An internal oxidant-directing strategy enabling transition metal-free C–S bond ligation

Article abstract of DOI:10.1016/j.tet.2019.05.021

Organic sulfur compounds have broad applications in biology, medicine and material sciences and intensive efforts have been devoted to developing mild and general C–S bond-forming methods. However, a mild, transition-metal-free, direct C–H bond functionalization method remains elusive. Here, we report the use of an internal oxidant-directing strategy to achieve this goal. The cascade reactions described here show excellent chemoselectivity and a wide substrate scope for both oxyamines and sulfenylation reagents. This study enlarges the synthesis toolbox for preparing structurally diverse sulfilimines under mild conditions.

Full text of DOI:10.1016/j.tet.2019.05.021

Tetrahedron xxx (xxxx) xxx
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
An internal oxidant-directing strategy enabling transition metal-free
CeS bond ligation
,
,
, c, *
Yingying Zuo a 1, Feng Xiong b 1, Jing Zhao b
a Key Laboratory of Chemical Genomics, Key Laboratory of Structural Biology, School of Chemical Biology and Biotechnology, Shenzhen Graduate School,
Peking University, Shenzhen 518055, China
b State Key Laboratory of Coordination Chemistry, Institute of Chemistry and BioMedical Sciences, School of Chemistry and Chemical Engineering,
Collaborative Innovation Center of Chemistry for Life Sciences, Nanjing University, Nanjing 210093, China
c Shenzhen Research Institute of Nanjing University, Shenzhen, 518057, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Organic sulfur compounds have broad applications in biology, medicine and material sciences and
intensive efforts have been devoted to developing mild and general CeS bond-forming methods.
However, a mild, transition-metal-free, direct CeH bond functionalization method remains elusive. Here,
we report the use of an internal oxidant-directing strategy to achieve this goal. The cascade reactions
described here show excellent chemoselectivity and a wide substrate scope for both oxyamines and
sulfenylation reagents. This study enlarges the synthesis toolbox for preparing structurally diverse sul-
filimines under mild conditions.
Received 4 April 2019
Received in revised form
8 May 2019
Accepted 10 May 2019
Available online xxx
Keywords:
Sulfenylation reagents
Metal free
© 2019 Elsevier Ltd. All rights reserved.
Sulfilimines
Internal oxidant
Cascade reaction
1. Introduction
a CeH bond [9]. Two major strategies among these methods are
transition-metal-catalyzed CeH bond functional-ization and
Organic sulfur compounds play important roles in material,
biological, and pharmaceutical sciences [1e6]. In materials science,
the presence of sulfur components is an important determinant of
physical, electronic, and surface properties [1]. In biology, sulfur
bonding helps maintain the strength and shape of proteins and
mediates electron transfer reactions [7]. Traditional methods for
construction of a CeS bond involve thiol coupling with organic
halides or thiol addition to unsaturated CeC bonds [8]. However,
such classic methods suffer from significant limitations, such as the
use of malodorous sulfur sources, highly pre-functionalized pre-
cursors and the formation of undesired toxic by-products.
oxidative CeS bond coupling (Schemes 1a and 1b). In the first
strategy, various transition metal complexes were used to selec-
tively functionalize a CeH bond, enabling the subsequent CeS bond
formation. In the latter strategy, the CeS bond formation was
realized under oxidative, transition metal-free conditions either
through a radical process or by forming an active organosulfur in-
termediate. However, many reported reactions suffered from
requirement of a high reaction temperature, poor substrate scope,
or low selectivity. Recently, pivotal progress has been made in CeH
sulfenylation of arenes under metal-free conditions [10e13], but a
mild, transition metal-free method of direct CeH bond function-
alization still remains elusive.
The sulfilimine bond (S]N) is a useful functional group and can
undergo unique rearrangements in the synthesis of natural prod-
ucts or pharmacological agents [14e21]. However, the synthesis of
sulfilimines traditionally involves oxidative imination of thioethers
[22e28], and this requires the preparation of thioethers and the use
of elaborate imidation reagents, which in turn limit the scope of
synthetic sulfilimines.
In parallel with the development of modern CeC and CeN
coupling reactions, a number of highly efficient coupling methods
have been developed in recent decades to produce a CeS bond from
* Corresponding author. State Key Laboratory of Coordination Chemistry, Insti-
tute of Chemistry and BioMedical Sciences, School of Chemistry and Chemical
Engineering, Collaborative Innovation Center of Chemistry for Life Sciences, Nanjing
University, Nanjing 210093, China.
Based on our continuing effort in OeN bond-directed synthesis
of o-functionalized phenols [29e31] and our previous metal-free
E-mail address: jingzhao@nju.edu.cn (J. Zhao).
Y.Z. and F.X. contributed equally to this work.
1
https://doi.org/10.1016/j.tet.2019.05.021
0040-4020/© 2019 Elsevier Ltd. All rights reserved.
Please cite this article as: Y. Zuo et al., An internal oxidant-directing strategy enabling transition metal-free CeS bond ligation, Tetrahedron,
https://doi.org/10.1016/j.tet.2019.05.021

2
Y. Zuo et al. / Tetrahedron xxx (xxxx) xxx
solvent plays a key role in this reaction.
With the optimum conditions in hand, a series of oxyamide
substrates and o-phenolic sulfenylation reagents were tested in this
cascade reaction (Table 2). N-Phenoxyacetamide with either
electron-rich or electron-deficient substituents reacted smoothly.
The reaction was compatible with a variety of functional groups
such as fluoro, chloro, bromo, ester and amide. The naphthyl sub-
strate afforded high regioselectivity and excellent yield, and func-
tionalized only the ortho CeH at C-1 (3g). The m-substituted N-
phenoxyacetamide reacted at only the less hindered o-position. The
high degree of regiospecificity manifested in 3j suggests that the
steric effect is important. Replacing the acetyl group of substrate 1
with the more bulky pivaloyl moiety also affords the sulfilimine
product (3k) in good yield. Symmetrical diphenolic sulfilimines (3l,
3m) can be obtained by controlling the substituents R2 and R3. In
addition, a series of o-phenolic sulfenylation reagents were shown
to reacted with N-phenoxy- acetamide to afford products 3ne3p in
62e78% yield.
Scheme 1. CeS bond forming strategies. a) Transition metal-catalyzed CeS bond for-
mation. b) Oxidative CeS bond coupling. c) An internal oxidant-directing strategy.
To extend the diversity of sulfilimines, we tested a series of
modified styrene sulfenylation reagents. Thus the product 5a was
isolated in high yield when the solvent Et2O was changed to ben-
zene (Table S1). The structure of 5a was confirmed by NMR spec-
troscopy, HR mass specrometry, and X-ray crystallography (Fig. S1
in Supplementary Data). As shown in Table 3, various aryox-
yamides and sulfenylation reagents (4) with different substituents
including electron-neutral, electron-donating and electron-
withdrawing groups were well tolerated, providing the desired
products in high yields and with good to excellent Z/E ratios.
In general, o-phenolic sulfenylation reagents (2) and modified
styrene sulfenylation reagents (4) are usually prepared by the re-
action of N-(chlorosulfenyl)phthalimide with phenols or styrene,
respectively. If the modified sulfenylation reagents can be produced
in situ, a more practical and attractive one-pot protocol could be
developed. In fact, it was found that treatment of a mixture of N-
coupling method to synthesize sulfilimines [32], we sought to
further extend the synthesis toolbox. Accordingly, we developed
more sulfenylation reagents for synthesis of structurally diverse
sulfilimines under mild conditions (Scheme 1c).
2. Results and discussion
To begin this study, we studied the reaction of N-phenoxy-
acetamide (1a) with 2-((5-(t-butyl)-2-hydroxyphenyl)-thio)iso-
indoline-1,3-dione (2a) (Table 1). Under the standard conditions
described in our previous reports [32], CsOAc (0.5 equiv) was used
in MeOH at room temperature for 3 h to examine the coupling
reaction. The reaction proceeded smoothly and furnished
a
phenolic sulfilimine product (3a) in 78% yield (Table 1, entry 1). We
examined different bases, but failed to obtain a higher yield. Then
we turned our attention to evaluation of the effect of solvent and
screened a variety of solvents. The reaction in THF delivered a yield
of 48% but Et2O proved to be the most effective solvent, affording
the product in 90% yield (Table 1, entry 4), suggesting that the
Table 2
Substrate scope of aryloxyamides and ortho-phenolic sulfenylation reagents.a
Table 1
Optimization of reaction conditions.
Entry
Solvent
time
Additive (eq.)
Yield (%)b
1
2
3
4
5
6
7
8
MeOH
DCM
CHCl3
Et2O
CH3CN
THF
dioxane
PhCH3
Benzene
Et2O
Acetone
t-AmOH
TFE
PhCF3
Et2O
3 h
3 h
3 h
3 h
3 h
3 h
3 h
3 h
3 h
3 h
3 h
3 h
3 h
3 h
8 h
CsOAc (0.5)
CsOAc (0.5)
CsOAc (0.5)
CsOAc (0.5)
CsOAc (0.5)
CsOAc (0.5)
CsOAc (0.5)
CsOAc (0.5)
CsOAc (0.5)
CsOAc (0.5)
CsOAc (0.5)
CsOAc (0.5)
CsOAc (0.5)
CsOAc (0.5)
CsOAc (0.5)
78
80
78
90
76
48
64
76
76
88a
80
68
62
80
90
9
10
11
12
13
14
15
a
Yields of isolated products.
b
Crude yield, as determined by1H NMR spectroscopy with 1,4-dimethoxy-ben-
zene as an internal standard.
Please cite this article as: Y. Zuo et al., An internal oxidant-directing strategy enabling transition metal-free CeS bond ligation, Tetrahedron,
https://doi.org/10.1016/j.tet.2019.05.021

Y. Zuo et al. / Tetrahedron xxx (xxxx) xxx
3
Table 3
Substrate scope of aryloxyamides and modified styrene sulfenylation reagents 4.a
(chlorosulfenyl)phthalimide with 4-t-butyl-phenol or 3-chloro-
styrene in CH2Cl2 at room temperature for 12 h, and subsequent
addition of N-phenoxyacetamide and CsOAc, after 6 h led to the
formation of the corresponding sulfilimines (3a, 5k) in 78% and 72%
yields, respectively (Table 4).
To further probe the reaction mechanism, the mixture of thio-
phthalimide 4a/CsOAc/toluene in the absence of N-phenox-
yacetamide was conducted and the corresponding elimination
product was not observed (scheme 2a). On the basis of these results
and our earlier work [32], a mechanism for the convenient syn-
thesis of o-phenolic sulfilimines is proposed and is shown in
Scheme 2. In the presence of a weak base such as CsOAc [33], an
intermediate (INT1) is generated from N-phenoxyacetamide (1a),
and then attacks the sulfur of the sulfenylation reagent (2a or 4a) to
form the intermediate (INT2 or INT2’). The reaction then proceeds
Scheme 2. Proposed reaction pathway for the cascade reaction.
through an intramolecular [2,3] sigmatropic rearrangement fol-
lowed by aromatization to afford the product (3a). In Scheme 2c,
the b
-H elimination in the presence of ꢀOAc occurred to afford the
product 5a.
3. Conclusion
Table 4
In conclusion, a strategy for the synthesis of diverse phenolic
sulfilimines using different sulfenylation reagents under mild
conditions has been developed. Various oxyamides and sulfenyla-
tion reagents are well tolerated and afford phenolic sulfilimines in
moderate to excellent isolated yields (56e96%). Symmetrical
diphenolic sulfilimines can be obtained by controlling the substit-
uent groups of both substrates, and a convenient and efficient one-
pot reaction for the synthesis of sulfilimines has been developed.
Research into the applications of oxyamides to other types of
cascade reactions and the development of other new approaches to
the synthesis of sulfilimines is currently in progress in our
laboratory.
One-pot protocol of N-phenoxyacetamide 1 reacted with phenols or styrene.
4. Experimental section
4.1. General information
Commercially available chemicals were obtained from Sigma-
Aldrich, Alfa Aesar, TCI and Aladdin and used as received unless
otherwise stated. Reactions were monitored with analytical thin-
layer chromatography (TLC) on silica. 1H NMR and 13C NMR data
were recorded on Bruker nuclear resonance (300 MHz, 400 MHz
and 500 MHz) spectrometers unless otherwise specified,
Please cite this article as: Y. Zuo et al., An internal oxidant-directing strategy enabling transition metal-free CeS bond ligation, Tetrahedron,
https://doi.org/10.1016/j.tet.2019.05.021

4
Y. Zuo et al. / Tetrahedron xxx (xxxx) xxx
respectively. Chemical shifts (
d
) are given in ppm relative to TMS.
6.99 (d, J ¼ 8.7 Hz, 1H), 6.90 (d, J ¼ 8.8 Hz, 1H), 2.19 (s, 3H), 1.22 (s,
9H); 13C NMR (101 MHz, CDCl3)
181.6, 158.0, 157.2, 144.3, 137.4,
The residual solvent signals were used as references and the
chemical shifts converted to the TMS scale (CDCl3: dH ¼ 7.26 ppm,
dC ¼ 77.16 ppm). HRMS (ESI) analysis was performed by The
Analytical Instrumentation Center at Peking University, Shenzhen
Graduate School and (HRMS) data were reported with ion mass/
charge (m/z) ratios as values in atomic mass units.
d
132.6, 130.4, 125.3, 121.8, 120.1, 119.0, 113.0, 112.2, 34.4, 31.1, 23.9.
HRMS (ESI) calculated for
Found: 408.0271.
C
18H19BrNO3S [M ꢀ H]e:408.0269;
4.2.6. Methyl(E)-3-(N-acetyl-S-(5-(tert-butyl)-2-hydroxyphenyl)
sulfinimidoyl)-4-hydroxybenzoate (3f)
4.2. General procedure for CeS bond coupling reaction (Tables 2
White solid, yield: 90%. 1H NMR (400 MHz, CDCl3)
d 11.51 (s, 2H),
and 3)
8.05 (d, J ¼ 2.0 Hz, 1H), 7.99 (dd, J ¼ 8.7, 1.9 Hz, 1H), 7.38 (dd, J ¼ 8.7,
2.3 Hz, 1H), 7.25 (d, J ¼ 2.3 Hz, 1H), 6.97 (d, J ¼ 8.7 Hz, 1H), 6.90 (d,
J ¼ 8.7 Hz, 1H), 3.84 (s, 3H), 2.22 (s, 3H), 1.18 (s, 9H); 13C NMR
N-phenoxyacetamide (1) (0.2 mmol), sulfenylation reagent
(0.24 mmol), and CsOAc (0.10 mol) were weighed into a 25 mL
pressure tube, to which was added Et2O or benzene (2 mL). The
reaction vessel was stirred at room temperature for 3 h. Then the
mixture was concentrated under vacuum and the residue was pu-
rified by column chromatography on silica gel with a gradient
eluent of petroleum ether and ethyl acetate to afford the corre-
sponding product.
(101 MHz, CDCl3)
d 181.3, 165.4, 163.0, 156.5, 144.0, 135.5, 132.3,
130.7, 124.7, 122.6, 119.6, 119.5, 115.9, 115.1, 52.3, 34.3, 31.1, 24.1.
HRMS (ESI) calculated for C20H22NO5S [M ꢀ H]e:388.1219; Found:
388.1226.
4.2.7. (E)-N-((5-(tert-butyl)-2-hydroxyphenyl)(2-
hydroxynaphthalen-1-yl)-4-sulfanylidene)acetamide (3g)
White solid, yield: 90%. 1H NMR (400 MHz, CDCl3)
d 12.24 (s,
4.2.1. (Z)-N-((5-(tert-butyl)-2-hydroxyphenyl)(2-hydroxyphenyl)-
2H), 8.00 (d, J ¼ 9.0 Hz, 1H), 7.77 (dd, J ¼ 15.9, 8.2 Hz, 2H), 7.48e7.42
(m, 1H), 7.40 (dd, J ¼ 8.6, 2.4 Hz, 1H), 7.38e7.33 (m, 1H), 7.30 (d,
J ¼ 9.0 Hz,1H), 7.05 (d, J ¼ 8.6 Hz,1H), 6.98 (d, J ¼ 2.3 Hz, 1H), 2.19 (s,
l
4-sulfanylidene)acetamide (3a)
White solid, yield: 88%. 1H NMR (400 MHz, CDCl3)
d 11.50 (s, 2H),
7.48e7.39 (m, 2H), 7.18 (dd, J ¼ 8.1, 1.5 Hz, 1H), 7.14 (d, J ¼ 2.3 Hz,
3H), 0.99 (s, 9H); 13C NMR (101 MHz, CDCl3)
d 181.3, 163.2, 155.5,
1H), 7.07 (dd, J ¼ 8.3, 1.0 Hz, 1H), 7.00 (d, J ¼ 8.7 Hz, 1H), 6.93e6.87
144.6, 135.8, 132.6, 131.1, 128.9, 128.8, 128.3, 124.4, 124.0, 121.4,
120.8, 120.2, 34.2, 30.9, 23.9. HRMS (ESI) calculated for C22H22NO3S
[M ꢀ H]e:380.1320; Found: 380.1327.
(m, 1H), 2.17 (s, 3H), 1.18 (s, 9H); 13C NMR (101 MHz, CDCl3)
d 181.5,
159.3,157.1,144.1,134.7, 132.2,128.9,125.3,120.9,120.2,119.9,116.4,
114.2, 34.3, 31.1, 23.9. HRMS (ESI) calculated for C18H28NO2S
[M ꢀ H]e: 330.1164; Found: 330.1165.
4.2.8. Tert-butyl(Z)-(3-(N-acetyl-S-(5-(tert-butyl)-2-
hydroxyphenyl)sulfinimidoyl)-4-hydroxyphenethyl)carbamate (3h)
4.2.2. (Z)-N-((5-(tert-butyl)-2-hydroxyphenyl)(2-hydroxy-5-
White solid, yield: 60%. 1H NMR (400 MHz, CDCl3)
d 11.42 (s, 2H),
methylphenyl)-4-sulfanylidene)acetamide (3b)
7.46 (dd, J ¼ 8.7, 2.3 Hz, 1H), 7.29 (s, 1H), 7.13 (s, 1H), 7.03 (dd,
J ¼ 10.8, 8.8 Hz, 3H), 4.53 (s, 1H), 3.25 (d, J ¼ 6.2 Hz, 2H), 2.67 (t,
J ¼ 6.9 Hz, 2H), 2.17 (s, 3H), 1.42 (s, 9H), 1.19 (s, 9H); 13C NMR
White solid, yield: 72%. 1H NMR (400 MHz, CDCl3)
d 11.40 (s, 2H),
7.46 (dd, J ¼ 8.7,1.4 Hz,1H), 7.23 (d, J ¼ 8.5 Hz,1H), 7.12 (d, J ¼ 1.6 Hz,
1H), 7.00 (t, J ¼ 8.1 Hz, 2H), 6.95 (s, 1H), 2.20 (s, 3H), 2.15 (s, 3H), 1.18
(101 MHz, CDCl3)
d 181.4, 158.2, 156.8, 155.8, 144.1, 139.1, 135.2,
(s, 9H); 13C NMR (101 MHz, CDCl3)
d
181.4, 157.2, 157.0, 144.1, 135.7,
132.2, 131.7, 128.6, 125.1, 120.4, 119.9, 115.3, 79.4, 41.6, 35.1, 34.3,
132.2, 130.6, 128.6, 125.4, 120.1, 120.0, 115.3, 114.9, 34.3, 31.1, 23.8,
20.4. HRMS (ESI) calculated for C19H22NO3S [M ꢀ H]e:344.1320;
Found: 344.1327.
31.1, 28.4, 23.9. HRMS (ESI) calculated for
C25H33N2O5S
[M ꢀ H]e:473.2110; Found: 473.2114.
4.2.9. (E)-N-((5-(tert-butyl)-2-hydroxyphenyl)(3-chloro-2-
4.2.3. (E)-N-((5-(tert-butyl)-2-hydroxyphenyl)(5-fluoro-2-
hydroxyphenyl)-4-sulfanylidene)acetamide (3c)
hydroxyphenyl)-4-sulfanylidene)acetamide (3i)
White solid, yield: 56%. 1H NMR (400 MHz, CDCl3)
d 11.56 (s, 2H),
White solid, yield: 60%. 1H NMR (400 MHz, CDCl3)
d
11.32 (s, 2H),
7.50 (dd, J ¼ 8.6, 2.2 Hz, 1H), 7.18 (d, J ¼ 2.2 Hz, 1H), 7.12e7.05 (m,
7.48 (dd, J ¼ 8.8, 2.4 Hz,1H), 7.22 (d, J ¼ 2.3 Hz,1H), 7.10 (ddd, J ¼ 9.1,
2H), 7.03 (d, J ¼ 8.7 Hz, 1H), 6.88 (dd, J ¼ 8.6, 1.4 Hz, 1H), 2.19 (s, 3H),
7.7, 3.0 Hz, 1H), 7.02e6.96 (m, 2H), 6.92 (dd, J ¼ 7.7, 3.0 Hz, 1H), 2.18
1.23 (s, 9H); 13C NMR (101 MHz, CDCl3)
d 181.6, 159.7, 157.4, 144.3,
(s, 3H), 1.22 (s, 9H); 13C NMR (101 MHz, CDCl3)
d
181.7, 157.4, 157.3,
140.7, 132.5, 129.6, 125.4, 121.4, 120.4, 120.1, 116.2, 112.7, 34.4, 31.1,
23.8. HRMS (ESI) calculated for C18H19ClNO3S [M ꢀ H]e:364.0774;
Found: 364.0780.
154.9, 144.2, 132.5, 125.4, 122.1, 121.8, 121.34, 121.26, 120.0, 118.7,
118.6, 114.3, 114.1, 112.2, 34.3, 31.1, 23.9; 19F NMR (376 MHz, CDCl3)
d
ꢀ120.99.
HRMS
(ESI)
calculated
for
C18H19FNO3S
[M ꢀ H]e:348.1070; Found: 348.1073.
4.2.10. (Z)-N-((4-bromo-2-hydroxyphenyl)(5-(tert-butyl)-2-
hydroxyphenyl)-4-sulfanylidene)acetamide (3j)
4.2.4. (E)-N-((5-(tert-butyl)-2-hydroxyphenyl)(5-chloro-2-
White solid, yield: 60%. 1H NMR (400 MHz, CDCl3)
d 11.57 (s, 1H),
hydroxyphenyl)-4-sulfanylidene)acetamide (3d)
7.46 (d, J ¼ 7.0 Hz, 1H), 7.23 (d, J ¼ 1.9 Hz, 1H), 7.16 (s, 1H), 7.06 (t,
White solid, yield: 58%. 1H NMR (500 MHz, CDCl3)
d 11.39 (s, 2H),
J ¼ 8.0 Hz, 1H), 7.01 (d, J ¼ 8.5 Hz, 1H), 6.97 (d, J ¼ 8.7 Hz, 1H), 2.19 (s,
7.46 (dd, J ¼ 8.7, 2.2 Hz, 1H), 7.31e7.27 (m, 1H), 7.24 (d, J ¼ 2.3 Hz,
1H), 7.21 (d, J ¼ 2.4 Hz, 1H), 6.97 (d, J ¼ 8.7 Hz, 1H), 6.93 (d,
J ¼ 8.7 Hz, 1H), 2.20 (s, 3H), 1.22 (s, 9H); 13C NMR (126 MHz, CDCl3)
3H), 1.22 (s, 9H); 13C NMR (101 MHz, CDCl3)
d 181.6, 159.3, 157.2,
144.2,132.4,129.3,128.8,125.3,124.2, 123.2,119.9, 116.9,112.8, 34.4,
31.2, 24.0. HRMS (ESI) calculated for
C18H19BrNO3S
d
181.6, 157.5, 157.2, 144.2, 134.5, 132.4, 127.5, 125.5, 125.2, 121.3,
[M ꢀ H]e:408.0269; Found: 408.0276.
120.0, 118.7, 113.1, 34.3, 31.1, 23.9. HRMS (ESI) calculated for
C
18H19ClNO3S [M ꢀ H]e:364.0774; Found: 364.0779.
4.2.11. (Z)-N-((5-(tert-butyl)-2-hydroxyphenyl)(2-hydroxyphenyl)-
4-sulfanylidene)pivalamide (3k)
4.2.5. (E)-N-((5-bromo-2-hydroxyphenyl)(5-(tert-butyl)-2-
White solid, yield: 78%. 1H NMR (400 MHz, CDCl3)
d 11.76 (s, 2H),
hydroxyphenyl)-4-sulfanylidene)acetamide (3e)
7.33 (dtd, J ¼ 9.5, 8.4,1.5 Hz, 3H), 7.27e7.24 (m,1H), 6.98 (dd, J ¼ 8.3,
White solid, yield: 62%. 1H NMR (400 MHz, CDCl3)
d
11.45 (s, 2H),
1.0 Hz, 1H), 6.90e6.84 (m, 1H), 6.81 (d, J ¼ 8.7 Hz, 1H), 1.29 (s, 9H),
7.51e7.42 (m, 2H), 7.29 (d, J ¼ 2.1 Hz, 1H), 7.20 (d, J ¼ 2.1 Hz, 1H),
1.20 (s, 9H); 13C NMR (101 MHz, CDCl3)
d 189.4, 159.3, 156.7, 143.5,
Please cite this article as: Y. Zuo et al., An internal oxidant-directing strategy enabling transition metal-free CeS bond ligation, Tetrahedron,
https://doi.org/10.1016/j.tet.2019.05.021

Y. Zuo et al. / Tetrahedron xxx (xxxx) xxx
5
134.3, 131.7, 128.8, 124.4, 120.5, 119.9, 119.1, 116.6, 114.9, 40.4, 34.3,
d 180.5, 142.8, 141.4, 135.1, 130.3, 130.0, 129.7, 129.6, 128.3, 128.1,
31.2,
28.3.
HRMS
(ESI)
calculated
for
C
21H26NO3S
127.1, 119.7, 119.3, 24.4, 21.5, 20.3. HRMS (ESI) calculated for
C
[M ꢀ H]e:372.1633; Found: 372.1637.
18H18NO2S [M ꢀ H]e:312.1058; Found: 312.1063.
4.2.12. N-(bis(2-hydroxy-5-methylphenyl)-4-sulfanylidene)
4.2.19. N-((E)-(5-chloro-2-hydroxyphenyl)((E)-4-methylstyryl)-l4-
acetamide (3l)
sulfanylidene)acetamide (5c)
White solid, yield: 76%. 1H NMR (400 MHz, CDCl3)
d
11.45 (s, 2H),
7.29e7.27 (m, 2H), 7.03 (d, J ¼ 8.5 Hz, 2H), 6.92 (s, 2H), 2.23 (s, 6H),
2.15 (s, 3H); 13C NMR (101 MHz, CDCl3)
181.5, 157.3, 135.8, 130.7,
White solid, yield: 72%, E/Z ¼ 12.5:1.1H NMR (400 MHz, CDCl3)
7.45 (d, J ¼ 15.4 Hz, 1H), 7.35 (t, J ¼ 5.6 Hz, 3H), 7.32 (dd, J ¼ 8.8,
d
d
2.5 Hz, 1H), 7.19 (d, J ¼ 8.0 Hz, 2H), 6.91 (d, J ¼ 8.8 Hz, 1H), 6.70 (d,
J ¼ 15.3 Hz, 1H), 2.37 (d, J ¼ 6.4 Hz, 3H), 2.19 (s, 3H); 13C NMR
128.7, 120.4, 115.1, 23.8, 20.4. HRMS (ESI) calculated for C16H16NO3S
[M ꢀ H]e:302.0851; Found: 302.0858.
(101 MHz, CDCl3)
d 181.1, 158.3, 143.5, 141.7, 134.0, 130.1, 129.8,
128.2, 127.4, 124.9, 121.2, 118.7, 117.0, 24.4, 21.5. HRMS (ESI) calcu-
lated for C17H15ClNO2S [M ꢀ H]e:332.0512; Found: 332.0516.
4.2.13. N-(bis(5-bromo-2-hydroxyphenyl)-4-sulfanylidene)
acetamide (3m)
White solid, yield: 62%. 1H NMR (400 MHz, CDCl3)
d 11.49 (s, 2H),
4.2.20. N-((E)-(5-bromo-2-hydroxyphenyl)((E)-4-methylstyryl)-
7.50 (dd, J ¼ 8.8, 2.3 Hz, 2H), 7.38 (d, J ¼ 2.3 Hz, 2H), 6.91 (d,
J ¼ 8.8 Hz, 2H), 2.24 (s, 3H); 13C NMR (101 MHz, CDCl3)
d 181.8,
l
4-sulfanylidene)acetamide (5d)
White solid, yield: 78%, E/Z ¼ 20:1.1H NMR (500 MHz, CDCl3)
7.46 (d, J ¼ 2.4 Hz, 1H), 7.45e7.37 (m, 2H), 7.33 (d, J ¼ 8.1 Hz, 2H),
158.1, 137.8, 130.4, 122.0, 117.0, 112.4, 24.0. HRMS (ESI) calculated for
C
14H10Br2NO3S [M ꢀ H]e:429.8748; Found: 429.8753.
d
7.16 (d, J ¼ 8.0 Hz, 2H), 6.81 (d, J ¼ 8.8 Hz, 1H), 6.67 (d, J ¼ 15.3 Hz,
1H), 2.35 (s, 3H), 2.17 (s, 3H); 13C NMR (126 MHz, CDCl3)
d 181.1,
4.2.14. (Z)-N-((2-hydroxy-5-methylphenyl)(2-hydroxyphenyl)-l4-
158.5, 143.3, 141.6, 136.7, 130.1, 130.0, 129.7, 128.2, 121.4, 118.7, 117.9,
111.5, 24.4, 21.5. HRMS (ESI) calculated for C17H15BrNO2S [M ꢀ H]e:
376.0007; Found: 376.0011.
sulfanylidene)acetamide (3n)
White solid, yield: 76%. 1H NMR (400 MHz, CDCl3)
d 11.51 (s, 2H),
7.44e7.38 (m, 1H), 7.23 (dd, J ¼ 8.4, 1.7 Hz, 1H), 7.16 (dd, J ¼ 8.1,
1.5 Hz, 1H), 7.06 (dd, J ¼ 8.3, 1.0 Hz, 1H), 6.97 (d, J ¼ 8.5 Hz, 2H),
6.92e6.86 (m, 1H), 2.21 (s, 3H), 2.16 (s, 3H); 13C NMR (101 MHz,
4.2.21. Methyl 3-((E)-N-acetyl-S-((E)-4-methylstyryl)
sulfinimidoyl)-4-hydroxybenzoate (5e)
CDCl3)
d 181.5, 159.2, 157.3, 135.7, 134.7, 130.6, 128.9, 128.6, 120.9,
120.4, 120.2, 116.4, 114.6, 23.9, 20.4. HRMS (ESI) calculated for
White solid, yield: 92%, E/Z ¼ 20:1.1H NMR (400 MHz, CDCl3)
C
15H14NO3S [M ꢀ H]e:288.0694; Found: 288.0701.
d
8.07 (dd, J ¼ 8.3, 1.6 Hz, 2H), 7.45 (d, J ¼ 15.4 Hz, 1H), 7.36 (d,
J ¼ 8.1 Hz, 2H), 7.19 (d, J ¼ 8.0 Hz, 2H), 7.04 (dd, J ¼ 7.9, 1.2 Hz, 1H),
4.2.15. (Z)-N-((5-chloro-2-hydroxyphenyl)(2-hydroxyphenyl)-l4-
6.73 (d, J ¼ 15.3 Hz, 1H), 3.89 (s, 3H), 2.37 (s, 3H), 2.18 (s, 3H); 13C
sulfanylidene)acetamide (3o)
NMR (101 MHz, CDCl3) d 180.4,165.4,164.4,143.7,141.8,135.3,131.2,
White solid, yield: 70%. 1H NMR (400 MHz, CDCl3)
d
11.34 (s, 2H),
130.0, 129.8, 128.3, 122.2, 120.2, 119.4, 114.5, 52.2, 24.3, 21.5. HRMS
7.43e7.33 (m, 2H), 7.31e7.24 (m, 2H), 6.99 (d, J ¼ 8.2 Hz, 1H), 6.92 (t,
(ESI) calculated for
358.1109.
C
19H20NO4S [MþH]þ: 358.1113; Found:
J ¼ 7.6 Hz, 1H), 6.87 (d, J ¼ 8.5 Hz, 1H), 2.25 (s, 3H); 13C NMR
(101 MHz, CDCl3)
d 181.6, 159.1, 157.2, 134.8, 134.4, 128.6, 127.1,
125.4,121.0,120.8,120.0,118.1, 114.7, 24.2. HRMS (ESI) calculated for
C
4.2.22. N-((E)-((E)-4-chlorostyryl)(2-hydroxyphenyl)-4-
sulfanylidene)acetamide (5f)
14H11ClNO3S [M ꢀ H]e:308.0148; Found: 308.0153.
White solid, yield: 75%, E/Z ¼ 20:1.1H NMR (400 MHz, CDCl3)
4.2.16. (Z)-N-((5-bromo-2-hydroxyphenyl)(2-hydroxyphenyl)-l4-
d
9.02 (s, 1H), 7.45 (d, J ¼ 7.7 Hz, 1H), 7.40e7.29 (m, 7H), 7.00 (d,
sulfanylidene)acetamide (3p)
J ¼ 8.2 Hz, 1H), 6.93 (t, J ¼ 7.5 Hz, 1H), 6.84 (d, J ¼ 15.4 Hz, 1H), 2.19
White solid, yield: 62%. 1H NMR (400 MHz, CDCl3)
d 11.55 (s, 2H),
(s, 3H); 13C NMR (101 MHz, CDCl3)
d
180.3, 159.4, 141.3, 136.9, 134.5,
7.45 (dd, J ¼ 11.3, 4.5 Hz, 2H), 7.30 (d, J ¼ 2.2 Hz, 1H), 7.25 (d,
131.4, 131.2, 129.34, 129.27, 129.1, 128.6, 128.4, 120.8, 120.5, 119.7,
24.3; HRMS (ESI) calculated for C16H13ClNO2S [M ꢀ H]e:318.0356;
Found: 318.0369.
J ¼ 7.7 Hz, 1H), 7.05 (d, J ¼ 8.3 Hz, 1H), 6.93 (t, J ¼ 7.6 Hz, 1H), 6.89 (d,
J ¼ 8.8 Hz, 1H), 2.20 (s, 3H); 13C NMR (101 MHz, CDCl3)
d 182.0,
159.4,158.1, 137.5, 135.0, 130.4, 128.9, 121.9, 121.0, 120.5, 118.2, 114.5,
112.2, 24.0. HRMS (ESI) calculated for
C14H11BrNO3S
[M ꢀ H]e:351.9643; Found: 351.9648.
4.2.23. N-((E)-((E)-4-bromostyryl)(2-hydroxyphenyl)-4-
sulfanylidene)acetamide (5g)
White solid, yield: 80%, E/Z ¼ 12.5:1.1H NMR (400 MHz, CDCl3)
4.2.17. N-((E)-(2-hydroxyphenyl)((E)-4-methylstyryl)-4-
d
7.52e7.47 (m, 2H), 7.44e7.35 (m, 2H), 7.33e7.27 (m, 3H), 7.01 (dd,
sulfanylidene)acetamide (5a)
White solid, yield: 85%, E/Z > 20:1.1H NMR (400 MHz, CDCl3)
7.47e7.32 (m, 5H), 7.18 (d, J ¼ 8.0 Hz, 2H), 7.04 (dd, J ¼ 8.4, 1.0 Hz,
J ¼ 8.3, 1.0 Hz, 1H), 6.95 (td, J ¼ 8.0, 1.2 Hz, 1H), 6.78 (d, J ¼ 15.3 Hz,
1H), 2.18 (s, 3H); 13C NMR (101 MHz, CDCl3)
d
181.0, 160.0, 140.9,
d
134.4, 132.2, 131.9, 129.5, 128.6, 125.2, 121.7, 120.3, 120.1, 114.5, 24.4;
HRMS (ESI) calculated for C16H13BrNO2S [M ꢀ H]e: 361.9850;
Found: 361.9854.
1H), 6.97e6.91 (m, 1H), 6.76 (d, J ¼ 15.3 Hz, 1H), 2.37 (s, 3H), 2.17 (s,
3H); 13C NMR (101 MHz, CDCl3)
d 180.7, 160.2, 142.8, 141.5, 134.3,
130.2, 129.7, 128.9, 128.1, 120.3, 120.2, 119.6, 114.9, 24.4, 21.5. HRMS
(ESI) calculated for
298.0909.
C
17H16NO2S [M ꢀ H]e:298.0902; Found:
4.2.24. N-((E)-((E)-4-(tert-butyl)styryl)(2-hydroxyphenyl)-4-
sulfanylidene)acetamide (5h)
4.2.18. N-((E)-(2-hydroxy-5-methylphenyl)((E)-4-methylstyryl)-
White solid, yield: 82%, E/Z ¼ 11:1.1H NMR (500 MHz, CDCl3)
l
4-sulfanylidene)acetamide (5b)
d
7.41e7.33 (m, 7H), 6.97 (d, J ¼ 7.9 Hz, 1H), 6.90 (t, J ¼ 7.6 Hz, 1H),
White solid, yield: 87%, E/Z ¼ 16:1.1H NMR (400 MHz, CDCl3)
9.09 (s, 1H), 7.38 (d, J ¼ 15.2 Hz, 1H), 7.32 (d, J ¼ 8.1 Hz, 2H), 7.17
6.74 (d, J ¼ 15.3 Hz, 1H), 2.17 (s, 3H), 1.28 (s, 9H). 13C NMR (126 MHz,
d
CDCl3)
d 180.8, 159.7, 154.4, 142.4, 134.1, 130.2, 128.4, 127.9, 125.9,
(dd, J ¼ 13.9, 8.2 Hz, 4H), 6.92 (d, J ¼ 8.1 Hz, 1H), 6.78 (d, J ¼ 15.3 Hz,
120.2, 119.81, 119.75, 115.5, 34.9, 31.1, 24.4; HRMS (ESI) calculated
1H), 2.34 (s, 3H), 2.27 (s, 3H), 2.17 (s, 3H); 13C NMR (101 MHz, CDCl3)
for C20H22NO2S [M ꢀ H]e: 340.1371; Found: 340.1377.
Please cite this article as: Y. Zuo et al., An internal oxidant-directing strategy enabling transition metal-free CeS bond ligation, Tetrahedron,
https://doi.org/10.1016/j.tet.2019.05.021

6
Y. Zuo et al. / Tetrahedron xxx (xxxx) xxx
4.2.25. N-((E)-((E)-2-([1,10-biphenyl]-4-yl)vinyl)(2-
hydroxyphenyl)-4-sulfanylidene)acetamide (5i)
353e356.
[6] A. Natarajan, Y. Guo, F. Harbinski, Y.H. Fan, H. Chen, L. Luus, J. Diercks, H. Aktas,
M. Chorev, J.A. Halperin, Novel ArylsulfoanilideꢀOxindole hybrid as an anti-
cancer agent that inhibits translation initiation, J. Med. Chem. 47 (2004)
4979e4982.
White solid, yield: 81%, E/Z > 20:1.1H NMR (400 MHz, CDCl3)
d
7.64e7.58 (m, 4H), 7.53 (d, J ¼ 8.3 Hz, 2H), 7.50e7.47 (m, 1H), 7.45
[7] S.S. Mansy, J.A. Cowan, IronꢀSulfur cluster Biosynthesis: toward an under-
standing of cellular machinery and molecular mechanism, Acc. Chem. Res. 37
(2004) 719e725.
[8] E. Schaumann, Sulfur-mediated rearrangements, Top. Curr. Chem. 274 (2007)
1e34.
[9] C. Shen, P. Zhang, Q. Sun, S. Bai, T.S. Hor, X. Liu, Recent advances in C-S bond
formation via C-H bond functionalization and decarboxylation, Chem. Soc.
Rev. 44 (2015) 291e314.
[10] T. Miao, P. Li, Y. Zhang, L. Wang, A sulfenylation reaction: direct synthesis of 3-
arylsulfinylindoles from arylsulfinic acids and indoles in water, Org. Lett. 17
(2015) 832e835.
(ddd, J ¼ 7.8, 4.0, 1.8 Hz, 3H), 7.42e7.38 (m, 2H), 7.07 (dd, J ¼ 8.4,
1.0 Hz, 1H), 6.99e6.94 (m, 1H), 6.86 (dd, J ¼ 12.2, 8.3 Hz, 1H), 2.20 (s,
3H); 13C NMR (101 MHz, CDCl3)
d 180.8, 160.3, 143.6, 142.2, 139.8,
134.4, 131.9, 130.5, 128.9, 128.6, 128.0, 127.6, 127.1, 120.7, 120.4,
120.3, 114.7, 24.4; HRMS (ESI) calculated for C22H18NO2S [M ꢀ H]e:
360.1058; Found: 360.1062.
4.2.26. N-((E)-(2-hydroxyphenyl)((E)-2-(naphthalen-2-yl)vinyl)-
l
4-sulfanylidene)acetamide (5j)
[11] T. Hostier, V. Ferey, G. Ricci, D. Gomez Pardo, J. Cossy, TFA-promoted direct C-
H sulfenylation at the C2 position of non-protected indoles, Chem. Commun.
51 (2015) 13898e13901.
White solid, yield: 72%, E/Z ¼ 15:1.1H NMR (400 MHz, CDCl3)
8.41 (s, 1H), 7.83e7.73 (m, 4H), 7.59e7.47 (m, 5H), 7.43e7.36 (m,
d
[12] J.A. Fernandez-Salas, A.P. Pulis, D.J. Procter, Metal-free C-H thioarylation of
1H), 7.16e7.04 (m, 2H), 6.95 (t, J ¼ 7.6 Hz, 1H), 2.24 (s, 3H); 13C NMR
arenes using sulfoxides:
Commun. 52 (2016) 12364e12367.
a direct, general diaryl sulfide synthesis, Chem.
(101 MHz, CDCl3)
d 179.3, 159.3, 143.7, 134.7, 134.4, 133.0, 130.4,
[13] D. Chen, Q. Feng, Y. Yang, X.M. Cai, F. Wang, S. Huang, Metal-free O-H/C-H
difunctionalization of phenols by o-hydroxyarylsulfonium salts in water,
Chem. Sci. 8 (2017) 1601e1606.
[14] A. Armstrong, D.P.G. Emmerson, Enantioselective synthesis of allenamides via
sulfimide [2,3]-Sigmatropic rearrangement, Org. Lett. 11 (2009) 1547e1550.
[15] M. Candy, C. Guyon, S. Mersmann, J.R. Chen, C. Bolm, Synthesis of sulfondii-
mines by N-Chlorosuccinimide-Mediated oxidative imination of sulfiliminium
salts, Angew. Chem. Int. Ed. 51 (2012) 4440e4443.
[16] D.J. Cram, J. Day, D.R. Rayner, D.M.V. Schriltz, D.J. Duchamp, D.C. Garwood,
Stereochemistry of sulfur compounds. I. Stereochemical reaction cycles
involving an open chain sulfoxide, sulfimide, and sulfoximide, J. Am. Chem.
Soc. 92 (1970) 7369e7384.
[17] T.L. Gilchrist, C.J. Moody, The chemistry of sulfilimines, Chem. Rev. 77 (1977)
409e435.
130.2, 128.9, 128.68, 128.66, 127.81, 127.77, 127.0, 123.2, 120.5, 119.6,
119.3, 114.9, 24.2. HRMS (ESI) calculated for C20H16NO2S [M ꢀ H]e:
334.0902; Found: 334.0910.
4.2.27. N-((E)-((E)-3-chlorostyryl)(2-hydroxyphenyl)-l4-
sulfanylidene)acetamide (5k)
White solid, yield: 72%, E/Z ¼ 15:1.1H NMR (400 MHz, CDCl3)
d
7.43 (dd, J ¼ 8.4, 1.5 Hz, 2H), 7.40 (dd, J ¼ 5.1, 1.6 Hz, 1H), 7.38e7.33
(m, 2H), 7.33e7.29 (m, 2H), 7.04e7.00 (m, 1H), 6.98e6.93 (m, 1H),
6.80 (d, J ¼ 15.3 Hz, 1H), 2.19 (s, 3H); 13C NMR (101 MHz, CDCl3)
d
181.0, 160.0, 140.4, 135.0, 134.7, 134.5, 130.6, 130.2, 128.7, 127.8,
[18] J.P. Marino, N. Zou, Chemoselective syntheses of g-butyrolactams using vinyl
126.3, 122.5, 120.4, 120.1, 114.4, 24.4; HRMS (ESI) calculated for
sulfilimines and dichloroketene, Org. Lett. 7 (2005) 1915e1917.
[19] G.P. Silveira, J.P. Marino, Enantioselective synthesis of dihydro-1H-benzin-
doles, J. Org. Chem. 78 (2013) 3379e3383.
C
16H13ClNO2S [M ꢀ H]e: 318.0356; Found: 318.0360.
[20] H. Takada, et al., Catalytic asymmetric sulfimidation, J. Org. Chem. 62 (1997)
6512e6518.
[21] Q. Wang, S. Nara, A. Padwa, A new synthesis of g-lactams based on the re-
Acknowledgments
action of vinyl sulfilimines with dichloroketene, Org. Lett. 7 (2005) 839e841.
[22] G.Y. Cho, C. Bolm, Silver-catalyzed imination of sulfoxides and sulfides, Org.
Lett. 7 (2005) 4983e4985.
[23] F. Collet, R.H. Dodd, P. Dauban, Stereoselective rhodium-catalyzed imination
of sulfides, Org. Lett. 10 (2008) 5473e5476.
[24] A.L. Marzinzik, K.B. Sharpless, A simple method for the preparation of N-
sulfonylsulfilimines from sulfides, J. Org. Chem. 66 (2001) 594e596.
[25] H. Okamura, C. Bolm, Rhodium-catalyzed imination of sulfoxides and Sulfides:
efficient preparation of N-unsubstituted sulfoximines and sulfilimines, Org.
Lett. 6 (2004) 1305e1307.
This work was supported by the National Science Foundation of
China (21622103, 21571098, and 91753121), the Natural Science
Foundation of Jiangsu Province (BK20160022), the Shenzhen Basic
Research Program (JCYJ20170413150538897), and the Fundamental
Research Funds for the Central Universities (020514380139).
Appendix A. Supplementary data
[26] H. Takada, K. Ohe, S. Uemura, Catalytic diastereoselective imidation of diaryl
sulfides bearing a chiral oxazolinyl moiety with chloramine T trihydrate,
Angew. Chem. Int. Ed. 38 (1999) 1288e1289.
[27] C.S. Tomooka, E.M. Carreira, Enantioselective nitrogen transfer to sulfides
from nitridomanganese(V) complexes, Helv. Chim. Acta 85 (2002)
3773e3784.
Supplementary data to this article can be found online at
https://doi.org/10.1016/j.tet.2019.05.021.
References
[28] J. Wang, M. Frings, C. Bolm, Enantioselective nitrene transfer to sulfides
catalyzed by
8661e8665.
a chiral iron complex, Angew. Chem. Int. Ed. 52 (2013)
ꢀ
[1] A.R. Murphy, J.M.J. Frechet, Organic semiconducting oli-gomers for use in thin
film transistors, Chem. Rev. 107 (2007) 1066e1096.
[29] Y. Chen, D. Wang, P. Duan, R. Ben, L. Dai, X. Shao, M. Hong, J. Zhao, Y. Huang,
A multitasking functional group leads to structural diversity using designer
CeH activation reaction cascades, Nat. Commun. 5 (2014) 4610.
[30] Q. Wu, Y. Chen, D.Y. Yan, M.Y. Zhang, Y. Lu, W.Y. Sun, J. Zhao, Unified synthesis
of mono/bis-arylated phenols via RhIII-catalyzed dehydrogenative coupling,
Chem. Sci. 8 (2017) 169e173.
[31] Q. Wu, D.Y. Yan, Y. Chen, T. Wang, F. Xiong, W. Wei, Y. Lu, W.Y. Sun, J. Li,
J. Zhao, A redox-neutral catechol synthesis, Nat. Commun. 8 (2017) 14227.
[32] F. Xiong, L. Lu, T.Y. Sun, Q. Wu, D.Y. Yan, Y. Chen, X. Zhang, W. Wei, Y. Lu,
W.Y. Sun, J. Li, J. Zhao, A bioinspired and biocompatible ortho-sulfiliminyl
phenol synthesis, Nat. Commun. 8 (2017) 15912.
[2] N.S. Li, J.K. Frederiksen, J.A. Piccirilli, Synthesis, proper-ties, and applications of
oligonucleotides containing an RNA dinucleotide phosphorothiolate linkage,
Acc. Chem. Res. 44 (2011) 1257e1269.
[3] M. Banerjee, A. Poddar, G. Mitra, A. Surolia, T. Owa, B. Bhattacharyya, Sul-
fonamide drugs binding to the colchicine site of Tubulin: thermodynamic
analysis of the DrugꢀTubulin interactions by isothermal titration calorimetry,
J. Med. Chem. 48 (2004) 547e555.
[4] A. Casini, J.Y. Winum, J.L. Montero, A. Scozzafava, C.T. Supuran, Carbonic
anhydrase inhibitors: inhibition of cytosolic isozymes I and II with sulfamide
derivatives, Bioorg. Med. Chem. Lett 13 (2003) 837e840.
[5] D.C. Cole, W.J. Lennox, S. Lombardi, J.W. Ellingboe, R.C. Bernotas, G.J. Tawa,
H. Mazandarani, D.L. Smith, G. Zhang, J. Coupet, L.E. Schechter, Discovery of 5-
arylsulfonamido-3- (pyrrolidin-2-ylmethyl)-1H-indole derivatives as potent,
selective 5-HT6 receptor agonists and antagonists, J. Med. Chem. 48 (2004)
[33] G. Liu, Y. Shen, Z. Zhou, X. Lu, Rhodium (III)-catalyzed redox-neutral coupling
of N-phenoxyacetamides and alkynes with tunable selectivity, Angew. Chem.
Int. Ed. 52 (2013) 6033e6037.
Please cite this article as: Y. Zuo et al., An internal oxidant-directing strategy enabling transition metal-free CeS bond ligation, Tetrahedron,
https://doi.org/10.1016/j.tet.2019.05.021