Mild and Selective Rhodium-Catalyzed Transfer Hydrogenation of Functionalized Arenes

Article abstract of DOI:10.1021/acs.orglett.1c00341

Diboron-mediated rhodium-catalyzed transfer hydrogenation of functionalized arenes is reported. In addition to good functional group tolerance, the reaction features operational simplicity and controllable chemoselectivity. The general applicability of this procedure is demonstrated by the selective hydrogenation of a range of arenes, including functionalized benzenes, biphenyls, and polyaromatics.

Full text of DOI:10.1021/acs.orglett.1c00341

pubs.acs.org/OrgLett
Letter
Mild and Selective Rhodium-Catalyzed Transfer Hydrogenation of
Functionalized Arenes
Yuhan Wang, Zhiqian Chang, Yan Hu, Xiao Lin, and Xiaowei Dou*
Cite This: Org. Lett. 2021, 23, 1910−1914
Read Online
sı
*
Metrics & More
Article Recommendations
Supporting Information
ACCESS
ABSTRACT: Diboron-mediated rhodium-catalyzed transfer hydrogenation of
functionalized arenes is reported. In addition to good functional group
tolerance, the reaction features operational simplicity and controllable
chemoselectivity. The general applicability of this procedure is demonstrated
by the selective hydrogenation of a range of arenes, including functionalized
benzenes, biphenyls, and polyaromatics.
ydrogenation of unsaturated compounds is arguably one
hydrogenation of diversely functionalized arenes, including
Hof the most useful transformations in organic synthesis. aromatic ketones,5 fluoroarenes,6 silylated arenes,7 di/trifluor-
1
omethylated arenes,8 borylated arenes,9 and phenol deriva-
In particular, hydrogenation of arenes provides a convenient
tives10 were successfully achieved, mainly by the groups of
Zeng and Glorius. These breakthroughs greatly improve the
chemoselectivity and scope of arene hydrogenation. However,
mild and selective arene hydrogenation methods that avoid the
use of pressurized H2 gas and elaborate setups, which is highly
desirable for laboratory synthesis, are still underdeveloped.
Transfer hydrogenation represents a practically useful
hydrogenation strategy. It uses easy to handle hydrogen source
other than hazardous H2 gas and avoids the elaborate
experimental setups, thus featuring operational simplicity and
safety. Despite the extensive studies on transfer hydrogenation
of various unsaturated substrates,11 progress on transfer
hydrogenation of arenes largely lags behind. Not surprisingly,
the known reports mainly focus on the reactive azaarenes,12
but the transfer hydrogenation of challenging benzene
derivatives, especially the functionalized benzenes, remains
scarce.13 To realize the operationally simple and selective
transfer hydrogenation of functionalized arenes, there are
several prerequisites to be considered. First, the reducing
reagent is supposed to be nontoxic, bench stable, and easy to
handle; second, the catalyst should be reactive enough for
hydrogenation under mild conditions while inert to labile
functional groups. Diborons have been recently explored as
effective and user-friendly mediators for transition-metal-
catalyzed transfer hydrogenation reactions.14 At the same
time, rhodium-based catalysts have shown high reactivity and
good functional group tolerance in hydrogenation reactions.1
approach to access saturated carbo- and heterocycles.2
Nevertheless, because of the inherent resonance stabilization
energy, hydrogenation of arenes is far more challenging than
those nonaromatic substrates.3 Harsh reaction conditions such
as high reaction temperature and highly pressurized H2 gas
were traditionally employed to overcome the higher kinetic
barrier, which inevitably resulted in poor functional group
(FG) tolerance.1,2 As a result, in contrast to the remarkable
advances of hydrogenation of simple arenes, the selective
hydrogenation of functionalized arenes remained an unsolved
problem.4 Recently, with the use of cyclic (alkyl)(aminol)-
carbene/rhodium catalyst (CAAC-Rh, Scheme 1), selective
Scheme 1. Hydrogenation of Functionalized Arenes
Received: January 28, 2021
Published: February 18, 2021
https://dx.doi.org/10.1021/acs.orglett.1c00341
© 2021 American Chemical Society
Org. Lett. 2021, 23, 1910−1914
1910

Organic Letters
pubs.acs.org/OrgLett
Letter
We recently studied the rhodium-catalyzed diboron-mediated
transfer hydrogenation reaction of alkenes and carbonyls, and
high reactivity of the catalytic system was observed.15 Given
the unique reactivity and selectivity of rhodium in hydro-
genation, we envisioned the rhodium/diboron system might
work for the selective transfer hydrogenation of functionalized
arenes. During the course of our study, the Glorius group
reported the transfer hydrogenation of arenes and heteroarenes
with ammonia borane/TFE (2,2,2,-trifluoroethanol) as the
hydrogen donor, and several types of functionalized arenes
were efficiently hydrogenated.16 Herein, we report the transfer
hydrogenation of functionalized arenes using B2(OH)4/EtOH
as the hydrogen donor. This new protocol shows good
functional group tolerance, operational simplicity, and control-
lable chemoselectivity (Scheme 1).
the Wilkinson’s catalyst, were not active (entries 4−6). The
commercial Rh/C was found to be active for the transfer
hydrogenation but showed a lower efficiency (entry 7).
Different diborons were next investigated with [Rh(OH)-
(cod)]2 as the catalyst, and bis(catecholate) diboron B2(cat)2
was found to be ineffective while both bis(pinacolate) diboron
B2(pin)2 and bis(neopentylglycolate) diboron B2(neop)2 gave
low yield of the desired product (entries 8−10). Thus,
[Rh(OH)(cod)]2 was chosen as the catalyst and B2(OH)4 was
chosen as the diboron reagent for further studies.
With the established conditions for transfer hydrogenation
of arylboronic acid pinacol ester in hand (Table 1, entry 3), the
substrate scope was then studied. As shown in Scheme 2, a
e
Scheme 2. Transfer Hydrogenation of Aryl Boronate Esters
We commenced the investigation with phenylboronic acid
pinacol ester 1a (Table 1). With cyclooctodiene (cod)-
Table 1. Study on the Transfer Hydrogenation of Phenyl
a
Boronate Ester 1a
conv
b
c
entry
catalyst and additive
[RhCl(cod)]2
[Rh(OH)(cod)]2
diboron
(%)
yield (%)
1
2
3
4
5
6
7
8
9
10
B2(OH)4
B2(OH)4
B2(OH)4
B2(OH)4
B2(OH)4
B2(OH)4
B2(OH)4
B2(cat)2
80
>95
>95
<5
7
<5
55
<5
27
24 (23)
44 (41)
81 (74)
<5
<5
<5
55 (53)
<5
<5
[Rh(OH)(cod)]2, pinacol
[Rh(OH)(binap)]2, pinacol
[Rh(OH)(dppe)]2, pinacol
RhCl(PPh3)3, pinacol
Rh/C, pinacol
[Rh(OH)(cod)]2, pinacol
[Rh(OH)(cod)]2, pinacol
[Rh(OH)(cod)]2, pinacol
B2(pin)2
B2(neop)2
28
17
a
Reaction conditions: 1a (0.20 mmol), diboron (0.90 mmol), catalyst
(5 mol % Rh), pinacol (1.0 mmol, if added), EtOH (1.0 mL), 50 °C,
b
1
18 h. Conversion of 1a, determined by H NMR analysis of the
crude reaction mixture with 1,1,2,2-tetrachloroethane (0.20 mmol) as
c
1
the internal standard. Yield of 2a based on the crude H NMR with
1,1,2,2-tetrachloroethane (0.20 mmol) as the internal standard.
Isolated yield is shown in parentheses.
a
b
iPrOH instead of EtOH. Et3N (0.30 mmol) was added.
c
d
[Rh(OH)(cod)]2 (10.0 μmol) was used. B2(OH)4 (0.80 mmol)
e
was used. General conditions: aryl boronate ester (0.20 mmol),
coordinated rhodium(I) chloride as the catalyst, the desired
cyclohexylboronic acid pinacol ester 2a was obtained using
tetrahydroxydiboron as the reducing reagent in ethanol, and
the conversion was higher by using the hydroxorhodium
catalyst (Table 1, entries 1 and 2). In contrast to the high
conversion of 1a in these two reactions, the yield of 2a was
low. Given that other arylboronic esters undergo trans-
metalation with rhodium catalyst much easier than the
corresponding pinacol ester17 and no side product was
B2(OH)4 (0.90 mmol), [Rh(OH)(cod)]2 (5.0 μmol), pinacol (1.0
mmol), EtOH (1.0 mL), 50 °C, 18 h. Conversion and NMR yields are
given (1,1,2,2-tetrachloroethane as the internal standard), and isolated
yields are shown in parentheses.
range of arylboronic acid pinacol esters bearing diverse
substitutions (2b−2g) and substitutions at different positions
(2h−2i) were all tolerated, giving the cis products as the major
isomer. When the naphthyl substrates were employed, the
unsubstituted ring was preferentially hydrogenated (semi:full
>20:1) to give the tetrahydro-naphthylboronic acid pinacol
esters (2j−2k) in high yields, and no fully hydrogenated
product was observed. Note that the lower isolated yields of
some products than NMR yields were mainly due to their
instability on the silica gel column.
1
detected by H NMR analysis of the crude reaction mixture,
we reasoned that solvolysis of 1a/2a with EtOH followed by
rhodium-catalyzed protodeboronation can be the possible side
reaction to give volatile side products. Additional pinacol was
then added to minimize the possible solvolysis of substrate/
product, and gratifyingly the isolated yield of 2a was improved
to 74% (entry 3). Rhodium phosphine complexes, including
1911
https://dx.doi.org/10.1021/acs.orglett.1c00341
Org. Lett. 2021, 23, 1910−1914

Organic Letters
pubs.acs.org/OrgLett
Letter
g
Scheme 3. Transfer Hydrogenation of Diverse Arenes
a
b
c
The corresponding ketone was used as substrate. Determined by 19F NMR of the reaction mixture; no side product was detected. B2(OH)4
d
e
f
g
(0.60 mmol) was used. [Rh(OH)(cod)]2 (10.0 μmol) was used. B2(OH)4 (1.60 mmol) was used. B2(OH)4 (1.80 mmol) was used. General
conditions: 3 (0.20 mmol), B2(OH)4 (0.90 mmol), [Rh(OH)(cod)]2 (5.0 μmol), EtOH (1.0 mL), 50 °C, 18 h. Conversion and NMR yields are
given (1,1,2,2-tetrachloroethane as the internal standard), and isolated yields are shown in parentheses.
The general applicability of the developed method was
further demonstrated by selective hydrogenation of diverse
functionalized arenes (Scheme 3). Benzenes bearing different
functionalities, including carboxylic acid (4a), ester (4b),
amide (4c−4d), alkyl chain with functional groups (4e−4g),
trifluoromethyl group (4h), amino acid moiety (4i), amino
group (4j), and phosphonate (4k), were all efficiently reduced
to the corresponding cyclohexanes, with functional groups
unperturbed. The current method showed moderate to good
selectivities for partial reduction of polyaromatic hydrocarbons
and biphenyls. For example, the functionalized naphthalenes
were selectively reduced on the less hindered ring (5a−5c)18
and 1,2,3,4,5,6,7,8-octahydroanthracene was obtained by
hydrogenation of anthracene (5d). Unusual chemoselectivity
1912
https://dx.doi.org/10.1021/acs.orglett.1c00341
Org. Lett. 2021, 23, 1910−1914

Organic Letters
pubs.acs.org/OrgLett
Letter
was observed in the case of 1-substituted isoquinoline, and
selective reduction of the fused benzene ring over pyridine ring
was observed (5e−5f). When biphenyl substrates were
employed, the phenyl ring with less substitution group was
preferentially reduced (5g−5i), and this semihydrogenation
provides a convenient route to prepare the key intermediate for
synthesizing the FDA approved new drug siponimod.19 One
important advantage of transfer hydrogenation is the easily
tunable amount of added reductant, which might be used to
control the degree of reduction. In this study, we achieved the
controllable hydrogenation of unbiased arenes in a substrate.
Products from semi- or full reduction of the unbiased
naphthalene ring in BINOL (5j and 5k) and unbiased phenyl
ring in 3,3′-Ph-SPINOL20 (5l and 5m) were attainable by
adjusting the amount of diboron reagent.
Although further investigation is required to fully understand
the reaction mechanism, successive homogeneous rhodium
catalysis for hydrogen generation−heterogeneous rhodium
catalysis for hydrogenation was considered as a working
model on the basis of our previous study15 and literature
reports21 (see Scheme S1 in the SI). Homogeneous rhodium
catalysis led to the fast generation of hydrogen gas from
diboron and ethanol (see Figure S1 in the SI), and the
rhodium catalyst was then reduced to heterogeneous rhodium
particles (see Figure S2 in the SI). The heterogeneous rhodium
catalyst catalyzed the hydrogenation of arenes with the
generated hydrogen gas.21
Complete contact information is available at:
https://pubs.acs.org/10.1021/acs.orglett.1c00341
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
We thank the Natural Science Foundation of Jiangsu Province
(BK20200080) and the “Double First-Class” University project
of China Pharmaceutical University (CPU2018GY35) for
financial support.
REFERENCES
■
(1) (a) de Vries, J. G.; Elsevier, C. J. The Handbook of Homogeneous
Hydrogenation; Wiley−VCH: Weinheim, 2007. (b) Nishimura, S.
Heterogeneous Catalytic Hydrogenation for Organic Synthesis; John
Wiley & Sons: New York, 2001.
(2) For reviews, see: (a) Wiesenfeldt, M. P.; Nairoukh, Z.; Dalton,
T.; Glorius, F. Selective Arene Hydrogenation for Direct Access to
Saturated Carbo- and Heterocycles. Angew. Chem., Int. Ed. 2019, 58,
10460−10476. (b) Wertjes, W. C.; Southgate, E. H.; Sarlah, D.
Recent Advances in Chemical Dearomatization of Nonactivated
Arenes. Chem. Soc. Rev. 2018, 47, 7996−8017. (c) Giustra, Z. X.;
Ishibashi, J. S. A.; Liu, S.-Y. Homogeneous Metal Catalysis for
Conversion between Aromatic and Saturated Compounds. Coord.
Chem. Rev. 2016, 314, 134−181. (d) Wang, D.-S.; Chen, Q.-A.; Lu,
S.-M.; Zhou, Y.-G. Asymmetric Hydrogenation of Heteroarenes and
Arenes. Chem. Rev. 2012, 112, 2557−2590.
In summary, we have reported a new strategy for selective
hydrogenation of functionalized arenes by diboron-mediated
rhodium-catalyzed transfer hydrogenation. This protocol
showed broad substrate scope, good functional group
tolerance, and controllable chemoselectivity. Given the opera-
tional simplicity of the method, as well as commercial
availability of the catalyst and diboron reagent, it shall provide
a practically useful tool for laboratory synthesis. Further studies
on the detailed mechanism of this rhodium-catalyzed transfer
hydrogenation are currently ongoing in our laboratory.
(3) The resonance stabilization energy of benzene is 36 kcal/mol.
Wheland, G. W. Resonance in Organic Chemistry; Wiley: New York,
1955; p 98.
(4) (a) Moos, G.; Emondts, M.; Bordet, A.; Leitner, W. Selective
Hydrogenation and Hydrodeoxygenation of Aromatic Ketones to
Cyclohexane Derivatives Using a Rh@SILP Catalyst. Angew. Chem.,
Int. Ed. 2020, 59, 11977−11983. (b) Joannou, M. W.; Bezdek, M. J.;
Chirik, P. J. Pyridine(diimine) Molybdenum-Catalyzed Hydro-
genation of Arenes and Hindered Olefins: Insights into Precatalyst
Activation and Deactivation Pathways. ACS Catal. 2018, 8, 5276−
5285. (c) Yan, Z.; Xie, H.-P.; Shen, H.-Q.; Zhou, Y.-G. Ruthenium-
Catalyzed Hydrogenation of Carbocyclic Aromatic Amines: Access to
Chiral Exocyclic Amines. Org. Lett. 2018, 20, 1094−1097. (d) Stalzer,
M. M.; Nicholas, C. P.; Bhattacharyya, A.; Motta, A.; Delferro, M.;
Marks, T. J. Single-Face/All-cis Arene Hydrogenation by a Supported
Single-Site d0 Organozirconium Catalyst. Angew. Chem., Int. Ed. 2016,
55, 5263−5267. (e) Cui, X.; Surkus, A.-E.; Junge, K.; Topf, C.;
Radnik, J.; Kreyenschulte, C.; Beller, M. Highly Selective Hydro-
genation of Arenes Using Nanostructured Ruthenium Catalysts
Modified with a Carbon-nitrogen Matrix. Nat. Commun. 2016, 7,
11326−11333. (f) Mahdi, T.; Heiden, Z. M.; Grimme, S.; Stephan, D.
W. Metal-Free Aromatic Hydrogenation: Aniline to Cyclohexyl-amine
Derivatives. J. Am. Chem. Soc. 2012, 134, 4088−4091. (g) Kuwano,
R.; Morioka, R.; Kashiwabara, M.; Kameyama, N. Catalytic
Asymmetric Hydrogenation of Naphthalenes. Angew. Chem., Int. Ed.
2012, 51, 4136−4139.
(5) Wei, Y.; Rao, B.; Cong, X.; Zeng, X. Highly Selective
Hydrogenation of Aromatic Ketones and Phenols Enabled by Cyclic
(Amino)(alkyl)carbene Rhodium Complexes. J. Am. Chem. Soc. 2015,
137, 9250−9253.
(6) (a) Wiesenfeldt, M. P.; Nairoukh, Z.; Li, W.; Glorius, F.
Hydrogenation of Fluoroarenes: Direct Access to All-cis-(multi)
Fluorinated Cycloalkanes. Science 2017, 357, 908−912. (b) Nairoukh,
Z.; Wollenburg, M.; Schlepphorst, C.; Bergander, K.; Glorius, F. The
Formation of All-cis-(multi)fluorinated Piperidines by a Dearomatiza-
tion-Hydrogenation Process. Nat. Chem. 2019, 11, 264−270.
(7) Wiesenfeldt, M. P.; Knecht, T.; Schlepphorst, C.; Glorius, F.
Silylarene Hydrogenation: A Strategic Approach that Enables Direct
ASSOCIATED CONTENT
* Supporting Information
■
sı
The Supporting Information is available free of charge at
https://pubs.acs.org/doi/10.1021/acs.orglett.1c00341.
Experimental procedures, characterization data, and
1
copies of H and 13C NMR spectra (PDF)
AUTHOR INFORMATION
■
Corresponding Author
Xiaowei Dou − Department of Chemistry, School of Science,
China Pharmaceutical University, Nanjing 211198, China;
orcid.org/0000-0002-0748-1279; Email: dxw@
cpu.edu.cn
Authors
Yuhan Wang − Department of Chemistry, School of Science,
China Pharmaceutical University, Nanjing 211198, China
Zhiqian Chang − Department of Chemistry, School of Science,
China Pharmaceutical University, Nanjing 211198, China
Yan Hu − Department of Chemistry, School of Science, China
Pharmaceutical University, Nanjing 211198, China
Xiao Lin − Department of Chemistry, School of Science, China
Pharmaceutical University, Nanjing 211198, China
1913
https://dx.doi.org/10.1021/acs.orglett.1c00341
Org. Lett. 2021, 23, 1910−1914

Organic Letters
pubs.acs.org/OrgLett
Letter
Access to Versatile Silylated Saturated Carbo- and Heterocycles.
Angew. Chem., Int. Ed. 2018, 57, 8297−8300.
(8) (a) Zhang, X.; Ling, L.; Luo, M.; Zeng, X. Accessing
Difluoromethylated and Trifluoromethylated cis-Cycloalkanes and
Saturated Heterocycles: Preferential Hydrogen Addition to the
Substitution Sites for Dearomatization. Angew. Chem., Int. Ed. 2019,
(15) Lin, X.; Wang, Y.; Hu, Y.; Zhu, W.; Dou, X. Diboron-Mediated
Rhodium-Catalysed Transfer Hydrogenation of Alkenes and Carbon-
yls. Eur. J. Org. Chem. 2020, 2020, 1046−1049.
(16) Gelis, C.; Heusler, A.; Nairoukh, Z.; Glorius, F. Catalytic
Transfer Hydrogenation of Arenes and Heteroarenes. Chem. - Eur. J.
2020, 26, 14090−14094.
(17) (a) Partyka, D. V. Transmetalation of Unsaturated Carbon
Nucleophiles from Boron-Containing Species to the Mild to Late d-
Block Metals of Relevance to Catalytic C−X Coupling Reactions (X =
C, F, N, O, Pb, S, Se, Te). Chem. Rev. 2011, 111, 1529−1595.
(b) Tian, P.; Dong, H.-Q.; Lin, G.-Q. Rhodium-Catalyzed
Asymmetric Arylation. ACS Catal. 2012, 2, 95−119.
(18) He, Y.; Tang, J.; Luo, M.; Zeng, X. Regioselective and
Chemoselective Reduction of Naphthols Using Hydrosilane in
Methanol: Synthesis of the 5,6,7,8-Tetrahydronaphthol Core. Org.
Lett. 2018, 20, 4159−4163.
(19) Pan, S.; Gray, N. S.; Gao, W.; Mi, Y.; Fan, Y.; Wang, X.;
Tuntland, T.; Che, J.; Lefebvre, S.; Chen, Y.; Chu, A.; Hinterding, K.;
Gardin, A.; End, P.; Heining, P.; Bruns, C.; Cooke, N. G.; Nuesslein-
Hildesheim, B. Discovery of BAF312 (Siponimod), a Potent and
Selective S1P Receptor Modulator. ACS Med. Chem. Lett. 2013, 4,
333−337.
(20) Yin, L.; Xing, J.; Wang, Y.; Shen, Y.; Lu, T.; Hayashi, T.; Dou,
X. Enantioselective Synthesis of 3,3′-Diaryl-SPINOLs: Rhodium-
Catalyzed Asymmetric Arylation/BF3-Promoted Spirocyclization
Sequence. Angew. Chem., Int. Ed. 2019, 58, 2474−2478.
̈
tt, A.; Roschenthaler, G.-V.; Lebl,
̈
58, 16785−16789. (b) Yu, C.; Ku
T.; Cordes, D. B.; Slawin, A. M. Z.; Bu
̈
hl, M.; O’Hagan, D. Janus Face
All-cis 1,2,4,5-tetrakis(trifluoromethyl)- and All-cis 1,2,3,4,5,6-hexakis-
(trifluoromethyl)- Cyclohexanes. Angew. Chem., Int. Ed. 2020, 59,
19905−19909.
(9) (a) Wollenburg, M.; Moock, D.; Glorius, F. Hydrogenation of
Borylated Arenes. Angew. Chem., Int. Ed. 2019, 58, 6549−6553.
(b) Ling, L.; He, Y.; Zhang, X.; Luo, M.; Zeng, X. Hydrogenation of
(Hetero)aryl Boronate Esters with a Cyclic (Alkyl)(amino)carbene−
Rhodium Complex: Direct Access to cis-Substituted Borylated
Cycloalkanes and Saturated Heterocycles. Angew. Chem., Int. Ed.
2019, 58, 6554−6558.
(10) Wollenburg, M.; Heusler, A.; Bergander, K.; Glorius, F. trans-
Selective and Switchable Arene Hydrogenation of Phenol Derivatives.
ACS Catal. 2020, 10, 11365−11370.
(11) Wang, D.; Astruc, D. The Golden Age of Transfer
Hydrogenation. Chem. Rev. 2015, 115, 6621−6686.
(12) For a review, see: (a) Kim, A. N.; Stoltz, B. M. Recent
Advances in Homogeneous Catalysts for the Asymmetric Hydro-
genation of Heteroarenes. ACS Catal. 2020, 10, 13834−13851. For
selected examples, see: (b) Chen, F.; Sahoo, B.; Kreyenschulte, C.;
Lund, H.; Zeng, M.; He, L.; Junge, K.; Beller, M. Selective Cobalt
Nanoparticles for Catalytic Transfer Hydrogenation of N-Hetero-
arenes. Chem. Sci. 2017, 8, 6239−4246. (c) Wang, Y.; Huang, Z.;
Leng, X.; Zhu, H.; Liu, G.; Huang, Z. Transfer Hydrogenation of
Alkenes Using Ethanol Catalyzed by a NCP Pincer Iridium Complex:
Scope and Mechanism. J. Am. Chem. Soc. 2018, 140, 4417−4429.
(d) Li, S.; Meng, W.; Du, H. Asymmetric Transfer Hydrogenations of
2,3-Disubstituted Quinoxalines with Ammonia Borane. Org. Lett.
2017, 19, 2604−2606. (e) Zhou, Q.; Zhang, L.; Meng, W.; Feng, X.;
Yang, J.; Du, H. Borane-Catalyzed Transfer Hydrogenations of
Pyridines with Ammonia Borane. Org. Lett. 2016, 18, 5189−5191.
(f) Tao, L.; Zhang, Q.; Li, S.-S.; Liu, X.; Liu, Y.-M.; Cao, Y.
Heterogeneous Gold-Catalyzed Selective Reductive Transformation
of Quinolines with Formic Acid. Adv. Synth. Catal. 2015, 357, 753−
760.
(13) (a) Sawama, Y.; Ban, K.; Akutsu-Suyama, K.; Nakata, H.; Mori,
M.; Yamada, T.; Kawajiri, T.; Yasukawa, N.; Park, K.; Monguchi, Y.;
Takagi, Y.; Yoshimura, M.; Sajiki, H. Birch-Type Reduction of Arenes
in 2-Propanol Catalyzed by Zero-Valent Iron and Platinum on
Carbon. ACS Omega 2019, 4, 11522−11531. (b) Sawama, Y.; Mori,
M.; Yamada, T.; Monguchi, Y.; Sajiki, H. Hydrogen Self-Sufficient
Arene Reduction to Cyclohexane Derivatives Using a Combination of
Platinum on Carbon and 2-Propanol. Adv. Synth. Catal. 2015, 357,
3667−3670.
(14) (a) Cummings, S. P.; Le, T.-N.; Fernandez, G. E.; Quiambao,
L. G.; Stokes, B. J. Tetrahydroxydiboron-Mediated Palladium-
Catalyzed Transfer Hydrogenation and Deuteriation of Alkenes and
Alkynes Using Water as the Stoichiometric H or D Atom Donor. J.
Am. Chem. Soc. 2016, 138, 6107−6110. (b) Xuan, Q.; Song, Q.
Diboron-Assisted Palladium-Catalyzed Transfer Hydrogenation of N-
Heteroaromatics with Water as Hydrogen Donor and Solvent. Org.
Lett. 2016, 18, 4250−4253. (c) Ojha, D. P.; Gadde, K.; Prabhu, K. R.
Generation of Hydrogen from Water: A Pd-Catalyzed Reduction of
Water Using Diboron Reagent at Ambient Conditions. Org. Lett.
2016, 18, 5062−5065. (d) Flinker, M.; Yin, H.; Juhl, R. W.; Eikeland,
E. Z.; Overgaard, J.; Nielsen, D. U.; Skrydstrup, T. Efficient Water
Reduction with sp3-sp3 Diboron(4) Compounds: Application to
Hydrogenations, H-D Exchange Reactions, and Carbonyl Reductions.
Angew. Chem., Int. Ed. 2017, 56, 15910−15915. (e) Han, X.; Hu, J.;
Chen, C.; Yuan, Y.; Shi, Z. Copper-Catalysed, Diboron-Mediated cis-
Dideuterated Semihydrogenation of Alkynes with Heavy Water.
Chem. Commun. 2019, 55, 6922−6925.
(21) (a) Miyamura, H.; Suzuki, A.; Yasukawa, T.; Kobayashi, S.
Polysilane-Immobilized Rh-Pt Bimetallic Nanoparticles as Powerful
Arene Hydrogenation Catalysts: Synthesis, Reactions under Batch and
Flow Conditions and Reaction Mechanism. J. Am. Chem. Soc. 2018,
140, 11325−11334. (b) Bayram, E.; Linehan, J. C.; Fulton, J. L.;
̈
Roberts, J. A. S.; Szymczak, N. K.; Smurthwaite, T. D.; Ozkar, S.;
Balasubramanian, M.; Finke, R. G. Is It Homogeneous or
Heterogeneous Catalysis Derived from [RhCp*Cl2]2? In Operando
XAFS, Kinetic, and Crucial Kinetic Poisoning Evidence for
Subnanometer Rh4 Cluster-Based Benzene Hydrogenation Catalysis.
J. Am. Chem. Soc. 2011, 133, 18889−18902. (c) Tran, B. L.; Fulton, J.
L.; Linehan, J. C.; Lercher, J. A.; Bullock, R. M. Rh(CAAC)-Catalyzed
Arene Hydrogenation: Evidence for Nanocatalysis and Sterically
Controlled Site-Selective Hydrogenation. ACS Catal. 2018, 8, 8441−
8449. (d) Tran, B. L.; Fulton, J. L.; Linehan, J. C.; Balasubramanian,
M.; Lercher, J. A.; Bullock, R. M. Operando XAFS Studies on
Rh(CAAC)-Catalyzed Arene Hydrogenation. ACS Catal. 2019, 9,
4106−4114. (e) Kim, S.; Loose, F.; Bezdek, M. J.; Wang, X.; Chirik,
P. J. Hydrogenation of N-Heteroarenes Using Rhodium Precatalysts:
Reductive Elimination Leads to Formation of Multimetallic Clusters.
J. Am. Chem. Soc. 2019, 141, 17900−17908. (f) Moock, D.;
Wiesenfeldt, M. P.; Freitag, M.; Muratsugu, S.; Ikemoto, S.;
̈
Knitsch, R.; Schneidewind, J.; Baumann, W.; Schafer, A. H.;
Timmer, A.; Tada, M.; Hansen, M. R.; Glorius, F. Mechanistic
Understanding of the Heterogeneous, Rhodium-Cyclic (Alkyl)-
(Amino)Carbene-Catalyzed (Fluoro-)Arene Hydrogenation. ACS
Catal. 2020, 10, 6309−6317.
1914
https://dx.doi.org/10.1021/acs.orglett.1c00341
Org. Lett. 2021, 23, 1910−1914