Manganese-Catalyzed Asymmetric Oxidation of Methylene C-H of Spirocyclic Oxindoles and Dihydroquinolinones with Hydrogen Peroxide

Article abstract of DOI:10.1021/acs.orglett.8b03652

A highly efficient strategy for the enantioselective oxidation of methylene C-H of spirocyclic oxindoles and dihydroquinolinones has been established, in which an earth-abundant manganese catalyst and hydrogen peroxide are used. Noteworthy, the manganese catalyst can be applied to the asymmetric hydroxylation of spirocyclic 2,3-dihydroquinolin-4-ones with 94-99% ee.

Full text of DOI:10.1021/acs.orglett.8b03652

Letter
pubs.acs.org/OrgLett
Cite This: Org. Lett. XXXX, XXX, XXX−XXX
Manganese-Catalyzed Asymmetric Oxidation of Methylene C−H of
Spirocyclic Oxindoles and Dihydroquinolinones with Hydrogen
Peroxide
Bin Qiu,†,‡ Daqian Xu,† Qiangsheng Sun,† Jin Lin,†,‡ and Wei Sun*,†
†State Key Laboratory for Oxo Synthesis and Selective Oxidation, Center for Excellence in Molecular Synthesis, Suzhou Research
Institute of LICP, Lanzhou Institute of Chemical Physics (LICP), Chinese Academy of Sciences, Lanzhou 730000, China
‡University of Chinese Academy of Sciences, Beijing 100049, China
S
* Supporting Information
ABSTRACT: A highly efficient strategy for the enantioselective oxidation of methylene
C−H of spirocyclic oxindoles and dihydroquinolinones has been established, in which an
earth-abundant manganese catalyst and hydrogen peroxide are used. Noteworthy, the
manganese catalyst can be applied to the asymmetric hydroxylation of spirocyclic 2,3-
dihydroquinolin-4-ones with 94−99% ee.
C−H bonds are ubiquitous structural units in readily available
hydrocarbons as well as other organic molecules; thus,
methods for direct transforming of C(sp3)−H bonds into
oxygen-containing compounds (e.g., alcohol, ketone) have
been explored extensively.1 Enantioselective oxidation of
C(sp3)−H bonds that can produce chiral alcohols or ketones
directly, however, has proven to be a long-standing challenging
goal.2 Previous studies focused on the use of chiral metal-
loporphyrins and analogues. For example, the asymmetric
hydroxylation of ethylbenzenes was first demonstrated by
Groves and co-workers in 1989.3 Over the past decades several
further examples with Mn, Ru metalloporphyrins have been
reported. Nevertheless, only moderate enantioselectivities were
observed.4 Alternatively, salen manganese complexes have also
been studied in the asymmetric hydroxylation of benzylic C−H
and oxidation of benzylic methylene group to chiral ketones,
but these methods only provided poor substrate conversions
and low to moderate enantioselectivities.5 Notably, the Bach
group has reported the first example of porphyrin Ru(II)-
catalyzed asymmetric oxidation of spirocyclic oxindoles in
good to excellent enantioselectivities with 2,6-dichloropyridine
N-oxide as a terminal oxidant.6 While this work offers a novel
strategy for enantioselective preparation of valuable spirocyclic
ketones via late-stage oxidation, this method requires further
oxidative treatment with pyridinium chlorochromate (PCC) or
Swern conditions for the oxidation of an intermediate alcohol
to achieve a satisfactory yield. Considering the utility of this
method, the development of a more efficient catalyst would be
especially desirable.
asymmetric oxidation reactions with H2O2 as the terminal
oxidant.9 Very recently, we have reported a manganese catalyst
system that catalyzes the asymmetric oxidation of the benzylic
methylene C−H of spirocyclic compounds with high
enantioselectivity.10 More importantly, Costas and co-workers
elegantly developed an enantioselective oxidation of aliphatic
methylene C−H catalyzed by a similar N4 manganese catalyst
using H2O2 as the oxidant (Scheme 1A).11 Inspired by these
successes, we envisioned that the catalytic system involving
chiral manganese catalyst and H2O2 could be applicable to
enantioselective oxidation of methylene C−H of prochiral
spirocyclic oxindoles and other azaheterocycles (Scheme 1B).
In view of the fact that the enantioselective hydroxylation of
C(sp3)−H remains challenging,12 it would be more attractive
to realize this reaction. Herein, we describe the asymmetric
oxidation of the benzylic methylene C−H of spirocyclic
oxindoles and quinolinones catalyzed by manganese complexes
of N4 ligands, using aqueous H2O2 as the terminal oxidant.
More importantly, this work also realizes the highly
enantioselective hydroxylation of quinolinone precursors (up
to 99% ee) (Scheme 1B).
Initially, the spirocyclic oxindole precursor 1a was chosen as
the model substrate. Our previous studies have demonstrated
that small-molecule manganese complex C1 is effective in
enantioselective oxidation reactions.10,11 Thus, Mn complex
C1 was selected as the catalyst to optimize the reaction
conditions. We were pleased to observe that product 2a was
obtained in 34% yield and 89% ee in the presence of aqueous
H2O2 and 1.0 mol % C1 as the catalyst (Table 1, entry 1).
The past several decades have witnessed the significant
developments of biomimetic oxidation catalysis.7,8 Our group
has been engaging in the development of chiral bioinspired
metal complex (e.g., Mn, Fe, with chiral N4 ligands) catalyzed
Received: November 15, 2018
© XXXX American Chemical Society
A
DOI: 10.1021/acs.orglett.8b03652
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Letter
Scheme 1. Asymmetric Oxidation of Methylene C−H
Catalyzed by N4 Manganese Complex Using H2O2
Table 1. Optimization of Asymmetric Oxidation Using
a
Manganese Catalyst
Mn
cat.
H2O2
(equiv)
acid
additive
conv
(%)
yield (2a)
ee
(%)
b
c
entry
(%)
d
1
C1
C1
C1
C1
C1
C1
C1
C1
C2
C3
C4
C5
C6
C1
7
7
7
5
3
7
7
7
7
7
7
7
7
7
DMBA
DMBA
DMBA
DMBA
DMBA
DMBA
AcOH
EHA
DMBA
DMBA
DMBA
DMBA
DMBA
DMBA
64
80
72
70
64
82
72
64
68
64
68
83
74
71
34
63
49
44
34
60
32
45
52
50
43
62
46
49
89
91
90
90
88
91
81
81
75
2
3
e
4
5
f
6
g
7
h
8
9
10
11
12
13
91
−79
−90
−84
89
i
14
Further screening of reaction conditions, a catalytic system
consisting of Mn catalyst C1 (2.0 mol %), 2,2-dimethylbuta-
noic acid (DMBA, 14.0 equiv), and an oxidant (H2O2, 7.0
equiv), was found to promote the oxidation reaction at 0 °C,
affording the product 2a in satisfactory yield (63%) and 91%
ee (Table 1, entries 2, 4, and 5). Lowering the temperature
from 0 °C to −20 °C did not increase the yield and
enantioselectivity (Table 2, entry 6). As previously reported,
the reactivity and enantioselectivity of an epoxidation reaction
promoted by metal complexes of N4 ligands are affected
significantly by the carboxylic acid additives.13 In the present
reaction, the enantioselectivity decreased clearly when acetic
acid or 2-ethylhexanoic acid was used as an additive instead of
DMBA (Table 1, entries 7 and 8). In addition, replacement of
manganese catalyst C1 with other manganese complexes led to
lower yields and enantioselectivities; only manganese complex
C5 provided a comparable result to that of C1 (Table 1,
entries 9−13). Reaction under air provides a lower yield
(Table 1, entry 14).
With the optimized reaction conditions in hand, we then
studied the scope of this asymmetric oxidation reaction
(Scheme 2). In general, a variety of spirocyclic oxindoles
bearing both electron-donating and -withdrawing groups at the
oxindole ring were suitable for the reaction, providing the
corresponding ketones 2a−2h in good enantioselectivities
(77−91% ee) and yields (45−67%). The reactions of
spirocyclic substrates containing methoxy substitution on the
Indane aromatic ring proceeded smoothly to afford the desired
chiral ketones 2i−2k in good yields (53−57%) with moderate
enantioselectivities (55−69% ee). For the substrate 2l bearing
a pivaloyl group on the nitrogen instead of the N-Boc
protecting group, it also reacted well with good enantiose-
a
Reaction conditions: substrate 1a (0.2 mmol), manganese catalyst
(2.0 mol %), and 2,2-dimethylbutanoic acid (DMBA, 14.0 equiv)
were dissolved in 1.0 mL of CH2Cl2 at 0 °C under an Ar atmosphere,
and then H2O2 (30% aqueous solution diluted in 1.0 mL of MeCN)
was added dropwise over 2 h using a syringe pump and stirred for
additional 2 h. Isolated yield of 2a. Determined by HPLC analysis
on a Chiralcel AD-H column. 1.0 mol % of manganese catalyst C1 as
catalyst, and a 23% yield of alcohol 3a was isolated. DMBA (7.0
equiv) was used. The reaction was performed at −20 °C. AcOH
(14.0 equiv) was used instead of DMBA. 2-Ethylhexanoic acid
b
c
d
e
f
g
h
i
(EHA, 14.0 equiv) was used instead of DMBA. Reaction was
performed under air.
lectivity. But for the substrate without a protecting group on
the nitrogen, nearly no reaction took place (see SI, substrate
1m). The absolute configuration of 2c was confirmed by
comparison with the reported optical rotation after depro-
tection of the N-Boc group of 2c.6
To further demonstrate the synthetic utility of our method
catalyzed by the small-molecule manganese catalyst, we then
examined the spirocyclic compounds based on 2,3-dihydro-
quinolin-4(1H)-ones, which are ubiquitous scaffolds of
pharmaceuticals and natural products.14 To our delight,
spirocyclic precursor 4a could be transformed into the desired
β,β′-diketones with good to excellent enantioselectivity
smoothly (Scheme 3, 94% ee). In particular, alcohol 6a was
isolated with a 26% yield and 97% ee (Scheme 3), despite
racemization of the spiro alcohol generated from spirocyclic
oxindole that would occur easily via a retro-aldol cleavage
demonstrated previously by Bach and co-workers.6 In light of
the greater significance of enantioselective hydroxylation of C−
B
DOI: 10.1021/acs.orglett.8b03652
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Letter
The substrates containing substituted groups on the phenyl
ring of 2,3-dihydroquinolin-4(1H)-one could be tolerated to
afford the corresponding alcohol as major products in 22−41%
yields with 94−99% ee (Scheme 4). The absolute config-
Scheme 2. Substrate Scope of Asymmetric Oxidation of
Spirocyclic Oxindoles
a
Scheme 4. Substrate Scope of Asymmetric Oxidation of
a
Spirocyclic 2,3-Dihydroquinolin-4(1H)-ones
a
Reaction conditions: substrate 1 (0.2 mmol), manganese catalyst C1
(2.0 mol %), and 2,2-dimethylbutanoic acid (DMBA, 14.0 equiv)
were dissolved in 1.0 mL of CH2Cl2 at 0 °C under an Ar atmosphere,
and then H2O2 (7.o equiv, 30% aqueous solution diluted in 1.0 mL of
MeCN) was added dropwise over 2 h using a syringe pump and
stirred for additional 2 h; isolated yield.
a
Reaction conditions: substrate 4 (0.2 mmol), manganese catalyst C1
(1.0 mol %), and 2,2-dimethylbutanoic acid (DMBA, 14.0 equiv)
were dissolved in 1.0 mL of CH2Cl2 at −20 °C under an Ar
atmosphere, and H2O2 (1.0 equiv, 30% aqueous solution diluted in
0.5 mL of MeCN) was added dropwise over 30 min and stirred for
additional 30 min; afterward, C1 (1.0 mol %) was added to the
reaction again, and a second addition of H2O2 (1.0 equiv) was
performed in the same manner; total reaction time of 2 h; isolated
yield.
Scheme 3. Asymmetric Oxidation of Methylene Group in
Spirocyclic 2,3-Dihydroquinolin-4-one
uration was confirmed by the determination of the crystal
structure of 6b (CCDC 1875664), and other alcohol products
as well as β,β′-diketone 5a were assigned analogously.
H bonds, the reaction condtions for the asymmetric oxidation
of 4a were examined carefully (detail see Table S1). The
alcohol 6a was isolated as the major product in 38% yield with
the addition of catalyst C1 (1.0 mol %) and H2O2 (1.0 equiv)
twice over a period of 2 h at −20 °C. In this case, the ketone
5a was isolated only in 15% yield and 96% ee (see SI, Table
S1). This result indicates that the ketone product is produced
by the oxidation of the corresponding chiral alcohol. We then
explored the substrate scope with the optimized conditions.
It is believed that the methylene oxidation catalyzed by the
manganese catalyst may occur via an alcohol intermedi-
ate.6,10,15 In Bach’s work, a PCC or Swern oxidation following
C−H oxidation greatly improved the yield of the correspond-
ing chiral ketone, indicating that the chiral Ru catalyst induced
enantioselective oxidation of C−H to firstly generate a chiral
alcohol.6 According to the system based on the manganese
complex of the N4 ligand, H2O2, and carboxylic acid, a Mn(V)-
C
DOI: 10.1021/acs.orglett.8b03652
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Letter
M. Chem. Commun. 2018, 54, 9559−9570. (c) Herrmann, P.; Bach, T.
Chem. Soc. Rev. 2011, 40, 2022−2038.
oxo species bearing a carboxylate moiety has been supported
experimentally and theoretically; then it serves as the oxidizing
intermediate via H-atom abstraction and following oxygen
rebound to provide an alcohol product.13a,16 Afterward, the
alcohol product is oxidized by a carboxylate Mn(V)-oxo
species to produce the desired ketone product.
In summary, we have developed a manganese-catalyzed
protocol that allows for the enantioselective oxidation of
methylene C−H in oxindoles or 2,3-dihydroquinolin-4-ones to
ketones. It is noteworthy that the same manganese catalyst has
been successfully applied to the asymmetric hydroxylation of
spirocyclic 2,3-dihydroquinolin-4-ones with 70−99% ee. Over-
all, the current reaction is more environmentally friendly due
to the involvement of the manganese complex as the catalyst
and aqueous hydrogen peroxide as the terminal oxidant.
Further applications of manganese-catalyzed enantioselective
oxidation of unactivated C−H and mechanistic studies are
currently ongoing in our laboratory.
(3) (a) Groves, J. T.; Viski, P. J. Am. Chem. Soc. 1989, 111, 8537−
8538. (b) Groves, J. T.; Viski, P. J. Org. Chem. 1990, 55, 3628−3634.
(4) (a) Zhang, R.; Yu, W.-Y.; Lai, T.-S.; Che, C.-M. Chem. Commun.
1999, 18, 1791−1792. (b) Zhang, R.; Yu, W.-Y.; Che, C.-M.
Tetrahedron: Asymmetry 2005, 16, 3520−3526. (c) Srour, H.; Maux,
P. L.; Simonneaux, G. Inorg. Chem. 2012, 51, 5850−5856. (d) Maux,
P. L.; Srour, H. F.; Simonneaux, G. Tetrahedron 2012, 68, 5824−
5828.
(5) (a) Hamachi, K.; Irie, R. Tetrahedron Lett. 1996, 37, 4979−4982.
(b) Hamada, T.; Irie, R.; Mihara, J.; Hamachi, K.; Katsuki, T.
Tetrahedron 1998, 54, 10017−10028. (c) Komiya, N.; Noji, S.;
Murahashi, S.-I. Tetrahedron Lett. 1998, 39, 7921−7924. (d) Muraha-
shi, S.-I.; Noji, S.; Hirabayashi, T.; Komiya, N. Tetrahedron:
Asymmetry 2005, 16, 3527−3535. (e) Murahashi, S.-I.; Noji, S.;
Komiya, N. Adv. Synth. Catal. 2004, 346, 195−198. (f) Punniyamur-
thy, T.; Miyafuji, A.; Katsuki, T. Tetrahedron Lett. 1998, 39, 8295−
8298. (g) Miyafuji, A.; Katsuki, T. Synlett 1997, 1997, 836−838.
(h) Suematsu, H.; Tamura, Y.; Shitama, H.; Katsuki, T. Heterocycles
2007, 71, 2587−2593. (i) Punniyamurthy, T.; Miyafuji, A.; Katsuki,
T. Tetrahedron 1999, 55, 9439−9454. (j) Miyafuji, A.; Katsuki, T.
Tetrahedron 1998, 54, 10339−10348.
ASSOCIATED CONTENT
* Supporting Information
■
S
(6) Frost, J. R.; Huber, S. M.; Breitenlechner, S.; Bannwarth, C.;
Bach, T. Angew. Chem., Int. Ed. 2015, 54, 691−695.
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.or-
glett.8b03652.
(7) For reviews on the nonheme metal complexes and catalysis, see:
(a) Que, L., Jr.; Tolman, W. B. Nature 2008, 455, 333−340.
(b) Costas, M.; Mehn, M. P.; Jensen, M. P.; Que, L., Jr. Chem. Rev.
2004, 104, 939−986. (c) Oloo, W. N.; Que, L., Jr. Acc. Chem. Res.
2015, 48, 2612−2621. (d) Nam, W.; Lee, Y.-M.; Fukuzumi, S. Acc.
Chem. Res. 2014, 47, 1146−1154. (e) Chen, Z.; Yin, G.-C. Chem. Soc.
Syntheses of the spirocyclic substrates (1a−1l and 4a−
4h); general procedure for the asymmetric oxidation of
1a−1l and 4a−4h catalyzed by manganese complex C1
and analyses of the products (2a−2l and 6a−6h) (PDF)
́
Rev. 2015, 44, 1083−1100. (f) Engelmann, X.; Monte-Perez, I.; Ray,
K. Angew. Chem., Int. Ed. 2016, 55, 7632−7649. (g) Ray, K.; Pfaff, F.
F.; Wang, B.; Nam, W. J. Am. Chem. Soc. 2014, 136, 13942−13958.
(h) Bryliakov, K. P. Chem. Rev. 2017, 117, 11406−11459.
(i) Bryliakov, K. P.; Talsi, E. P. Coord. Chem. Rev. 2014, 276, 73−
Accession Codes
CCDC 1875664 contains the supplementary crystallographic
data for this paper. These data can be obtained free of charge
via www.ccdc.cam.ac.uk/data_request/cif, or by emailing
data_request@ccdc.cam.ac.uk, or by contacting The Cam-
bridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
́
96. (j) Cusso, O.; Ribas, X.; Costas, M. Chem. Commun. 2015, 51,
́
14285−14298. (k) Olivo, G.; Cusso, O.; Costas, M. Chem. - Asian J.
2016, 11, 3148−3158.
(8) For selected examples for oxidation reactions catalyzed by N4
metal complexes, see: (a) White, M. C.; Doyle, A. G.; Jacobsen, E. N.
J. Am. Chem. Soc. 2001, 123, 7194−7195. (b) Chen, M. S.; White, M.
C. Science 2007, 318, 783−787. (c) Chen, M. S.; White, M. C. Science
AUTHOR INFORMATION
■
Corresponding Author
*E-mail: wsun@licp.cas.cn.
ORCID
́
2010, 327, 566−571. (d) Cusso, O.; Cianfanelli, M.; Ribas, X.;
Gebbink, R. J. M. K.; Costas, M. J. Am. Chem. Soc. 2016, 138, 2732−
2738. (e) Costas, M.; Tipton, A. K.; Chen, K.; Jo, D. H.; Que, L., Jr. J.
Am. Chem. Soc. 2001, 123, 6722−6723. (f) Zang, C.; Liu, Y.; Xu, Z.-J.;
Tse, C. W.; Guan, X.; Wei, J.; Huang, J.-S.; Che, C.-M. Angew. Chem.,
Qiangsheng Sun: 0000-0002-7721-1290
Wei Sun: 0000-0003-4448-2390
Notes
́
Int. Ed. 2016, 55, 10253−10257. (g) Company, A.; Gomez, L.; Guell,
̈
M.; Ribas, X.; Luis, J. M.; Que, L., Jr.; Costas, M. J. Am. Chem. Soc.
́
2007, 129, 15766−15767. (h) Gomez, L.; Garcia-Bosch, I.; Company,
The authors declare no competing financial interest.
A.; Benet-Buchholz, J.; Polo, A.; Sala, X.; Ribas, X.; Costas, M. Angew.
Chem., Int. Ed. 2009, 48, 5720−5723. (i) Murphy, A.; Dubois, G.;
Stack, T. D. P. J. Am. Chem. Soc. 2003, 125, 5250−5251. (j) Wu, X.-J.;
Seo, M. S.; Davis, K. M.; Lee, Y.-M.; Chen, J.-Y.; Cho, K.-B.; Pushkar,
Y. N.; Nam, W. J. Am. Chem. Soc. 2011, 133, 20088−20091.
(k) Gomez, L.; Garcia-Bosch, I.; Company, A.; Sala, X.; Fontrodona,
X.; Ribas, X.; Costas, M. Dalton Trans 2007, 47, 5539−5545.
(l) Chow, T. W. S.; Liu, Y.; Che, C.-M. Chem. Commun. 2011, 47,
11204−11206. (m) Nehru, K.; Kim, S. J.; Kim, I. Y.; Seo, M. S.; Kim,
Y.; Kim, S.-J.; Kim, J.; Nam, W. Chem. Commun. 2007, 44, 4623−
4625. (n) Talsi, E. P.; Samsonenko, D. G.; Ottenbacher, R. V.;
Bryliakov, K. P. ChemCatChem 2017, 9, 4580−4586.
ACKNOWLEDGMENTS
■
This work was supported by the National Natural Science
Foundation of China (21773273, 21473226), Key Research
Program of Frontier Sciences, CAS (QYZDJ-SSW-SLH051),
and Natural Science Foundation of Jiangsu Province
(BK20170420).
REFERENCES
■
(1) (a) Newhouse, T.; Baran, P. S. Angew. Chem., Int. Ed. 2011, 50,
3362−3374. (b) Che, C.-M.; Lo, V. K.-Y.; Zhou, C.-Y.; Huang, J.-S.
Chem. Soc. Rev. 2011, 40, 1950−1975. (c) Lindhorst, A. C.; Haslinger,
(9) (a) Wu, M.; Wang, B.; Wang, S.-F.; Xia, C.-G.; Sun, W. Org. Lett.
2009, 11, 3622−3625. (b) Wu, M.; Miao, C.-X.; Wang, S.-F.; Hu, X.-
̈
X.; Xia, C.-G.; Kuhn, F. E.; Sun, W. Adv. Synth. Catal. 2011, 353,
3014−3022. (c) Wang, B.; Miao, C.-X.; Wang, S.-F.; Xia, C.-G.; Sun,
W. Chem. - Eur. J. 2012, 18, 6750−6753. (d) Wang, B.; Wang, S.-F.;
Xia, C.-G.; Sun, W. Chem. - Eur. J. 2012, 18, 7332−7335. (e) Miao,
S.; Kuhn, F. E. Chem. Commun. 2015, 51, 17193−17212. (d) Talsi, E.
̈
P.; Bryliakov, K. P. Coord. Chem. Rev. 2012, 256, 1418−1434.
(2) (a) Saint-Denis, T. G.; Zhu, R.-Y.; Chen, G.; Wu, Q.-F.; Yu, J.-Q.
Science 2018, 359, No. EAAO4798. (b) Milan, M.; Bietti, M.; Costas,
D
DOI: 10.1021/acs.orglett.8b03652
Org. Lett. XXXX, XXX, XXX−XXX

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Letter
C.-X.; Wang, B.; Wang, Y.; Lee, Y.-M.; Nam, W.; Sun, W. J. Am.
Chem. Soc. 2016, 138, 936−943. (f) Shen, D.-Y.; Qiu, B.; Xu, D.-Q.;
Miao, C.-X.; Xia, C.-G.; Sun, W. Org. Lett. 2016, 18, 372−375.
(g) Wang, W.-F.; Sun, Q.-S.; Xia, C.-G.; Sun, W. Chin. J. Catal. 2018,
39, 1463−1469. (h) Miao, C.-X.; Li, X.-X.; Lee, Y.-M.; Xia, C.-G.;
Wang, Y.; Nam, W.; Sun. Chem. Sci. 2017, 8, 7476−7482.
(10) Qiu, B.; Xu, D.-Q.; Sun, Q.-S.; Miao, C.-X.; Lee, Y.-M.; Li, X.-
X.; Nam, W.; Sun, W. ACS Catal. 2018, 8, 2479−2487.
(11) Milan, M.; Bietti, M.; Costas, M. ACS Cent. Sci. 2017, 3, 196−
204.
̈
(12) Burg, F.; Gicquel, M.; Breitenlechner, S.; Pothig, A.; Bach, T.
Angew. Chem., Int. Ed. 2018, 57, 2953−2957. (b) Talsi, E. P.;
Samsonenko, D. G.; Bryliakov, K. P. ChemCatChem 2017, 9, 2599−
2607.
(13) (a) Lyakin, O. Y.; Ottenbacher, R. V.; Bryliakov, K. P.; Talsi, E.
P. ACS Catal. 2012, 2, 1196−1202. (b) Ottenbacher, R. V.;
Samsonenko, D. G.; Talsi, E. P.; Bryliakov, K. P. ACS Catal. 2016,
́
6, 979−988. (c) Cusso, O.; Garcia-Bosch, I.; Ribas, X.; Lloret-Fillol,
́
J.; Costas, M. J. Am. Chem. Soc. 2013, 135, 14871−14878. (d) Cusso,
O.; Ribas, X.; Lloret-Fillol, J.; Costas, M. Angew. Chem., Int. Ed. 2015,
54, 2729−2733.
(14) Sridharan, V.; Suryavanshi, P. A.; Menendez, J. C. Chem. Rev.
́
2011, 111, 7157−7259.
(15) (a) Shen, D.-Y.; Miao, C.-X.; Wang, S.-F.; Xia, C.-G.; Sun, W.
Org. Lett. 2014, 16, 1108−1111. (b) Shen, D.-Y.; Miao, C.-X.; Xia, C.-
G.; Sun, W. Org. Lett. 2015, 17, 54−57.
(16) Du, J.-Y.; Miao, C.-X.; Xia, C.-G.; Lee, Y.-M.; Nam, W.; Sun,
W. ACS Catal. 2018, 8, 4528−4538.
E
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