C(sp 3)-H Peroxidation of 3-Substituted Indolin-2-ones under Metal-Free Conditions

Article abstract of DOI:10.1055/s-0036-1591520

A C(sp ³)-H peroxidation of 3-substituted indolin-2-ones through radical coupling reaction has been developed under metal-free conditions. Using tert -butyl hydroperoxide both as an oxidant and as a peroxidation reagent to couple with the C(sp ³)-H bonds of 3-substituted indolin-2-ones can form a new C-O bond without using any additives. This simple strategy provides a green and efficient approach to 3-peroxyindolin-2-ones in moderate to excellent yields. The resulting 3-peroxyindolin-2-ones could be further transformed into 3-hydroxyindolin-2-ones.

Full text of DOI:10.1055/s-0036-1591520

SYNLETT
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©
Georg Thieme Verlag Stuttgart · New York
2017, 28, A–E
letter
A
en
Synlett
W.-W. Ying et al.
Letter
3
C(sp )–H Peroxidation of 3-Substituted Indolin-2-ones under
Metal-Free Conditions
◊
Wei-Wei Ying
Wen-Ming Zhu
Zhanghua Gao
Hongze Liang
R2
R2
OOt-Bu
Metal-Free
◊
R1
+
t-BuOOH
R1
O
O
DCE, air, 85 °C
N
R3
N
R3
Wen-Ting Wei*
1
2
Metal-free
R
R
= H, OMe, Cl, Br
= Ph, 2,5-Me2C6H3
Me, Et, n-Pr
3
C(sp )–H peroxidation
School of Materials Science and Chemical Engineering,
Ningbo University, Ningbo 315211, P. R. of China
weiwenting@nbu.edu.cn
R3 = H, Me, Bn, Ph, Boc
17 Examples, 61–92% yield
◊
These authors contributed equally to this work
3
Received: 09.09.2017
Accepted after revision: 29.10.2017
Published online: 11.12.2017
moted C(sp )–H bond functionalization of benzyl ethers
with t-BuOOH. Various tert-butyl peroxyacetals were readi-
DOI: 10.1055/s-0036-1591520; Art ID: st-2017-w0679-l
ly prepared from benzyl ethers, t-BuOOH, and a catalytic
9
amount of Fe(acac) at 80 °C (Scheme 1, a). Very recently,
3
3
Abstract A C(sp )–H peroxidation of 3-substituted indolin-2-ones
3
M. Stoltz and co-workers developed a Cu-catalyzed C(sp )–
through radical coupling reaction has been developed under metal-free
H peroxidation of oxindole derivatives with t-BuOOH by us-
conditions. Using tert-butyl hydroperoxide both as an oxidant and as a
3
ing CuCl as a catalyst and dichloromethane (CH Cl ) as sol-
peroxidation reagent to couple with the C(sp )–H bonds of 3-substitut-
2
2
vent (Scheme 1, b).10
ed indolin-2-ones can form a new C–O bond without using any addi-
tives. This simple strategy provides a green and efficient approach to
3
3
-peroxyindolin-2-ones in moderate to excellent yields. The resulting
-peroxyindolin-2-ones could be further transformed into 3-hydroxy-
Previous work:
OOt-Bu
OR2
Fe(acac)3 (10 mol%)
MS, MeCN, 80 °C
indolin-2-ones.
R1
OR2
(a)
(b)
+
t-BuOOH
R1
3
Key words C(sp )–H peroxidation, metal-free, 3-substituted indolin-
-ones, tert-butyl hydroperoxide
R
R
2
OOt-Bu
CuCl (10 mol%)
CH2Cl2, 23 °C
O
+
t-BuOOH
O
3
N
N
The direct and selective functionalization of C(sp )–H
H
H
bond is a ‘young’ and rapid-developing area in synthetic
This work:
R2
R2
1
chemistry. Transition-metal-catalyzed methods have re-
OOt-Bu
Metal-Free
3
cently become the mainstream of C(sp )–H functionaliza-
R1
t-BuOOH
R1
(c)
O +
O
2
DCE, air, 85 °C
tion. However, from green chemistry and environmental
N
R3
N
R3
points of view, establishing a metal-free approach to
3
3
C(sp )–H functionalization would be a more elegant strate-
Scheme 1 C(sp )–H peroxidation using t-BuOOH
3
gy. Thus, the metal-free methods have emerged as a pow-
erful ‘chemical weapon’ because it can overcome the draw-
backs of the expensive and poisonous properties of metals
or organometallics.
However, to the best of our knowledge, no example of
metal-free direct C(sp )–H peroxidation has been de-
3
4
scribed. In this regard, it is important to seek for a simple
and efficient method to broaden this area. As part of our
continuing efforts in modification indolin-2-ones and re-
Organic peroxides are ubiquitous and indispensable and
are present in biologically active compounds with antima-
5
6
7
3
11
larial, anthelmintic, and antitumor activity. tert-Butyl
hydroperoxide (t-BuOOH) plays a dual role as an oxidant
and as a peroxidation reagent in the synthesis of organic
peroxides. While significant results have been accom-
plished in the field of difunctionalization of alkenes by the
cent interests in the C(sp )–H peroxidation, herein we
3
present a C(sp )–H peroxidation of 3-substituted indolin-2-
ones using t-BuOOH under metal-free conditions (Scheme
1, c). It is worth noting that this simple metal-free approach
successfully provides a versatile method for obtaining a
wide range of 3-peroxyindolin-2-ones.
8
use of t-BuOOH, reactions involving direct peroxidation of
3
C(sp )–H bonds remain rare. One efficient example was re-
ported by Urabe and co-workers, who reported a Fe-pro-
©
Georg Thieme Verlag Stuttgart · New York — Synlett 2017, 28, A–E

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Synlett
W.-W. Ying et al.
Letter
Initially, the reaction of 3-phenylindolin-2-one (1a)
with t-BuOOH (70% in water, 2a) was chosen as a model re-
action for optimizing the reaction conditions including sol-
vent and temperature (Table 1). The reaction proceeded un-
der the commonly used solvent dichloroethane (DCE) un-
der air at 85 °C, and an unknown product was obtained in
not significantly affect the yield (products 3b–e), giving the
corresponding products in 70–81% yields (Table 2, entries
2–5). Next, we studied the effect of the aryl rings on this re-
action. A range of the 3-substituted indolin-2-ones bearing
an electron-donating group (R = OMe) or an electron-with-
drawing groups (R = Cl, Br) in the 5-position of the aryl
rings underwent the peroxidation and afforded the desired
products with up to 92% yield (3f–h, Table 2, entries 6–8).
Particularly noteworthy was the smooth transformation of
the aryl halide substrates, thus allowing further modifica-
tions via cross-coupling reactions. To our delight, a large va-
riety of functional groups (N-Me, N-Bn, and N-Ph substitu-
ents) as N-substituents of the 3-substituted indolin-2-ones
were tolerated and gave the corresponding products in 87%,
86%, and 82% yields, respectively (3i–k, Table 2, entries 9–
11). Moreover, the N-Boc-substituted substrate also reacted
effectively with 2a to give the corresponding product 3l in
66% yield after prolonging the reaction time (Table 2, entry
12). It is interesting to note that this method was also effec-
tive for the synthesis of 3-peroxyindolin-2-ones 3m–p and
gave the peroxidation products in moderate yields (Table 2,
entries 13–16). Unfortunately, indolin-2-one has poor se-
lectivity for this peroxidation reaction and was converted
into indoline-2,3-dione in 81% yield under the standard re-
action conditions (Table 2, entry 17). In general, this meth-
od was successfully applied to a variety of 3-substituted in-
dolin-2-ones, and these substrates were smoothly convert-
ed into the corresponding 3-peroxyindolin-2-ones in
moderate to excellent yields.
91% yield that after identification turned out to be 3-(tert-
butylperoxy)-3-phenylindolin-2-one (3a, Table 1, entry 1).
In the light of this result, we turned our attention to exam-
ine the reaction temperature. While a lower reaction tem-
perature only gave the desired product 3a in 30% yield (Ta-
ble 1, entry 2), a higher reaction temperature gave the same
result as that at 85 °C (Table 1, entry 3). Notably, the
amount of t-BuOOH affected the reaction: A decrease to 2.0
equiv was not beneficial to the formation of product 3a (Ta-
ble 1, entry 4), whereas an increase to 3.0 equiv only result-
ed in an identical result to that of 2.4 equiv t-BuOOH (Table
1
, entry 5). Finally, the effect of solvent on the reaction per-
formance was evaluated. When the reaction was carried
out in MeCN, THF, and EtOH, the efficiency was lower than
in DCE (Table 1, entry 1 vs entries 6–8). On the basis of
these results, entry 1 represents the best conditions.
Having optimized the reaction conditions, the scope of
3
the C(sp )–H peroxidation reaction by different 3-substitut-
ed indolin-2-ones with t-BuOOH was investigated (Table
12
2
). It is satisfactory that under the optimum reaction con-
ditions, the 3-phenylindolin-2-one gave the desired prod-
uct 3a in 91% yield. In addition, introduction of an aryl- or
alkyl-substituent at the C3-position of indolin-2-ones did
The study findings of transformations on the 3-peroxy-
indolin-2-ones are shown in Scheme 2. 3-Hydroxyindolin-
Table 1 Optimization of the Reaction Conditionsa
2
-ones were obtained in 72–76% yields when 3-peroxyin-
Ph
Ph
OOt-Bu
13
dolin-2-ones were subjected to reduction conditions.
To obtain information about the reaction mechanism,
several control experiments were carried out as shown in
Scheme 3. When 3-phenylindolin-2-one (1a) and 2-(tert-
butylperoxy)-2-methylpropane (t-BuOOt-Bu, 2b) reacted
under the standard reaction conditions, the desired product
Solvent, Temp.
O
+
t-BuOOH
O
N
2a
N
H
H
1
a
3a
Entry
Solvent
Temp. (°C)
Yield (%)b
3
r was not detected at all, and 95% of 1a was recovered
1
DCE
DCE
DCE
DCE
DCE
MeCN
THF
85
50
91
30
91
78
92
77
20
5
(Scheme 3, a). Subsequently, two radical inhibitors, 2,2,6,6-
2
tetramethylpiperidinyloxyl (TEMPO) and 2,6-di-tert-butyl-
3
100
85
3
4-methyl phenol (BHT), were added to the C(sp )–H peroxi-
4c
5d
6
dation reaction: Adding 3.0 equiv of TEMPO or BHT com-
pletely inhibited the conversion of 1a, which indicated that
a radical process might be involved in this reaction (Scheme
85
85
3
, b and c). However, a hydroxylation product 4d was ob-
tained in 32% yield when 3.0 equiv of TEMPO were added
Scheme 3, b). In addition, t-BuOOH was transformed by
7
85
8
EtOH
85
(
aReaction conditions: 1a (0.3 mmol), 2a (70% in water, 0.72 mmol, 2.4
BHT into 3,5-di-tert-butyl-4-(tert-butylperoxy)-4-methyl-
cyclohexa-2,5-dien-1-one (5a) in 71% yield, which suggest
that a t-BuOO radical is involved (Scheme 3, c).
equiv), and solvent (2 mL) under air for 12 h.
b
Isolated yields.
2
c
a (0.6 mmol, 2.0 equiv).
a (0.9 mmol, 3.0 equiv).
14
d
2
©
Georg Thieme Verlag Stuttgart · New York — Synlett 2017, 28, A–E

C
Synlett
W.-W. Ying et al.
Letter
3
a
Table 2 Reaction Scope of C(sp )–H Peroxidation
Table 2 (continued)
Entry Substrate
Product
Yield (%)
86
R2
R2
N
R3
3
OOt-Bu
DCE, air, 85 °C
Ph
Ph
R1
+
t-BuOOH
R1
OOt-Bu
O
O
N
2a
O
O
O
O
1
0
1
R3
N
N
1
Bn
Bn
1
1
j
3j
Entry Substrate
Product
Yield (%)
91
Ph
Ph
OOt-Bu
Ph
Ph
OOt-Bu
O
1
82
N
N
O
O
1
Ph
Ph
N
N
H
H
k
3k
1
a
3a
Ph
Ph
OOt-Bu
Me
Me
t-BuOO
Me
O
66b
Me
12
N
N
2
81
Boc
Boc
O
O
N
1l
3l
N
H
H
3
b
1
1
1
1
b
Me
Me
t-BuOO
Me
Me
Me
Me
OOt-Bu
Cl
Cl
1
3
73
71
O
O
O
O
O
76
73
70
92
83
73
O
3
4
5
6
7
8
N
N
N
N
H
H
H
H
3
m
c
3c
3d
3e
1m
Et
Et
OOt-Bu
Me
Me
t-BuOO
Me
Me
O
Br
Br
N
N
14
H
H
O
O
O
N
d
e
N
H
H
3
n
n-Pr
n-Pr
1n
OOt-Bu
Ph
Ph
O
OOt-Bu
Cl
Cl
N
N
H
H
O
1
5
82
N
N
Me
Me
Ph
Ph
OOt-Bu
3o
1
o
MeO
MeO
O
O
Me
Me
OOt-Bu
N
H
N
H
O
O
O
61b
1
f
3f
1
6
7
N
N
Ph
Ph
Boc
Boc
OOt-Bu
Cl
Cl
1p
3
p
q
O
O
N
N
H
OOt-Bu
H
1
g
3g
1
O
tracec
N
H
N
Ph
Ph
H
OOt-Bu
1
q
Br
Br
3
O
O
aReaction conditions: 1 (0.3 mmol), t-BuOOH (70% in water, 0.72 mmol),
and DCE (2 mL) under air at 85 °C for 12 h.
N
N
H
H
b
1
h
3h
3i
For 24 h.
c
Indoline-2,3-dione was obtained in 81% yield.
Ph
Ph
OOt-Bu
O
O
9
87
N
N
Me
Me
1
i
©
Georg Thieme Verlag Stuttgart · New York — Synlett 2017, 28, A–E

D
Synlett
W.-W. Ying et al.
Letter
R2
R2
Δ
OOt-Bu
OH
t-BuOOH
t-BuO
t-BuO
+
OH
R1
t-BuOOH
+
OH
t-BuOO
R2
+
H2O
Zn (5.0 equiv)
R2
R2
R1
R1
OOt-Bu
O
O
t-BuOO
AcOH, 70 °C
N
H
N
H
R1
R1
O
O
O
3
4
N
R3
N
R3
N
R3
t-BuOH
Me
HO
1
A
3
Ph
Ph
Me
OH
OH
Scheme 4 Plausible mechanism
Cl
Br
O
O
O
N
N
H
N
H
H
2-ones without using any metal catalysts. This method pro-
4a, 72%
4b, 74%
4c, 76%
vides a practical route to 3-peroxyindolin-2-ones and ex-
hibits a broad substrate scope with good functional group
tolerance. Applications of this method toward asymmetric
synthesis of 3-peroxyindolin-2-ones are the subject of on-
going investigations in our laboratory.
Scheme 2 Synthesis application of 3-peroxyindolin-2-ones
Ph
Ph
Ot-Bu
DCE, air, 85 °C
O
+
t-BuOOt-Bu
O
(a)
N
2b
N
H
H
1a
Funding Information
3r, 0%
This research is sponsored by research funds of NBU (No.
ZX2016000706), foundation of Ningbo University (No. XYL17009),
and the K. C. Wong Magna Fund in Ningbo University. Prof. Z. H. Gao
also thanks the Natural Science Foundation of Ningbo City (No.
Ph
OOt-Bu
O
N
Ph
H
TEMPO (3.0 equiv)
DCE, air, 85 °C
3a, 0%
2016A610080).
N
n
i
g
b
o
Unveiytrsi
X(
Y
L
1
7
0
0
9)
O
+
t-BuOOH
2a
+
(b)
Ph
N
OH
H
1a
Supporting Information
O
N
H
Supporting information for this article is available online at
https://doi.org/10.1055/s-0036-1591520.
4
d, 32%
S
u
p
p
ortioIgnfmr oaitn
S
u
p
p
o
nrtogI
i
f
rm oaitn
Ph
OOt-Bu
References and Notes
O
N
Ph
(1) (a) Godula, K.; Sames, D. Science 2006, 312, 67. (b) Baran, P. S.;
Ishihara, Y. Synlett 2010, 1733. (c) Newhouse, T.; Baran, P. S.
Angew. Chem. Int. Ed. 2011, 50, 3362. (d) Davies, H. M. L.; Bois, J.
D.; Yu, J.-Q. Chem. Soc. Rev. 2011, 40, 1855. (e) Wenzel, M. N.;
Owens, P. K.; Bray, J. T. W.; Lynam, J. M.; Aguiar, P. M.; Reed, C.;
Lee, J. D.; Hamilton, J. F.; Whitwood, A. C.; Fairlamb, I. J. S. J. Am.
Chem. Soc. 2017, 139, 1177. (f) Guo, S.-R.; Kumar, P. S.; Yang, M.-H.
Adv. Synth. Catal. 2017, 1, 2.
H
3
a, trace
BHT (3.0 equiv)
DCE, air, 85 °C
O
+
t-BuOOH
+
(c)
N
2a
O
H
1a
t-Bu
t-Bu
Me OOt-Bu
a, 71%
5
(
2) (a) Baudoin, O. Acc. Chem. Res. 2017, 50, 1114. (b) Yang, D. J. Am.
Chem. Soc. 2015, 137, 1130. (c) Kim, J. H.; Greßies, S.; Mélissa,
B.-A.; Daniliuc, C.; Glorius, F. ACS Catal. 2016, 6, 7652. (d) Zhu,
Q.-H.; Ji, D.-Z.; Liang, T.-T.; Wang, X.-Y.; Xu, Y.-G. Org. Lett. 2015,
Scheme 3 Control experiments
3
The mechanism for the metal-free C(sp )–H peroxida-
tion was proposed on the basis of present results and relat-
17, 3798.
(3) (a) Fan, R.; Li, W.; Pu, D.; Zhang, L. Org. Lett. 2009, 11, 1425.
(b) Ochiai, M.; Miyamoto, K.; Kaneaki, T.; Hayashi, S.; Nakanishi,
W. Science 2011, 332, 448. (c) Kantak, A. A.; Potavathri, S.;
Barham, R. A.; Romano, K. M.; DeBoef, B. J. Am. Chem. Soc. 2011,
1
5–17
ed works (Scheme 4).
Initially, the t-BuO and t-BuOO
15
radicals were generated from the present system. Subse-
quently, the t-BuO radical abstracts a hydrogen atom from
substrate 1 to generate a key intermediate radical A.16 Final-
ly, radical A couples with a t-BuOO radical to afford the per-
133, 19960. (d) Shirakawa, E.; Hayashi, T. Chem. Lett. 2012, 41,
130. (e) Hari, D. P.; Schroll, P.; König, B. J. Am. Chem. Soc. 2012,
134, 2958. (f) Souto, J. A.; Zian, D.; Muñiz, K. J. Am. Chem. Soc.
2012, 134, 7242. (g) Luo, W.-K.; Shi, X.; Zhou, W.; Yang, L. Org.
17
oxidation product 3.
In summary, we have demonstrated a simple, efficient,
and green sequence for C(sp )–H peroxidation. In this pro-
Lett. 2016, 18, 2036. (h) Chaudhari, M. B.; Sutar, Y.; Malpathak,
S.; Hazra, A.; Gnanaprakasam, B. Org. Lett. 2017, 19, 3628.
4) (a) Sun, C.-L.; Li, H.; Yu, D.-G.; Yu, M.; Zhou, X.; Lu, X.-Y.; Huang,
3
(
cess, t-BuOOH was used as a peroxidation reagent which
3
K.; Zheng, S.-F.; Li, B.-J.; Shi, Z.-J. Nat. Chem. 2010, 2, 1044.
coupled with the C(sp )–H bonds of 3-substituted indolin-
(b) Shirakawa, E.; Itoh, K.; Higashino, T.; Hayashi, T. J. Am. Chem.
©
Georg Thieme Verlag Stuttgart · New York — Synlett 2017, 28, A–E

E
Synlett
W.-W. Ying et al.
Letter
Soc. 2010, 132, 15537. (c) Liu, W.; Cao, H.; Zhang, H.; Zhang, H.;
Chung, K. H.; He, C.; Wang, H.; Kwong, F. Y.; Lei, A. J. Am. Chem.
Soc. 2010, 132, 16737.
cated time until complete consumption of starting material as
monitored by TLC analysis. After the reaction was complete, the
solution was concentrated under reduced pressure, and the
mixture was purified by flash column chromatography over
silica gel (hexane/ethyl acetate) to afford the desired products 3.
The products were analyzed by H NMR and C NMR spectros-
copy, and mass spectrometry (see Supporting Information).
Typical Data for Representative Compound: 3-(tert-Butylper-
(
5) (a) Jefford, C. W. Curr. Top. Med. Chem. 2012, 12, 373. (b) Yadav,
N.; Sharma, C.; Awasthi, S. K. RSC Adv. 2014, 4, 5469. (c) Hao, H.
D.; Wittlin, S.; Wu, Y. Chem. Eur. J. 2013, 19, 7605.
6) Ingram, K.; Yaremenko, I. A.; Krylov, I. B.; Hofer, L.; Terent’ev, A.
O.; Keiser, J. J. Med. Chem. 2012, 55, 8700.
1
13
(
(
7) (a) Kumar, N.; Sharma, M.; Rawat, D. S. Curr. Med. Chem. 2011,
oxy)-3-phenylindolin-2-one (3a)
White solid (0.0811 g, 91% yield). H NMR (400 MHz, CDCl ):
1
18, 3889. (b) Terzić, N.; Opsenica, D.; Milić, D.; Tinant, B.; Smith,
3
K. S.; Milhous, W. K.; Šolaja, B. A. J. Med. Chem. 2007, 50, 5118.
8) (a) Yang, W.-C.; Weng, S.-S.; Ramasamy, A.; Rajeshwaren, G.;
Liao, Y.-Y.; Chen, C.-T. Org. Biomol. Chem. 2015, 13, 2385.
δ = 8.62 (s, 1 H), 7.45–7.43 (m, 2 H), 7.34–7.25 (m, 5 H), 7.08 (t,
(
J = 8.0 Hz, 1 H), 6.90 (d, J = 7.6 Hz, 1 H), 1.19 (s, 9 H). 13C NMR
(100 MHz, CDCl ): δ= 176.3, 141.7, 136.0, 129.8, 129.0, 128.9,
3
(
b) Jiang, J.-W.; Liu, J.-J.; Yang, L.; Shao, Y.; Cheng, J.; Bao, X.-G.;
128.5, 127.0, 126.5, 122.6, 110.2, 86.5, 80.9, 26.6. IR (KBr): 1678,
1113, 864 cm . ESI-HRMS: m/z calcd for C18H20NO3 [M + H] :
298.1438; found: 298.1434.
–1
+
Wan, X.-B. Chem. Commun. 2015, 51, 14728. (c) Banerjee, A.;
Santra, S. K.; Khatun, N.; Ali, W.; Patel, B. K. Chem. Commun.
2
015, 51, 15422. (d) Liu, W.-P.; Li, Y.-M.; Liu, K.-S.; Li, Z.-P. J. Am.
(13) (a) Cheng, J.-K.; Loh, T.-P. J. Am. Chem. Soc. 2015, 137, 42. (b) Dai,
P.; Dussault, P. H.; Trullinger, T. K. J. Org. Chem. 2004, 69, 2851.
(14) Ratnikov, M. O.; Farkas, L. E.; McLaughlin, E. C.; Chiou, G.; Choi,
H.; El-Khalafy, S. H.; Doyle, M. P. J. Org. Chem. 2011, 76, 2585.
(15) (a) Zhang, X.; Wang, L. Green Chem. 2012, 14, 2141. (b) Zhang,
X.; Wang, M.; Zhang, Y.; Wang, L. RSC Adv. 2013, 3, 1311. (c) Zi,
Y.; Cai, Z.; Wang, S.; Ji, S. Org. Lett. 2014, 16, 3094. (d) Du, B.; Jin,
B.; Sun, P. Org. Biomol. Chem. 2014, 12, 4586. (e) Zhang, H.;
Dong, D.; Hao, S.; Wang, Z. RSC Adv. 2016, 6, 8465.
Chem. Soc. 2011, 133, 10756. (e) Cheng, J.-K.; Loh, T.-P. J. Am.
Chem. Soc. 2015, 137, 42. (f) Bertrand, S.-C.; Demaerel, J.; Engler,
H.; Klussmann, M. Angew. Chem. Int. Ed. 2014, 53, 8737.
(
9) Iwata, S.; Hata, T.; Urabe, H. Adv. Synth. Catal. 2012, 354, 3480.
10) Klare, H. F. T.; Goldberg, A. F. G.; Duquette, D. C.; Stoltz, B. M.
Org. Lett. 2017, 19, 988.
11) (a) Wei, W.-T.; Zhu, W.-M.; Ying, W.-W.; Wu, Y.; Huang, Y.-L.;
Liang, H. Z. Org. Biomol. Chem. 2017, 15, 5254. (b) Wei, W.-T.;
Zhu, W.-M.; Ying, W.-W.; Wang, Y.-N.; Bao, W.-H.; Gao, L.-H.;
Luo, Y.-J.; Liang, H. Z. Adv. Synth. Catal. 2017, 359, in press; DOI:
(
(
(16) (a) Shu, Z.; Ye, Y.; Deng, Y.; Zhang, Y.; Wang, J. Angew. Chem. Int.
Ed. 2013, 52, 10573. (b) Hashemi, H.; Saberi, D.; Poorsadeghic,
S.; Niknam, K. RSC Adv. 2017, 7, 7619.
1
0.1002/adsc.201700870.
(
12) General Procedure
(17) (a) Wei, W.-T.; Yang, X.-H.; Li, H.-B.; Li, J.-H. Adv. Synth. Catal.
2015, 357, 59. (b) Chen, X.-L.; Li, Y.; Wu, M.-H.; Guo, H.-B.; Jiang,
L.-Q.; Wang, J.; Sun, S.-F. RSC Adv. 2016, 6, 102023.
To a Schlenk tube were added 3-substituted indolin-2-ones 1
(0.3 mmol), t-BuOOH (2a, 70% in water, 0.72 mmol), and DCE (2
mL). Then the tube was stirred at 85 °C under air for the indi-
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Georg Thieme Verlag Stuttgart · New York — Synlett 2017, 28, A–E