Journal of the American Chemical Society
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2007, 107, 2365; (c) Sakakura, T.; Kohno, K., The synthesis of
Scheme 3. Plausible Reaction Mechanism
organic carbonates from carbon dioxide. Chem. Commun. 2009, 1312;
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a building block in organic synthesis. Nat. Commun. 2015, 6, 5933;
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Carbon Dioxide. Angew. Chem. Int. Ed. 2018, 57, 15948; (f) Wang,
L.; Sun, W.; Liu, C., Recent Advances in Homogeneous
Carbonylation Using CO2 as CO Surrogate. Chin. J. Chem. 2018, 36,
353; (g) Zhang, Z.; Ye, J.-H.; Wu, D.-S.; Zhou, Y.-Q.; Yu, D.-G.,
Synthesis of Oxazolidin-2-ones from Unsaturated Amines with CO2
by Using Homogeneous Catalysis. Chem. Asian J. 2018, 13, 2292.
(2) (a) Huang, K.; Sun, C.-L.; Shi, Z.-J., Transition-metal-catalyzed
C-C bond formation through the fixation of carbon dioxide. Chem.
Soc. Rev. 2011, 40, 2435; (b) Martín, R.; Kleijꢀ, A. W., Myth or
Reality? Fixation of Carbon Dioxide into Complex Organic Matter
under Mild Conditions. ChemSusChem 2011, 4, 1259; (c) Tsuji, Y.;
1
2
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Cz
Cz
CN
Cz
NC
Cz
CN
Cz
Ph
N
RSH
+
Ph
visible light
Cz
Cz
Cz
4CzIPN
4CzPEBN
SH
Cz
R
4CzPEBN*
-H+
visible light
9
Photoredox
catalytic cycle
Organocatalytic
cycle
4CzPEBN
SET
R
S
10
11
12
13
14
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60
4CzPEBN
R
SH
SET
HAT
H
Fujihara, T., Carbon dioxide as a carbon source in organic
Ph
Ph
transformation: carbon-carbon bond forming reactions by transition-
metal catalysts. Chem. Commun. 2012, 48, 9956; (d) Börjesson, M.;
Moragas, T.; Gallego, D.; Martin, R., Metal-Catalyzed Carboxylation
of Organic (Pseudo)halides with CO2. ACS Catal. 2016, 6, 6739; (e)
Cao, Y.; He, X.; Wang, N.; Li, H.-R.; He, L.-N., Photochemical and
Electrochemical Carbon Dioxide Utilization with Organic
Compounds. Chin. J. Chem. 2018, 36, 644; (f) Yeung, C. S.,
Photoredox Catalysis as a Strategy for CO2 Incorporation: Direct
Access to Carboxylic Acids from a Renewable Feedstock. Angew.
Chem. Int. Ed. 2019, 58, 5492.
(3) (a) Yu, D. Y.; Zhang, Y. G., Copper- and copper-N-
heterocyclic carbene-catalyzed C-H activating carboxylation of
terminal alkynes with CO2 at ambient conditions. Proc. Nat. Acad. Sci.
U.S.A. 2010, 107, 20184; (b) Zhang, X.; Zhang, W.-Z.; Ren, X.;
Zhang, L.-L.; Lu, X.-B., Ligand-Free Ag(I)-Catalyzed Carboxylation
of Terminal Alkynes with CO2. Org. Lett. 2011, 13, 2402.
Ph
CO2
COO
COO
H
H+
Ph
Ph
To summarize, we have designed a novel and atom-
economic strategy for the carboxylation of C-H bonds with
CO2. An unprecedented visible-light-mediated benzylic C-H
bond carboxylation was achieved via the synergistic merger of
photoredox and organocatalysis. It is noteworthy that this
reaction proceeds smoothly without adding any metal reagent,
sacrificial electron donor, electron acceptor or stoichiometric
additive, affording the desired carboxylic acids in moderate to
excellent yields with a broad substrate scope. Particularly, our
protocol is applicable to the synthesis of several drugs, such as
Fenoprofen, Flurbiprofen and Naproxen. Further studies
aiming to achieve other types of C-H bond carboxylation by
this strategy are currently under investigation.
(4) (a) Boogaerts, I. I. F.; Nolan, S. P., Carboxylation of C-H
Bonds Using N-Heterocyclic Carbene Gold(I) Complexes. J. Am.
Chem. Soc. 2010, 132, 8858; (b) Boogaerts, I. I. F.; Fortman, G. C.;
Furst, M. R. L.; Cazin, C. S. J.; Nolan, S. P., Carboxylation of N-H/C-
H Bonds Using N-Heterocyclic Carbene Copper(I) Complexes.
Angew. Chem. Int. Ed. 2010, 49, 8674.
ASSOCIATED CONTENT
Supporting Information
(5) (a) Mizuno, H.; Takaya, J.; Iwasawa, N., Rhodium(I)-Catalyzed
Direct Carboxylation of Arenes with CO2 via Chelation-Assisted C-H
Bond Activation. J. Am. Chem. Soc. 2011, 133, 1251; (b) Sasano, K.;
Takaya, J.; Iwasawa, N., Palladium(II)-Catalyzed Direct
Carboxylation of Alkenyl C-H Bonds with CO2. J. Am. Chem. Soc.
2013, 135, 10954; (c) Suga, T.; Mizuno, H.; Takaya, J.; Iwasawa, N.,
Direct carboxylation of simple arenes with CO2 through a rhodium-
catalyzed C-H bond activation. Chem. Commun. 2014, 50, 14360; (d)
Song, L.; Cao, G.-M.; Zhou, W.-J.; Ye, J.-H.; Zhang, Z.; Tian, X.-Y.;
Li, J.; Yu, D.-G., Pd-catalyzed carbonylation of aryl C-H bonds in
benzamides with CO2. Org. Chem. Front. 2018, 5, 2086; (e) Song, L.;
Zhu, L.; Zhang, Z.; Ye, J.-H.; Yan, S.-S.; Han, J.-L.; Yin, Z.-B.; Lan,
Y.; Yu, D.-G., Catalytic Lactonization of Unactivated Aryl C-H
Bonds with CO2: Experimental and Computational Investigation. Org.
Lett. 2018, 20, 3776; (f) Fu, L.; Li, S.; Cai, Z.; Ding, Y.; Guo, X.-Q.;
Zhou, L.-P.; Yuan, D.; Sun, Q.-F.; Li, G., Ligand-enabled site-
selectivity in a versatile rhodium(II)-catalysed aryl C-H carboxylation
with CO2. Nat. Catal. 2018, 1, 469.
(6) Other selected examples, see (a) Vechorkin, O.; Hirt, N.; Hu,
X., Carbon Dioxide as the C1 Source for Direct C-H
Functionalization of Aromatic Heterocycles. Org. Lett. 2010, 12,
3567; (b) Tanaka, S.; Watanabe, K.; Tanaka, Y.; Hattori, T.,
EtAlCl2/2,6-Disubstituted Pyridine-Mediated Carboxylation of
Alkenes with Carbon Dioxide. Org. Lett. 2016, 18, 2576; (c) Luo, J.;
Preciado, S.; Xie, P.; Larrosa, I., Carboxylation of Phenols with CO2
at Atmospheric Pressure. Chem. Eur. J. 2016, 22, 6798; (d) Liu, Q.;
Li, M.; Xiong, R.; Mo, F., Direct Carboxylation of the Diazo Group
ipso-C(sp2)-H bond with Carbon Dioxide: Access to Unsymmetrical
Diazomalonates and Derivatives. Org. Lett. 2017, 19, 6756; (e) Juhl,
M.; Lee, J.-W., Umpolung Reactivity of Aldehydes toward Carbon
Dioxide. Angew. Chem. Int. Ed. 2018, 57, 12318; (f) Shigeno, M.;
Experimental procedures, methods and product characterization.
This material is available free of charge via the Internet at
AUTHOR INFORMATION
Corresponding Author
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENT
Financial support from the German Science Foundation (DFG;
KO 1537/18-1) is acknowledged. This project has received
funding from the European Research Council (ERC) under the
European Union’s Horizon 2020 research and innovation
programme (grant agreement No. 741623). We thank Dr. Rudolf
Vasold (University of Regensburg) for his assistance in GC-MS
measurements, Regina Hoheisel (University of Regensburg) for
her assistance in cyclic voltammetry measurements, Julia Zach
(University of Regensburg) for her assistance in preparing high
power LEDs setup.
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