Rhodium-Catalyzed Formylation of Aryl Halides with CO2 and H2

Article abstract of DOI:10.1021/acs.orglett.8b02027

The reductive formylation of aryl iodides/bromides to aryl aldehydes using CO₂/H₂ is presented for the first time. It was realized over a catalytic system composed of RhI₃ or RhI₃/Pd(dppp)Cl₂ (dppp = 1,3-bis(diphenyphosphino)propane) and PPh₃ in the presence of Ac₂O/Et₃N at 100 °C, affording aromatic aldehydes in good to excellent yields, together with good functional-group tolerance and broad substrate scope. The reaction proceeds through three cascade steps, involving HCOOH formation, CO release, and formylation of aryl halides.

Full text of DOI:10.1021/acs.orglett.8b02027

Letter
pubs.acs.org/OrgLett
Cite This: Org. Lett. XXXX, XXX, XXX−XXX
Rhodium-Catalyzed Formylation of Aryl Halides with CO2 and H2
Zhenghui Liu,†,‡,§ Zhenzhen Yang,†,§ Bo Yu,† Xiaoxiao Yu,†,‡ Hongye Zhang,† Yanfei Zhao,†
Peng Yang,†,‡ and Zhimin Liu*,†,‡
†Beijing National Laboratory for Molecular Sciences, Key Laboratory of Colloid, Interface and Thermodynamics, Institute of
Chemistry, Chinese Academy of Sciences, Beijing 100190, China
‡University of Chinese Academy of Sciences, Beijing 100049, China
S
* Supporting Information
ABSTRACT: The reductive formylation of aryl iodides/bromides to aryl aldehydes using
CO2/H2 is presented for the first time. It was realized over a catalytic system composed of
RhI3 or RhI3/Pd(dppp)Cl2 (dppp = 1,3-bis(diphenyphosphino)propane) and PPh3 in the
presence of Ac2O/Et3N at 100 °C, affording aromatic aldehydes in good to excellent yields,
together with good functional-group tolerance and broad substrate scope. The reaction proceeds through three cascade steps,
involving HCOOH formation, CO release, and formylation of aryl halides.
arbon monoxide (CO) represents the most important C1
building block on an industrial scene in a myriad of
protocol for the reduction of CO2 to CO in the presence of
CsF and disilane in dimethyl sulfoxide (DMSO) at room
temperature, and the reduction could be coupled to an
aminocarbonylation reaction using a two-chamber system
(Scheme S1g, SI).2,20 Later, they reported the conversion of
CO2 with diaryldisilanes and aryl halides to produce
diarylketones through CO generation (Scheme S1h, SI).21 In
recent years, catalytic transformations involving CO2 for
carbonylative alkene functionalization have emerged to provide
chemicals such as carboxylic acids,22 esters,23 and alcohols.24
Ding and Xia et al. realized the one-pot hydroformylation of
olefins with CO2, hydrosilane, and H2 to afford aldehydes
through a tandem sequence of PMHS-mediated CO2
reduction to CO and a conventional rhodium-catalyzed
hydroformylation with CO/H2 (Scheme S1i, SI).25 From a
sustainable point of view, H2 is a far better choice of reductant
than hydrosilanes or hydroboranes, and reduction of CO2 to
CO, as well as the subsequent utilization of CO2 as C1 source
in the formylation reaction of of aryl halides is highly desirable
and has not been realized up to now (Scheme 1).
C
industrial carbonylation processes.1−3 However, the high
toxicity, flammability, and production from fossil fuels make
the handling and transportation of this gas complicated and
limit its applications. Hence, the exploration of CO surrogates
is of particular interest. As a sustainable and renewable C1
building block, the efficient conversion of carbon dioxide
(CO2) for the synthesis of value-added chemicals is of great
significance in regard to reducing the predominant dependence
on petrochemical feedstocks for the chemical supply chain.4−8
Over the past decades, several approaches have been
developed for CO2 reduction using different types of
reductants, such as H2, hydrosilanes, and hydroboranes,5,9,10
to afford CO, formic acid, formaldehyde, methanol, and
methane successively.11 Notably, although CO production
from CO2 hydrogenation could be achieved through a reverse
water−gas shift pathway, the reaction is generally conducted at
high temperature (>250 °C) together with low conversion and
selectivity, in which the generated CO is difficult to use in the
subsequent chemical conversion.11 Therefore, development of
efficient catalytic systems for the use of CO2 as a surrogate for
CO under mild conditions is attractive and challenging.
Scheme 1. Formylation of Aryl Halides To Produce
Aromatic Aldehydes
Formylation of aryl halides employing CO12−14 or CO
surrogates (e.g., N-formylsaccharin,15 isocyanide,16 paraformal-
dehyde17) (Scheme S1a−d, Supporting Information (SI)) is an
efficient and complementary method to synthesize aromatic
aldehydes, which are valuable intermediates in C−C bond-
forming reactions. However, the inherent drawbacks of the
reported approaches, such as the need for toxic CO or
expensive CO surrogates and hydrosilanes, promote the
continuous exploration of cleaner and less expensive routes
for the synthesis of aromatic aldehydes. Our group realized the
formylation of aryl iodides and bromides with CO2 using
poly(methylhydrosiloxane) (PMHS) as the reductant over Pd
catalysts combined with 1,8-diazabicyclo[5.4.0]undec-7-ene
(DBU),18,19 leading to aryl aldehydes in moderate to excellent
yields (Scheme S1e,f, SI). Skrydstrup et al. developed a
Herein, we developed a catalytic system composed of RhI3
and PPh3, which realized the reductive formylation of aryl
iodides with CO2/H2 in the presence of acetic anhydride and
Et3N at 100 °C, affording aryl aldehydes in good to excellent
yields, together with good functional-group tolerance and
Received: June 28, 2018
© XXXX American Chemical Society
A
DOI: 10.1021/acs.orglett.8b02027
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Letter
broad substrate scope. Moreover, with additional Pd(dppp)-
Cl2, this catalytic system was also very effective for the
formylation of aryl bromides. Detailed investigation on the
reaction mechanism by isotope-labeling and control experi-
ments showed that the reaction proceeded through three
cascade steps involving initial HCOOH formation from CO2
hydrogenation, subsequent CO release from the reaction of
HCOOH with acetic anhydride, and final formylation of aryl
halides by CO insertion and reductive elimination.
55% (entries 2−11, Table S1, SI). In contrast, the reaction was
sluggish using other solvents including 1,3-dimethyl-2-
imidazolidinone (DMI), N-methyl-2-pyrrolidinone (NMP),
tetrahydrofuran (THF), toluene, and 1,4-dioxane (entries 12−
16, Table S1, SI). For base screening, Et3N was found to be the
most effective (entries 17−20, Table S1, SI). In addition, other
bi-, tri-, and tetradentate phosphine ligands or nitrogen-
containing ligands hardly afforded the formylated product
(entries 21−30,Table S1, SI). Further detailed investigation on
the reaction parameters (entries 31−48, Table S1, SI) showed
that 100% conversion and 86% yield of 1 could be achieved
under the optimum reaction conditions (entry 8, Table 1). In
addition, large-scale formylation reaction of iodobenzene with
CO2/H2 was carried out, affording benzaldehyde in 82% yield
(entry 8, Table 1). Subsequently, formylation of bromoben-
zene with CO2/H2 was conducted under the above optimum
conditions, but almost no conversion of bromobenzene
occurred, probably due to the low activation ability of the
rhodium species toward the C−Br bond (entry 9, Table 1). As
previously reported, Pd(dppp)Cl2 was able to effectively
catalyze the formylation of aryl bromides with CO2/hydro-
silane.19 Therefore, RhI3/Pd(dppp)Cl2/PPh3 was applied in
the reaction of bromobenzene with CO2/H2, and delightfully,
99% conversion of bromobenzene together with 87% yield of 1
was achieved (entry 10, Table 1). Moreover, it was shown that
both PPh3 and RhI3 were necessary for high product yield
(entries 11−13, Table 1). Addition of similar Pd complexes
with different phosphorus ligands, including Pd(dppe)Cl2,
Pd(dppf)Cl2, and Pd(PPh3)2Cl2, also afforded moderate yields
of 1 (65−73%) (entries 49−51, Table S1, SI). However, PdCl2
and Pd(OAc)2 gave 1 in relatively low yields (34% and 13%,
respectively) (entries 52−53, Table S1, SI).
Having demonstrated the feasibility of benzaldehyde syn-
thesis from iodobenzene with CO2/H2 as the building block
for the formyl group, the scope of this transformation was then
explored (Scheme 2). Neutral iodoarenes including iodoben-
zene, 4-iodobiphenyl, 1-iodonaphthalene, and 2-iodonaphtha-
lene provided the corresponding aromatic aldehydes 1−4 in
moderate to high yields (55−80%). For iodobenzene
derivatives with electron-donating groups (Me, OMe), the
product yields (5−10, 72−92%) were influenced by the
position of the substituent groups, following the order of o- <
m- < p-, probably owing to the steric hindrance effect.
Employing 4-tert-butyliodobenzene as the substrate afforded a
product (11) yield of 79%. Notably, other electron-rich
iodoarenes with two or three methyl groups reacted well,
providing 45% (12), 40% (13), and 89% (14) yields of the
aromatic aldehydes, respectively. Aryl iodides with other halide
substitutes (F, Cl, Br) were also compatible under our reaction
conditions, with 65−84% (15−23) yields of the formylated
products being obtained. In addition, the influence of the
substituent group position followed the order of o- < m- < p-
due to steric hindrance effects. Other aryl iodides with
electron-withdrawing groups such as trifluoromethyl, cyano,
acetyl, acetyl amino groups also provided acceptable yields
(59−81%, 24−27), demonstrating the compatibility of this
catalytic system to reducible groups even under high H2
pressure. Generally, dehalogenation and direct coupling
reaction easily occurred for electron deficient aryl halides.19
Aryl aldehydes with two electron-withdrawing groups could be
obtained in moderate yields (56% and 45% for 28 and 29,
respectively). Heterocyclic iodides were amenable to the
As part of our ongoing studies on CO2 transformations,19,26
we sought to develop a catalytic system for the formylation of
aryl halides with CO2 as the CO surrogate in the presence of
H2. For the reduction of CO2 to CO, deoxygenative cleavage of
the OCO bond is needed, which is difficult to realize
owing to its high bond energy (532 kJ mol−1).27 In our
preliminary study, acetic anhydride as a deoxygenation reagent
was applied in the reaction of iodobenzene with CO2/H2
(1:1). A quick survey of the reaction conditions showed that
100% conversion of iodobenzene together with 61% yield of
benzaldehyde (1) was obtained over RhI3/PPh3 in the
presence of acetic anhydride, Et3N as a base, and N,N-
dimethylacetamide (DMA) as the solvent (Table 1, entry 1).
Table 1. Rhodium-Catalyzed Formylation of Iodobenzene/
a
Bromobenzene with CO2/H2 To Afford Benzaldehyde 1
b
b
deviation from standard
conditions
conversion
(%)
yield
entry substrate
(%)
1
2
3
4
5
6
7
8
9
10
11
12
13
PhI
PhI
PhI
PhI
PhI
PhI
PhI
PhI
PhBr
PhBr
PhBr
PhBr
PhBr
none
100
97
99
61
0
0
0
0
no PPh3
no Et3N
no Ac2O
no CO2
no H2
no DMA
none
none
99
100
100
43
100
33
99
62
26
33
0
8
c
c
e
86 (82 )
<1
87
26
6
cd
,
none
cd
,
no PPh3
no RhI3
no RhI3 and PPh3
cd
,
cd
,
4
a
Standard conditions: PhI (1 mmol), RhI3 (5 mol %), PPh3 (15 mol
%), Et3N (5 mmol), Ac2O (2 mmol), DMA (2 mL), CO2 (3 MPa) +
b
H2 (3 MPa), 100 °C, 24 h. Determined by GC using dodecane as an
c
internal standard. Ac2O (4.5 mmol), Et3N (1.2 mmol), CO2 (4
d
MPa) + H2 (4 MPa). Additional Pd(dppp)Cl2 (5 mol %) was added.
e
PhI (10 mmol), RhI3 (5 mol %), PPh3 (15 mol %), Et3N (12 mmol),
Ac2O (45 mmol), DMA (20 mL), CO2 (4 MPa) + H2 (4 MPa), 100
°C, 24 h, conducted in an autoclave with the inner volume of 100 mL.
Dehalogenation and direct coupling products (e.g., benzene
and biphenyl) were detected as the main byproducts. It was
indicated that all of the reagents were necessary, and the yield
of 1 decreased to only 8% without solvent (entries 2−7, Table
1). Other rhodium salts including RhCl3, [RhCl(CO)2]2,
Rh(PPh3)3Cl, RhCl(CO)(PPh3)2, [RhCl(COD)]2, Rh-
(PPh3)3Br, Rh(acac)(CO)2, Rh(OAc)2·2H2O, [Rh-
(CF3COO)]2, and Rh/C were examined, and they exhibited
low to moderate catalytic activities, affording 1 in yields of 6−
B
DOI: 10.1021/acs.orglett.8b02027
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Letter
Scheme 2. Substrate Scope for the Rh-Catalyzed
Formylation of Aryl Iodides/Bromides Using CO2/H2
Scheme 3. Isotope-Labeling Experiments and Control
Experiments
a
detected by GC in the gas phase after the reaction (Figure S2,
SI), and in the case of using 13CO2, the molecular ion peak of
m/z 29 for 13CO was detected by GC−MS (Figure S3, SI).
1
The H NMR spectrum of the reaction mixture indicated the
formation of HCOOH and CH3COOH during the reaction
process of entry 8 in Table 1, which were also detected by
GC−MS (Figure S4 and S5, SI). From the above results, it can
be deduced that HCOOH may be generated from the CO2
hydrogenation catalyzed by a Rh-based catalytic system similar
to the reported results,28 and the subsequent reaction of
HCOOH with Ac2O led to the release of CO and the
formation of CH3COOH.29 Actually, it was found that
HCOOH could react with Ac2O to release CO at 100 °C
without any catalyst (Scheme 3d). Subsequently, several
control experiments were conducted. It was indicated that in
the case of using CO instead of CO2 a high yield of 1 (95%)
was obtained in the presence of H2 (4 MPa), while no 1 was
detected in the absence of H2 (Scheme 3e), suggesting that H2
played an important role probably in the reductive elimination
step (Scheme 4, step III, E to F). In the control experiment
using HCOOH instead of CO2, 95% and 87% yields of 1 were
obtained in the presence and absence of H2, respectively, and
CO was detected in the gas phase (Scheme 3f). Hence, it can
be deduced that HCOOH could also act as a hydrogen source
for the reductive elimination process.29
a
The reaction was conducted under the condition of entry 8 (aryl
iodides) and 10 (aryl bromides) in Table 1. Isolated yields of the
products are given and the structures were determined by GC−MS
and NMR. For details, see the SI.
formylation reaction as well, leading to the corresponding
aldehydes 30−34 with yields of 55−61%.
Subsequently, formylation of aryl bromides with CO2/H2
was conducted over RhI3/Pd(dppp)Cl2/PPh3. Various aro-
matic aldehydes were obtained in good to excellent yields,
including benzaldehyde 1 (83%) and its derivatives bearing
electron-neutral (2, 78% and 4, 65%), electron-rich (5, 6, 7,
10, 11, 14, 78−93%), and electron-deficient groups (15−17,
20, 24−27, 54−91%). Formylation of heterocyclic aromatic
bromides also performed well, affording the target aldehydes
(30, 32, 35 in moderate yields (38−43%).
To gain insight into the details of aryl iodide formylation
with CO2/H2, isotope-labeling experiments were performed
under the conditions of entry 8 in Table 1 using 13CO2 and D2
instead of CO2 and H2, respectively, to verify the sources of the
carbon and hydrogen in the formyl group. The molecular ion
peaks of m/z 107, 107, and 108 in the GC−MS spectrum of
the reaction solution (Figure S1, SI), can be assigned to
C6H513CHO, C6H5CDO, and C6H513CDO, respectively,
confirming that both CO2 and H2 are involved the formation
of the formyl group (Scheme 3a−c). Moreover, CO was
Kinetic study results showed that at the beginning of the
reaction, no CO or HCOOH was detected within the first 2 h
(Figure S6, SI). At 3 h, 0.19 mmol of CO was detected in the
gas phase and no HCOOH was detectable, together with 9%
yield of 1, suggesting that in this case the generated CO was
excess while the generated HCOOH was completely
consumed. As the reaction proceeded, both CO and
C
DOI: 10.1021/acs.orglett.8b02027
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Letter
hodium complex (E) is obtained after the coordination and
insertion of CO. The aldehyde product is obtained after
metathesis with H2 and the active Rh species are regenerated
from the rhodium hydroiodide (F) complex by reaction with
Et3N.14 For aryl bromides, the Step III is catalyzed by
Pd(dppp)Cl2 in a CO insertion and reductive elimination
pathway as previously reported.14
Scheme 4. Proposed Reaction Mechanism for the Rh-
Catalyzed Formylation of Aryl Iodides Using CO2/H2
In conclusion, we have demonstrated the catalytic
formylation of aryl iodides/bromides using CO2/H2. The use
of commercially available RhI3/PPh3 together with Ac2O as a
deoxygenation reagent afforded the aryl aldehydes in good to
excellent yields. This transformation provides an atom-efficient
alternative to traditional formylation methodologies and
utilizes CO2 as a C1 source. In particular, if hydrogen is
provided from renewable sources, the new synthetic route
clearly has the potential to significantly reduce the dependence
on petrochemical feedstocks for the chemical supply chain.
ASSOCIATED CONTENT
* Supporting Information
■
S
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.or-
glett.8b02027.
Experimental procedures, supplementary scheme and
figures, NMR and MS spectra (PDF)
AUTHOR INFORMATION
■
Corresponding Author
*E-mail: liuzm@iccas.ac.cn.
ORCID
Zhimin Liu: 0000-0001-7953-7414
Author Contributions
§Z.L. and Z.Y. contributed equally to this work.
Notes
HCOOH began to accumulate, and the yield of 1 increased
rapidly from 9% (3 h) to 66% (12 h). Finally, when the
reaction finished, 1.06 mmol of HCOOH and 1.50 mmol of
CO was obtained, and it were estimated that 0.82 mmol of CO
was involved in the formylation reaction to afford 82% yield of
1.
The authors declare no competing financial interest.
The investigation results of the influence of PPh3 amount on
the catalytic activity showed that under the otherwise identical
conditions, the maximum yield of 1 (70%) was achieved with
the molar ratio of RhI3/PPh3 as 1:3, while more or less PPh3 all
led to decreased yields of 1 (entry 18 vs 23−25, Table S1, SI).
This indicates that molar ratio of [Rh]:PPh3 in the actual
catalytic species was 1:3, which was probably Rh(PPh3)3I.
Thus, Rh(PPh3)3I was synthesized and used as the catalyst
instead of RhI3 and PPh3, and 83% yield of 1 was afforded
under otherwise identical reaction conditions.
On the basis of the experimental results and previous
reports, a cascade reaction mechanism for the formylation of
aryl iodides is proposed (Scheme 4). Initially, in step I,
HCOOH (or [HCOO]−[Et3NH]+ in the presence of Et3N) is
formed through hydrogenation of CO2 catalyzed by Rh-
(PPh3)3I species (A), which involves the formation of
(PPh3)3Rh−H (B) in the presence of H2, CO2 insertion into
the Rh−H bond (C) and metathesis with H2 to release
HCOOH and regenerate (PPh3)3Rh−H (B).30 Subsequently,
in step II, the produced HCOOH reacts with acetic anhydride
to afford the HC(O)OC(O)CH3 intermediate, which then
decomposes to CH3COOH with simultaneous release of CO.
Finally, in step III, the reaction starts with the oxidative
addition of Rh(PPh3)3I (A) to aryl iodide, affording the
corresponding arylrhodium complex (D). Then, the benzoylr-
ACKNOWLEDGMENTS
■
We thank the National Natural Science Foundation of China
(Nos. 21673256 and 21533011) and the Chinese Academy of
Sciences (QYZDY-SSW-SLH013-2).
REFERENCES
■
(1) Peng, J.-B.; Wu, X.-F. Ligand- and solvent-controlled regio- and
chemodivergent carbonylative reactions. Angew. Chem., Int. Ed. 2018,
57, 1152−1160.
(2) Friis, S. D.; Lindhardt, A. T.; Skrydstrup, T. The development
and application of two-chamber reactors and carbon monoxide
precursors for safe carbonylation reactions. Acc. Chem. Res. 2016, 49,
594−605.
̈
(3) Franke, R.; Selent, D.; Borner, A. Applied Hydroformylation.
Chem. Rev. 2012, 112, 5675−5732.
(4) Abanades, J. C.; Rubin, E. S.; Mazzotti, M.; Herzog, H. J. On the
climate change mitigation potential of CO2 conversion to fuels. Energy
Environ. Sci. 2017, 10, 2491−2499.
(5) Klankermayer, J.; Wesselbaum, S.; Beydoun, K.; Leitner, W.
Selective catalytic synthesis using the combination of carbon dioxide
and hydrogen: Catalytic chess at the interface of energy and
chemistry. Angew. Chem., Int. Ed. 2016, 55, 7296−7343.
(6) Sakakura, T.; Choi, J.-C.; Yasuda, H. Transformation of carbon
dioxide. Chem. Rev. 2007, 107, 2365−2387.
(7) Liu, Q.; Wu, L.; Jackstell, R.; Beller, M. Using carbon dioxide as
a building block in organic synthesis. Nat. Commun. 2015, 6, 5933.
D
DOI: 10.1021/acs.orglett.8b02027
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Letter
(8) Song, Q.-W.; Zhou, Z.-H.; He, L.-N. Efficient, selective and
sustainable catalysis of carbon dioxide. Green Chem. 2017, 19, 3707−
3728.
(27) Thomas, B.; David, L. In CRC Handbook of Chemistry and
Physics, 96th ed.; Haynes, W. M., Eds.; CRC Press/Taylor and
Francis: Boca Raton, 2016; pp 9−75.
(28) Hutschka, F.; Dedieu, A.; Eichberger, M.; Fornika, R.; Leitner,
W. Mechanistic aspects of the rhodium-catalyzed hydrogenation of
CO2 to formic acida theoretical and kinetic study. J. Am. Chem. Soc.
1997, 119, 4432−4443.
(29) Qi, X.; Li, C.-L.; Wu, X.-F. A. Convenient palladium-catalyzed
reductive carbonylation of aryl iodides with dual role of formic acid.
Chem. - Eur. J. 2016, 22, 5835−5838.
(30) Jessop, P. G.; Ikariya, T.; Noyori, R. Homogeneous
hydrogenation of carbon dioxide. Chem. Rev. 1995, 95, 259−272.
(9) Klankermayer, J.; Leitner, W. Love at second sight for CO2 and
H2 in organic synthesis. Science 2015, 350, 629−630.
́
(10) Alvarez, A.; Bansode, A.; Urakawa, A.; Bavykina, A. V.;
Wezendonk, T. A.; Makkee, M.; Gascon, J.; Kapteijn, F. Challenges in
the greener production of formates/formic acid, methanol, and DME
by heterogeneously catalyzed CO2 hydrogenation processes. Chem.
Rev. 2017, 117, 9804−9838.
(11) Porosoff, M. D.; Yan, B.; Chen, J. G. Catalytic reduction of CO2
by H2 for synthesis of CO, methanol and hydrocarbons: challenges
and opportunities. Energy Environ. Sci. 2016, 9, 62−73.
(12) Schoenberg, A.; Heck, R. F. Palladium-catalyzed formylation of
aryl, heterocyclic, and vinylic halides. J. Am. Chem. Soc. 1974, 96,
7761−7764.
(13) Klaus, S.; Neumann, H.; Zapf, A.; Strubing, D.; Hubner, S.;
̈ ̈
Almena, J.; Riermeier, T.; Groß, P.; Sarich, M.; Krahnert, W.-R.;
Rossen, K.; Beller, M. A general and efficient method for the
formylation of aryl and heteroaryl bromides. Angew. Chem., Int. Ed.
2006, 45, 154−158.
(14) Sergeev, A. G.; Spannenberg, A.; Beller, M. Palladium-catalyzed
formylation of aryl bromides: elucidation of the catalytic cycle of an
industrially applied coupling reaction. J. Am. Chem. Soc. 2008, 130,
15549−15563.
(15) Ueda, T.; Konishi, H.; Manabe, K. Palladium-catalyzed
reductive carbonylation of aryl halides with n-formylsaccharin as a
CO source. Angew. Chem., Int. Ed. 2013, 52, 8611−8615.
(16) Jiang, X.; Wang, J.-M.; Zhang, Y.; Chen, Z.; Zhu, Y.-M.; Ji, S.-J.
Palladium-Catalyzed Formylation of aryl halides with tert-butyl
isocyanide. Org. Lett. 2014, 16, 3492−3495.
(17) Natte, K.; Dumrath, A.; Neumann, H.; Beller, M. Palladium-
Catalyzed carbonylations of aryl bromides using paraformaldehyde:
synthesis of aldehydes and esters. Angew. Chem., Int. Ed. 2014, 53,
10090−10094.
(18) Yu, B.; Zhao, Y.; Zhang, H.; Xu, J.; Hao, L.; Gao, X.; Liu, Z.
Pd/C-catalyzed direct formylation of aromatic iodides to aryl
aldehydes using carbon dioxide as a C1 resource. Chem. Commun.
2014, 50, 2330−2333.
(19) Yu, B.; Yang, Z.; Zhao, Y.; Hao, L.; Zhang, H.; Gao, X.; Han,
B.; Liu, Z. An efficient and general method for formylation of aryl
bromides with CO2 and poly(methylhydrosiloxane). Chem. - Eur. J.
2016, 22, 1097−1102.
(20) Lescot, C.; Nielsen, D. U.; Makarov, I. S.; Lindhardt, A. T.;
Daasbjerg, K.; Skrydstrup, T. Efficient fluoride-catalyzed conversion
of CO2 to CO at room temperature. J. Am. Chem. Soc. 2014, 136,
6142−6147.
(21) Lian, Z.; Nielsen, D. U.; Lindhardt, A. T.; Daasbjerg, K.;
Skrydstrup, T. Cooperative redox activation for carbon dioxide
conversion. Nat. Commun. 2016, 7, 13782.
(22) Ostapowicz, T. G.; Schmitz, M.; Krystof, M.; Klankermayer, J.;
Leitner, W. Carbon dioxide as a c1 building block for the formation of
carboxylic acids by formal catalytic hydrocarboxylation. Angew. Chem.,
Int. Ed. 2013, 52, 12119−12123.
(23) Wu, L.; Liu, Q.; Fleischer, I.; Jackstell, R.; Beller, M.
Ruthenium-catalysed alkoxycarbonylation of alkenes with carbon
dioxide. Nat. Commun. 2014, 5, 3091.
(24) Liu, Q.; Wu, L.; Fleischer, I.; Selent, D.; Franke, R.; Jackstell,
R.; Beller, M. Development of a ruthenium/phosphite catalyst system
for domino hydroformylation−reduction of olefins with carbon
dioxide. Chem. - Eur. J. 2014, 20, 6888−6894.
(25) Ren, X.; Zheng, Z.; Zhang, L.; Wang, Z.; Xia, C.; Ding, K.
Rhodium-complex-catalyzed hydroformylation of olefins with CO2
and hydrosilane. Angew. Chem., Int. Ed. 2017, 56, 310−313.
(26) Zhao, Y.; Yu, B.; Yang, Z.; Zhang, H.; Hao, L.; Gao, X.; Liu, Z.
A protic ionic liquid catalyzes CO2 conversion at atmospheric
pressure and room temperature: synthesis of quinazoline-2,4(1H,3H)-
diones. Angew. Chem., Int. Ed. 2014, 53, 5922−5925.
E
DOI: 10.1021/acs.orglett.8b02027
Org. Lett. XXXX, XXX, XXX−XXX