Synthesis of aromatic carboxylic acids by carbonylation of aryl halides in the presence of epoxide-modified cobalt carbonyls as catalysts

Article abstract of DOI:10.1007/s11167-005-0619-y

A new procedure was developed for synthesis of aromatic and heteroaromatic acids and their derivatives (esters, salts) by carbonylation of the corresponding aryl halides. The acids are selectively formed in a high yield under very mild conditions. Highly active catalytic systems, base-containing alcoholic solutions of cobalt carbonyl modified with epoxides, were used to activate aryl halides. 2005 Pleiades Publishing, Inc.

Full text of DOI:10.1007/s11167-005-0619-y

Russian Journal of Applied Chemistry, Vol. 78, No. 11, 2005, pp. 1844 1848. Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 11,
2005, pp. 1875 1880.
Original Russian Text Copyright
2005 by Boyarskii, Zhesko, Lanina.
APPLIED ELECTROCHEMISTRY
AND CORROSION PROTECTION OF METALS
Synthesis of Aromatic Carboxylic Acids by Carbonylation
of Aryl Halides in the Presence of Epoxide-Modified Cobalt
Carbonyls as Catalysts
V. P. Boyarskii, T. E. Zhesko, and S. A. Lanina
VNIINeftekhim Joint-Stock Company, St. Petersburg, Russia
Galar Research and Production Limited Liability Company, St. Petersburg, Russia
Received July 19, 2005
Abstract A new procedure was developed for synthesis of aromatic and heteroaromatic acids and their deri-
vatives (esters, salts) by carbonylation of the corresponding aryl halides. The acids are selectively formed in
a high yield under very mild conditions. Highly active catalytic systems, base-containing alcoholic solutions
of cobalt carbonyl modified with epoxides, were used to activate aryl halides.
Aromatic acids and their derivatives (esters and
salts) are widely used both in preparative organic
chemistry and as commercial raw materials to produce
pharmaceuticals, plant protecting agents, paint and
varnish materials, lubricants, and corrosion inhibitors.
In addition, aromatic carboxylic acids are used as the
base of modern liquid-crystal materials. Di- and poly-
aryl carboxylic acids are used in production of poly-
ester fibers and liquid-crystal thermoplastics as well
as electroluminophores in development of new equip-
ment.
bonylated under extremely mild conditions in alcohols
in the presence of a base and conventional catalyst of
oxosynthesis, octacarbonyldicobalt [1, 4, 5].
Alkylcobalt carbonyl complexes are formed in situ
by the reaction of alkyl halides reactive in nucleophil-
ic substitution (e.g., methyl chloroacetate) with di-
cobalt octacarbonyl in alcoholic solutions containing a
base. These complexes can activate weakly active aryl
halides, involving them in carnolylation [6]. In this
case, alkyl halides are cocatalysts (activators) of
cobalt carbonyl in carbonylation of aryl halides:
The conventional methods for preparing aromatic
acids under industrial and laboratory conditions are
different and involve classical organic reactions:
alkylation, acylation, oxidation, and cyanidation. The
disadvantages of these methods are their low selectiv-
ity and high consumption of raw materials. The syn-
thesis is multistep and requires complex process
schemes. Many of these methods are environmentally
hazardous.
Co (CO) + A
2
8
ArHal + CO
ArCOOR,
ROH + B
where A and B are cocatalyst and base, respectively.
The facts that acceptor substituents accelerate car-
bonylation of substituted bromobenzenes and one-
electron acceptors (nitrobenzene and anthraquinone)
inhibit carbonylation of aryl halides suggests radical
anion mechanism of aryl halide activation (S 1).
Recently, researchers turned attention to an alterna-
tive one-step selective procedure for preparing aromat-
ic carboxylic acids: carbonylation of the correspond-
ing aryl halides. Aryl halides are readily available and
cheap. However, these compounds, especially the
cheapest aryl chlorides, have low reactivity.
RN
The actual carbonylation catalyst is, apparently, the
anionic complex [RCo(CO) COOCH ] formed by
3
3
the nucleophilic attack of the carbon atom of one of
the carbonyl groups by the methylate anion. The
nucleophilic power of this complex is high. Since
benzyl chloride is also carbonylated under these con-
ditions, its was gradually fed by a special procedure to
the reaction mixture to maintain the catalyst in the ac-
tive form and to increase the conversion (see figure).
A series of valuable aromatic acids were prepared by
carbonylation of the corresponding aryl halides in
Originally, soft aryl halides (iodides and brom-
ides) were used for this purpose. These compounds
can be activated by oxidative addition to complexes
of palladium in a low oxidation state [1 3].
At the same time, alkylaromatic halides are car-
1070-4272/05/7811-1844 2005 Pleiades Publishing, Inc.

SYNTHESIS OF AROMATIC CARBOXYLIC ACIDS
1845
methanol in the presence of cobalt carbonyl benzyl
, %
chloride base catalytic system. This system is the most
suitable for carbonylation of 5,6-dichloroacenaphthene
to acenaphthene dicarboxylic acid used for preparing
a valuable commercial product, 1,4,5,8-naphthalene-
tetracarboxylic acid [9].
To prepare more efficient catalytic systems for car-
bonylation of aryl halides, dicobalt octacarbonyl
was modified.
Since aryl halides are activated by strongly nucleo-
philic anionic cobalt complexes, we examined catalyt-
ic systems generating new reactive intermediate anion-
ic cobalt complexes.
, h
of -chloronaphthalene in the presence of
Conversion
It is known [10] that Co(CO) in alcoholic solu-
4
different cocatalysts: (1) ClCH COOCH , (2) PhCH Cl
2
3
2
tions containing a base undergoes nucleophilic attack
of epoxides to form immediately anionic alkylcobalt
carbonyl complexes in which the negative charge is
localized on the alkyl group. We suggest that catalytic
properties of these complexes will differ from those of
the anionic complexes formed with alkyl halides after
attack of methylate anion on the carbonyl group of the
neutral alkylcobalt carbonyl complex. Indeed, as seen
from the figure, the cobalt carbonyl olefin oxide sys-
tem is more active by a factor of approximately 2 than
our most active alkylcobalt carbonyl catalytic system
containing benzyl chloride [7 9]. Based on these
results, we developed a series of highly active catalyt-
ic systems [8, 11, 12] containing olefin oxides, epi-
chlorohydrin, and ethylenechlorohydrin as cocatalysts
(see figure). All these cocatalysts, as well as epoxides,
form intermediate anionic complexes, with epichloro-
hydrin being more active owing to the presence of two
functional groups. These cocatalysts are not consumed
by the parallel pathway of self-carbonylation (as does
benzyl chloride). These compounds may undergo
methanolysis but this reaction is insignificant in the
presence of weak bases such as alkali metal carbo-
nates. The methanolysis products, monomethyl ethers
of glycols can be readily separated from the target
products, arylcarboxylic acids.
(dashed line reflects the reaction course after introduction
of additional portion of benzyl chloride), (3) C H Br,
8
17
(4) ClCH CH OH, and (5)
as a function of
CH CH CH
2
2
3
2
O
time . T = 60 C, P
= 1 atm, [Co (CO) ] = 0.017 M.
CO
2 8
The mechanism of carbonylation of aryl halides in
the presence of Co (CO) epoxide catalytic system is
2
8
similar to that of the reaction catalyzed by cobalt car-
bonyl modified with benzyl chloride [4, 8]. The mech-
anism of carbonylation of aryl halides in the presence
of cobalt carbonyl epoxide base catalytic system can
be described by a catalytic cycle (see scheme).
In this system, Co(CO) anion reacts with epoxide
4
with opening of the three-membered epoxy ring to
form intermediate anionic complex. Probably, this
complex is subjected to cyclization into negatively
charged metallalactone M which is a true catalyst of
aryl halide carbonylation.
This complex is highly nucleophilic and activates
ArHal by the S 1 mechanism (which is confirmed
RN
by the fact that this reaction is inhibited by aromatic
nitro compounds and other one-electron acceptors) via
formation of arylalkylcobalt carbonyl complex. For-
mation of metallalactones from metal carbonyls has
been demonstrated with an example of alkylcobalt
carbonyl complexes of iron [13].
An important advantage of epoxide cocatalysts is
the absence of halogen atom in their composition.
Hence, the base is not consumed for binding the
halogen. Propylene oxide is the most available, cheap,
and convenient in use.
The main examples of highly efficient synthesis of
mono- and polyaromatic acids performed for the first
time by carbonylation of the corresponding aryl hal-
ides in methanol in the presence of Co(CO) propyl-
4
The activity of the examined cocatalysts decreases
in the following order:
ene oxide K CO catalytic system are presented in
2
3
Tables 1 and 2.
>
>
ClCH
CH
> OHCHRCH Cl >
2
3
2
As seen from Tables 1 and 2, Co(CO) propylene
4
O
O
O
oxide K CO catalytic system can be used for selec-
2
3
PhCH Cl > p-ClC H CH Cl > CH I > C H I >
tive synthesis of aromatic mono- and dicarboxylic
acids in a high yield in methanol under very mild
2
6
17
4
2
3
2 5
C H Br > n-C H Br > ClCH COOCH .
2
5
8
2
3
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 78 No. 11 2005

1846
BOYARSKII et al.
Catalytic cycle of ArHal carbonylation
conditions. This method is suitable for both laboratory
preparation and industrial production of aromatic car-
boxylic acids. It should be noted that a large amount
of the activator (epoxide) should be used to prepare
the target product in a high yield. This is due to con-
sumption of the epoxide by its methanolysis with the
solvent in the presence of a weak base. However, this
fact does not minimize the importance of both the
laboratory and industrial procedures. Methanolysis of
propylene oxide and ethylene oxide (more convenient
Table 1. Carbonylation of aryl monohalides
Run
Reaction
time, h
Aryl halide
Molar ratiob
Aryl halide conversion,c % Yield,d %
no.a
1
2
3
4
5
6
7
8
9
10
11
12
13
14
PhBr
p-FC6H4Br
o-CF3C6H4Br
m-CF3C6H4Br
30 : 1 : 30 : 90
50 : 1 : 40 : 120
133 : 80 : 311
123 : 1 : 86 : 307
15 : 1 : 30 : 40
143 : 1 : 106 : 394
20 : 1 : 40 : 60
25 : 1 : 20 : 70
67 : 1 : 100 : 220
130 : 1 : 157 : 260
290 : 1 : 153 : 447
81 : 1 : 67 : 193
97 : 1 : 104 : 245
43 : 1 : 50 : 104
6.0
6.0
8.0
7.0
3.5
10.0
4.0
2.5
10.5
6.0
6.0
89
94
98
100
83
60
90
96
100
70
78
82 (92)
89 (95)
92 (94)
96 (96)
80 (96)
58 (97)
87 (97)
92 (96)
100 (100)
50 (71)e
74 (95)
80 (84)
64 (86)
20 (77)
p-BuC6H4Br
4-F-2-CH3C6H3Br
p-(cyclo-C6H11)C6H4Br
-C10H7Cl
6-MeO-2-Br-C10H6
5-Br-acenaphthene
p-CH3COC6H4Br
4-MeO-3-BrC6H3CHO
4-BnO-3-BrC6H3CHO
2-EtO-5-BrC6H3CHO
9.0
10.0
9.0
95
74
26
a
1
b
T = 60 C, P
= 1 atm, [Co (CO) ] = 2.7 g l (0.008 mol). Aryl halide : cobalt carbonyl : propylene oxide : potassium carbonate
2 8
CO
c
d
molar ratio. Determined by GLC. Preparative yield of the corresponding arenecarboxylic acid (in parentheses, the yield deter-
mined taking into account isolated unchanged aryl halide). Unchanged aryl halide recovered from the reaction mixture contains
e
25% acenaphthene formed by reduction of the initial 5-bromoacenaphthene (9% of the initial aryl halide).
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 78 No. 11 2005

SYNTHESIS OF AROMATIC CARBOXYLIC ACIDS
Table 2. Carbonylation of aryl dihalides
1847
Run
no.a
Reaction
time, h
Aryl halide con- Content of dicarboxylic acid
Aryl halide
Molar ratiob
version,c
%
in the reaction product,d %
1
2
3
4
5
41 : 1 : 20 : 125
7.0
7.0
4.0
4.0
4.5
99
95
Br
Cl
Br
Cl
50 : 1 : 50 : 220
35 : 1 : 30 : 100
24 : 1 : 30 : 90
94
81
99
96
94
87
93
82
Cl Cl
Br
Cl
Br
Cl
O
O
S
10 : 1 : 20 : 60
O
a
1
b
T = 60 C, P
= 1 atm, [Co (CO) ] = 2.7 g l (0.008 mol). Aryl halide : cobalt carbonyl : propylene oxide : potassium carbonate
CO
2
8
c
d
molar ratio. Determined by GLC. Reaction mixture contained not only dicarboxylic acids but also the corresponding monohalo-
arenecarboxylic acids. Base is KOH.
for industrial purposes) yields monomethyl ether of
propylene glycol and methyl Cellosolve, respectively.
These compounds are quite compatible as solvents
with methanol and can be readily separated from the
aromatic carboxylic acid (the main reaction product).
If necessary, they can be recovered separately in the
step of methanol regeneration.
series of polyaromatic and polyhaloaromatic car-
boxylic acids which can be used for both laboratory
synthesis and industrial production of a number of
unique chemical products for preparing new (e.g.,
electroluminescent) materials. It should be noted
that many of these compounds were prepared for the
first time by the above procedure. Thus, we proposed
a new procedure for processing PCBs under mild
conditions in the presence of available catalytic
systems [14].
A number of aromatic carboxylic acids were suc-
cessfully prepared from the corresponding aryl halides
by this procedure in a 100-l pilot reactor. This method
was also tested for dechlorination of environmentally
hazardous highly heat-resistant dielectrics prepared
from polychlorobiphenyls (PCB). These compounds
belong to the family of dioxin-like stable organic pol-
lutants. For this purpose, we tested the new catalytic
systems. Previously we found that the least reactive
aryl chlorides, chlorobenzene, chlorodiphenyl, and
4,4 -dichlorodiphenyl, are not carbonylated. At the
same time, model PCB (congeners) containing 3
4 chlorine atoms are carbonylated under these condi-
tions to form various polychlorobiphenylcarboxylic
acids (Table 3).
EXPERIMENTAL
Carbonylation was performed in laboratory tem-
perature-controlled glass reactors in a CO flow under
vigorous stirring at atmospheric pressure. The reaction
1
products were analyzed by GLC and H NMR spec-
troscopy. The products were identified by NMR
1
1
1
13
(PFG, DQF H, H COSY; PFG H, C HMQC;
1
13
PFG H, C HMBC) spectroscopy and mass spec-
trometry.
CONCLUSIONS
We found that from 1 to 4 halogen atoms can be
involved in the carbonylation. Carbonylation of in-
dividual PCBs is a new procedure for preparing a
(1) A new procedure was developed for preparing
aromatic and heteroaromatic carboxylic acids and their
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 78 No. 11 2005

1848
BOYARSKII et al.
Table 3. Carbonylation products of individual PCBs
(3) A series of mono- and dicarboxylic aromatic
acids were prepared for the first time by this proce-
dure.
Initial PCB
Cl
Reaction products
HOOC
Cl
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Cl
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