Methanol as the Hydrogen Source in the Selective Transfer Hydrogenation of Alkynes Enabled by a Manganese Pincer Complex

Article abstract of DOI:10.1021/acs.orglett.0c02151

The first base metal-catalyzed transfer hydrogenation of alkynes with methanol is described. An air and moisture stable manganese pincer complex catalyzes the reduction of a variety of different alkynes to the corresponding (Z)-olefins in high yields. The

Full text of DOI:10.1021/acs.orglett.0c02151

pubs.acs.org/OrgLett
Letter
Methanol as the Hydrogen Source in the Selective Transfer
Hydrogenation of Alkynes Enabled by a Manganese Pincer Complex
Jan Sklyaruk, Viktoriia Zubar, Jannik C. Borghs, and Magnus Rueping*
Cite This: https://dx.doi.org/10.1021/acs.orglett.0c02151
Read Online
sı
*
Metrics & More
Article Recommendations
Supporting Information
ACCESS
ABSTRACT: The first base metal-catalyzed transfer hydro-
genation of alkynes with methanol is described. An air and
moisture stable manganese pincer complex catalyzes the reduction
of a variety of different alkynes to the corresponding (Z)-olefins in
high yields. The reaction is stereo- and chemoselective and
scalable.
lefins play an important role in bioactive molecules,
“methanol economy”, methanol is considered as a promising
hydrogen storage material, which can also be directly used as
an alternative fuel for internal combustion and other engines,
either in combination with gasoline or neat and in methanol
fuel cells.8 In the case of methanol, the dehydrogenation step is
more energy demanding than for other alcohols.9 Hence, it is
challenging to develop catalysts that are active for both the
dehydrogenation step of methanol and the semihydrogenation
of unsaturated triple bonds to selectively form (Z)-olefins. This
research field is so far rather underdeveloped, and to the best
of our knowledge, no general studies of the base metal-
catalyzed highly selective semihydrogenation of alkynes toward
the formation of (Z)-olefins using methanol as a hydrogen
source have been published.
O
pharmaceuticals, polymers, and functional materials.1,2
Furthermore, olefins can be functionalized into a vast variety of
different compounds.3 A common method for the synthesis of
(Z)-olefins is the semihydrogenation of alkynes using the Pd-
based Lindlar catalyst and hydrogen gas (Scheme 1A).4 In
Scheme 1. Different Methods for the (Transfer)
Hydrogenation of Alkynes
Recently, the field of manganese pincer-catalyzed (de-)
hydrogenation reactions has received a great deal of
attention.9,10 Various publications described the manganese
complex-catalyzed activation and synthetic utilization of
methanol, whereby methanol was mainly applied as a
methylating reagent.11 However, recently reported manga-
nese-catalyzed hydrogen borrowing and transfer hydrogenation
catalysis11,12 indicated that manganese pincer complexes may
be suitable for the activation of methanol in the semitransfer
hydrogenation of alkynes (Scheme 1C).
Thus, we evaluated different manganese complexes Mn-1−
Mn-5 as catalysts in the transfer hydrogenation of 1-methoxy-
4-(phenylethynyl)benzene (1a) (Table 1, entries 1−5,
respectively). Surprisingly, complex Mn-1, which is known to
be active in the alkylation of ketones and nitriles,12a,v gave a
addition, several cis-selective hydrogenation methods that
mainly rely on the use of noble metals have been developed.5
To avoid the use of pressurized hydrogen gas, transfer
hydrogenation methods that apply hydrogen donors, such as
ammonia formates,6a formic acid,6b,c silanes,6d and boranes,6e
evolved as alternatives. However, these methods may have
disadvantages due to functional group tolerance, their relatively
high prices, and significant byproduct formation (Scheme 1B).
In this regard, alcohols, especially methanol, are highly
desirable as hydrogen donors.7 Methanol is a very attractive
hydrogen source, is produced on a large scale, and is one of the
most important C1 building blocks for the production of bulk
and fine chemicals. The possibility of producing methanol
from the greenhouse gas carbon dioxide highlights the
sustainability of this hydrogen donor. In the proposed
Received: June 29, 2020
https://dx.doi.org/10.1021/acs.orglett.0c02151
© XXXX American Chemical Society
Org. Lett. XXXX, XXX, XXX−XXX
A

Organic Letters
pubs.acs.org/OrgLett
Letter
a
base and cosolvent screening is summarized in the Supporting
Information.
Table 1. Optimization of the Reaction Conditions
Increasing the reaction temperature provided an almost
quantitative yield of 97% with (Z)-product 2a formed
predominantly (Table 1, entry 11). Control experiments
proved the efficiency of the chosen catalytic system (Table
1, entries 14−17). When other alcohols such as ethanol and
isopropanol were used as hydrogen sources, quantitative yields
were also obtained (see the Supporting Information). Addi-
tionally, no impact was observed when a drop of mercury was
added to the reaction mixture, which suggests the homoge-
neous nature of the catalyst under these reaction conditions.14
After the kinetic profile of the reaction had been measured
(see the Supporting Information), the reaction time was set to
14 h. In the further course of the work, we applied the
optimized reaction conditions (Table 1, entry 11) in the
transfer hydrogenation of various internal alkynes (Scheme 2).
Unfortunately, terminal alkynes proved to be inactive in the
transfer hydrogenation reaction.
Generally, the alkyne derivatives 1a−1x were reduced to the
corresponding olefins 2a−2x with high selectivity in moderate
to quantitative yields. Stilbene 2a was isolated in a very good
yield of 88% with a Z/E ratio of 98/2. In the further course of
the evaluation of scope, both electron-donating (2b−2g and
2n) and electron-withdrawing substituents (2j−2m) were
tolerated in ortho, meta, and para positions of the aromatic
moiety of the alkynes. Various heterocycle-containing alkynes
(1o and 1q−1u) were tolerated in the transformation. Also,
the longer chain internal olefins 2v and 2w were isolated in
high yields with good selectivity. It is important to note that for
substrates such as 1h, 1j, 1l, 1w, and 1x some over-
hydrogenation into the corresponding diarylethanes was
observed. To present the generality of the transformation, we
applied our catalytic system in a gram scale synthesis of (Z)-
stilbene (2b) (Scheme 3). The desired product 2b was
obtained in quantitative yield with an excellent Z/E ratio of
97/3. When (Z)- or (E)-stilbenes 2b were used, no
isomerization or hydrogenation occurred (see the Supporting
Information).
b
entry
catalyst (mol %)
base (equiv)
yield (%)
Z/E
1
2
3
4
5
Mn-1 (2)
Mn-2 (2)
Mn-3 (2)
Mn-4 (2)
Mn-5 (2)
Mn-1 (2)
Mn-1 (4)
Mn-1 (2)
Mn-1 (2)
Mn-1 (2)
Mn-1 (2)
Mn-1 (2)
Mn-1 (1)
Mn(CO)5Br (5)
Mn-1 (2)
L-1 (5)
2
2
2
2
2
2
2
4
2
2
2
1
2
2
−
3
2
49
−
3
−
−
60
83
27
92
91
97
16
39
−
98/2
−
−
−
−
98/2
98/2
98/2
98/2
98/2
98/2
98/2
98/2
−
c
6
7
8
9
d
e
10
d
11
d
12
d
13
c
14
15
16
17
−
−
−
−
−
−
−
a
Reaction conditions: 1a (0.1 mmol), [Mn], Cs2CO3, methanol (0.1
mL), 14 h, 135 °C for entries 1−10 and 150 °C for entries 11−17.
b
Yields were determined by 1H NMR spectroscopy using acetonitrile
as the internal standard. Heating inside an aluminum block.
Methanol (0.2 mL). Toluene as the cosolvent (0.1 mL). Methanol
c
d
e
(0.2 mL) and toluene (0.2 mL).
yield of 49%, forming almost exclusively the corresponding Z-
isomer 2a (Table 1, entry 1).
Next, we used fully deuterated methanol CD3OD to
investigate the incorporation position of hydrogen (Scheme 4).
In the olefinic position, the value of deuterium incorporation
reached 94% and this result indicates the possibility of cis-
selective deuterium incorporation. Due to the importance of
deuterium-labeled compounds,15 this transformation might be
evaluated in further work (Scheme 4). Beyond that, we
observed significant H/D exchange in the ortho position next
to the methoxy group of 2a.
On the basis of these observations, we propose the following
catalytic cycle (Scheme 5). In the first step, the air and
moisture stable precursor Mn-1 is activated by a base to give
the active species Mn-1a. Methanol coordinates to the active
species Mn-1a, which is the deprotonated via metal ligand
interactions, forming the manganese methoxide complex Mn-
1b.12d The following deprotonation of the methoxide moiety
results in formaldehyde elimination, so that the hydride species
Mn-1c is obtained. Subsequent alkyne coordination and
insertion into the manganese−hydride bond leads to the
formation of Mn-1d. In the next step, the elimination of (Z)-
stilbene occurs, to regenerate the active Mn-1a catalyst.
However, an alternative pathway starting from Mn-1d is
conceivable in which methanol facilitates elimination of the
(Z)-stilbene and directly provides the Mn-1b intermediate.
On the other hand, the pyridyl-based complex Mn-2,
previously used in the α-methylation of ketones,11i was
shown to be completely inactive in this transformation
(Table 1, entry 2). To evaluate the importance of the
phosphine moiety, we applied the aliphatic phosphine-based
complex Mn-3 in the transformation. Although this complex is
also known to be active in the alkylation of ketones,12a only
trace amounts of product 2a were obtained (Table 1, entry 3).
Also, the bidentate complex Mn-4, which is catalytically
active in ester hydrogenation,13 was inactive in the transfer
hydrogenation reaction (Table 1, entry 4), highlighting the
non-innocent behavior of the pincer backbone. Furthermore,
N-Me-based complex Mn-5 did not give any yield, illustrating
the necessity of the NH functionality (Table 1, entry 5). The
catalyst screening emphasized the importance of the aliphatic
pincer backbone and the significance of aromatic phosphines
in the semitransfer hydrogenation of alkynes. Increasing the
amount of methanol and the amount of catalyst improved the
yield (Table 1, entries 6 and 7).
In contrast, the catalytic activity decreased for a higher base
loading (Table 1, entry 8). Moreover, the utilization of toluene
as a cosolvent increased the yield significantly (Table 1, entry
9), while decreasing the concentration of the reaction system
did not improve the yield (Table 1, entry 10). More detailed
B
https://dx.doi.org/10.1021/acs.orglett.0c02151
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
pubs.acs.org/OrgLett
Letter
Scheme 2. Manganese-Catalyzed Transfer Hydrogenation of
Alkynes
Scheme 4. Deuterium Labeling Using CD3OD in the
Transfer Deuteration of Alkynes
a
Scheme 5. Proposed Catalytic Cycle for the Manganese-
Catalyzed Transfer Hydrogenation of Alkynes with
Methanol
Alternatively, Mn-1a can also be directly converted to Mn-1c
via a six-membered transition state.12e
a
Reaction conditions: 1 (0.3 mmol), Cs2CO3 (0.6 mmol), Mn-1 (2
In conclusion, we developed the first base metal-catalyzed
semitransfer hydrogenation of alkynes, using methanol as a
hydrogen donor. The applicability of this transformation was
demonstrated for a variety of different alkynes, giving the
corresponding (Z)-olefins in moderate to quantitative yields
and high chemoselectivity. The reaction is scalable, and
deuterium labeling experiments demonstrate the cis-selective
hydrogen incorporation.
b
mol %) in CH3OH (0.3 mL) and toluene (0.3 mL) at 150 °C. At
c
130 °C. Mn-1 (4 mol %). The overhydrogenation product is
presented in parentheses. Heating inside an aluminum block.
Scheme 3. Gram Scale Synthesis of (Z)-Stilbene (2b)
ASSOCIATED CONTENT
* Supporting Information
■
sı
The Supporting Information is available free of charge at
https://pubs.acs.org/doi/10.1021/acs.orglett.0c02151.
C
https://dx.doi.org/10.1021/acs.orglett.0c02151
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
pubs.acs.org/OrgLett
Letter
Jacobi von Wangelin, A. Chem. Commun. 2014, 50, 2261−2264.
(g) Fiorio, J. L.; Goncalves, R. V.; Teixeira-Neto, E.; Ortuno, M. A.;
Lopez, N.; Rossi, L. M. ACS Catal. 2018, 8, 3516−3524. (h) Reina,
A.; Favier, I.; Pradel, C.; Gomez, M. Adv. Synth. Catal. 2018, 360,
3544−3552.
Experimental procedures and characterization of com-
pounds (PDF)
AUTHOR INFORMATION
Corresponding Author
■
́
(6) (a) Cortese, N. A.; Heck, R. F. J. Org. Chem. 1978, 43, 3985−
3987. (b) Shen, R.; Chen, T.; Zhao, Y.; Qiu, R.; Zhou, Y.; Yin, S.;
Wang, X.; Goto, M.; Han, L. J. Am. Chem. Soc. 2011, 133, 17037−
17044. (c) Wang, D.; Astruc, D. Chem. Rev. 2015, 115, 6621−6686.
(d) Trost, B. M.; Braslau, R. Tetrahedron Lett. 1989, 30, 4657−4660.
(e) Kijima, M.; Nambu, Y.; Endo, T. Chem. Lett. 1985, 14, 1851−
1854.
Magnus Rueping − KAUST Catalysis Center (KCC), King
Abdullah University of Science and Technology (KAUST),
Thuwal 23955-6900, Saudi Arabia; orcid.org/0000-0003-
4580-5227; Email: magnus.rueping@kaust.edu.sa
Authors
(7) Examples, which use alcohols as a hydrogen source. Use of
isopropanol: (a) Djukic, J. P.; Parkhomenko, K.; Hijazi, A.; Chemmi,
A.; Allouche, L.; Brelot, L.; Pfeffer, M.; Ricard, L.; Le Goff, X. F. J.
Chem. Soc. Dalt. Trans. 2009, 2695−2711. (b) Belger, C.; Neisius, N.
M.; Plietker, B. Chem. - Eur. J. 2010, 16, 12214−12220. (c) Horn, S.;
Albrecht, M. Chem. Commun. 2011, 47, 8802−8804. (d) Kamitani,
M.; Nishiguchi, Y.; Tada, R.; Itazaki, M.; Nakazawa, H. Organo-
metallics 2014, 33, 1532−1535. (e) Payra, S.; Saha, A.; Banerjee, S.
RSC Adv. 2016, 6, 52495−52499. (f) Alshakova, I. D.; Gabidullin, B.;
Nikonov, G. I. ChemCatChem 2018, 10, 4874−4883. Use of glucose:
(g) Manna, S.; Antonchick, A. P. ChemSusChem 2019, 12, 3094−
3098. Use of ethanol: (h) Alonso, F.; Osante, I.; Yus, M. Adv. Synth.
Catal. 2006, 348, 305−308. Use of methanol: (i) Tani, K.; Iseki, A.;
Yamagata, T. Chem. Commun. 1999, 1821−1822. Use of ethanol for
the transfer hydrogenation of ylides: (j) Siva Reddy, A.; Kumara
Swamy, K. C. Angew. Chem. 2017, 129, 7088−7092.
Jan Sklyaruk − Institute of Organic Chemistry, RWTH Aachen
University, 52074 Aachen, Germany
Viktoriia Zubar − Institute of Organic Chemistry, RWTH
Aachen University, 52074 Aachen, Germany; KAUST Catalysis
Center (KCC), King Abdullah University of Science and
Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
Jannik C. Borghs − Institute of Organic Chemistry, RWTH
Aachen University, 52074 Aachen, Germany
Complete contact information is available at:
https://pubs.acs.org/10.1021/acs.orglett.0c02151
Notes
The authors declare no competing financial interest.
(8) (a) Olah, G. A. Angew. Chem., Int. Ed. 2005, 44, 2636−2639.
(b) Olah, G. A.; Prakash, G. K. S.; Goeppert, A. J. Am. Chem. Soc.
2011, 133, 12881−12898. (c) Olah, G. A. Angew. Chem., Int. Ed.
2013, 52, 104−107. (d) Asinger, F. Methanol-Chemie-Und Energier-
ohstoff; Springer-Verlag, 1986.
ACKNOWLEDGMENTS
■
J.S. thanks the VCI (Verband der Chemischen Industrie) for
the Chemiefonds-Stipendium. J.C.B. acknowledges the DBU
(Deutsche Bundesstiftung Umwelt) for the doctoral fellowship.
This work was financially supported by the King Abdullah
University of Science and Technology (KAUST), Saudi
Arabia, Office of Sponsored Research (FCC/1/1974).
(9) Crabtree, R. H. Chem. Rev. 2017, 117, 9228−9246.
(10) For reviews, see: (a) Corma, A.; Navas, J.; Sabater, M. J. Chem.
Rev. 2018, 118, 1410−1459. (b) Garbe, M.; Junge, K.; Beller, M. Eur.
J. Org. Chem. 2017, 2017, 4344−4362. (c) Maji, B.; Barman, M.
Synthesis 2017, 49, 3377−3393. (d) Zell, T.; Langer, R. ChemCatCh-
em 2018, 10, 1930−1940. (e) Sordakis, K.; Tang, C.; Vogt, L. K.;
Junge, H.; Dyson, P. J.; Beller, M.; Laurenczy, G. Chem. Rev. 2018,
118, 372−433. (f) Filonenko, G. A.; van Putten, R.; Hensen, E. J. M.;
Pidko, E. A. Chem. Soc. Rev. 2018, 47, 1459−1483. (g) Mukherjee, A.;
Milstein, D. ACS Catal. 2018, 8, 11435−11469. (h) Gorgas, N.;
Kirchner, K. Acc. Chem. Res. 2018, 51, 1558−1569. (i) Kallmeier, F.;
Kempe, R. Angew. Chem., Int. Ed. 2018, 57, 46−60. (j) Reed-Berendt,
B. G.; Polidano, K.; Morrill, L. C. Org. Biomol. Chem. 2019, 17, 1595−
1607. (k) Vogiatzis, K. D.; Polynski, M. V.; Kirkland, J. K.; Townsend,
J.; Hashemi, A.; Liu, C.; Pidko, E. A. Chem. Rev. 2019, 119, 2453−
2523. (l) Irrgang, T.; Kempe, R. Chem. Rev. 2019, 119, 2524−2549.
(m) Liu, W.; Ackermann, L. Manganese-Catalyzed C−H Activation.
REFERENCES
■
(1) (a) Cushman, M.; Nagarathnam, D.; Gopal, D.; Chakraborti, A.
K.; Lin, C. M.; Hamel, E. J. Med. Chem. 1991, 34, 2579−2588.
(b) Sackett, D. L. Pharmacol. Ther. 1993, 59, 163−228. (c) Ohsumi,
K.; Nakagawa, R.; Fukuda, Y.; Hatanaka, T.; Morinaga, Y.; Nihei, Y.;
Ohishi, K.; Suga, Y.; Akiyama, Y.; Tsuji, T. J. Med. Chem. 1998, 41,
3022−3032. (d) Tron, G. C.; Pirali, T.; Sorba, G.; Pagliai, F.; Busacca,
S.; Genazzani, A. A. J. Med. Chem. 2006, 49, 3033−3044. (e) Baur, J.
A.; Sinclair, D. A. Nat. Rev. Drug Discovery 2006, 5, 493−506.
(2) (a) Cameron, G. G.; Grassie, N. Makromol. Chem. 1962, 51,
130−136. (b) Xu, J. F.; Chen, Y. Z.; Wu, D.; Wu, L. Z.; Tung, C. H.;
Yang, Q. Z. Angew. Chem., Int. Ed. 2013, 52, 9738−9742.
(c) Sakaguchi, T.; Yumoto, K.; Shiotsuki, M.; Sanda, F.; Yoshikawa,
M.; Masuda, T. Macromolecules 2005, 38, 2704−2709. (d) Yamauchi,
K.; Takashima, Y.; Hashidzume, A.; Yamaguchi, H.; Harada, A. J. Am.
Chem. Soc. 2008, 130, 5024−5025. (e) Ikejiri, S.; Takashima, Y.;
Osaki, M.; Yamaguchi, H.; Harada, A. J. Am. Chem. Soc. 2018, 140,
17308−17315.
ACS Catal. 2016, 6, 3743−3752. (n) Li, H.; Gonca
̧ lves, T. P.; Lupp,
D.; Huang, K.-W. ACS Catal. 2019, 9, 1619−1629.
(11) (a) Elangovan, S.; Neumann, J.; Sortais, J.-B.; Junge, K.; Darcel,
C.; Beller, M. Nat. Commun. 2016, 7, 12641. (b) Neumann, J.;
Elangovan, S.; Spannenberg, A.; Junge, K.; Beller, M. Chem. - Eur. J.
2017, 23, 5410−5413. (c) Bruneau-Voisine, A.; Wang, D.; Dorcet, V.;
Roisnel, T.; Darcel, C.; Sortais, J. B. J. Catal. 2017, 347, 57−62.
(3) (a) Lane, B. S.; Burgess, K. Chem. Rev. 2003, 103, 2457−2473.
(b) Yuan, Y. A.; Lu, D. F.; Chen, Y. R.; Xu, H. Angew. Chem., Int. Ed.
2016, 55, 534−538. (c) Chen, J.; Guo, J.; Lu, Z. Chin. J. Chem. 2018,
36, 1075−1109.
́
́
(d) Anderez-Fernandez, M.; Vogt, L. K.; Fischer, S.; Zhou, W.; Jiao,
H.; Garbe, M.; Elangovan, S.; Junge, K.; Junge, H.; Ludwig, R.; Beller,
M. Angew. Chem., Int. Ed. 2017, 56, 559−562. (e) Mastalir, M.;
Pittenauer, E.; Allmaier, G.; Kirchner, K. J. Am. Chem. Soc. 2017, 139,
8812−8815. (f) Natte, K.; Neumann, H.; Beller, M.; Jagadeesh, R. V.
Angew. Chem., Int. Ed. 2017, 56, 6384−6394. (g) Chakraborty, S.;
Gellrich, U.; Diskin-Posner, Y.; Leitus, G.; Avram, L.; Milstein, D.
Angew. Chem., Int. Ed. 2017, 56, 4229−4233. (h) Wei, Z.; de Aguirre,
A.; Junge, K.; Beller, M.; Jiao, H. Catal. Sci. Technol. 2018, 8, 3649−
3665. (i) Sklyaruk, J.; Borghs, J.; El-Sepelgy, O.; Rueping, M. Angew.
Chem., Int. Ed. 2019, 58, 775−779. (j) Bruneau-Voisine, A.; Pallova,
(4) Lindlar, H. Helv. Chim. Acta 1952, 35, 446−450.
(5) (a) Schrock, R. R.; Osborn, J. A. J. J. Am. Chem. Soc. 1976, 98,
2143−2147. (b) Sharma, V. M.; Choudary, M.; Sarma, M. R.; Rao, K.
K. J. Org. Chem. 1989, 54, 2997−2998. (c) van Laren, M. W.; Elsevier,
C. J. Angew. Chem., Int. Ed. 1999, 38, 3715−3717. (d) Chernichenko,
K.; Madarasz, A.; Papai, I.; Nieger, M.; Leskela, M.; Repo, T. Nat.
Chem. 2013, 5, 718−723. (e) Oger, C.; Balas, L.; Durand, T.; Galano,
J.-M. Chem. Rev. 2013, 113, 1313−1350 and references cited herein.
(f) Gieshoff, T. N.; Welther, A.; Kessler, M. T.; Prechtl, M. H. G.;
D
https://dx.doi.org/10.1021/acs.orglett.0c02151
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
pubs.acs.org/OrgLett
Letter
́
L.; Bastin, S.; Cesar, V.; Sortais, J.-B. Chem. Commun. 2019, 55, 314−
317.
́
(12) (a) Pena-Lopez, M.; Piehl, P.; Elangovan, S.; Neumann, H.;
̃
Beller, M. Angew. Chem., Int. Ed. 2016, 55, 14967−14971. (b) Valyaev,
D. A.; Lavigne, G.; Lugan, N. Coord. Chem. Rev. 2016, 308, 191−235.
(c) Docherty, J. H.; Peng, J.; Dominey, A. P.; Thomas, S. P. Nat.
Chem. 2017, 9, 595−600. (d) Fu, S.; Shao, Z.; Wang, Y.; Liu, Q. J.
Am. Chem. Soc. 2017, 139, 11941−11948. (e) Nguyen, D. H.; Trivelli,
X.; Capet, F.; Paul, J.-F.; Dumeignil, F.; Gauvin, R. M. ACS Catal.
2017, 7, 2022−2032. (f) Zhou, Y.; Mo, Z.; Luecke, M.; Driess, M.
Chem. - Eur. J. 2018, 24, 4780−4784. (g) Brzozowska, A.; Azofra, L.
M.; Zubar, V.; Atodiresei, I.; Cavallo, L.; Rueping, M.; El-sepelgy, O.
ACS Catal. 2018, 8, 4103−4109. (h) Chakraborty, S.; Daw, P.; Ben
David, Y.; Milstein, D. ACS Catal. 2018, 8, 10300−10305. (i) Liu, T.;
Wang, L.; Wu, K.; Yu, Z. ACS Catal. 2018, 8, 7201−7207. (j) Yang,
X.; Wang, C. Angew. Chem. 2018, 130, 935−940. (k) Carney, J. R.;
Dillon, B. R.; Campbell, L.; Thomas, S. P. Angew. Chem., Int. Ed.
2018, 57, 10620−10624. (l) Kulkarni, N. V.; Brennessel, W. W.;
Jones, W. D. ACS Catal. 2018, 8, 997−1002. (m) El-sepelgy, O.;
Matador, E.; Brzozowska, A.; Rueping, M. ChemSusChem 2019, 12,
3099−3102. (n) Jang, Y. K.; Kruckel, T.; Rueping, M.; El-Sepelgy, O.
̈
Org. Lett. 2018, 20, 7779−7783. (o) Jana, A.; Reddy, C. B.; Maji, B.
ACS Catal. 2018, 8, 9226−9231. (p) Liu, T.; Wang, L.; Wu, K.; Yu, Z.
ACS Catal. 2018, 8, 7201−7207. (q) Barman, M. K.; Jana, A.; Maji, B.
Adv. Synth. Catal. 2018, 360, 3233−3238. (r) Banerjee, D.; Kabadwal,
L. M.; Das, J. Chem. Commun. 2018, 54, 14069−14072. (s) Borghs, J.
C.; Zubar, V.; Azofra, L. M.; Sklyaruk, J.; Rueping, M. Org. Lett. 2020,
22, 4222−4227. (t) Zubar, V.; Borghs, J.; Rueping, M. Org. Lett. 2020,
22, 3974−3978. (u) Brzozowska, A.; Zubar, V.; Ganardi, R.-C.;
Rueping, M. Org. Lett. 2020, 22, 3765−3769. (v) Borghs, J. C.; Tran,
M. A.; Sklyaruk, J.; Rueping, M.; El-Sepelgy. J. Org. Chem. 2019, 84,
7927−7935. (w) Borghs, J. C.; Azofra, L. M.; Biberger, T.;
Linnenberg, O.; Cavallo, L.; Rueping, M.; El-Sepelgy, O. Chem-
SusChem 2019, 12, 3083−3088. (x) Matador, E.; Brzozowska, A.; El-
Sepelgy, O.; Rueping, M. ChemSusChem 2019, 12, 3099−3102.
(y) Borghs, J. C.; Lebedev, Y.; Rueping, M.; El-Sepelgy, O. Org. Lett.
2019, 21, 70−74. (z) Garbe, M.; Budweg, S.; Papa, V.; Wei, Z.;
Hornke, H.; Bachmann, S.; Scalone, M.; Spannenberg, A.; Jiao, H.;
Junge, K.; Beller, M. Catal. Sci. Technol. 2020, 10, 3994−4001.
(13) Van Putten, R.; Uslamin, E. A.; Garbe, M.; Liu, C.; Gonzalez-
de-Castro, A.; Lutz, M.; Junge, K.; Hensen, E. J. M.; Beller, M.; Lefort,
L.; Pidko, E. A. Angew. Chem., Int. Ed. 2017, 56, 7531−7534.
(14) Chernyshev, V. M.; Astakhov, A. V.; Chikunov, I. E.; Tyurin, R.
V.; Eremin, D. B.; Ranny, G. S.; Khrustalev, V. N.; Ananikov, V. P.
ACS Catal. 2019, 9, 2984−2995.
(15) (a) Gant, T. G. J. Med. Chem. 2014, 57, 3595−3611.
(b) Atzrodt, J.; Derdau, V.; Kerr, W. J.; Reid, M. Angew. Chem., Int.
Ed. 2018, 57, 1758−1784.
E
https://dx.doi.org/10.1021/acs.orglett.0c02151
Org. Lett. XXXX, XXX, XXX−XXX