Copper-catalyzed carboxylation of aryl iodides with carbon dioxide

Article abstract of DOI:10.1021/cs400443p

A method for carboxylation of aryl iodides with carbon dioxide has been developed. The reaction employs low loadings of copper iodide/N,N,N′, N′-tetramethylethylenediamine (TMEDA) or N,N′- dimethylethylenediamine (DMEDA) catalyst, 1 atm of CO₂, dimethylsulfoxide (DMSO) or dimethylacetamide (DMA) solvent, and proceeds at 25-70 C. Good functional group tolerance is observed, with ester, bromide, chloride, fluoride, ether, hydroxy, amino, and ketone functionalities tolerated. Additionally, hindered aryl iodides such as iodomesitylene can also be carboxylated

Full text of DOI:10.1021/cs400443p

Research Article
pubs.acs.org/acscatalysis
Copper-Catalyzed Carboxylation of Aryl Iodides with Carbon Dioxide
Hung Tran-Vu and Olafs Daugulis*
Department of Chemistry, University of Houston, Houston, Texas 77204-5003, United States
S
* Supporting Information
ABSTRACT: A method for carboxylation of aryl iodides with
carbon dioxide has been developed. The reaction employs low
loadings of copper iodide/N,N,N′,N′-tetramethylethylene-
diamine (TMEDA) or N,N′-dimethylethylenediamine
(DMEDA) catalyst, 1 atm of CO2, dimethylsulfoxide
(DMSO) or dimethylacetamide (DMA) solvent, and proceeds at 25−70 °C. Good functional group tolerance is observed,
with ester, bromide, chloride, fluoride, ether, hydroxy, amino, and ketone functionalities tolerated. Additionally, hindered aryl
iodides such as iodomesitylene can also be carboxylated
KEYWORDS: carbon dioxide, copper catalysis, aryl halides, carboxylation, arenecarboxylic acids
arbon dioxide is a cheap and abundant C1-synthon.1
Billions of tons of CO2 have been released into Earths’
shown that aryl halides react with copper clusters to form aryl
copper reagents.10 Consequently, it should be possible to
carboxylate aryl halides if zerovalent copper species could be
directly generated from copper carboxylates.
The initial optimization reactions were carried out by using a
combination of 4-iodo-t-butylbenzene, diethyl zinc, ligand, and
catalytic copper(I) iodide under 1 atm of CO2 at 80 °C.
Arylcopper reagents react with CO2 in polar aprotic solvents.4
Consequently, DMA solvent was chosen for reaction
optimization. Reaction was efficient with bidentate nitrogen-
based ligands, and N,N,N′,N′-tetramethylethylenediamine
(TMEDA) or N,N′-dimethylethylenediamine (DMEDA) li-
gands were chosen because of cost considerations (Table 1).
C
atmosphere as a consequence of fossil fuel consumption.
Consequently, there is substantial drive for the decrease of CO2
emissions and sequestration of released carbon dioxide.2
However, despite substantial interest in carbon dioxide
utilization, relatively few chemical processes incorporate it in
the final products. This may be caused by low reactivity of
carbon dioxide. Thus, both fundamental investigations in CO2
chemistry and development of new processes that utilize CO2
are quite important.
Carbon dioxide has been utilized in the synthesis of aliphatic
carboxylic acids since 1858, when Wanklyn showed that
reaction of ethylsodium with CO2 affords sodium propionate.3a
́
In 1866, Kekule reported that arylsodium reagents react with
carbon dioxide.3b One of the earliest examples of transition-
metal aryl reactions with carbon dioxide were reported by
DePasquale and Tamborski who showed that pentafluorophe-
nylcopper can be transformed into pentafluorobenzoic acid in
DMA solvent.4 Subsequently, rhodium, nickel, and other
transition metal aryls and alkyls were shown to react with
carbon dioxide.5 More recently, the focus of research has
shifted to development of transition-metal catalyzed carbox-
ylation reactions. Specifically, boronic acid derivatives, alkenes,
stannanes, and organozinc reagents have been carboxylated
under nickel, rhodium, and copper catalysis.6 A elegant paper
Table 1. Ligand Optimization
a
entry
ligand
yield (%)
1
2
3
4
5
6
7
8
triphenylphosphine
44
43
23
73
79
82
70
67
tricyclohexylphosphine
b
DIPHOS
1,10-phenanthroline
́
by Martin describes a palladium-catalyzed aryl halide
c
carboxylation by carbon dioxide at 40 °C.7 Bulky phosphine
ligand, diethylzinc reducing agent, and 10 atm of CO2 were
used. Two recent papers report catalytic aryl- and benzyl halide
carboxylation by using the more accessible first-row transition
metal nickel.8 We report here a copper-catalyzed aryl iodide
carboxylation by carbon dioxide.
TMEDA
d
N,N′-DMEDA
2,2′-bipyridine
trans-1,2-diaminocyclohexane
a
Yields determined by GC. Please see Supporting Information for
b
c
details. 1,2-bis(Diphenylphosphino)ethane. N,N,N′,N′-Tetramethy-
lethylenediamine. N, N′-Dimethyl-ethylenediamine.
d
Copper complexes have been used in aryl boronate
carboxylation by CO2.6b,j The reactions proceed via aryl copper
reagents that are known to react with carbon dioxide.4 Since
aryl boronates are usually made from aryl halides,9 it would be
advantageous to directly carboxylate aryl halides. Rieke has
Received: June 12, 2013
Revised: August 30, 2013
Published: September 25, 2013
© 2013 American Chemical Society
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Research Article
a
Table 2. Aryl Iodide Carboxylation
a
Entries 1−9, DMSO (dimethyl sulfoxide) solvent; entries 10−19, DMA (dimethylacetamide) solvent. Entries 1−6, 25 °C; entries 7−19, 70 °C.
Reaction time: 4−20 h. TMEDA ligand: entries 1−2, 6, 8, 10−19. DMEDA ligand: entries 3−5, 7, 9. Yields are isolated yields. Please see Supporting
b
Information for details. Et2Zn (3.5 equiv).
The optimized reaction conditions for most electron-rich aryl
iodide carboxylation involve 3 mol % CuI catalyst, 3 mol %
TMEDA or DMEDA ligand, dimethylsulfoxide (DMSO)
solvent, and 1 atm of CO2. The carboxylation of electron-
poor aryl iodides requires DMA solvent. The results are
summarized in Table 2.
methods. Some reduction of ArI to ArH is observed. For
entries 17−19, decreased yields are due to incomplete
reactions, and substantial amounts of starting materials were
recovered. No conversion was observed in the absence of either
CuI or Et2Zn.
The reaction may involve the generation of Cu(0) species
which have been shown by Rieke to oxidatively add aryl
halides.10 The presence of colloidal metal was tested by using a
mercury additive (Scheme 1).11,12 With no mercury additive,
the carboxylation of 4-iodo-t-butylbenzene afforded 79% yield
of the corresponding acid. If 200 equiv of Hg with respect to
Cu were added, the yield decreased to 24%. Addition of 500
equiv of Hg decreased the yield of product to 10%. Thus, it is
The carboxylation of electron-rich aryl iodides proceeds at
25−70 °C (entries 1−8). Hindered aryl iodides, such as 2-
iodotoluene (entry 3), iodomesitylene (entry 5), and 1-
iodonaphthalene (entry 9) are reactive. Heterocyclic 2-
iodothiophene (entry 6) is carboxylated in a good yield.
Alkoxy groups are tolerated and 3- and 4-iodoanisoles are
reactive (entries 7 and 8). Carboxylation of electron-poor aryl
iodides requires more forcing conditions. Reactions proceed at
70 °C and higher yields are obtained in DMA solvent. Selective
carboxylation of iodide in presence of bromo- or chloro
substituent, which could be used for further transformations, is
possible (entries 10−12). Ethyl-4-iodobenzoate is carboxylated
in good yield (entry 13). Fluoroiodobenzenes are also
carboxylated in a good yields (entries 14−16). Moreover, the
method allows for the carboxylation of aryl iodides that possess
unprotected amino, hydroxy, and ketone functionalities (entries
17−19). Consequently, the procedure shows higher functional
group tolerance compared with other direct carboxylation
Scheme 1. Reaction in the Presence of Hg Additive
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Research Article
highly likely that copper clusters are present in the reaction
mixture.
ACKNOWLEDGMENTS
■
We thank the Welch Foundation (Grant E-1571), Norman
Hackerman Texas Advanced Research Program, NIGMS
(Grant R01GM077635), and Camille and Henry Dreyfus
Foundation for supporting this research. We thank Mr. Chieng-
Hung Li for help with TEM analysis.
The possible reaction mechanism is shown in Scheme 2.13
Reduction of Cu(I) with diethylzinc affords Cu(0) via EtCu
Scheme 2. Proposed Reaction Mechanism
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ASSOCIATED CONTENT
■
S
* Supporting Information
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(12) Analysis by TEM was inconclusive. Please see Supporting
Information for TEM data.
AUTHOR INFORMATION
■
(13) A reviewer suggested that Et2Zn may react with ArI to generate
ArZnR species. Acid quench of reaction run under standard conditions
but omitting CuI catalyst and CO2 does not give a measurable amount
of ArH showing that non-catalyzed transmetallation does not occur to
a measurable extent. However, CuI catalyzes transmetallation between
Corresponding Author
*E-mail: olafs@uh.edu.
Notes
The authors declare no competing financial interest.
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