Copper-catalyzed synthesis of aromatic carboxylic acids from arylboronic acids and acetyl acetate

Article abstract of DOI:10.1016/j.tetlet.2014.08.090

A simple and efficient copper-catalyzed method for the synthesis of aromatic carboxylic acids in moderate to high yields with great functional-group compatibility in the substrates has been developed. The new method uses readily available arylboronic acids and acetyl acetate as the starting materials and inexpensive CuI as the catalyst.

Full text of DOI:10.1016/j.tetlet.2014.08.090

Accepted Manuscript
Copper-Catalyzed Synthesis of aromatic carboxylic acids from arylboronic
acids and acetyl acetate
Rui Zheng, Qizhong Zhou, Haining Gu, Huajiang Jiang, Jiashou Wu,
Zhengneng Jin, Deman Han, Guoliang Dai, Rener Chen
PII:
S0040-4039(14)01443-9
DOI:
http://dx.doi.org/10.1016/j.tetlet.2014.08.090
TETL 45057
Reference:
To appear in:
Tetrahedron Letters
Received Date:
Revised Date:
Accepted Date:
9 July 2014
12 August 2014
22 August 2014
Please cite this article as: Zheng, R., Zhou, Q., Gu, H., Jiang, H., Wu, J., Jin, Z., Han, D., Dai, G., Chen, R., Copper-
Catalyzed Synthesis of aromatic carboxylic acids from arylboronic acids and acetyl acetate, Tetrahedron Letters
(
2014), doi: http://dx.doi.org/10.1016/j.tetlet.2014.08.090
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Copper-Catalyzed Synthesis of aromatic
carboxylic acids from arylboronic acids and
acetyl acetate
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Rui Zheng, Qizhong Zhou*, Haining Gu, Huajiang Jiang, Jiashou Wu, Zhengneng Jin, Deman Han,
Guoliang Dai, and Rener Chen*

1
Tetrahedron Letters
jo u rn al h ome p ag e : w ww .e lse vie r .c om
Copper-Catalyzed Synthesis of aromatic carboxylic acids from arylboronic acids
and acetyl acetate
1
Rui Zheng, Qizhong Zhou*, Haining Gu, Huajiang Jiang, Jiashou Wu, Zhengneng Jin, Deman Han,
1,3
2
1
1
1
1
1
Guoliang Dai, and Rener Chen*
1
1
Department of Chemistry, Taizhou University, Taizhou 318000, China
Department of Chemistry, Zhejiang University, Hangzhou 310027, China;
Department of Chemistry, Fudan University, Shanghai 200433, China;
2
3
Email address: qizhongchou@yahoo.com (Q. Zhou); cre@tzc.edu.cn (R. Chen); Fax: +86 571 8866 0177; tel: 86-576-88660177
ARTICLE INFO
ABSTRACT
Article history:
Received
A simple and efficient copper-catalyzed method for the synthesis of aromatic carboxylic acids in
moderate to high yields with great functional-group compatibility in the substrates has been
developed. The new method uses readily available arylboronic acids and acetyl acetate as the
starting materials and inexpensive CuI as the catalyst.
Received in revised form
Accepted
Available online
2
009 Elsevier Ltd. All rights reserved.
Keywords:
copper
arylboronic acids
acetyl acetate
aromatic carboxylic acids
Oxidation of aromatic compounds is the common method
acetyl acetate was first investigated as a model reaction using
different ligands and bases. The results are listed in Table 1.
1-8
for the preparation of aromatic carboxylic acids. However,
many functional groups cannot survive the harsh conditions of
oxidation. Aromatic carboxylic acids can also be prepared by
2 3
When the reaction was performed in DMSO using K CO as
base, we found that N,N-dimethylglycine hydrochloride was
the best ligand (Table 1, entries 1-11). Then the reaction was
carried out at different temperatures and times, and we found
that 100 °C and 24 hours were suitable (Table 1, entries 12-
27). Further screening of catalytic systems revealed that CuI
(10%)/N,N-dimethylglycine hydrochloride (15%) afforded the
highest yield (Table 1, entries 15, 17 and 18), while, among
other, K CO was the best base (Table 1, entries 15 and 28-
9
10
the reactions of Grignard and organolithium reagents,
11
12
arylzinc reagents, and arylboronic esters with carbon
dioxide. These reagents, however, may exhibit poor
functional group tolerance or are expensive. Chemoselective
carboxylation of aromatics with a superelectrophilically
2 6
activated carbon dioxide-Al Cl /Al system was also
1
3
reported. The reaction needs high pressure which hinders its
utility. Palladium-catalyzed carboxylation of haloarenes with
2
3
36).
14
carbon monoxide can proceed under mild conditions, which,
however, highly depends on the use of expensive catalysts
and ligands. Thus, the development of new efficient methods
for the preparation of aromatic carboxylic acids is still of
importance.
Table 1. Copper-catalyzed synthesis of benzoic acid from
phenylboronic acid and acetyl acetate: Screening of the
ligands, bases, temperature and time
a,b
1
5
Arylboronic acids are widely used in Suzuki and Chan-
Lam reactions,
16
and in recent years also attracted
7
1
considerable attention in discrete organic synthesis. We
previously reported palladium-catalyzed regioselective 2-
entry ligand or Fe
base
temp. Time Yield
(
h)
(%)
8
1
8
arylation of 2,x-dibromopyridines from arylboronic acids.
1
2
3
4
5
Fe(acac)
1,10-Phenanthroline (15%)
L-proline (15%)
Me NCH H·HCl (15%)
DMEDA (15%) K
3
(15%)
K
2
CO
CO
CO
CO
CO
3
110 °C 24
110 °C 24
110 °C 24
110 °C 24
100 °C 24
Herein, we describe a simple, practical and efficient copper-
catalyzed synthesis of aromatic carboxylic acids from
arylboronic acids and acetyl acetate, which is different from
K
2
3
18
9
K
2
3
2
2
CO
2
K
2
3
42
1
1
6
the Chan-Lam reaction.
The CuI-catalyzed coupling of phenylboronic acid and
2
3

2
Tetrahedron
6
TMEDA
PMEDA
(15%) K
(15%) K
(15%) K
(15%) K
2
CO
CO
CO
CO
CO
CO
CO
CO
CO
CO
CO
CO
CO
CO
CO
CO
CO
CO
CO
CO
CO
CO
H·HCl (15%) KHCO
H·HCl (15%) Na CO
H·HCl (15%) PO
3
100 °C 24
100 °C 24
100 °C 24
100 °C 24
100 °C 24
100 °C 24
70 °C 24
80 °C 24
90 °C 24
100 °C 24
100 °C 24
100 °C 24
100 °C 24
120 °C 24
130 °C 24
140 °C 24
150°C 24
100 °C 6
13
investigated the reactions of 1 with different methylene
derivatives. The results are summarized in Table 3. It can be
found that the reaction of acetyl acetate afford the acid in
highest yield. We were pleased to find that the yield could be
as high as 96% when 5.0 equiv of acetyl acetate was used in
the absence of any ligand.
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
2
3
19
39
20
14
32
4
2-Picolinic acid
dtbpy
2
3
2
3
0
1
2
3
4
5
pyrocatechol violet (15%) K
8-aminoquinoline (15%)
Me CO H·HCl (15%)
Me CO H·HCl (15%)
Me CO H·HCl (15%)
Me CO H·HCl (15%)
Me CO H·HCl (15%)
Me CO H·HCl (7.5%) K
Me CO H·HCl (30%)
Me CO H·HCl (15%)
Me CO H·HCl (15%)
Me CO H·HCl (15%)
Me CO H·HCl (15%)
Me CO H·HCl (15%)
Me CO H·HCl (15%)
Me CO H·HCl (15%)
Me CO H·HCl (15%)
Me CO H·HCl (15%)
Me CO
Me CO
Me CO
Me CO
Me CO
Me CO
Me CO
Me CO
Me CO
2
3
K
2
3
2
NCH
NCH
NCH
NCH
NCH
NCH
NCH
NCH
NCH
NCH
NCH
NCH
NCH
NCH
NCH
NCH
NCH
NCH
NCH
NCH
NCH
NCH
NCH
NCH
NCH
2
2
K
2
3
K
2
3
11
25
51
43
34
36
34
39
39
41
23
28
36
33
31
34
6
a
2
2
2
Table 3. Screening of Carbon Sources
2
2
2
K
2
3
2
2
2
K
2
3
c
6
2
2
2
K
2
3
d
7
2
2
2
2
3
e
entry ligand
carbon source
yield
b
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
2
2
2
K
2
3
(
%)
2
2
2
K
2
3
1
Me
2
NCH CO
2
2
H·HCl
49
2
2
2
K
2
3
(
(
(
2.0 mmol)
2.0 mmol)
2.0 mmol)
2
2
2
K
2
3
2
3
Me
2
NCH CO
2
2
H·HCl
39
0
2
2
2
K
2
3
2
2
2
K
2
3
Me NCH CO H·HCl
2
2
2
2
2
2
K
2
3
100 °C 12
100 °C 20
100 °C 36
100 °C 48
100 °C 24
100 °C 24
100 °C 24
4
5
Me
Me
2
NCH
NCH
2
CO
CO
2
H·HCl
H·HCl
(2.0 mmol)
0
51
2
2
2
K
2
3
K
2
3
2
2
2
2
2
2
(
(
(
2.0 mmol)
5.0 mmol)
5.0 mmol)
2
2
2
K
2
3
6
7
Me
2
NCH CO
2
2
H·HCl
84
57
96
2
2
2
3
2
2
2
2
3
c
Me
2
NCH CO
2
2
H·HCl
2
2
2
K
3
4
3
2
2
2
H·HCl (15%) KOAc 100 °C 24
H·HCl (15%) Cs
H·HCl (15%) LiOH
H·HCl (15%) NaOH 100 °C 24
H·HCl (15%) MeONa 100 °C 24
H·HCl (15%) t-BuOK 100 °C 24
0
8
2
2
2
2
CO
3
100 °C 24
100 °C 24
0
(5.0 mmol)
a
2
2
2
0
Reaction conditions: phenylboronic acid 1 (1 mmol), 2 (2 mmol or 5 mmol),
b
c
0
2 3
K CO (2 mmol), DMSO (5 mL). Isolated yield. DMSO (analytically pure)
2
2
2
2
2
2
0
With the optimized reaction conditions available, the scope
2
2
2
0
of the reaction was then investigated (Table 4). It can be
found that arylboronic acids bearing electron-rich groups
generally afforded products (3a−3d, 3f-3l, 3t-3v) in good to
high yields (68−96%). 4-Fluorophenylboronic acid and 4-
chlorophenylboronic acid also gave rise to high yields (80-
a
Reaction conditions: 1 (1.0 mmol), 2 (1.1 mmol), CuI (10%), base (2.0
b
c
Isolated yield. K
mmol), DMSO (5 mL, anhydrous), N
d
CuI (5%). CuI (20%).
pentamethyldiethylenetriamine.
2
.
PMEDA (CAS: 3030-47-5): 1,1,4,7,7-
2 3
CO (1.1 mmol).
e
We then further screened copper sources for the reaction
with N,N-dimethylglycine hydrochloride as ligand under the
established conditions in different solvents. The results are
provided in Table 2. We found that CuI was most efficient in
catalyzing the reaction, and anhydrous DMSO was the
suitable solvent.
82%, 3n and 3o). Even 4-trifluoromethylphenylboronic acid
gave a good yield (67%, 3p). 2-Methoxyphenylboronic acid
and 2,4,6-trimethylboronic acid provided low yields (10-46%,
e and 3m), probably due to steric hindrance. Electron-
3
withdrawing acetyl or NO -substituted phenylboronic acid
2
generally gave low yields (18-32%, 3q-3r). This was also the
case for heterocyclic boronic acids (3-32%, 3w-3z). Fu et al.
had reported copper-catalyzed aerobic oxidative synthesis of
aromatic carboxylic acids from aryl halides and
a
Table 2. Screening of Copper Catalysts and Solvents
19
malononitrile. Our new method has the advantages of higher
yield, more generality, as well as a simpler and cheaper
catalyst system.
b
entry
copper
solent
yield (%)
1
2
3
4
5
6
7
8
9
Cu
CuBr
CuCl
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
dioxane
HCONH
DMAc
DMF
26
34
49
12
11
26
11
37
0
3
0
16
23
trace
Table 4. Copper-Catalyzed Synthesis of Aromatic Carboxylic
a
Acids
Cu
CuO
Cu(OAc)
CuBr
2
O
2
2
Cu(OTf)
CuI
CuI
CuI
CuI
2
b
1
1
1
1
1
0
1
2
3
4
2
entry arylboronic acid
1
arylcarboxylic acid
yield (%)
96
1a
1b
3a
CuI
CuI
t-AmylOH
2
3
4
90
95
85
2
H O
3
b
a
Reaction conditions: 1 (1.0 mmol), 2 (1.1 mmol), copper source (10%),
CO (2.0 mmol), solvent (5 mL, DMSO is anhydrous and the other
K
2
3
1c
3c
b
solvents are analytically pure). Isolated yield.
1d
3d
Under the reaction conditions established above, we

3
5
6
46
85
CO
the carboxyl group came mainly from acetyl acetate and a
minority may come from K CO , which was different from
2
really did work in the reaction. Thus, we propose that
1
e
3e
3f
2
3
1
6
the Chan-Lam reaction.
1
f
O
7
8
84
68
O
1
g
OH
3g
3h
1h
9
76
1
i
3i
3j
1
1
0
1
93
94
1
j
1
k
3k
3l
1
1
2
3
86
10
1
l
1
m
3m
1
4
80
1
n
3n
3o
3p
1
1
1
5
6
7
82
67
18
1
o
Scheme 1. Control Experiments.
We believe that the main reaction mechanism of the present
1
p
reaction (Scheme 2) is similar to that of the Cu-catalyzed
12b, 12c
carboxylation reaction.
Arylcopper species are generated
1
q
3q
3r
by transmetalation of the corresponding arylboronic acids
with Cu(I) salts and undergo carboxylation with in situ
generated carbon dioxide from acetyl acetate by hydrolysis
and followed by decarboxylation to give Cu-carboxylates,
which work as the real active species to further undergo
transmetalation and carboxylation catalytically.
1
1
2
8
9
0
32
42
83
1
r
1
s
3
s
1t
3t
2
2
1
2
90
87
1
u
3u
1
v
3v
3w
3x
3y
3z
2
2
3
4
27
32
1w
B(OH)2
S
1x
Scheme 2. Proposed main reaction mechanism
2
2
5
6
3
In summary, we have developed an efficient copper-
mediated method for the synthesis of aromatic carboxylic
acids in moderate to good yields. The protocol uses
inexpensive CuI as the catalyst, and readily available
arylboronic acids and acetyl acetate as starting materials. The
method shows high functional-group tolerance in the
substrates.
1y
13
1
z
a
Reaction conditions: arylboronic acid (1.0 mmol), acetyl acetate (5.0 mmol).
Isolated yield.
b
Control experiments were further performed to establish the
source of the carboxyl group in the product. The reactions are
listed in Scheme 1. First, phenylboronic acid reacted with
acetyl acetate under the catalysis of CuI (10%) in the presence
of K at 100 C in DMSO under air for 24 hours to give
30% yield, which was lower than that under nitrogen
Acknowledgments
o
2
CO
3
This work was supported by the Natural Science
Foundation of China (No. 21172166, 21203135 and
atmosphere (eq 1 and entry 8, Table 3). Second, in the
absence of CuI, phenylboronic acid reacted with acetyl acetate
under the above conditions to give 12% yield (eq 2). Third,
2
(
2
1375092), Natural Science Foundation of Zhejiang Province
LY14B020012), China Postdoctoral Science Foundation (No.
013M541456 and 2013M541771), Postdoctoral Research
2 3
treating phenylboronic acid with K CO in DMSO afforded
Foundation of Zhejiang Province (No. BSH1302072), the
Project of Zhejiang Key Scientific and Technological
Innovation Team (No. 2010R50017), Key Disciplines of
Applied Chemistry of Zhejiang Province, Taizhou University,
and the Opening Foundation of Zhejiang Key Course of
Chemical Engineering and Technology, Zhejiang University
of Technology.
benzoic acid in 14% yield (eq 3). In the presence of CuI, the
reaction afforded benzoic acid in 2% yield (eq 4). Why the
yield is higher without CuI than with CuI in the absence of
acetyl acetate? We proposed that CuI may inhibit carboxy
group exchange between phenylboronic acid and K
2 3
CO . At
last, we used CO as a reagent instead of acetyl acetate under
2
the standard reaction condition and got 31% yield (eq 5).
Obviously, the yield of eq 5 is higher than the yield of eq 4.

4
Tetrahedron
Supplementary Material
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M.; Toste, F. D. J. Am. Chem. Soc. 2014, 136, 4101. (g) Yang, Y.;
Wang, L.; Zhang, J.; Jin, Y.; Zhu, G. Chem. Commun. 2014, 50, 2347.
Supplementary data and other materials associated with this
article can be found in the online version.
(
2
h) Chinnagolla, R. K.; Jeganmohan, M. Chem. Commun. 2014, 50,
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