Ammonium Iodide-Mediated Sulfenylation of 4-Hydroxycoumarins or 4-Hydroxyquinolinones with a Sulfonyl Chloride as a Sulfur Source

Article abstract of DOI:10.1055/s-0036-1589083

A novel ammonium iodide-induced sulfenylation of 4-hydroxycoumarins or 4-hydroxyquinolinones by using an aryl- or alkylsulfonyl chloride as the sulfur source gave a wide range of 3-sulfanyl-4-hydroxycoumarins or 3-sulfanyl-4-hydroxyquinolinones, respectiv

Full text of DOI:10.1055/s-0036-1589083

SYNLETT
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© Georg Thieme Verlag Stuttgart · New York
2017, 28, A–F
letter
A
en
T. Guo, X.-N. Wei
Letter
Synlett
Ammonium Iodide-Mediated Sulfenylation of 4-Hydroxycouma-
rins or 4-Hydroxyquinolinones with a Sulfonyl Chloride as a Sulfur
Source
Tao Guo*a,b
OH
OH
Xu-Ning Weia
SR2
O
NH4I
R1
R1
R2SO2Cl
+
1,4-dioxane
110 °C
a School of Chemistry and Chemical Engineering, Henan
University of Technology, Zhengzhou, Henan 450001,
P. R. of China
X
O
X
X = O or NR3
35 examples
up to 84% yield
taoguo@haut.edu.cn
b School of Pharmaceutical Sciences, Zhengzhou University,
100 Kexue Avenue, Zhengzhou, Henan 450001,
P. R. of China
Received: 31.05.2017
Accepted after revision: 03.07.2017
Published online: 02.08.2017
HO
OH
HO
DOI: 10.1055/s-0036-1589083; Art ID: st-2017-w0410-l
MeO
O
O
O
O
Abstract A novel ammonium iodide-induced sulfenylation of 4-hydroxy-
coumarins or 4-hydroxyquinolinones by using an aryl- or alkylsulfonyl
chloride as the sulfur source gave a wide range of 3-sulfanyl-4-hydroxy-
coumarins or 3-sulfanyl-4-hydroxyquinolinones, respectively, in moder-
ate to good yields. This method provides as a simple approach to the
direct formation of C–S bonds, which is of high value and utility in the
pharmaceutical industry.
Inhibitor of HIV-1 replication
HRP inhibitor
O
O
OH
S
O
Br
N
O
O
O
Key words sulfanylhydroxycoumarins, sulfanylhydroxyquinolinones,
C–S bond formation, sulfenylation, sulfonyl chlorides, ammonium
iodide
Fluorescence turning-on
sensing of cadmium(II) ions
herbicide
Cl
Cl
N
Among bioactive heterocycles, coumarin and quinoli-
none derivatives play particularly significant roles in me-
dicinal chemistry.1 In recent decades, coumarins and quino-
linones have attracted immense attention, as these com-
pounds are important motifs in natural products and in
compounds with pharmaceutical and biological activities,
such as antiviral,2 anticancer,3 antibacterial,4 fungicidal,5 or
antiprotozoal activities6 (Figure 1). Coumarins and quinoli-
nones are significant classes of organic molecules and form
core entities in many commercially available drugs, includ-
ing dicoumarol, warfarin, and acenocoumarol. Moreover,
coumarin and quinolinone derivatives display outstanding
turn-on-type fluorescence selectivity toward Cd2+, Hg2+,
Cr3+, I–, CN–, F–, and other ions.7
Organic sulfides are widely found in medicinal agents,
and are considered as privileged scaffolds.8 Recently, several
research groups have focused on sulfenylation of 4-hy-
droxycoumarins and 4-hydroxyquinolinones with various
sulfenylating reagents. For example, Parumala and Peddin-
ti9 described a method for preparing 3-sulfanyl-4-hydroxy-
coumarin derivatives by iodine-catalyzed cross-dehydroge-
native C–S coupling with arylthiols under solvent-free con-
ditions [Scheme 1(a)]. Sinha and co-workers10 realized an
easy access to 3-sulfanyl-4-hydroxycoumarin derivatives
OMe
N
NH2
F3C
CO2Et
N
O
Cl
N
O
H
treatment of male erectile dysfunction
antitumor
Figure 1 Examples of coumarin and quinolinone derivatives with bio-
activities or fluorescent properties
through bovine serum albumin/I2-catalyzed sulfenylation
of 4-hydroxycoumarins [Scheme 1(b)]. Lee and co-work-
ers11 developed an efficient CuBr·Me2S-catalyzed direct
sulfenylation of 4-hydroxycoumarins and 4-hydroxyquino-
linones by using arylsulfonyl hydrazides as sulfenylating re-
agents [Scheme 1(c)]. However, several drawbacks, includ-
ing limited substrate scopes and the use of inconvenient
sulfenylating reagents such as arylsulfonyl hydrazides, nar-
row the range of use of these methods. Consequently, a new
approach that provides direct and efficient access to 3-sul-
fanyl-4-hydroxycoumarin and 3-sulfanyl-4-hydroxyquino-
linone derivatives by relying on the characteristic reactivity
of sulfonyl chlorides12 as sulfenylating agents is urgently re-
© Georg Thieme Verlag Stuttgart · New York — Synlett 2017, 28, A–F

B
T. Guo, X.-N. Wei
Letter
Synlett
Previous work
OH
O
OH
R1
R1
S
SH
I2/DMSO
+
(a)
(b)
O
Neat, 80 °C
O
O
OH
OH
X
SH
S
X
I2, BSA, O2
H2O, 50 °C
+
Y
n
Y
R1
O
O
O
O
R1
n
n = 0, 1
OH
OH
X
SAr
O
CuBr•Me2S
R1
+
ArSO2NHNH2
R1
(c)
DABCO
X
O
dioxane, reflux
X = O or NR3
This work
OH
X
OH
SR2
NH4I
R2SO2Cl
R1
R1
+
(d)
1,4-dioxane
110 °C
O
X
O
X = O or NR3
Scheme 1 Construction of 3-sulfanyl-4-hydroxycoumarin and 3-sulfanyl-4-hydroxyquinolinone derivatives
quired. This study describes a new method for the synthesis
of sulfonylated coumarin and quinolinone derivatives in
good yields by using NH4I as an inducer [Scheme 1(d)].
To optimize the reaction conditions, we selected 4-hy-
droxy-1-methylquinolin-2(1H)-one (1a) and tosyl chloride
(2a) as model substrates for the sulfenylation reaction. 1,4-
Dioxane was found to be the most effective solvent (Table 1,
entry 2); the use of other solvents such as DMSO, xylene,
NMP, MeCN, or DMF led to significantly lower reaction
yields (entries 1 and 3–7). Inspired by this result, we exam-
ined the effect of various iodine sources. CuI as the inducer
was not efficient and gave an unsatisfactory yield (entry 8).
However, TBAI, I2, and KI, gave the desired product 3a in 41,
47, and 38% yield, respectively (entries 9–11). NH4I was the
most suitable inducer, affording the desired product 3a in
78% yield (entry 7). Further attempts to adjust the reactant
concentrations, solvent, temperature, or inducer loading
did not lead to any improvement in the yield of the sulfe-
nylated product 3a (entries 12–15). Therefore, the condi-
tions employed in entry 7 were used as the standard reac-
tion conditions.
Having successfully identified the optimal reaction con-
ditions for synthesizing 3-sulfanyl-4-hydroxyquinolinones,
we turned our attention to the substrate scope and general-
ity of the reaction. As summarized in Scheme 2, a broad
range of sulfonyl chlorides were first screened. The reac-
tions of 4-hydroxyquinolinones and sulfonyl chlorides with
electron-donating or electron-withdrawing groups (Me,
OMe, Cl, Br, or F) were favorable, affording the desired prod-
ucts 3a–f in moderate to good yields. Of note, a polycyclic
and a hetaryl sulfonyl chloride could also be used, giving
Table 1 Screening and Optimization of the Reaction Conditionsa
OH
OH
S
SO2Cl
catalyst
+
solvent
T °C
N
O
N
O
1a
2a
3a
Entry
Inducer
Solvent
DMSO
Temp (°C)
Yieldb (%)
1
2
NH4I
NH4I
NH4I
NH4I
NH4I
NH4I
NH4I
CuI
100
100
100
100
100
110
110
110
110
110
110
110
130
120
110
NR
41
NR
37
29
54
78
8
1,4-dioxane
xylene
3
4
NMP
5
MeCN
6
DMF
7
1,4-dioxane
1,4-dioxane
1,4-dioxane
1,4-dioxane
1,4-dioxane
1,4-dioxane
DMF
8
9
TBAI
I2
41
47
38
70
32
59
56
10
11
12c
13
14
15d
KI
NH4I
NH4I
NH4I
NH4I
1,4-dioxane
1,4-dioxane
a Reaction conditions: 1a (0.25 mmol); TosCl (2a; 1.5 equiv); I2 (2.0 equiv),
TBAI, KI, or NH4I (4.0 equiv), or CuI (0.2 equiv); solvent (0.5 mL); 6 h.
b Isolated yield.
c 1,4-Dioxane (1 mL).
d NH4I (2.0 equiv).
© Georg Thieme Verlag Stuttgart · New York — Synlett 2017, 28, A–F

C
T. Guo, X.-N. Wei
Letter
Synlett
the corresponding products 3g and 3h in 67% and 41%
yields, respectively. Next, the effects of various quinolinone
components in the reactions with sulfonyl chlorides were
examined. Electronic effects in the quinolinone structure
turned out to stronger, and quinolinones with electron-
withdrawing groups (Br, and NO2) or electron-donating
groups (Me) afforded the corresponding products in sharp-
ly decreased yields. Replacement of the methyl group on
the quinolinone nitrogen atom by an ethyl group or a hy-
drogen atom had little effect on the reaction efficiency, and
slightly lower yield (55%) was obtained when an N-ben-
zylquinolinone was used. It was gratifying to find that a 4-
hydroxypyridin-2(1H)-one was a also viable substrate for
this protocol, and gave the C-3 sulfenylated product 3o in
48% yield.
Having established a simple approach for the synthesis
of 3-sulfanyl-4-hydroxyquinolinones, we next examined
whether valuable 3-sulfanyl-4-hydroxycoumarins could be
obtained from 4-hydroxycoumarins under similar condi-
tions. Various substituted 4-hydroxycoumarins and sulfo-
nyl chlorides were screened. Substituents, such as methyl,
methoxy, chloro, bromo, or fluoro on the benzene ring of
the coumarin or the sulfonyl chloride were tolerated, and
several sulfonyl chlorides bearing 4-tert-butylphenyl and 1-
naphthyl groups coupled readily with 4-hydroxycoumarins
to afford the desired products in moderate to good yields
(5a–g and 5j–o, 64–84%). A substrate with a strongly elec-
tron-withdrawing group (CN) gave the desired product 5h
in a markedly reduced yield of 44%. Fortunately, 2-thiophe-
necarbonyl chloride was also suitable for this kind of trans-
formation in the presence of NH4I. More importantly, the
reactions between 4-hydroxycoumarin and alkylsulfonyl
chlorides permitted an efficient synthesis of alkyl sulfides
(Scheme 3) without some of the disadvantages of previous
protocols, which have been rarely applied to aliphatic prod-
ucts.
To determine whether the reaction conditions were also
suitable for the sulfenylation of other compounds, we ex-
amined the reactions of indoles and imidazo[1,2-a]pyridine
with tosyl chloride (2a) under the same reaction condi-
tions. Fortunately, the sulfenylation reaction worked well,
affording the desired products 7a, 7b, and 9 in 64, 76, and
67% yield, respectively (Scheme 4). These results illustrate
the wide scope of our thioether-generating method.
OH
OH
S
NH4I
Ar
R1
R1
+
ArSO2Cl
1,4-dioxane
110 °C
N
R2
O
N
R2
O
3
2
1
OH
N
OH
N
OH
OH
N
S
S
S
S
O
O
OCH3
N
O
Cl
O
3b, 80%
3a, 78%
3d, 74%
3c, 83%
OH
OH
S
OH
OH
S
S
S
S
N
O
Br
N
O
F
N
O
N
O
3e, 69%
3f, 72%
3g, 67%
OH
3h, 41%
OH
OH
OH
S
O2N
S
Br
S
S
N
O
N
O
N
O
N
O
H
3l, 67%
3k, 38%
3j, 51%
3i, 69%
OH
OH
OH
S
S
S
N
O
N
O
N
O
Et
Bn
3m, 64%
3o, 48%
3n, 55%
Scheme 2 Synthesis of 3-sulfanyl-4-hydroxyquinolinones and related compounds. Reagents and conditions: 1 (0.25 mmol), 2 (1.5 equiv), NH4I (4.0
equiv), 1,4-dioxane (0.5 mL), 110 °C, 6 h. Isolated yields are indicated.
© Georg Thieme Verlag Stuttgart · New York — Synlett 2017, 28, A–F

D
T. Guo, X.-N. Wei
Letter
Synlett
OH
OH
SR2
O
NH4I
R2SO2Cl
R1
R1
+
1,4-dioxane
110 °C
O
O
O
2
4
5
OH
OH
OH
OH
O
S
S
S
S
O
O
tBu
O
O
OMe
O
O
O
5d, 81%
5b, 82%
5c, 71%
5a, 80%
OH
OH
S
OH
OH
S
S
Br
S
F
O
O
Cl
O
O
CN
O
O
O
O
5h, 44%
5e, 84%
5f, 79%
5g, 82%
OH
OH
OH
OH
S
S
S
S
S
MeO
O
O
O
O
O
O
O
O
5l, 64%
5i, 49%
5k, 74%
5j, 72%
OH
OH
OH
OH
SMe
Cl
S
Br
S
F
S
O
O
O
O
O
O
O
O
5n, 73%
5o, 78%
5p, 61%
5m, 72%
OH
O
S
O
5q, 52%
Scheme 3 Synthesis of 3-sulfanyl-4-hydroxycoumarins. Reagents and conditions: 4-hydroxycoumarin 1 (0.25 mmol), sulfonyl chloride 2 (1.5 equiv),
NH4I (4.0 equiv), 1,4-dioxane (0.5 mL), 110 °C, 12 h. Isolated yields are indicated.
OH
O
OH
O
S
S
SO2Cl
NH4I, BHT
SO2Cl
+
NH4I
1,4-dioxane
110 °C
+
O
O
N
1,4-dioxane
110 °C
N
4a
R
2a
5a, 78%
R
6
2a
7a R = H, 64%
7b R = Me, 76%
Scheme 5 Control experiment
S
SO2Cl
NH4I
N
On the basis of these results and those of previous stud-
ies,8g,i,13 a possible reaction mechanism was proposed
(Scheme 6). First, NH4I splits into NH3 and HI, and then the
HI reduces the sulfonyl chloride 2 to the electrophilic spe-
cies II. This reacts with the 4-hydroxycoumarin or the 4-hy-
droxyquinolinone to form intermediate III. Note that the
oxidation product I2 can also react with the sulfonyl chlo-
ride to afford species II and an IO– ion. Finally, the product 3
or 5 is obtained by deprotonation and aromatization of III.
N
Ph
+
Ph
1,4-dioxane
110 °C
N
N
2a
8
9, 67%
Scheme 4 Extension of the sulfenylation reaction
To investigate the reaction mechanism, we conducted a
control experiment. In the presence of the radical scavenger
2,6-di-tert-butyl-4-methylphenol (BHT; 2.0 equiv.), 5a was
obtained in 78% yield, showing that radical intermediates
are not involved in the coupling reaction (Scheme 5).
© Georg Thieme Verlag Stuttgart · New York — Synlett 2017, 28, A–F

E
T. Guo, X.-N. Wei
Letter
Synlett
References and Notes
NH4I
O
S
I
Δ
NH3
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Cl
HI
R
HI
I2 +
H2O
O
R
S
Cl
R
S
Cl
II
O
2
IO–
OH
X
OH
SR
O
O
Cl–
X
3 and 5
NH3
OH+
H
SR
O
X
III
Scheme 6 Proposed mechanism for the formation of products 3 and 5
In conclusion, we have developed a practical and effi-
cient approach for the ammonium iodide-mediated sulfe-
nylation of 4-hydroxycoumarins or 4-hydroxyquinolinones
with sulfonyl chlorides to afford various 3-sulfanyl-4-
hydroxycoumarins or 3-sulfanyl-4-hydroxyquinolinones in
moderate to good yields.14 In addition, this method was ex-
tended to alkylsulfonyl chlorides. This method offers a sim-
ple approach to the direct formation of C–S bonds by using
sulfonyl chlorides as sulfenylating agents, making it attrac-
tive for the efficient synthesis of organic sulfides. Currently,
the construction of a compound library is underway in our
laboratory.
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Funding Information
Financial support from Open Project of Grain and Corn
Engineering Technology Research Center in State Administration of
Grain (No. 24400042), the Doctoral Fund of Henan University of Tech-
nology (No. 2013BS053), the Colleges and Universities Key Research
Program Foundation of Henan Province (No. 17A150006), the Science
and Technology Foundation of Henan Province (No. 172102310621),
and the Fundamental Research Funds for the Henan Provincial Col-
leges and Universities in Henan University of Technology (No.
2015QNJH08) are greatly appreciated
H
e
n
a
n
Unvieytrsi
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y
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Acknowledgment
The authors are also grateful to Jun Liu, Henan University of Technolo-
gy, for her assistance with the NMR analyses.
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Supporting Information
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Finet, J.-P.; Azas, N.; Combes, S. Eur. J. Med. Chem. 2010, 45, 864.
Supporting information for this article is available online at
https://doi.org/10.1055/s-0036-1589083.
S
u
p
p
ortioInfgrmoaitn
S
u
p
p
ortiInfogrmoaitn
© Georg Thieme Verlag Stuttgart · New York — Synlett 2017, 28, A–F

F
T. Guo, X.-N. Wei
Letter
Synlett
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(14) 4-Hydroxy-3-sulfanylquinolin-2(1H)-ones 3a–o and 4-
Hydroxy-3-sulfanyl-2H-chromen-2-ones 5a–q; General Pro-
cedure
1,4-Dioxane (0.5 mL) was added to flask charged with the
appropriate 4-hydroxyquinolinone or 4-hydroxycoumarin (0.25
mmol), sulfonyl chloride (0.25 mmol), and NH4I (1 mmol), and
the mixture was stirred at 110 °C under air for 6–12 hours until
the reaction was complete (TLC). The mixture was then cooled
to r.t., diluted with EtOAc (20 mL), and washed with H2O (10
mL). The aqueous layer was extracted with EtOAc (2 × 5 mL),
and the organic phases were combined and dried (Na2SO4).
After evaporation of the solvents, the residue was purified by
flash column chromatography [silica gel, PE–EtOAc (4:1 to 1:1)]
to afford the desired product 3 or 5.
4-Hydroxy-1-methyl-3-(4-tolylsulfanyl)quinolin-2(1H)-one
(3a)[11]
Yellow solid; yield: 58 mg (78%); mp 234–236 °C. IR (KBr):
2922, 2362, 1614, 1583, 1500, 1159, 1074, 802, 756 cm–1 1H
.
NMR (400 MHz, CDCl3): δ = 2.26 (s, 3 H), 3.71 (s, 3 H), 7.03 (d, J =
8.0 Hz, 2 H), 7.22–7.30 (m, 3 H), 7.36 (d, J = 8.8 Hz, 1 H), 7.65 (td,
J = 1.6, 8.8 Hz, 1 H), 7.90 (s, 1 H), 8.06 (dd, J = 1.2, 8.0 Hz, 1 H).
13C NMR (125 MHz, CDCl3): δ = 21.1, 30.3, 103.2, 114.3, 114.4,
122.1, 125.1, 128.7, 130.1, 130.7, 132.8, 137.0, 140.4, 161.8,
163.2. HRMS: m/z [M + H]+ calcd for C17H16NO2S: 298.0896;
found: 298.0909.
4-Hydroxy-3-(phenylsulfanyl)-2H-chromen-2-one (5a)[11]
Yellow solid; yield: 54 mg (80 %); mp 198–200 °C. 1H NMR (400
MHz, DMSO-d6): δ = 7.15–7.21 (m, 3 H), 7.29 (d, J = 8.0 Hz, 2 H),
7.40–7.45 (m, 2 H), 7.70–7.75 (m, 1 H), 7.97 (dd, J = 1.2, 8.0 Hz, 1
H). 13C NMR (100 MHz, DMSO-d6): δ = 94.3, 115.7, 116.5, 124.2,
124.4, 125.5, 126.2, 129.1, 133.7, 135.9, 153.0, 160.9, 168.5.
HRMS: m/z [M + H]+ calcd for C15H11O3S: 271.04234; found:
271.04205.
(11) Paul, S.; Shrestha, R.; Edison, T. N. J. I.; Lee, Y. R.; Kim, S. H. Adv.
Synth. Catal. 2016, 358, 3050.
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© Georg Thieme Verlag Stuttgart · New York — Synlett 2017, 28, A–F