H, s), 2.35 (3H, s).
4-Acetyl-benzoic Acid Methyl Ester
1
GC-MS (m=z, %): 178 (15), 163 (Mþ, 100), 135 (20), 76 (7), 28 (37); H NMR
(500 MHz, CDCl3): d 8.14–8.00 (4H, m), 3.96 (3H, s), 2.65 (3H, s).
RESULTS AND DISCUSSION
Cyclic Voltammetric Behavior of Bromobenzene
Cyclic voltammograms recorded for reduction of bromobenzene at the Ag elec-
trode in DMF containing 0.1 M TEABF4 are depicted in Fig. 1. As shown in curve (a)
of Fig. 1, no peaks were found. The curve (b) of Fig. 1 shows a single irreversible
reductive peak (Ep) under a nitrogen atmosphere at ꢁ1.89 V that corresponds to
two-electron reductive cleavage of the carbon–bromide bond. The voltammetry beha-
vior of bromobenzene was very similar in appearence to those pictured in an earlier
report pertaining to the cathodic behavior of alkyl halides at glass carbon electro-
des.[12] The Ep of the bromobenzene is positively shifted from ꢁ1.89 V to ꢁ1.66 V

ELECTROCATALYTIC CARBOXYLATION OF ARYLIC BROMIDES
3723
Figure 1. Cyclic voltammograms of bromobenzene recorded at Ag electrode in DMF–0.1 M TEABF4.
(a) DMF þ TEABF4; (b) a þ 0.05 M bromobenzene; (c) b þ CO2. v ¼ 0.1 V ꢃ sꢁ1
,
t ¼ 25 ꢀC; Inset:
linear relationship between ip and concentration, t ¼ 25 ꢀC, v ¼ 0.1 V ꢃ sꢁ1
.
after bubbling CO2 into the solution. This indicates a rapid chemical reaction between
CO2 and electrogenerated radical anion. According to our previous study, the electro-
chemical reduction of CO2 at the Ag cathode occurs at ꢁ2.13 V. The inset is the study
of peak current (ip) for the main reduction process of bromobenzene over the concen-
tration range 10–30 mM, which revealed a linear relationship between ip and concen-
tration, showing that the reduction proceeds rather cleanly at the Ag electrode (that
is, without serious filming effects).
To examine the electrocatalytic effect of the Ag electrode toward the reduction
of bromobenzene, the voltammetry behaviors of bromobenzene were also investi-
gated at the most commonly used cathodes [e.g., Cu, Ni, and Ti (Fig. 2)]. The
reduction peak of bromobenzene at Cu electrode appeared at ꢁ1.87 V, which is
similar to that required for its reduction at the Ag electrode (ꢁ1.89 V). Compared
with the Ag electrode, an obvious thin film was formed at the Cu electrode surface
after several voltammetry cycles, which was attributed to the absorption of electro-
generated intermediate species at the Cu electrode and will result in progressive
degradation of the Cu cathode during the electrocarboxylation of arylic bromides.
In addition, in our previously study,[13] we reported that Cu was also a good material
for the reduction of CO2. The two points mentioned previously are unfavorable to
electrocarboxylation of bromobenzene. A broad reduction peak (Ep ꢂ ꢁ2 V)
appeared at the Ni or Ti electrode, which was considerably more negative than
the Ep value obtained at Ag and very close to the reduction peak of CO2.
Experimental Investigations on the Electrocarboxylation
of Arylic Bromides
Bromobenzene was chosen as a model molecule to be investigated in detail,
and then the investigations were extended to other arylic bromides. To optimize

3724
J. ZHANG ET AL.
Figure 2. Cyclic voltammograms of bromobenzene in DMFꢁ0.1 M TEABF4 recorded at Cu, Ni, and Ti
electrodes, v ¼ 0.1 V ꢃ sꢁ1, t ¼ 25 ꢀC.
the yields, we first focused our attention on the influences of various synthetic para-
meters of the process, such as the cathode electrode materials, current densities, and
temperature. The results of the electrolysis are reported in Table 1.
Influence of cathode materials. The cyclic voltammograms demonstrated
that Ag shows a significant electrocatalytic effect on the reduction of bromobenzene.
To confirm this, we first investigated electrocarboxylation of bromobenzene at the
Ag electrode (Table 1, entry 1) and then at Cu, Ni and Ti electrodes (Table 1, entries
2–4) for comparison. The electrocarboxylation yield decreased depending on the
employed cathode materials in the following order: Ag > Cu> Ti > Ni. The electroly-
sis results accord with the result of cyclic voltammograms of bromobenzene. Owing
Table 1. Influence of various experimental parameters on the yield of benzoic
acida
Entry Cathode Current density (mA ꢃ cmꢁ2
)
Temp. (ꢀC) Yieldb (%)
1
Ag
Ti
4.54
4.54
4.54
4.54
2.27
3.97
5.11
5.67
4.54
4.54
4.54
0
0
78
9
2
3
Ni
0
4
4
Cu
Ag
Ag
Ag
Ag
Ag
Ag
Ag
0
41
56
63
71
55
40
64
65
5
0
6
0
7
0
8
0
9
20
10
ꢁ10
10
11
aGeneral
conditions:
DMF ¼ 10 mL,
bromobenzene ¼ 0.1 M,
TBAI ¼ 0.1 M, electric charge 2.5 F molꢁ1, Mg as anode.
bGC yield, based on the starting bromobenzene.

ELECTROCATALYTIC CARBOXYLATION OF ARYLIC BROMIDES
3725
to the very negative potentials required for the reduction of bromobenzene at Ni and
Ti electrodes, concomitant reduction of CO2 probably took place, which resulted in
high consumption of charge and gave oxalate, CO and carbonate.[14]
Influence of current density. The yields are also strongly affected by the
current density (Table 1, entries 1, and 5–8). The working electrode potential will
become more negative with the increase in current density, so there will be other
undesired reactions taking place on the electrode surface, such as the reduction of
CO2 or TBAI, which will decrease the carboxylation yield. Tributylamine was
detected in GC-MS, which was generated by the dissociation of supporting electro-
lyte. On the other hand, the lower the current density is, the more positive the elec-
trode potential will be. Thus, the proportion of the Faradaic current will decline,
which will also decrease the carboxylation yield. As a result, the optimized current
density is 4.54 mA ꢃ cmꢁ2 on the electrodes of Mg-Ag.
Table 2. Electrochemical carboxylation of arylic bromides in DMF–TBAIa
Entry
1c
Substrate
Product
Yieldb (%)
78
2d
69
62
3e
4f
60
30
5g
aGeneral conditions: Ag cathode, Mg anode, t ¼ 0 ꢀC.
bGC yield, based on the starting arylic bromides.
cThis experiment (Table 1, entry 1) was repeated here for clarity.
dCurrent density ¼ 5 mA ꢃ cmꢁ2, electric charge ¼ 2 F molꢁ1
.
eCurrent density ¼ 4 mA ꢃ cmꢁ2, electric charge ¼ 2.5 F molꢁ1
.
fCurrent density ¼ 4.33 mA ꢃ cmꢁ2, electric charge ¼ 2 F molꢁ1
.
gCurrent density ¼ 5 mA ꢃ cmꢁ2, electric charge ¼ 2 F molꢁ1
.

3726
J. ZHANG ET AL.
Influence of temperature. To investigate the effect of the temperature on the
electrochemical carboxylation of bromobenzene, electrolysis was carried out at
different temperatures (Table 1, entries 1 and 9–11). According to the Arrhenius
equation, the activation energy required for the electroreduction of bromobenzene
decreased with increasing temperature. Conversely, the solubility of CO2 in DMF
solution also declined with elevating temperate. In view of the two contradictory fac-
tors, temperatures either too high or too low are unfavorable to the electrochemical
carboxylation of bromobenzene. Hence, the optimal temperature is 0 ꢀC.
Electrocarboxylation of other arylic bromides. To test the applicability of
this electrochemical carboxylation, the investigation was extended to other arylic
bromides. The results are reported in Table 2. In all cases, the corresponding
carboxylic acids were obtained. It indicates that this electrochemical synthesis works
well for arylic bromides.
CONCLUSION
In conclusion, we have demonstrated a simple and efficient electrochemical
route with a silver cathode for electrocarboxylation of arylic bromides. The reaction
does not need the presence of a catalyst and can be carried out under mild tempera-
ture and atmospheric pressure conditions. Under suitable conditions, arylic bro-
mides were electrochemically reduced in the presence of CO2 to the corresponding
carboxylic acids. This electrochemical route appears to be a simple and efficient
approach for electrocarboxylation of arylic bromides.
ACKNOWLEDGMENTS
This work was supported by the National Natural Science Foundation of
China (20973065), Basic Research in Natural Science issued by Shanghai Municipal
Committee of Science (08dj1400100), and Shanghai Leading Academic Discipline
Project (B409).
REFERENCES
1. Yoshida, M.; Ohsawa, Y.; Ihara, M. Palladium-catalyzed carbon dioxide elimination–
fixation reaction of 6-methoxycarbonyloxy-2,4-hexadien-1-ols. Tetrahedron 2006, 62,
11218–11226.
2. Gibson, D. H. The organometallic chemistry of carbon dioxide. Chem. Rev. 1996, 96,
2063–2095.
3. (a) Vjacheslav, G. K.; Vladimir, E. T.; Victoria, A. L. Electrochemical carboxylation of
benzoyl bromide as effective phenylglyoxylic acid synthesis route. Electrochem. Commun.
2002, 4, 655–658; (b) Senboku, H.; Fujimura, Y.; Kamekawa, H.; Tokuda, M. Divergent
electrochemical carboxylation of vinyl triflates: New electrochemical synthesis of phenyl-
substituted a,b-unsaturated carboxylic acids and aliphatic b-keto carboxylic acids.
Electrochim. Acta 2000, 45, 2995–3003.
4. (a) Scialdone, O.; Sabatino, M. A.; Belfiore, C.; Galia, A.; Paternostro, M. P.; Filardo, G.
An unexpected ring carboxylation in the electrocarboxylation of aromatic ketones.
Electrochim. Acta 2006, 51, 3500–3505; (b) Abdirisak, A. I.; Alessandro, G.; Carmelo,

ELECTROCATALYTIC CARBOXYLATION OF ARYLIC BROMIDES
3727
B.; Giuseppe, S.; Armando, G. Electrochemical reduction and carboxylation of haloben-
zophenones. J. Electroanal. Chem. 2002, 526, 41–52.
5. (a) Wang, H.; Zhang, G. R.; Liu, Y. Z.; Luo, Y. W.; Lu, J. X. Electrocarboxylation of
activated olefins in ionic liquid BMIMBF4. Electrochem. Commun. 2007, 9, 2235–2239;
(b) Wang, H.; Lin, M. Y.; Fang, H. J.; Chen, T. T.; Lu, J. X. Electrochemical dicarbox-
ylation of styrene: Synthesis of 2-phenylsuccinic acid. Chin. J. Chem. 2007, 25, 913–916.
6. Goossen, L. J.; Rodriguez, N.; Goossen, K. Carboxylic acids as substrates in homo-
geneous catalysis. Angew. Chem. Int. Ed. 2008, 47, 3100–3120.
7. (a) Kobayashi, K.; Kondo, Y. Transition-metal-free carboxylation of organozinc reagents
using CO2 in DMF solvent. Org. Lett. 2009, 11, 2035–2037; (b) Correa, A.; Martin, R.
Metal-catalyzed carboxylation of organometallic reagents with carbon dioxide. Angew.
Chem. Int. E. 2009, 48, 6201–6204.
8. Correa, A.; Martin, R. J. Am. Chem. Soc. 2009, (in press). Doi: 10.1021=ja905264a.
9. (a) Fauvarque, J. F.; Zelicourt, Y. D.; Amatore, C.; Jutand, A. Nickel-catalyzed electro-
synthesis of anti-inflammatory agents. III. A new electrolyzer for organic solvents;
Oxidation of metal powder as an alternative to sacrificial anodes. J. Appl. Electrochem.
1990, 20, 338–340; (b) Damodar, J.; Mohan, S. R. K.; Reddy, S. R. J. Synthesis of 2-aryl-
propionic acids by electrocarboxylation of benzyl chlorides catalysed by PdCl2(PPh3)2.
Electrochem. Commun. 2001, 3, 762–766.
10. Amatore, C.; Jutand, A.; Khalil, F.; Nielsen, M. F. Carbon dioxide as a C1 building
block: Mechanism of palladium-catalyzed carboxylation of aromatic halides. J. Am.
Chem. Soc. 1992, 114, 7076–7085.
11. (a) Isse, A. A.; Ferlin, M. G.; Gennaro, A. Electrocatalytic reduction of arylethyl chlorides
at silver cathodes in the presence of carbon dioxide: Synthesis of 2-arylpropanoic acids. J.
Electroanal. Chem. 2005, 581, 38–45; (b) Scialdone, O.; Galia, A.; Errante, G.; Isse, A. A.;
Gennaro, A.; Filardo, G. Electrocarboxylation of benzyl chlorides at silver cathode at the
preparative-scale level. Electrochim. Acta 2008, 53, 2514–2528; (c) Scortichini, C. L.;
Babinec, S. J. The effect of cathode composition on the efficiency of electrocarboxylation
of aromatic halides. J. Electroanal. Chem. 1994, 379, 111–120; (d) Isse, A. A.; Gennaro, A.
Electrocatalytic carboxylation of benzyl chlorides at silver cathodes in acetonitrile. Chem.
Commun. 2002, 2798.
12. Cleary, J. A.; Mubarak, M. S.; Vieira, K. L.; Anderson, M. R.; Peters, D. G. Electro-
chemical reduction of alkyl halides at vitreous carbon cathodes in dimethyhlformamide.
J. Electroanal. Chem. 1986, 198, 107–124.
13. Zhang, L.; Niu, D. F.; Zhang, K.; Zhang, G. R.; Luo, Y. W.; Lu, J. X. Electrochemical
activation of CO2 in ionic liquid (BMIMBF4): Synthesis of organic carbonates under mild
conditions. Green Chem. 2008, 10, 202–206.
14. Chaussard, J.; Troupel, M.; Robin, Y.; Jacob, G.; Juhasz, J. P. Scale-up of electrocarbox-
ylation reactions with a consumable anode. J. Appl. Electrochem. 1989, 19, 345–348.