Fast regioselective sulfonylation of pyridine/quinoline N-oxides induced by iodine

Article abstract of DOI:10.1039/c6ob00925e

Fast sulfonylation of pyridine/quinoline N-oxides induced by iodine is demonstrated herein. The regioselective protocol occurs under metal-free conditions in a short reaction time (10 min), exhibiting high efficiency (up to 92% yield) and good compatibili

Full text of DOI:10.1039/c6ob00925e

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Biomolecular Chemistry
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Fast regioselective sulfonylation of pyridine/
quinoline N-oxides induced by iodine†
Cite this: DOI: 10.1039/c6ob00925e
a,b
a
a
a
a
b
Ruijia Wang, Zebing Zeng,* Chuang Chen, Niannian Yi, Jun Jiang, Zhong Cao,
a
a
Wei Deng and Jiannan Xiang*
Received 29th April 2016,
Accepted 16th May 2016
Fast sulfonylation of pyridine/quinoline N-oxides induced by iodine is demonstrated herein. The regio-
selective protocol occurs under metal-free conditions in a short reaction time (10 min), exhibiting high
efficiency (up to 92% yield) and good compatibility (up to 33 examples). A gram-scale reaction was con-
ducted with only a slight loss of production.
DOI: 10.1039/c6ob00925e
www.rsc.org/obc
Introduction
Hetero-aryl compounds, especially pyridine/quinoline deriva-
tives, play important roles in agricultural, industrial and
1
pharmaceutical chemistry. For instance, substituted quino-
2
lines have been broadly used for the treatment of malaria.
Many functional groups have been introduced onto the quino-
line skeleton at the ortho position to block detoxification,
3
leading to a dramatic decrease in therapeutic activity. Among
these groups, sulfone has been considered a good option for
being a versatile synthetic intermediate, and for inhibiting a
4
broad range of physical properties. Thus, significant contri-
butions have been devoted to the synthesis of these important
molecules. Typically, pre-activated substrates such as haloge-
nated pyridines/quinolines are employed for coupling with
5
sodium sulfinic acid or thioetherification and subsequent oxi-
6
dation towards the sulfonylated products. However, low
efficiency and redundant steps restrict these methodologies for
general applications. Herein, construction of the carbon–hetero
bonds through C–H bond activation was employed for the for-
Scheme 1 Synthesis of sulfonyl quinolones.
7
mation of sulfonyl pyridines/quinolines because of the easy
operation and high step- and atom-economy. With this back-
ground, pyridine/quinoline was coupled successfully in the pres-
ence of transition metal catalysts such as copper with diverse
Within this context, Zhao and Li disclosed a novel reaction
between quinoline N-oxides and sulfonyl chlorides that was
mediated by H-phosphonate through a direct C–H bond acti-
8
sulfonylation reagents such as sulfonyl chloride (Scheme 1a).
9
vation pathway (Scheme 1b). Being aware of the fact that sulfonyl
However, from environmental and economic views, it is still
highly desirable to develop new protocols without the partici-
pation of noble or toxic transition metal catalysts.
10
hydrazides also act as versatile sulfonylation reagents; we
describe the unprecedented reaction between pyridine/quinoline
N-oxides and sulfonyl hydroazides, which was completed within
10 minutes in the presence of elemental iodine (Scheme 1c).
a
State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry
and Chemical Engineering, Hunan University, Changsha, 410082, P.R. China.
E-mail: jnxiang@hun.edu.cn, zbzeng@hnu.edu.cn
Results and discussion
b
Hunan Provincial Key Laboratory of Materials Protection for Electric Power and
Transportation, School of Chemistry and Biological Engineering, Changsha
University of Science and Technology, Changsha 410004, P.R. China
Firstly, the reaction between the model substrates quinoline
N-oxide (1a) and tosyl hydrazide (TsNHNH , 2a) was opti-
2
†
Electronic supplementary information (ESI) available. See DOI: 10.1039/
c6ob00925e
mized, as summarized in Table 1. In the presence of 1,8-diaza-
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a
Table 1 Optimization of the reaction conditions
also played a crucial role in the reaction. Among all the sol-
vents tested, acetonitrile was superior to the other solvents,
such as THF, toluene, DMSO, and DCE, for this transformation
(
entries 13–16). Usage of two equivalents of 2a was crucial for
the complete consumption of 1a (entry 17); otherwise, side reac-
11
tions and undesired sulfonothioate (4b) appeared. Addition-
ally, the efficiency of the transformation diminished remarkably
with decreased NaOH or H O loadings or a lower reaction
b
Entry
[I]
Base
[O]
Sol.
Yield (%)
2
2
1
2
3
4
I
2
DBU
DBU
DBU
DBU
DBU
DBU
TBHP
TBHP
TBHP
TBHP
TBHP
TBHP
TBHP
TBHP
TBHP
DTBP
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
THF
26
19
21
12
18
26
40
Trace
60
28
Trace
92(88)
63
34
Trace
40
55
74
temperature (entries 18–20), and a similar trend was recorded
as the loadings of the base increased. Thus, two equivalents of
hydrogen peroxide and a 1 : 3 or 1 : 4 ratio of iodine to sodium
hydroxide (entries 21 and 22) were used in our subsequent
investigations. Finally, the control reactions confirmed that no
or a trace amount of product formed in the absence of either
the iodine reagents or base (entries 23 and 24).
Using the optimal conditions (Table 1, entry 12), the scope
of heterocyclic N-oxides was examined for the present reaction
(Table 2). The methyl group-substituted substrates readily
underwent the regioselective sulfonylation reaction, for
example, 3-, 4-, 6-, 7- and 8-methyl quinolines 3ba–3fa were
successfully produced in yields ranging from 72%–82%
NIS
NaI
TBAI
c
5
6
I
2
I
2
I
2
I
2
I
2
I
2
I
2
I
2
I
2
I
2
I
2
I
2
I
2
I
2
I
2
I
2
I
2
I
2
d
7
8
9
2
K CO
3
Cs CO
2
3
NaOH
NaOH
NaOH
NaOH
NaOH
NaOH
NaOH
NaOH
NaOH
NaOH
NaOH
NaOH
NaOH
NaOH
NaOH
—
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
K
2
S
2
O
8
e
H
H
H
H
H
H
H
H
H
H
H
H
H
2
O
2
O
2
O
2
O
2
O
2
O
2
O
2
O
2
O
2
O
2
O
2
O
2
O
2
2
2
2
2
2
2
2
2
2
2
2
2
Toluene
DMSO
DCE
f
g
h
i
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
(
entries 1–5). In a similar way, 8-ethyl quinoline N-oxide (1g)
59
53
33
n.d.
n.d.
Trace
produced the desired compound 3ga in an acceptable yield of
up to 66% (entry 6). By comparison with 3ba, the substrate
with a methoxy group on the C6 position showed higher
efficiency, and the desired product 3ha was furnished in 86%
yield (entry 7). Additionally, the activity of the C5-occupied qui-
noline N-oxide was evaluated; for example, 2-sulfonyl-5-allyloxy
quinoline (1i) was generated in a medium yield, 79% for entry
was 8. Simultaneously, halo groups were well tolerated but had a
j
k
l
—
I
2
a
Reaction conditions: 1a (0.3 mmol), 2a (0.6 mmol), iodic reagent
(
1
0.3 mmol), base (0.6 mmol), oxidant (0.9 mmol) and 2.0 mL of sol. at
00 °C. Estimated by H NMR spectroscopy using diethyl phthalate
b
1
c
d
as an internal reference. 60 mol% I
used. Isolated yield. 1.5 equiv. of 2a was used. 1.5 equiv. of NaOH
was used. 2 equiv. of H
was used. 4.0 equiv. of NaOH was used. n.d. stands for not detected.
2
was used. 1.2 equiv. of I
2
e
f
g
negative effect on the transformation for 6-chloroquinoline
N-oxide (1j); 6-bromoquinoline N-oxide (1k) provided the
desired 2-sulfonyl quinolines 3ja and 3ka in 71% and 63%
yields, respectively (entries 9 and 10). However, the variation of
h
i
j
2
O
2
was used. At 80 °C. 3.0 equiv. of NaOH
k
l
bicyclo[5.4.0]undec-7-ene (DBU) as a base and tert-butyl hydro- the halo group on the heterocyclic moiety did not affect the
peroxide (70% in water, TBHP) as an oxidant, elemental iodine yields dramatically, as 2-sulfonyl-3-bromoquinoline (3la) and
successfully catalysed the reaction in acetonitrile, furnishing 2-sulfonyl-3-iodoquinoline (3ma) were provided in relatively
the desired 2-sulfonyl quinoline (3aa) in 26% yield as indi- lower yields of 60% and 65% for entries 11 and 12, respect-
cated by NMR calculations (entry 1). Other iodic sources, such ively. To our satisfaction, the reaction of 6-methoxycarbonyl
as N-iodosuccinimide (NIS, entry 2), NaI (entry 3) and tetra- quinoline N-oxide (1n) and 6-(2-phenylethynyl)quinoline
butyl ammonium iodide (TBAI, entry 4) had negative effects N-oxide (1o) with tosyl hydrazide (2a) is a good exemplification
on the conversion of the substrates, and less than 21% yields of the good compatibility, and the desired products 3na and
were achieved (entries 2–4). Disappointingly, changing the 3oa were produced in 63% and 70% yields, respectively
loadings of iodine had no positive effect on the transform- (entries 13 and 14). By chance, isoquinoline N-oxide (1p)
ation, with only 18% and 26% yields obtained when 0.6 reacted with 2a readily, offering 1-tosyl isoquinoline (3pa) as
2
equivalents and 1.2 equivalents of I were employed, respect- the exclusive product probably due the influence of the
ively (entries 5 and 6). NaOH, producing 60% yield of the N-oxide group on the C–H bond of the C1 position (entry 15).
desired 2-tosyl quinoline (3aa), exhibited higher efficiency Pyridine N-oxides were also tolerated in the system, and pyri-
compared with DBU, K
optimization of the oxidants was conducted, and the reactions 2-tosyl-4-chloro pyridine (3ra) were obtained in 66% and 65%
involving di-tert-butyl peroxide (DTBP, entry 10) and K
yields (entries 16 and 17). However, only mono-substituted
entry 11) provided decreased final yields of only 28% or even pyridines were produced likely because the ortho-C–H bond of
traces of the desired products, separately. On the other hand, the product remained inert without the assistance of the
inexpensive and environmentally friendly H provided the N-oxide group for activation.
best performance, and the yield was promoted to a 92% NMR
On the other hand, the compatibilities of the functional
yield and 88% isolated yield (entry 12). Meanwhile, the solvent groups on the sulfonyl hydrazides were also evaluated in the
2 3 2 3
CO and Cs CO (entries 7–9). Further dine derivatives such as 2-tosyl-4-methyl pyridine (3qa) and
2 2 8
S O
(
2 2
O
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a
a
Table 2 Substrate scope of heterocyclic N-oxides
Table 3 Substrate scope of sulfonyl hydrazides
b
b
Entry
1
2
3
R
C
3-CH
4-CH
2,3,5-(CH
4-FC
4-ClC
4-BrC
2-BrC
Yield (%)
Entry
1
3
R
Yield (%)
1
2
3
1f
1f
1f
1a
1f
1f
1f
1f
1f
1f
1a
1a
1f
1q
1r
1q
2b
2c
2d
2e
2f
2g
2h
2i
2j
2k
2l
2m
2n
2o
2d
2h
3fb
3fc
3fd
3ae
3ff
3fg
3fh
3fi
6
H
5
82
70
69
82
68
80
76
72
75
72
68
68
62
58
56
1
2
3
4
5
6
1b
1c
1d
1e
1f
1g
1h
3ba
3ca
3da
3ea
3fa
3ga
3ha
3-CH
4-CH
6-CH
7-CH
8-CH
8-C H
2 5
6-OCH
3
3
3
3
3
3
72
82
80
78
76
66
86
3
C
6
H
4
c
3
OC
6
H
4
C
4
5
6
7
8
9
3
)
3
H
6 2
6
H
4
6
H
4
c
6
H
H
4
4
7
6
8
1i
3ia
79
3fj
4-CNC
4-NO
6
H
4
1
1
0
1
3fk
3al
3am
3fn
3qo
3rd
3qh
2
C
H
6 4
2-Pyridinyl
Cl(CH
2-Naphthyl
4-(t-Bu)–C
4-CH OC
4-BrC
c
9
1j
1k
1l
1m
1n
3ja
3ka
3la
3ma
3na
6-Cl
6-Br
3-Br
3-I
71
63
60
65
63
12
13
14
15
16
2
)
3
c
1
1
1
1
0
1
2
3
c
c
c
d
d
d
6
H
4
3
6
H
4
6-COOCH
3
6
H
4
<10%
1
4
1o
3oa
70
a
Reaction conditions: 1 (0.5 mmol), 2 (1.0 mmol), I
(1.5 mmol) and 4.0 mL of CH
Isolated yields. 1 (0.5 mmol), 2 (1.0 mmol), NaI (1.0 mmol), TBHP
2
(0.5 mmol),
3
CN at 100 °C.
NaOH (1.0 mmol), H
O
2 2
b
c
c
d
1
1
5
6
1p
1q
3pa
3qa
67
66
3
(1.5 mmol) and 4.0 mL of CH CN at 100 °C. 1 (0.5 mmol),
2
(1.0 mmol), NaI (1.0 mmol), TBHP (1.5 mmol), t-BuOK (potassium
d
tert-butoxide, 1.0 mmol) and 4.0 mL of CH CN at 100 °C.
3
d
17
1r
3ra
65
By contrast, the position of the halo groups did not affect
the yield because 2-(2-bromophenylsulfonyl)quinoline (3fi) was
generated in a slightly decreased yield of 72%, entry 8. Other
electron-deficient aryl sulfonyl hydrazides were also compatible
a
Reaction conditions: 1 (0.5 mmol), 2a (1.0 mmol), I
(1.5 mmol) and 4.0 mL of CH
Isolated yields. 1 (0.5 mmol), 2a (1.0 mmol), NaI (1.0 mmol), TBHP
2
(0.5 mmol),
3
CN at 100 °C.
NaOH (1.0 mmol), H
O
2 2
b
c
d
(
1.5 mmol) and 4.0 mL of CH
1.0 mmol), NaI (1.0 mmol), TBHP (1.5 mmol), t-BuOK (potassium
CN at 100 °C.
3
CN at 100 °C. 1 (0.5 mmol), 2a with the transformation; as exemplified by entries 9 and 10,
-(4-nitrilphenyl)-sulfonyl quinoline (3fj) and 2-(4-nitrophenyl)-
(
2
tert-butoxide, 1.0 mmol) and 4.0 mL of CH
3
sulfonyl quinoline (3fk) were furnished in 75% and 72% yields,
respectively. Except the phenyl group, the other hetero-aromatic
groups were isolated in medium yields, such as 2-pyridinyl sul-
system. As shown in Table 3, with quinoline N-oxide (1a), fonyl-decorated quinoline (3al) in 68% yield, entry 11. Notably,
-methyl quinoline N-oxide (1f), 4-methyl pyridine N-oxide long-chain aliphatic groups were also tolerated in the reaction;
1q) and 4-chloropyridine N-oxide (1r) as the model substrates, 2-(1-chloropropyl)sulfonyl quinoline (3am) was successfully iso-
8
(
sulfonyl hydrazides bearing various groups produced diverse lated in medium yield, 68% in entry 12. 2-Naphthyl sulfonyl
sulfonyl-decorated quinolines in medium to good yields. hydrazide (2n) smoothly reacted with quinoline derivative 1f,
Under the optimal conditions, phenyl sulfonyl hydrazide (2b) affording the desired product (3fn) in an acceptable yield (62%
readily coupled with substrate 1f, producing the desired in entry 13). Finally, the results of the sulfonylation of pyridine
product 3fb in 82% yield (entry 1). However, electron-rich, aro- N-oxides indicate that electron-deficient aryl sulfonyl hydrazides
matic, fused, sulfonyl hydrazides underwent the sulfonylation have a negative effect on the transformation (entries 14–16).
reaction smoothly. 3-Methylphenyl sulfonyl hydrazide (2c) and
In order to study the reaction mechanism, firstly, we
4
-methoxyphenyl hydrazide (2d) provided the 2-sulfonyl quino- assumed that the reaction might take place through a radical
lines 3fc and 3fd in 70% and 69% yields, respectively (entries 2 pathway. However, the addition of radical particle scavengers,
and 3). Bulkier 2-(2,3,5-trimethylphenyl)sulfonyl quinoline such as tetra-methyl piperidine 1-oxyl (TEMPO) or benzoqui-
(
3ae) was isolated in 82% yield (entry 4). Moreover, the influ- none (BQ), for the capture of free-radical intermediates did not
ence of the halo groups over the yields was also tested in the affect the efficiency of the transformation; isolated yields of up
system. For instance, 2-(4-fluorophenylsulfonyl)quinoline (3ff), to 85% of the desired product were obtained without any loss
2
-(4-chlorophenylsulfonyl)quinoline (3fg) and 2-(4-bromophe- (Scheme 2, eqn (1)). The reaction mechanism remains unclear,
nylsulfonyl)quinoline (3fh) were produced in yields ranging but the experiments do not support a radical pathway for this
from 68% to 80% (entries 5–7).
coupling reaction.
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Method B: A 10 mL round-bottomed flask was charged with
quinoline N-oxides (1, 0.5 mmol), sulfonyl hydrazide (2,
1
1
.0 mmol), NaI (150.0 mg, 1.0 mmol), TBHP (70% in water,
92.8 mg, 1.5 mmol), and CH CN (4.0 mL). The mixture was
3
stirred in an ambient atmosphere at 100 °C. After completion
of the reaction (ca. 10 min), which was monitored by TLC, the
mixture was cooled to room temperature and quenched with
an aqueous solution of saturated Na S O (10 mL). After extrac-
Scheme 2 Control reactions.
2 2 3
tion with CH
bined and dried over anhydrous Na
2
Cl
2
(3 × 15 mL), the organic phases were com-
SO . The solvent was
2
4
removed, and the residual crude product was purified by flash
column chromatography with a mixture of n-hexane and ethyl
acetate to give the desired product in the noted yields. (Care
must be taken regarding the released nitrogen gas and aceto-
nitrile vapour.)
Method C: A 10 mL round-bottomed flask was charged with
pyridine N-oxides (1, 0.5 mmol), sulfonyl hydrazide (2,
Scheme 3 Gram-scale reaction between 1a and 2a.
1
1
.0 mmol), NaI (150.0 mg, 1.0 mmol), TBHP (70% in water,
92.8 mg, 1.5 mmol), t-BuOK (112.0 mg, 1.0 mmol), and
Moreover, to demonstrate the high efficiency of the newly
developed 2-sulfonylation protocol, a gram-scale reaction
between quinoline N-oxide (1a) and tosyl hydrazide (2a) was
CH CN (4.0 mL). The mixture was stirred in an ambient atmo-
3
sphere at 100 °C. After completion of the reaction, which was
monitored by TLC, the mixture was cooled to room tem-
perature and quenched with an aqueous solution of saturated
Na S O (10 mL). After extraction with CH Cl (3 × 15 mL), the
2 2 3 2 2
organic phases were combined and dried over anhydrous
Na SO . The solvent was removed, and the residual crude
product was purified by flash column chromatography with a
mixture of n-hexane and ethyl acetate to give the desired
product in the noted yields. (Care must be taken regarding the
released nitrogen gas and acetonitrile vapour.)
carried out (Scheme 3). Satisfactorily, 1.452
g of 1a
(10.0 mmol) reacted with TsNHNH2 under the optimal con-
ditions, affording 2.264 g of the final product 3aa in 80%
yield. These results indicate that the transformation exhibits
great potential for larger scale applications.
2
4
Conclusions
In conclusion, an iodine-induced sulfonylation protocol of
heterocyclic N-oxides was demonstrated herein. This novel
2
-sulfonyl quinoline/pyridine-oriented protocol features high Acknowledgements
efficiency and good functional group tolerance, affording a
practical avenue for complex pharmacologically or biologically
active molecules.
This work was supported by the National Natural Science
Foundation of China (No. 21502049 and 51573040), the
Planned Science and Technology Project of Hunan Province,
China (No. 2015WK3003), the Hunan Provincial Key Labora-
tory of Materials Protection for Electric Power and Transpor-
tation (No. 2015CL03), and Changsha University of Science &
Technology, P.R. China.
Experimental section
General procedure towards 2-sulfonyl quinolines/pyridines
Method A: A 10 mL round-bottomed flask was charged with
quinoline/pyridine N-oxides (1, 0.5 mmol), sulfonyl hydrazides
(
1
2, 1.0 mmol), I2 (126.9 mg, 0.5 mmol), NaOH (40.0 mg,
References
.0 mmol), H
2 2
O (30% in water, 170.0 mg, 1.5 mmol), and
CH CN (4.0 mL). The mixture was stirred in an ambient atmo-
3
1 (a) R. Dayam, L. Q. Al-Mawsawi, Z. Zawahir, M. Witvrouw,
Z. Debyser and N. Neamati, J. Med. Chem., 2008, 51, 1136;
(b) M. P. Maguire, K. R. Sheets, K. McVety, A. P. Spada and
A. Zilberstein, J. Med. Chem., 1994, 37, 2129; (c) R. A. Hartz,
A. G. Arvanitis, C. Arnold, J. P. Rescinito, K. L. Hung,
G. Zhang, H. Wong, D. R. Langley, P. J. Gilligan and
G. L. Trainor, Bioorg. Med. Chem. Lett., 2006, 16, 934;
(d) K. M. Maniecka, R. Musiol, W. Nitek, B. J. Oleksyn,
J. F. Mouscadet, M. Le Bret and J. Polanski, Bioorg. Med.
Chem. Lett., 2006, 16, 1005; (e) I. Hussain, M. A. Yawer,
M. Lalk, U. Lindequist, A. Villinger, C. Fischer and
sphere at 100 °C. After completion of the reaction (ca. 10 min),
which was monitored by TLC, the mixture was cooled to room
temperature and quenched with an aqueous solution of satu-
rated Na S O (10 mL). After extraction with CH Cl (3 ×
2
2
3
2
2
1
5 mL), the organic phases were combined and dried over
anhydrous Na SO . The solvent was removed, and the residual
2
4
crude product was purified by flash column chromatography
with a mixture of n-hexane and ethyl acetate to give the desired
product in the noted yields. (Care must be taken regarding the
released nitrogen gas and acetonitrile vapour.)
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Paper
P. Langer, Bioorg. Med. Chem., 2008, 16, 9898;
M. S. Sanford, Chem. Rev., 2010, 110, 1147; (h) S. H. Cho,
J. Yoon and S. Chang, J. Am. Chem. Soc., 2011, 133, 5996;
(i) R. Shrestha, P. Mukherjee, Y. Tan, Z. C. Litman and
J. F. Hartwig, J. Am. Chem. Soc., 2013, 135, 8480;
( j) D. H. Wang and J. Q. Yu, J. Am. Chem. Soc., 2011, 133,
5767; (k) B. Xiao, T. J. Gong, J. Xu, Z. J. Liu and L. Liu,
J. Am. Chem. Soc., 2011, 133, 1466; (l) H. Mizuno, J. Takaya
and N. Iwasawam, J. Am. Chem. Soc., 2011, 133, 1251;
(m) T. S. Mei, X. Wang and J. Q. Yu, J. Am. Chem. Soc., 2009,
131, 10806; (n) N. R. Deprez and M. S. Sanford, J. Am.
Chem. Soc., 2009, 131, 11235; (o) W. C. P. Tsang, N. Zheng
and S. L. Buchwald, J. Am. Chem. Soc., 2005, 127, 14560.
8 (a) Z. Y. Wu, H. Y. Song, X. L. Cui, C. Pi, W. W. Du and
Y. J. Wu, Org. Lett., 2013, 15, 1270; (b) H. W. Liang,
K. Jiang, W. Ding, Y. Yuan, L. Shuai, Y. C. Chen and Y. Wei,
Chem. Commun., 2015, 51, 16928; (c) H. J. Qiao, S. Y. Sun,
F. Yang, Y. Zhu, W. G. Zhu, Y. X. Dong, Y. S. Wu,
X. T. Kong, L. Jiang and Y. J. Wu, Org. Lett., 2015, 17, 6086.
9 K. Sun, X. L. Chen, X. Li, L. B. Qu, W. Z. Bi, X. Chen,
H. L. Ma, S. T. Zhang, B. W. Han, Y. F. Zhao and C. J. Li,
Chem. Commun., 2015, 51, 12111.
(
1
f) I. P. Beletskaya and V. P. Ananikov, Chem. Rev., 2011,
11, 1596; (g) J. P. Michael, Nat. Prod. Rep., 2005, 22, 627;
(
(
h) J. P. Michael, Nat. Prod. Rep., 2008, 25, 166;
i) J. Yamaguchi, A. D. Yamaguchi and K. Itami, Angew.
Chem., Int. Ed., 2012, 51, 8960.
N. G. Luthy, F. W. Bergstrom and H. S. Mosher, J. Am.
Chem. Soc., 1949, 71, 1109.
N. S. Simpkins, Sulfones in Organic Synthesis, Pergamon
Press, Oxford, 1993.
(a) H. Sasabe, Y. Seino, M. Kimura and J. Kido, Chem.
Mater., 2012, 24, 1404; (b) J. Zhou, P. Chen, C. Deng,
F. Meng, R. Cheng and Z. Zhong, Macromolecules, 2013, 46,
2
3
4
6
723.
(a) K. Maloney, J. Kuethe and K. Linn, Org. Lett., 2011, 13,
02; (b) E. J. Emmett, B. R. Hayter and M. C. Willis, Angew.
5
1
Chem., Int. Ed., 2013, 52, 12679.
W. Trankle and M. Kopach, Org. Process Res. Dev., 2007, 11,
6
7
9
13.
(a) J. Q. Yu and Z. J. Shi, C–H Activation, Springer-Verlag,
Berlin Heidelberg, 2010; (b) D. Alberico, M. E. Scott and
M. Lautens, Chem. Rev., 2007, 107, 174; (c) L. C. Campeau, 10 W. Wei, C. L. Liu, D. S. Yang, J. W. Wen, J. M. You,
D. R. Stuart and K. Fagnou, Aldrichimica Acta, 2007, 40, 35; Y. R. Suo and H. Wang, Chem. Commun., 2013, 49, 10239.
d) K. Godula and D. Sames, Science, 2006, 312, 67; 11 (a) F. Yang and S. Tian, Angew. Chem., Int. Ed., 2013,
(
(
e) P. B. Arockiam, C. Bruneau and P. H. Dixneuf, Chem.
52, 4929–4932; (b) R. Singh, B. Allam, N. Singh,
K. Kumari, S. Singh and K. Singh, Org. Lett., 2015,
17, 2656.
Rev., 2012, 112, 5879; (f) C.-L. Sun, B.-J. Li and Z.-J. Shi,
Chem. Rev., 2011, 111, 1293; (g) T. W. Lyons and
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