Rhodium-Catalyzed Hydrocarboxylation of Olefins with Carbon Dioxide

Article abstract of DOI:10.1002/ejoc.201600338

The catalytic hydrocarboxylation of styrenes derivatives and α,β-unsaturated carbonyl compounds with CO₂(101.3 kPa) in the presence of an air-stable rhodium catalyst was explored. The combination of [RhCl(cod)]₂(cod = cyclooctadiene) as a catalyst and diethylzinc as a hydride source allowed for effective hydrocarboxylation and provided the corresponding α-aryl carboxylic acids in moderate to excellent yields. In this catalytic process with carbon dioxide, intervention of the Rh^I–H species, which could be generated from the Rh^Icatalyst and diethylzinc, was clarified. Significantly, the catalytic asymmetric hydrocarboxylation of α,β-unsaturated esters with carbon dioxide was also performed by employing a cationic rhodium complex possessing (S)-(–)-4,4′-bi-1,3-benzodioxole-5,5′-diylbis(diphenylphosphine) [(S)-SEGPHOS] as a chiral diphosphine ligand. A plausible model for asymmetric induction was proposed by determination of the absolute configuration of the product.

Full text of DOI:10.1002/ejoc.201600338

DOI: 10.1002/ejoc.201600338
Communication
Hydrocarboxylation
Rhodium-Catalyzed Hydrocarboxylation of Olefins with Carbon
Dioxide
Shingo Kawashima,[a] Kohsuke Aikawa,[a] and Koichi Mikami*[a]
Dedicated to Professor Achille Umani-Ronchi on the occasion of his 80th birthday
Abstract: The catalytic hydrocarboxylation of styrenes deriva- and diethylzinc, was clarified. Significantly, the catalytic asym-
tives and α,ꢀ-unsaturated carbonyl compounds with CO2
(101.3 kPa) in the presence of an air-stable rhodium catalyst
was explored. The combination of [RhCl(cod)]2 (cod = cyclo-
octadiene) as a catalyst and diethylzinc as a hydride source al-
lowed for effective hydrocarboxylation and provided the corre-
sponding α-aryl carboxylic acids in moderate to excellent yields.
In this catalytic process with carbon dioxide, intervention of the
RhI–H species, which could be generated from the RhI catalyst
metric hydrocarboxylation of α,ꢀ-unsaturated esters with
carbon dioxide was also performed by employing a cationic
rhodium complex possessing (S)-(–)-4,4′-bi-1,3-benzodioxole-
5,5′-diylbis(diphenylphosphine) [(S)-SEGPHOS] as a chiral di-
phosphine ligand. A plausible model for asymmetric induction
was proposed by determination of the absolute configuration
of the product.
Introduction
unsaturated carbonyl compounds with carbon dioxide to pro-
vide the corresponding α-aryl carboxylic acids. Significantly, it
is also demonstrated that our rhodium catalyst system can be
applicable to asymmetric catalysis (Scheme 1).
The transformation of carbon dioxide as a cheap, nontoxic, and,
hence, attractive C1 source is a challenging subject in modern
synthetic organic chemistry.[1] Although carbon dioxide is ther-
modynamically stable and of kinetically low reactivity, various
transformations of carbon dioxide with homogeneous transi-
tion-metal catalysts have been reported.[1,2] In particular, the
catalytic hydrocarboxylation of olefins with carbon dioxide has
attracted much attention, owing to the fact that it is a direct
method for the synthesis of carboxylic acid derivatives, which
are important intermediates in the pharmaceutical industry.[1]
For example, the employment of styrene derivatives can lead
to non-steroidal anti-inflammatory[3] and anti-Alzheimer[4]
drugs such as ibuprofen derivatives. However, the transition-
metal-catalyzed hydrocarboxylation of olefins such as styrenes
and α,ꢀ-unsaturated compounds with carbon dioxide is ex-
tremely limited to few examples for which Ni,[5,6] Fe,[7] and Co[8]
complexes are used and thus remains undeveloped. Further-
more, there is no successful report on the catalytic asymmetric
hydrocarboxylation of olefins with carbon dioxide. In 2004, Mori
and co-workers reported a rare example of the MeO-MOP/Ni0-
catalyzed asymmetric carboxylation of bis-1,3-dienes through
nucleophilic attack of a π–allyl nickel intermediate to carbon
dioxide.[9] Herein, we report the rhodium-catalyzed hydrocar-
boxylation[10] of olefins, such as styrene derivatives and α,ꢀ-
Scheme 1. Rh-catalyzed hydrocarboxylations of olefins with CO2.
Results and Discussion
We initially examined the hydrocarboxylation of styrene deriva-
tive 1a bearing the sterically demanding o-CF3-substituent as a
model substrate with diethylzinc as the hydride source in the
presence of [RhCl(cod)]2 (5 mol-%, cod = cyclooctadiene) under
an atmosphere of carbon dioxide (1 atm = 101.3 kPa) (Table 1).
Various solvents were investigated (Table 1, entries 1–7), but
only a low yield (4 %) of desired carboxylated product 2a was
obtained in THF[5] at room temperature after 12 h (Table 1,
entry 8). Replacement of THF with more polar dimethylacet-
amide (DMA) and DMF provided higher yields (Table 1, entries 9
and 10). Increasing the concentration of the reaction mixture
further increased the yield, even in a catalytic fashion [turnover
number (TON) = 3.3, though] at a lower reaction temperature
(0 °C) and in a shorter reaction time (3 h) (Table 1, entry 11).
[a] Department of Applied Chemistry, Tokyo Institute of Technology,
O-okayama, Meguro-ku, Tokyo 152-8552, Japan
E-mail: mikami.k.ab@m.titech.ac.jp
www.apc.titech.ac.jp/~mikami/index-j.html
Supporting information and ORCID(s) from the author(s) for this article are
available on the WWW under http://dx.doi.org/10.1002/ejoc.201600338.
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Other hydride sources such as BEt3, AlEt3, and PhMe2SiH did
not provide better results (Table 1, entries 12–14). The addition
of a base such as Cs2CO3, which Rovis and co-workers reported
to be key to the nickel-catalyzed hydrocarboxylation of styrene
derivatives,[5] did not enhance the yield.
Table 2. Screening of styrene derivatives.[a]
Table 1. Rh-catalyzed hydrocarboxylation of styrene.
Entry
Hydride source
(equiv.)
Solvent[a]
Conditions
Yield [%][c]
1
2
3
4
5
6
7
8
ZnEt2 (2.5)
ZnEt2 (2.5)
ZnEt2 (2.5)
ZnEt2 (2.5)
ZnEt2 (2.5)
ZnEt2 (2.5)
ZnEt2 (2.5)
ZnEt2 (2.5)
ZnEt2 (2.5)
ZnEt2 (2.5)
ZnEt2 (1.2)
BEt3 (1.2)
Et2O
r.t., 12 h
r.t., 12 h
r.t., 12 h
r.t., 12 h
r.t., 12 h
r.t., 12 h
r.t., 12 h
r.t., 12 h
r.t., 12 h
r.t., 12 h
0 °C, 3 h
0 °C, 3 h
0 °C, 3 h
0 °C, 3 h
0
0
0
0
0
CH2Cl2
toluene
acetone
CH3CN
NMP
DMSO
THF
DMA
0
trace
4
12
18
33
0
9
10
11
12
13
14
DMF
DMF[b]
DMF[b]
DMF[b]
DMF[b]
AlEt3 (1.2)
HSiMe2Ph (1.2)
0
0
[a] 0.1
M concentration. NMP = 1-methylpyrrolidin-2-one. [b] 0.2 M concentra-
tion. [c] Yield of isolated product.
[a] Yields of isolated products are given. [b] ZnEt2 (0.7 equiv.) was used.
With the optimized reaction conditions (Table 1, entry 11),
the scope of the styrene derivatives was investigated (Table 2).
Relative to that obtained with o-CF3-substituted styrene 1a, the
same electron-withdrawing CF3 substituent in the para position
with less steric hindrance led to a higher yield of 2b (54 %).
Moreover, similar electron-withdrawing ester and ketone sub-
stituents in the para position enhanced the reactivity to give
products 2c–e and 2g–i in high yields, except for 2f with a
sterically more demanding tert-butyl group. A styrene derivative
with an amide substituent also underwent the reaction,
whereas the yield of 2j was moderate. Similar to 2a, electron-
withdrawing ester and ketone substituents in the ortho position
led to a decrease in the yields of 2k–o. Unfortunately, electron-
donating substituents such as methoxy and tert-butyl groups
significantly retarded the carboxylation reaction (see substrates
1p–r). Electron-neutral styrene 1s and heteroaromatic 2-vinyl-
pyridine 1t also gave no products.
investigation of 1r as shown in Table 2, we confirmed that re-
duction product 3r was obtained in up to 15 % yield. This result
implies that benzylic zinc complex F would be generated by
transmetalation between rhodium complex C and diethylzinc,
whereas transmetalation back can be involved between F and
a rhodium species. On the other hand, Rovis and co-workers
already reported that combination of a naphthylmethylzinc rea-
gent and carbon dioxide (1 atm) cannot undergo the carboxyla-
tion in THF at 23 °C.[5,12]
A plausible reaction mechanism is visualized in Scheme 2;
we suggest intervention of the RhI–H species in this catalytic
process. Transmetalation of the ethyl group between
[RhCl(cod)]2 and diethylzinc produces RhI–Et species A, which
undergoes ꢀ-hydride elimination to generate active RhI–H spe-
cies B. Insertion of the styrene derivative into RhI–H species B
leads to σ-benzyl rhodium complex C,[11] which has high
enough nucleophilicity for carbon dioxide to give carboxylated
rhodium complex D. Finally, transmetalation between D and
diethylzinc gives carboxylated zinc complex E, and RhI–Et spe-
cies A is reformed at the same time. During the course of the
Scheme 2. Plausible reaction mechanism.
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Communication
To support the generation of rhodium complex C in the cata- substituent instead of a phenyl one was also employed to give
lytic cycle, aldehydes were examined rather than less-reactive product 7i in 77 % yield. Even ꢀ-substituted esters provided
carbon dioxide (Scheme 3).[13] As expected, reductive aldol-type good yields, irrespective of the electron-donating substituents
products 5ab and 5bb were obtained in good yields under the in the aromatic rings (see products 7j–l).
reaction conditions with aldehydes 4 instead of carbon dioxide,
Table 4. Screening of α,ꢀ-unsaturated carbonyl compounds.[a]
despite low diastereoselectivities.
Scheme 3. Rh-catalyzed reductive aldol reaction.
Next, α,ꢀ-unsaturated carbonyl compounds were employed
as a better hydride acceptor rather than the styrene derivatives
(Table 3). The rhodium-catalyzed hydrocarboxylation of unsatu-
rated ester 6a gave a quantitative yield of desired product 7a
in DMF at 0 °C (Table 3, entries 1 and 2). The use of a sub-
stoichiometric amount of diethylzinc (0.7 equiv.) decreased the
yield of 7a to 66 % (Table 3, entry 1). The rhodium catalyst was
also confirmed to be essential for the catalytic reaction (Table 3,
entry 2). In addition, we examined other ligands such as norbor-
[a] Yield of isolated product.
nadiene (nbd) and ethylene; however, they only provided low
to moderate yields of 7a (Table 3, entries 3 and 4). The reaction
did not proceed at –40 °C, but at –20 °C lower yields of 7a were
afforded (Table 3, entries 5–7). The optimized reaction tempera-
ture was thus set at 0 °C to give a quantitative yield of 7a.
The asymmetric catalysis of the present hydrocarboxylation
of α,ꢀ-unsaturated esters with carbon dioxide was the final
challenge in this project (Table 5). Various chiral phosphine and
diene ligands were investigated, and cationic rhodium catalysts
bearing bidentate triarylphosphine ligands such as 4,4′-bi-1,3-
benzodioxole-5,5′-diylbis(diphenylphosphine) (SEGPHOS) were
found to be efficient for this catalytic asymmetric system.[14]
Moreover, the combination of (S)-SEGPHOS–Rh complex 8 and
a catalytic amount of AgSbF6 provided better and reproducible
results (41 %, 50 % ee), than without AgSbF6 (25 %, 42 % ee)
(Table 5, entry 1 vs. 2). The effect of AgSbF6 is currently under
investigation. In view of the electronic effects of benzyl substit-
uents, the electron-withdrawing CF3 substituent provided
higher yields than the electron-donating MeO substituent
(Table 5, entries 8–10 vs. 11–13). Interestingly, the electron-do-
nating MeO substituent constantly gave 60 % ee, irrespective of
the position of the substituent (Table 5, entries 8–10). In sharp
contrast, the electron-withdrawing CF3 substituent afforded
higher enantioselectivities, particularly at a position closer to
the reaction center, namely, the ortho position (Table 5, en-
tries 11–13).
Table 3. Rh-catalyzed hydrocarboxylation of α,ꢀ-unsaturated carbonyl com-
pound.
Entry
Diene
Conditions
Yield [%][a]
1
2
3
4
5
6
7
cod
cod
nbd
2 H2C=CH2
cod
0 °C, 3 h
>99 (66)[b]
0 °C, 30 min
0 °C, 30 min
0 °C, 30 min
–40 °C, 30 min
–20 °C, 30 min
–20 °C, 3 h
>99 (0)[c]
51
27
0
50
53
cod
cod
[a] Yield of isolated product. [b] ZnEt2 (0.7 equiv.) was used. [c] Reaction was
performed without [RhCl(cod)]2.
On the basis of the absolute configuration of product 7b,[14]
The substrate scope of α,ꢀ-unsaturated carbonyls 6 was then a plausible model for the asymmetric induction can be pro-
screened (Table 4). α,ꢀ-Unsaturated esters bearing Me, iPr, tBu, posed (Figure 1).[15,16] The corresponding (Z)-RhI–enolate is gen-
and benzyl (Bn) substituents provided high yields, independent erated by insertion into the RhI–H species of the α,ꢀ-unsatu-
of steric hindrance (see products 7b–e). However, α,ꢀ-unsatu- rated esters in an s-trans fashion.[15a] Attack of the enolate to
rated amides did not undergo the reaction. In sharp contrast to carbon dioxide by the Si face is prevented by the equatorial
the styrene system, even with electron-donating substituents phenyl group on the phosphorus atom. Consequently, attack
in the aromatic rings, the hydrocarboxylated products were ob- from the Re face of the rhodium side would be favored to afford
tained in good to high yields (see products 7g–h). A benzyl the corresponding product (S)-7.
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Communication
Table 5. Rh-catalyzed asymmetric hydrocarboxylation.
carbon dioxide (1 atm) was demonstrated. Only the combina-
tion of [RhCl(cod)]2 as a catalyst and diethylzinc as a hydride
source allowed effective hydrocarboxylation to provide the cor-
responding α-aryl carboxylic acids in moderate to excellent
yields. In this catalytic process, we suggested intervention of
the RhI–H species, which could be generated from a RhI com-
plex and diethylzinc. Additionally, we also performed the cata-
lytic asymmetric hydrocarboxylation of α,ꢀ-unsaturated esters
with carbon dioxide by employing a chiral cationic rhodium
complex, despite moderate enantioselectivities. The develop-
ment of novel catalytic asymmetric reactions with carbon diox-
ide is ongoing in our laboratory.
Acknowledgments
This research was supported by the Japan Science and Technol-
ogy Agency (JST) (ACT-C: Advanced Catalytic Transformation
Program for Carbon utilization). The authors thank Takasago In-
ternational Co. for a gift of (S)-SEGPHOS.
Keywords: Asymmetric catalysis · Hydrocarboxylation ·
Rhodium · Hydrides · Carboxylic acids
[1] For recent reviews of carbon dioxide fixation, see: a) T. Sakakura, J.-C.
Choi, H. Yasuda, Chem. Rev. 2007, 107, 2365; b) S. N. Riduan, Y. Zhang,
Dalton Trans. 2010, 39, 3347; c) M. Cokoja, C. Bruckmeier, B. Rieger, W. A.
Hermann, F. E. Kühn, Angew. Chem. Int. Ed. 2011, 50, 8510; Angew. Chem.
2011, 123, 8662; d) Y. Tsuji, T. Fujihara, Chem. Commun. 2012, 48, 9956;
e) I. Omae, Coord. Chem. Rev. 2012, 256, 1384.
[2] For selected recent reports, see: a) T. Fujihara, K. Nogi, T. Xu, J. Terao, Y.
Tsuji, J. Am. Chem. Soc. 2012, 134, 9106; b) T. León, A. Correa, R. Martin,
J. Am. Chem. Soc. 2013, 135, 1221; c) K. Sasano, J. Takaya, N. Iwasawa, J.
Am. Chem. Soc. 2013, 135, 10954; d) T. G. Ostapowicz, M. Schmitz, M.
Krystof, J. Klankermayer, W. Leitner, Angew. Chem. Int. Ed. 2013, 52,
12119; Angew. Chem. 2013, 125, 12341; e) A. Correa, T. León, R. Martin,
J. Am. Chem. Soc. 2014, 136, 1062; f) T. Fujihara, Y. Horimoto, T. Mizoe,
F. B. Sayyed, Y. Tani, J. Terao, S. Sakaki, Y. Tsuji, Org. Lett. 2014, 16, 4960;
g) Y. Liu, J. Cornella, R. Martin, J. Am. Chem. Soc. 2014, 136, 11212; h) T.
Moragas, J. Cornella, R. Martin, J. Am. Chem. Soc. 2014, 136, 17702; i) K.
Nogi, T. Fujihara, J. Terao, Y. Tsuji, Chem. Commun. 2014, 50, 13052; j) Y.
Tani, T. Fujihara, J. Terao, Y. Tsuji, J. Am. Chem. Soc. 2014, 136, 17706; k)
X. Wang, Y. Liu, R. Martin, J. Am. Chem. Soc. 2015, 137, 6467; l) X. Wang,
M. Nakajima, R. Martin, J. Am. Chem. Soc. 2015, 137, 8924.
[a] Reaction was performed without AgSbF6. [b] Yield of isolated product.
[c] [RhCl(cod)]2 (5 mol-%) was used instead of Rh cat.* 8/AgSbF6.
Conclusions
The catalytic hydrocarboxylation of olefins, such as styrene de-
rivatives and α,ꢀ-unsaturated carbonyl compounds, with
[3] J. K. Buer, Inflammopharmacology 2014, 22, 263.
[4] a) B. D. Strooper, G. König, Nature 2001, 414, 159; b) S. Weggen, J. L.
Eriksen, P. Das, S. A. Sagi, R. Wang, C. U. Pietrzik, K. A. Findlay, T. E. Smith,
M. P. Murphy, T. Bulter, D. E. Kang, N. Marquez-Sterling, T. E. Golde, E. H.
Koo, Nature 2001, 414, 212; c) T. Jonsson, J. K. Atwal, S. Steinberg, J.
Snaedal, P. V. Jonsson, S. Bjornsson, H. Stefansson, P. Sulem, D. Gudbjarts-
son, J. Maloney, K. Hoyte, A. Gustafson, Y. Liu, Y. Lu, T. Bhangale, R. R.
Graham, J. Huttenlocher, G. Bjornsdottir, O. A. Andreassen, E. G. Jönsson,
A. Palotie, T. W. Behrens, O. T. Magnusson, A. Kong, U. Thorsteinsdottir,
R. J. Watts, K. Stefansson, Nature 2012, 488, 96.
[5] C. M. Williams, J. B. Johnson, T. Rovis, J. Am. Chem. Soc. 2008, 130, 14936.
[6] The Ni-mediated stoichiometric fixation of carbon dioxide: a) G. Burkhart,
H. Hoberg, Angew. Chem. Int. Ed. Engl. 1982, 21, 76; Angew. Chem. 1982,
94, 75; b) H. Hoberg, Y. Peres, C. Krüger, Y.-H. Tsay, Angew. Chem. Int. Ed.
Engl. 1987, 26, 771; Angew. Chem. 1987, 99, 799.
[7] M. D. Greenhalgh, S. P. Thomas, J. Am. Chem. Soc. 2012, 134, 11900.
[8] a) C. Hayashi, T. Hayashi, T. Yamada, Bull. Chem. Soc. Jpn. 2015, 88, 862;
b) C. Hayashi, T. Hayashi, S. Kikuchi, T. Yamada, Chem. Lett. 2014, 43, 565.
[9] M. Takimoto, Y. Nakamura, K. Kimura, M. Mori, J. Am. Chem. Soc. 2004,
126, 5956.
Figure 1. Plausible model for asymmetric induction.
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[10]
[13] a) S. J. Taylor, J. P. Morken, J. Am. Chem. Soc. 1999, 121, 12202; b) S. J.
Taylor, M. O. Duffey, J. P. Morken, J. Am. Chem. Soc. 2000, 122, 4528; c)
A. E. Russell, N. O. Fuller, S. J. Taylor, P. Aurriset, J. P. Morken, Org. Lett.
2004, 6, 2309.
For examples of the Rh-catalyzed direct carboxylation of arenes with
carbon dioxide, see: a) H. Mizuno, J. Takaya, N. Iwasawa, J. Am. Chem.
Soc. 2011, 133, 1251; b) T. Suga, H. Mizuno, J. Takaya, N. Iwasawa, Chem.
Commun. 2014, 50, 14360.
[14] See the Supporting Information.
[11] There is a possibility that a π-benzyl rhodium complex is generated, for
a review, see: B. M. Trost, L. Czabaniuk, Angew. Chem. Int. Ed. 2014, 53,
2826; Angew. Chem. 2014, 126, 2868, and references cited therein.
[12] A variety of functionalized organozinc reagents can undergo the addi-
tion reaction to carbon dioxide in the presence of stoichiometric
amounts of MgCl2 at room temperature, see: a) S. Bernhardt, A. Metzger,
P. Knochel, Synthesis 2010, 3802; b) A. Metzger, S. Bernhardt, G. Manolik-
akes, P. Knochel, Angew. Chem. Int. Ed. 2010, 49, 4665; Angew. Chem.
2010, 122, 4769.
[15] a) H. Nishiyama, T. Shiomi, Y. Tsuchiya, I. Matsuda, J. Am. Chem. Soc.
2005, 127, 6972; b) Y. Motoyama, Y. Koga, K. Kobayashi, K. Aoki, H. Nishi-
yama, Chem. Eur. J. 2002, 8, 2968.
[16] T. Hayashi, M. Takahashi, Y. Takaya, M. Ogasawara, J. Am. Chem. Soc.
2002, 124, 5052.
Received: March 18, 2016
Published Online: ■
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Communication
Hydrocarboxylation
The Rh-catalyzed hydrocarboxylation
of styrene derivatives and α,ꢀ-unsatu-
rated carbonyl compounds with CO2 is
shown. The use of [RhCl(cod)]2 (cod =
cyclooctadiene) as a catalyst and di-
ethylzinc as a hydride source provides
the corresponding α-aryl carboxylic
acids in moderate to excellent yields.
Additionally, this catalyst system can
be used in the asymmetric version of
this reaction.
S. Kawashima, K. Aikawa,
K. Mikami* ............................................ 1–6
Rhodium-Catalyzed Hydrocarboxyl-
ation of Olefins with Carbon Dioxide
DOI: 10.1002/ejoc.201600338
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