The synthesis of sulfonated 4: H -3,1-benzoxazines via an electro-chemical radical cascade cyclization

Article abstract of DOI:10.1039/c9cc09551a

A new route for the synthesis of sulfonated 4H-3,1-benzoxazines has been accomplished by electrochemical radical cascade cyclizations of styrenyl amides with sulfonylhydrazines. This process demonstrates a wide substrate scope with diverse functional group compatibility under metal- and external oxidant-free conditions at ambient temperature.

Full text of DOI:10.1039/c9cc09551a

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DOI: 10.1039/C9CC09551A
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The Synthesis of Sulfonated 4H-3,1-Benzoxazines via an Electro-
chemcial Radical Cascade Cyclization
Tian-Jun He, a Wei-Qiang Zhong a and Jing-Mei Huang a*
Received 00th January 20xx,
Accepted 00th January 20xx
A new route for the synthesis of sulfonated 4H-3,1-benzoxazines has been accomplished by electrochemical radical cascade
cyclizations of styrenyl amides with sulfonylhydrazines. This process demonstrates a wide substrate scope with diverse func-
tional group compatibility under metal- and external oxidant-free conditions at ambient temperature.
DOI: 10.1039/x0xx00000x
4H-3,1-benzoxazine skeletons are
a
class of common complex organic compounds.5,6 Recently, RCCs via
structures that widely present in many pharmaceuticals and electrochemical means have flourished in an exponential
natural products, and are used as building blocks for remarkable manner.7 In continuation of our studies in the development of
bioactive molecules (e.g. I-IV, Figure 1).1 In general, two types new methods in the organic electrosynthesis, especially in C-S
of synthetic strategies were used for the synthesis of 4H-3,1- bond formation,8 herein we report the synthesis of sulfonated
benzoxazines. One was the condensation of aldehydes with o- 4H-3,1-benzoxazines via a C-S and C-O bond formation
aminobenzylicalcohols.2 The other was the cascade cyclization sequence by an electrochemical radical cascade cyclization.
of styrenyl amides with different electrophiles.3 Thus, in the last
a) Previous work: traditional organic chemistry or photochemistry
few years, diverse methodologies have been developed for the
PhSO2Na x H2O
construction of alkyl/chalcogen/halogen-containing benzoxazi-
nes. However, to the best of our knowledge, the methods for
the synthesis of sulfonated 4H-3,1-benzoxazine derivatives are
less developed (Figure 2).3i,3l Moreover, these protocols
required excess equivalents of oxidants, elevated
temperatures, or potentially explosive diazonium salts. For this
reason, mild and environmentally friendly methods to access
sulfonated 4H-3,1-benzoxazines are still desirable.
method I
R1
O
AgNO3 / (NH4)2Ce(NO3)6
R2
S
O
80 C
R1
O
NH
N
R3
R3
DABCO  SO2)2, ArN2BF4
method II
O
fac-Ir(ppy)3
35 W CFL
b) This work: electrochemistry
R1
O
R2
S
O
R1
ArSO2NHNH2
O
metal-free, oxidant-free
room temperature
R2 R3
NH
R1 R2
O
O
O
N
R3
R3
O
O
Ar
Cl
R1
O
N
N
Figure 2. Strategies for the formation of sulfonated 4H-3,1-
benzoxazines a). Traditional chemical (method I) or
photochemical conditions (method II). b). Electrochemical
conditions.
Cl
N
H
N
N
N
H
Etifoxine
I
Fungicide
II
Herbicides
III
PR agonist
IV
Figure 1. 4H-3,1-benzoxazine and related bioactive molecules
We took up our study by using N-(2-(prop-1-en-2-
yl)phenyl)benzamide (1a) and p-toluenesulfonyl hydrazide (2a)
as model substrates to optimize the reaction conditions. The
best result was achieved by running the reaction of 1a and 2a in
anhydrous MeCN containing n-Bu4NBF4 as the electrolyte
equipped with a carbon rod anode and a platinum foil cathode
in an undivided cell under a galvanostatic condition at room
temperature. Under these conditions, the desired product 3a
was collected in 78% yield (Table 1, entry 1). A lower yield at
65% was obtained when the electrolysis was carried out in the
air (Table 1, entry 2). The study revealed that DMF is not a
suitable solvent for this reaction, providing 3a in 24% yield only
(Table 1, entry 3). Among a series of electrolytes (Table 1,
entries 4-7), n-Bu4NBF4 salt gave the optimal result. Using
By utilization of electrons as traceless reagents to activate the
reactants directly or indirectly, organic electrosynthesis has
been demonstrated to be an eco-friendly and highly efficient
synthetic technique to solve lingering problems.4 On the other
hand, radical cascade cyclizations (RCCs) have been considered
as powerful and efficient approaches for the building of
a. Key Laboratory of Functional Molecular Engineering of Guangdong Province,
School of Chemistry and Chemical Engineering, South China University of
Technology, Guangzhou, Guangdong 510640, China. e-mail: chehjm@scut.edu.cn
†Electronic Supplementary Information (ESI) available: [details of any
supplementary information available should be included here]. See
DOI: 10.1039/x0xx00000x
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platinum foil as anode or carbon rod as cathode, no 3a could be group, a 16% yield of the desired product (3m) was obtained.
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DOI: 10.1039/C9CC09551A
detected (Table 1, entries 8 and 10). Replacing carbon rod with The present system could also be employed to N-(2-(1-
RVC as anode or platinum foil with nickel as cathode, a very low phenylvinyl)phenyl)benzamide (3n) with a yield of 66%.
yield was furnished (Table 1, entries 9 and 11). Changing the However, no desired product could be collected when mono- or
current density (Table 1, entries 12 and 13) led to the decrease tri-substituted alkene was treated with p-toluenesulfonyl
of the yield.
A control experiment demonstrated the hydrazide.
indispensable nature of the electricity (Table 1, entry 14).
Table 1. Optimization of Reaction Conditions a
R2
O
S
O
S
O
C-Pt, undivided cell
R1
O
O
R2
janode = 0.19 mA cm-2
O
O
N
H
Ph
O
+ H2N
S
C-Pt, undivided cell
N
O
rt, 3.5 h
janode = 0.19 mA cm-2
O
H
O
R1
N
Ph
N
H
Ph
+
H2N
S
N
1
2
3
O
rt, 3.5 h
N
Ph
H
3a, R2 = 4-Me, 76%
3b, R2 = 4-t-Bu, 60%
3c, R2 = 4-OMe, 75%
3d, R2 = 4-F, 63%
3e, R2 = 4-Cl, 55%
3f, R2 = 2-Cl, 51%
3g, R2 = 4-Br, 38%
3h, R2 = 4-CF3, 51%
3i, R2 = 4-NO2, <5%
3j, R2 = H, 76%
3k, R2 = OH, 0%
3l, R2 = NH2, 0%
3m, R2 = I, 16%
R2
1a
2a
3a
O
S
entry
variation from the above conditions
none
yield (%)b
78
O
O
1
N
Ph
2
in the air
65
F
3
DMF instead of MeCN
24
O
S
O
S
O
4
n-Bu4NPF6 instead of n-Bu4NBF4
n-Bu4NClO4 instead of n-Bu4NBF4
LiClO4 instead of n-Bu4NBF4
NaClO4 instead of n-Bu4NBF4
Pt instead of carbon rod as an anode
70
S
O
O
O
Ph
5
47
O
O
O
N
Ph
N
Ph
6
trace
21
N
3n, 66%
Ph
3p, 0%
3o, 0%
7
a
Figure 3. Substrate scope of sulfonylhydrazines Standard
conditions: 1 (0.2 mmol), 2 (0.5 mmol), MeCN (2.5 mL), with 0.1
M n-Bu4NBF4 as electrolyte, janode = 0.19 mA cm−2. A carbon rod
(ϕ = 5 mm, immersion length: 1.5 cm) as an anode and a Pt foil
electrode (1 × 1.5 cm2) as a cathode, an undivided cell, N2, 3.5
h, rt. Isolated yields are shown.
8
0
9c
10
11d
12
13
RVC instead of carbon rod as an anode
carbon rod instead of Pt foil as a cathode
Ni instead of Pt foil as a cathode
janode = 0.30 mA cm−2, 2.2 h
39
0
17
44%
trace
0
janode = 0.10 mA cm−2, 7 h
SO2Ph
14
a
no electric current
C-Pt, undivided cell
janode = 0.19 mA cm-2
O
O
N
H
R3
+
Standard conditions: 1a (0.2 mmol), 2a (0.5 mmol), MeCN (2.5
mL), with 0.1 M n-Bu4NBF4 as electrolyte, janode = 0.19 mA cm−2 for
entry 1. A carbon rod (ϕ = 5 mm, immersion length: 1.5 cm) as an
anode and a Pt foil electrode (1 × 1.5 cm2) as a cathode, an
undivided cell, N2, 3.5 h, rt. b Yields were determined by 1H NMR
analysis of the crude reaction mixture using nitromethane as the
H2N
SO2Ph
N
rt, 3.5 h
N
R3
H
1
2
4
SO2Ph
O
SO2Ph
SO2Ph
O
O
N
N
R3
N
c
R
internal standard. RVC (reticulated vitreous carbon, 100 PPI,
1.0×1.5×0.5 cm3). d Ni foil (1 × 1.5 cm2).
4a, 75%
4b, R = 4-t-Bu, 57%
4c, R = 4-OMe, 73%
4d, R = 4-F, 59%
4e, R = 4-Cl, 54%
4f, R = 4-Br, 54%
4g
4h, R3 = 2-naphthyl, 52%
4i, R3 = 2-furyl, 67%
4j, R3 = 2-thienyl, 71%
4k, R3 = benzyl, 45%
4l, R3 = t-Bu, 75%
Under the optimal conditions, a set of sulfonylhydrazines were
tested and proved to be suitable substrates for this protocol
(Figure 3). The reactions of sulfonylhydrazines bearing electron-
donating groups with para-substitution patterns as well as
benzenesulfonylhydrazine could run smoothly with N-(2-(prop-
1-en-2-yl)phenyl)benzamide (1a) to afford the corresponding
sulfonated 4H-3,1-benzoxazine derivatives in moderate to good
yields (3a-3c, 3j). Electron-withdrawing groups such as fluoro,
chloro, bromo and trifluoromethyl on para- or meta- positions
of phenyl ring were also tolerated, and these transformations
afforded the corresponding products in 38% to 63% yields (3d-
3h). Unfortunately, the reaction with a reductively labile nitro
group on the substrate gave the product (3i) in a yield of less
than 5%. In additon, the tolerance of the oxidatively liable
functional groups was studied. The reaction of the
sulfonylhydrazine with a hydroxy or an amino group on the
benzene ring could not afford the desired product (3k and 3l).
For the reaction of the sulfonyl hydrazide bearing the iodide
, R = 4-CF3, 62%
a
Figure 4. Substrate scope of styrenyl amides Standard
conditions: 1 (0.2 mmol), 2 (0.5 mmol), MeCN (2.5 mL), with 0.1
M n-Bu4NBF4 as electrolyte, janode = 0.19 mA cm−2. A carbon rod
(ϕ = 5 mm, immersion length: 1.5 cm) as an anode and a Pt foil
electrode (1 × 1.5 cm2) as a cathode, an undivided cell, N2, 3.5
h, rt. Isolated yields are shown.
To explore the substrate scope, we then investigated a
series of substrates with different amides (Figure 4). First,
the reactivity of N-(2-(prop-1-en-2-yl)phenyl)benzamide
with substituents on the benzamide ring was studied. The
sulfonyl radical cascade cyclization confirmed amenable to
both electron-donating group and electron-withdrawing
group substituents. Thus, a variety of useful functional
groups were tolerated, including methyl, tert-butyl,
2 | J. Name., 2012, 00, 1-3
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methoxyl, fluoro, chloro, bromo and trifluoromethyl
substituents (4a-4g). Notably, naphthyl and
heteroaromatic amides (4h-4j) were effective for this
reaction. Finally, it was delighted to find that alkyl amides
(4k-4l) could be converted to the corresponding products
in moderate to good yields.
On the basis of the above experimental results, a possible
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mechanism for the sulfonylation/cyclizDaOtioI:n10.o10f3s9u/Cb9sCtrCa0t9e551A
1a is shown (Figure 7). p-Toluenesulfonyl hydrazide 2a was
transformed to the corresponding sulfonyl radical 10
through electro-oxidation and deprotonation together
with the release of N2.8a,10 Then, the sulfonyl radical 10
added to alkene 1a to form the radical intermediate 11.
Subsequently, the radical intermediate 11 could be
oxidized by anode directly to afford the corresponding
carbon cation 12. After the nucleophilic attack and
deprotonation, the desired sulfonated 4H-3,1-
benzoxazine 3a was generated.11 Simultaneously, protons
converted to H2 via cathodic reduction.
O
standard conditions
H
N
H
Ph
a)
+
OH
N
H2N
Ts
2.0 eq. BHT
Ts
1a
2a
5
[M+Na]+: 397.1803
HRMS detected
H
>95% 1a recovered
O
N
S
NH2
O
4 H+
Ts
O
O
standard conditions
H
N
2a
N
Ph
b)
+
H
H2N
Ts
+4 e-
-3 H+, -3 e-
N
Ph
O
O
N
-N2
S
S
N
O
O
2 H2
7
2a
8, 26%
9
10
Figure 5. Control experiments
_
O
+
S
NH
O
O
O
N
H
1a
11
-e-
O
O
S
S
O
O
-H+
O
O
N
H
N
12
3a
Figure 7. Proposed mechanism
In summary, we have demonstrated an efficient methodology
for the formation of sulfonated 4H-3,1-benzoxazines by
electrochemical radical cascade cyclization. A wide range of
styrenyl amides and various sulfonylhydrazines could
participate in this reaction to afford 4H-3,1-benzoxazines cores
with the concomitant generation of C-S and C-O bonds under
metal- and external chemical oxidant-free conditions at
ambient temperature. Further exploration on the synthetic
applications and biological evaluations of the desired products
are undergoing in our lab.
Figure 6. Cyclic voltammograms of 0.1 M n-Bu4NBF4 solution
in MeCN at room temperature (a) None (b) 1a (1.5×10-6
mmol/L) (c) 2a (4×10-6 mmol/L) (d) 1a (1.5×10-6 mmol/L) + 2a
(4×10-6 mmol/L). The voltammogram was obtained with Pt wire
as an auxiliary electrode and a saturated calomel electrode
(SCE) as a reference electrode. The scan rate was 0.1 V/s on a
platinum disk electrode (d = 2 mm).
Further studies were performed to analyze the reaction
mechanism. First, the sulfonylation/cyclization of
substrate 1a was totally suppressed upon adding the
radical scavenger BHT (2,6-di-tert-butyl-4-methylphenol)
with the radical trapping adduct 5 detected (HR−MS
analysis), supportive of a radical process. (Figure 5a). The
radical clock substrate 7 was also examined, and the
reaction afforded the ring-closed product 8 in 26% yield
(Figure 5b). It was hypothesised that the ring-closed form
was thermodynamically favored, as the α-phenyl group
stabilized the cyclopropylcarbinyl radical.9 Meanwhile, CV
experiments have been conducted (Figure 6). The results
showed that anodic oxidation of 1a and 2a, occurred at
potentials of 1.74 V and 1.50 V vs. SCE, respectively (Fig. 6,
curves b and c). Thus, it was suggested that 2a was
Conflicts of interest
There are no conflicts to declare.
Acknowledgements
We are grateful to the National Natural Science Foundation of
China (Grant Nos. 21672074 and 21372089) for financial
support.
oxidized preferentially than 1a in this electrolysis process
.
Notes and references
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 3
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1
(a) E. V. Gromachevskaya, F. V. Kvitkovskii, T. P. Kosulina and
V. G. Kul’nevich, Chem. Heterocycl. Compd. 2003, 39,
137−155. (b) N. Djabrouhou and M.-H. Guermouche, J. Pharm.
Biomed. Anal. 2014, 100, 11−20. (c) H. Sugiyama, K. Hosoda,
Y. Kumagai, M. Takeuchi and M. Okada, US 4596801, 1986. (d)
P. Zhang, E. A. Terefenko, A. Fensome, J. Wrobel, R.
Winneker, S. Lundeen, K. B. Marschke and Z. Zhang, J. Med.
Chem. 2002, 45, 4379−4382. (e) P. Zhang, E. A. Terefenko, A.
Fensome, Z. Zhang, Y. Zhu, J. Cohen, R. Winneker, J. Wrobel
and J. Yardley, Bioorg. Med. Chem. Lett. 2002, 12, 787−790.
(a) J. J. V. Eynde, J. Godin, A. Mayence, A. Maquestiau and E.
Anders, Synthesis 1993, 9, 867−869. (b) G. Spagnol, A. Rajca
and S. Rajca, J. Org. Chem. 2007, 72, 1867−1869. (c) C. U.
Maheswari, G.S. Kumar, M. Venkateshwar, R. A. Kumar, M. L.
Kantam and K. R. Reddy, Adv. Synth. Catal. 2010, 352,
341−346. (d) B. Han, X.-L. Yang, C. Wang, Y.-W. Bai, T.-C. Pan,
X. Chen and W. J. Yu, Org. Chem. 2012, 77, 1136−1142.
(a) Y.-M. Wang, J. Wu, C. Hoong, V. Rauniyar and F. D. Toste,
J. Am. Chem. Soc. 2012, 134, 12928−12931. (b) S. Jana, A.
Ashokan, S. Kumar, A. Verma and S. Kumar, Org. Biomol.
Chem. 2015, 13, 8411−8415. (c) X.-Q. Chu, X.-P. Xu, H. Meng
and S.-J. Ji, RSC Adv. 2015, 5, 67829−67832. (d) H. Yang, X.-H.
Duan, J.-F. Zhao and L.-N. Guo, Org. Lett. 2015, 17,
1998−2001. (e) X.-H. Duan, J.-F. Zhao, H. Yang and L.-N. Guo,
J. Org. Chem. 2015, 80, 11149−11155. (f) Q.-H. Deng, J.-R.
Chen, Q. Wei, Q.-Q. Zhao, L.-Q. Lu and W.-J. Xiao, Chem.
Commun. 2015, 51, 3537−3540. (g) W. Fu, X. Han, M. Zhu, C.
Xu, Z. Wang, B. Ji, X.-Q. Hao and M.-P. Song, Chem. Commun.
2016, 52, 13413−13416. (h) X.-Q. Chu, D. Liu, Z.-H. Xing, X.-P.
Xu and S.-J. Ji, Org. Lett. 2016, 18, 776−779. (i) T. Liu, Q. Zheng,
Z. Li and J. Wu, Adv. Synth. Catal. 2018, 360, 865−869. (j) J.
Wang, R. Sang, X. Chong, Y. Zhao, W. Fan, Z. Li and J. Zhao,
Chem. Commun. 2017, 53, 7961−7964. (k) M. Chaitanya and
P. Anbarasan, Org. Lett. 2018, 20, 1183−1186. (l) J. Wu, Y.
Zong, C. Zhao, Q. Yan, L. Sun, Y. Li, J. Zhao, Y. Ge and Z. Li, Org.
Biomol. Chem. 2019, 17, 794−797.
For recent representative reviews about electrosynthesis,
see: (a) M. Yan, Y. Kawamata and P. S. Baran, Chem. Rev. 2017,
117, 13230−13319. (b) Y. Jiang, K. Xu and C.-C. Zeng, Chem.
Rev. 2018, 118, 4485−4540. (c) J.-I. Yoshida, A. Shimizu and R.
Hayashi, Chem. Rev. 2018, 118, 4702−4730. (d) K. Liu, C. L.
Song and A. Lei, Org. Biomol. Chem. 2018, 16, 2375–2387. (e)
A. Wiebe, T. Gieshoff, S. Mçhle, E. Rdrigo, M. Zirbes and S. R.
Waldvogel, Angew. Chem. Int. Ed. 2018, 57, 5594−5619. (f) S.
Mçhle, M. Zirbes, E. Rodrigo, T. Gieshoff, A. Wiebe and S. R.
Waldvogel, Angew. Chem. Int. Ed. 2018, 57, 6018−6041. (g) G.
S. Sauer and S. Lin, ACS Catal. 2018, 8, 5175−5187. (h) K. D.
Moeller, Chem. Rev. 2018, 118, 4817−4833. (i) N. Sauermann,
T. H. Meyer, Y. A. Qiu, and L. Ackermann, ACS Catal. 2018, 8,
7086−7103. (j) C. Ma, P. Fang and T.-S. Mei, ACS Catal. 2018,
8, 7179−7189. (k) M. D. Kärkäs, Chem. Soc. Rev. 2018, 47,
5786−5865. (l) R. Francke and D. Little, ChemElectroChem
2019, 6, 4373−4382. (m) C. Song, K. Liu, X. Dong, C.-W. Chiang
and A. Lei, Synlett 2019, 30, 1149−1163. (n) T. Noël, Y. Cao,
and G. Laudadio, Acc. Chem. Res. 2019, 52, 2858−2869. (o) P.
Xiong and H.-C. Xu, Acc. Chem. Res. 2019, 52, 3339−3350. (p)
289−306. (b) L. J. Sebren, J. J. Devery and C. R. JV. iSewteAprthicelenOsnolinne,
ACS Catal. 2014, 4, 703−716. (c) B. Zhang and A. Studer, Chem.
DOI: 10.1039/C9CC09551A
Soc. Rev. 2015, 44, 3505−3521. (d) X. J. Baringo and D. J.
Procter, Acc. Chem. Res. 2015, 48, 1263−1275. (e) R.
Ardkhean, D. F. J. Caputo, S. M. Morrow, H. Shi, Y. Xiong and
E. A. Anderson, Chem. Soc. Rev. 2016, 45, 1557−1569. (f) M.
D. Kärkäs, J. A. Jr. Porco and C. R. J. Stephenson, Chem. Rev.
2016, 116, 9683−9747. (g) M. P. Plesniak, H.-M. Huang and D.
J. Procter, Nat. Rev. Chem. 2017, 1, 0077.
For recent representative works about radical cascade
cyclizations triggered by sulfonyl radicals, see: (a) Q. Tian, P.
He and C. Kuang, Org. Biomol. Chem. 2014, 12, 6349−6353. (b)
J. Wen, W. Wei, S. Xue, D. Yang, Y. Lou, C. Gao and H. Wang,
J. Org. Chem. 2015, 80, 4966−4972. (c) Y.-L. Zhu, B. Jiang, W.-
J. Hao, J.-K. Qiu, J. Sun, D.-C. Wang, P. Wei, A.-F. Wang, G. Li
and S.-J. Tu, Org. Lett. 2015, 17, 6078−6081. (d) L. Shi, H.
Wang, H. Yang and H. Fu, Synlett 2015, 26, 688−694. (e) Y.-L.
Zhu, B. Jiang, W.-J. Hao, A.-F. Wang, J.-K. Qiu, P. Wei, D.-C.
Wang, G. Li and S.-J. Tu, Chem. Commun. 2016, 52,
1907−1910. (f) J.-K. Qiu, C. Shan, D.-C. Wang, P. Wei, B. Jiang,
S.-J. Tu, G. Li and K. Guo, Adv. Synth. Catal. 2017, 359,
4332−4339. (g) H. Li, Z. Cheng, C.-H. Tung and Z. Xu, ACS Catal.
2018, 8, 8237−8243. (h) K.-L. Zuo, Y.-H. He and Z. Guan, Eur. J.
Org. Chem. 2019, 5, 939−948.
For recent representative works about electrochemical
radical cascade cyclizations, see: (a) Y.-Y. Jiang, S. Liang, C.-C.
Zeng, L.-M. Hua and B.-G. Sun, Green Chem. 2016, 18,
6311−6319. (b) C. Adouama, R. Keyrouz, G. Pilet, C.
Monnereau, D. Gueyrard, T. Noël and M. Médebielle, Chem.
Commun. 2017, 53, 5653−5656. (c) J. Wen, W. Shi, F. Zhang,
D. Liu, S. Tang, H. Wang, X.-M. Lin and A. Lei, Org. Lett. 2017,
19, 3131−3134. (d) M. Lübbesmeyer, D. Leifert, H. Schäfer and
A. Studer, Chem. Commun. 2018, 54, 2240−2243. (e) K.-Y. Ye,
Z. Song, G. S. Sauer, J. H. Harenberg, N. Fu and S. Lin, Chem.
Eur. J. 2018, 24, 12274−12279. (f) P. Xiong, H.-H. Xu, J. Song
and H.-C. Xu, J. Am. Chem. Soc. 2018, 140, 2460−2464. (g) J.
Hua, Z. Fang, J. Xu, M. Bian, C. Liu, W. He, N. Zhu, Z. Yang and
K. Guo, Green Chem. 2019, 21, 4706−4711. (h) Z. Ruan, Z.
Huang, Z. Xu, G. Mo, X. Tian, X.-Y. Yu and L. Ackermann, Org.
Lett. 2019, 21, 1237−1240. (i) J. D. Herszman, M. Berger and
S. R. Waldvogel, Org. Lett. 2019, 21, 7893−7896. (j) M.-X. He,
Z.-Y. Mo, Z.-Q. Wang, S.-Y. Cheng, R.-R. Xie, H.-T. Tang and Y.-
M. Pan, Org. Lett. 2020, 22, 724−728. (k) X.-J. Meng, P.-F.
Zhong, Y.-M. Wang, H.-S. Wang, H.-T. Tang and Y.-M. Pan, Adv.
Synth. Catal. 2019, DOI: 10.1002/adsc.201901115.
6
2
3
7
4
8
9
(a) Y. Zhao, Y.-L. Lai, K.-S. Du, D.-Z. Lin and J.-M. Huang, J. Org.
Chem. 2017, 82, 9655−9661. (b) K.-S. Du and J.-M. Huang,
Green Chem. 2018, 20, 1405−1411. (c) T.-J. He, Z. Ye, Z. Ke and
J.-M. Huang, Nat. Commun. 2019, 10, 833. (d) S.-M. Yang, T.-
J. He, D.-Z. Lin and J.-M. Huang, Org. Lett. 2019, 21,
1958−1962.
(a) A. L. J. Beckwith and V. W. Bowry, J. Am. Chem. Soc. 1994,
116. 2710−2716. (b) M. Newcomb, Encyclopedia of Radicals in
Chemistry, Biology and Materials. 2012, John Wiley & Sons,
Ltd. (c) X. Li, F. Lin, K. Huang, J. Wei, X. Li, X. Wang, X. Geng
and N. Jiao, Angew. Chem. Int. Ed. 2017, 56, 12307−12311.
F. Marken and J. D. Wadhawan, Acc. Chem. Res. 2019, 52, 12, 10 For recent representative works about the formation of
3325−3338. (q) M. Elsherbini and T. Wirth, Acc. Chem. Res.
2019, 52, 12, 3287−3296. (r) Y. Yuan and A. Lei, Acc. Chem.
Res. 2019, 52, 12, 3309−3324. (s) S. R. Waldvogel, S. Lips, M.
Selt, B. Riehl and C. J. Kampf, Chem. Rev. 2018, 118,
6706−6765. (t) J. Chen, S. Lv and S. Tian, ChemSusChem, 2019,
12, 115−132. (u) X. Han, K. Wang, W. Gao and J. Chen, Adv.
sulfonyl radical via anode oxidation, see: (a) Y. Yuan, Y. Cao, Y.
Lin, Y. Li, Z. Huang and A. Lei, ACS Catal. 2018, 8,
10871−10875. (b) Y.-Z. Zhang, Z.-Y. Mo, H.-S. Wang, X.-A.
Wen, H.-T. Tang and Y.-M. Pan, Green Chem. 2019, 21,
3807−3811. (c) Y. J. Kim and D. Y. Kim, Tetrahedron Letters
2019, 60, 1287−1290.
Synth. Catal. 2019, 361, 2804−2824. (v) S. Lv, G. Zhang, J. Chen 11 An alternative mechanism involving 6-endo-trig cyclization of
and
W.
Gao,
Adv.
Synth.
Catal.
2019
the radical 11 could also occur, followed by subsequent
oxidation and deprotonation to form the product.
DOI:10.1002/adsc.201900750.
5
For recent representative reviews about radical cascade
cyclizations, see: (a) M. Malacria, Chem. Rev. 1996, 96,
4 | J. Name., 2012, 00, 1-3
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