Disulfonation of terminal alkynes for 1,2-bisulfonylethenes

Article abstract of DOI:10.1039/d0cc05849a

A highly efficient and operationally simple method for the synthesis of 1,2-disulfonylethenes involving a hypervalent iodineI(iii) reagent to promote disulfonation of terminal alkynes has been developed. This protocol provides a facile and practical pathway to selectively access (E)-1,2-disulfonylethenes that features good functional group compatibility, easily available starting materials, excellent stereoselectivity, and good yields. This journal is

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Disulfonation of Terminal Alkynes for 1,2- Bisulfonylethenes
Yu Wang, Kongshuang Tang, Zhaohong Liu* and Yongquan Ning*
Received 00th January 20xx,
Accepted 00th January 20xx
DOI: 10.1039/x0xx00000x
www.rsc.org/
A highly efficient and operationally simple method for the disulfonylation of an alkyne resulting in the formation of two
new C-S bonds is considered as a highly direct and powerful
approach to access 1,2-bisulfonylethenes (Figure 1a). For
synthesis of 1,2-disulfonylethenes involving a hypervalent iodine
1
6
iii
(
I ) reagent to promote disulfonation of terminal alkynes has been
developed. This protocol provides a facile and practical pathway
to selectively access (E)-1,2-disulfonylethenes that features good
functional group compatibility, easily available starting materials,
excellent stereoselectivity, and good yields.
(
a) Previous work:
Ar
Br
+
R'SO2Na
R' = Aryl
12 M HCl
Ar
COOH Cu(ClO4)2·H2O
NH4)2S2O8
Ar
(
Ar
CuI/BrCF2CO2Et
R' = Aryl
+
+
SO2R'
Sulfones are an important class of molecules because of their
diverse range of significant applications as pharmaceuticals,
R'O2S
R' = Aryl, Alkyl
R'SO2H
R'SO2Na
Unexplored for alkyl alkynes
1
agrochemicals, materials, and important synthetic intermediates.
Excessive strong oxidants or acidic conditions
Specifically, 1,2-disulfonylethenes are important intermediates in
organic synthesis and can undergo cycloaddition, rearrangement
(
b) This work:
2
Iodine(III) reagent
R
3
4
R
2
R'SO Na
reactions and radical reactions. As a result, the preparation of
these molecules has received significant attention. Classic methods
for preparing 1,2-disulfonylethenes include oxidation of 1,2-
+
2
SO R'
DMSO, 60 o
R'O2S
C
R, R' = aryl, alkyl
Readily avaiable substrates
Good chemo- and diastereoselectivities
Mild reaction conditions
Transition-metel free
5
dithioethenes or 1-thio-2-sulfonylethenes, condensation of 1-
sulfonyl-2,2-dichloroethanes with sodium sulfonates, nucleophilic
substitution of alkenyliodonium salts with sodium sulfonates, and Figure 1 The strategies for the synthesis of 1,2-bissulfonylethenes
cycloaddition or Michael-type addition of bis(sulfonyl)acetylene.
However, these approaches all have some obvious disadvantages,
such as the need for predecorated feedstocks, multistep processes,
strong oxidants, or metal catalysts. Thus, the development of a
simple and efficient method to construct 1,2-disulfonylethenes
remains an elusive and active topic in both organic synthesis and
drug discovery.
6
7
8
from alkynes.
example, Tang et al reported acid-mediated disulfonylation of
haloalkynes to prepare 1,2-bisulfonylethenes using
arylethynylene bromides with sodium arylsulfinates. Li et al
developed copper-catalyzed decarboxylative disulfonylation of
alkynyl carboxylic acids with sulfinic acids using excess
1
6a
1
6b
amounts of oxidants. More recently, Tang et al reported
copper-catalyzed disulfonation of terminal alkynes with
Radical-based difunctionalization reactions of alkynes have
attracted much attention because they offer a straightforward
way to afford tri- and tetrasubstituted alkenes with excellent
1
6c
sodium aryl sulfinates. Nevertheless, these methods are far
from general and suffer from some disadvantages like the use
of functionalized alkynes, expensive and toxic metals, excess
amounts of strong oxidants or the limited reaction scope, for
example, not suitable for alkyl-subtituted alkynes and
9
step and atom economy. Mechanistically, this reaction
pathway includes a vinyl radical intermediate, which is highly
reactive and readily couples with another radical to form an
alkene product.10 Considering this context, much effort has
been made to create new C−S bonds by sulfonative sulfinates. To address these limitations of existing synthetic
1
1
functionalization of alkynes, such as by halosulfonylation,
methods and as part of our continuous interest in
difunctionalization reactions of alkynes,
a facile and efficient protocol for the synthesis of 1,2-
bisulfonylethenes via I(iii) reagent-initiated radical
disulfonylation of alkynes (Figure 1b). To the best of our
sulfonyloxidation,12 sulfonamination, sulfonylcarbonation,
13
14
13, 17
we herein present
1
5
and carbosulfonylation.
Consequently, radical-based
Jilin Province Key Laboratory of Organic Functional Molecular Design & Synthesis, knowledge, this is the first example of metal-free disulfonation
Department of Chemistry, Northeast Normal University, Changchun 130024, China.
E-mail: liuzh944@nenu.edu.cn；ningyq508@nenu.edu.cn
of alkynes. Moreover, this reaction presents broad functional
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group compatibility and enables the rapid construction of reaction parameters such as the I(iii) reagent, VsieowlvAertnictle, Onalninde
complex molecules in a streamlined manner under mild temperature (Table 1). The reaction in the pDrOeIs:e1n0c.1e03o9f/4D0eCqCu0iv58I(4i9iiA)
reaction conditions.
reagent I in DMSO at 60 °C under air afforded desired product 3aa
in 95% yield (entry 1). Subsequently, we examined other I(iii)
reagents (I-IV); only I(iii) reagent II afforded the product in 57%
yield, while I(iii) reagents III, IV and phenyliodine (III) diacetate
(PIDA) were ineffective and alkyne 1aa recoveried (entries 2–5). The
reaction solvent also proved important, with DCM and CH CN giving
3
only trace amounts of the desired product using I(iii) reagent I
(entries 6 and 7) compared to polar aprotic solvents such as DMF
Table 1 Optimization of the Reaction Conditionsa.
Ts
Iiii reagent
O
S
Br
Tol
ONa
Solvent, T o
C
Ts
Br
1aa
2a
3aa
(
47%, entry 8). With regard to the amount of TsNa 2a and I(iii)
Entry
[M]
I
II
III
IV
Sol.
Temp.
Yield/%
reagent, when both were decreased to 3.0 equiv, the yield of the
product diminished (entry 1 vs entry 9). Finally, increasing or
reducing the reaction temperature led to a decrease in the product
yield (entries 10 - 11).
1
2
3
4
DMSO
DMSO
DMSO
DMSO
60
60
60
60
95
57
0
0
5
6
7
8
PIDA
DMSO
DCM
CH3CN
DMF
DMSO
DMSO
DMSO
60
60
60
60
60
40
80
0
Trace
Trace
47
82
66
The scope of the reaction with respect to the alkyne proved to
be broad, with a wide range of aryl- and heteroaryl-functionalized
terminal alkynes being suitable for this reaction, affording the
corresponding 1,2-disulfonylethenes in good to excellent yields
I
I
I
I
I
I
9
c
(
Scheme 1). We first investigated various aryl-substituted terminal
1
1
0
1
alkynes to explore the scope of this transformation. As shown in
Scheme 1, regardless of whether electron-donating or electron-
withdrawing groups were present at any position on the aryl ring,
the aryl-substituted terminal alkynes all reacted efficiently to afford
64
a
Reaction conditions: 1aa (0.3 mmol), 2a (1.2 mmol, 4.0 equiv), I(iii)
reagent (1.2 mmol, 4.0 equiv), solvent (4 mL), 12 h, Air. Isolated
yield. 2a (0.9 mmol, 3.0 equiv), I(iii) reagent (0.9 mmol, 3.0 equiv).
b
c
1
6
,2-disulfonylethene products in moderate to high yields (3ab−3ay,
0-95%). Pleasingly, common functional groups, such as methoxy,
Cl
F
Cl
Cl
I
I
I
I
alkyl, halogen, aldehyde, ketone, ester, cyano, and trifluoromethyl,
were all well tolerated, and a reactive functional group (3-OH) was
also suitable for this reaction, affording desired product 3av in 80%
yield. The structure of compound 3ac was unambiguously
confirmed by single-crystal X-ray crystallography analysis (CCDC No.
Cl
O
O
O
O
I
II
III
IV
The reaction of alkyne 1aa with TsNa 2a was chosen as a model
reaction for the optimization investigation, with variation of used to generate polyfunctionalized products. As depicted in
2
006122). Moreover, this disulfonylation methodology can also be
Scheme 1 The Reaction Scope. a, b
R2
Iiii reagent (I)
O
S
O
O
S
R1
R1
R2
ONa
DMSO, 60 oC, 12 h, air
O
S
O
R2
1
2a
3
The Scope of the Alkynes
3
aq, R = Me, 74%
Ts
Ts
3
3
3
3
3
ab, R = H, 61%
3ar, R = Cl, 78%
3as, R = OMe, 80%
Ts
R
Ts
Ts
ac, R = Me, 65%
ad, R = Et, 76%
ae, R = t-Bu, 79%
af, R = n-Bu, 74%
3aw, R = F, 60%
3ax, R = Cl, 79%
3ay, R = OMe, 63%
Ts
R
3at, R = F, 83%
Ts
Ts
Ts
3au, R = NO2, 85%
Ts
Ts
Ts
az, 73%
S
3av, R = OH, 80%
Ts
3ag, R = OMe, 68%
The structure of 3ac
CCDC: 2006122
3
3
ah, R = F, 73%
ai, R = Cl, 92%
3
3ba, 87%
Ts
Ts
Ts
Ts
Ts 3aj, R = Ph, 80%
Ts
R
Ts
3
3
3
3
3
3
ak, R = CHO, 74%
al, R = COMe, 77%
am, R = CO2Me, 89%
an, R = CN, 77%
ao, R = NO2, 85%
ap, R = CF3, 87%
N
S
Ts
S
Ts
S
Ts
Ts
Ts
Ts
3
bb, 84%
3bc, 68%
3bd, 72%
3be, 68% (38%)b
3bf, 74%
3bg, 67% (40%)b
3bh, 90% (50%)b
Ts
Ts
Ts
The Scope of Sodium Sulfinate
Cl
R
S
Ts
S
Ts
Ts
O
O
O
S
O
O
O
S
R
O
S
O
S
R
S
O
O
S
O
S
S
3
bi, 42%
3bj, 54% (24%)b
3bk, 44%
S
O
R
R
O
S
R
O
O
O
O
O
O
S
O
Br
O
S
O
R
O
4a, Ar = Ph, 90%
4b, Ar = p-ClPh, 79%
c, Ar = p-FPh, 83%
4d, Ar = p-OMePh, 89%
Br
Br
O
Br
4i, 75%
Br
4
4k, R = Me. 74%
4l, R = Et. 72%
4
4
4
e, m-FPh, 87%
f, m-CH3Ph, 87%
4g, Ar = o-MePh, 87%
4h, Ar = o-BrPh, 60%
R
4j, 79%
m, R = Cyclopropyl. 89%
Br
a
Reaction conditions: 1 (0.3 mmol), 2a (1.2 mmol, 4.0 equiv), I(iii) reagent I (1.2 mmol, 4.0 equiv) in 4 mL of DMSO at 60 °C for 12 h under
b
Air. Yields are of isolated products. The amount of recovered starting material is given in parentheses.
2
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DOI: 10.1039/D0CC05849A
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Then intermediate A could produce a radical B via I-O cleagve,
Scheme 1, 1,4-diethynylbenzene 1az provided 1,4-bis((E)-1,2-
ditosylvinyl)benzene 3az in 73% yield. In addition to aryl alkynes,
fused aryl (2-naphthyl), heterocyclic (2-thienyl, 3-thienyl, and 3-
pyridyl), and fused heterocyclic (3-dibenzothienyl) alkynes were all
smoothly transformed into 1,2-bis(arylsulfonyl)ethene products
1
9
which can easily isomerized the sulfonyl free radical C. the
addition of sulfonyl radical to c-c triple bond of alkyne leading to
alkenyl radical, which would further trapped by another sulfonyl
2
0
radical to deliver the final product.
3
ba-3bf in 42-87% yields. In addition, we also tested some aliphatic
In conclusion, a highly efficient and operationally simple method
for 1,2-bisulfonylethene synthesis via an I(iii) reagent to promote
disulfonation of terminal alkynes has been developed. This
transformation is characterized by its wide substrate scope, high
stereoselectivity for E isomers, mild reaction conditions, and
utilization of readily available reagents, thus providing an efficient
and practical approach to obtain (E)-1,2-disulfonylethenes.
Preliminary mechanistic studies revealed that this reaction might
involve a radical process. Further mechanistic investigations and
studies of the synthetic applications of this reaction are underway.
alkynes, which indeed were converted into the corresponding 1,2-
disulfonylethene derivatives, but with moderate to good reactivity,
affording 3bg−3bk in 40−45% yields. Furthermore, enyne systems,
such as 1-cyclohexenyl, also reacted efficiently, giving product 3bk
in reasonable yields. These alkyl-substituted 1,2-disulfonylethenes
are novel compounds that could prove useful as intermediates in
organic and medicinal chemistry research.
Next, we evaluated the reaction scope with respect to the
sodium sulfinate component in reactions with 4-Br phenylacetylene
1
aa (Scheme 1). Both electron-rich and electron-deficient aryl
sulfinates afforded the corresponding product in moderate to high
yields (4a–4h, 60–90%). In addition to aryl sulfinate salts, fused aryl
Conflicts of interest
There are no conflicts to declare.
(2-naphthyl), heterocyclic (3-thienyl) and alkyl sulfinate salts also
proved suitable reaction partners, giving products 4i-4m in similar
yields.
Acknowledgements
Scheme 2 Proposed Reaction Mechanism.
This work was supported Postdoctoral Innovation Talent Support
Program (BX20200079) and the Fundamental Re-search Funds for
the Central Universities (2412020QD005, 2412019ZD001).
Ts
O
S
s.r
(a) Br
+
Tol
ONa
TEMPO
Ts
Br
1aa
2a
3aa, 0%
(b)
NaCl
O
Cl
Notes and references
O
I
O
S
I
Tol
O
O
1
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S
O
Tol
Tol
O
S
I
B
I
A
OH
Tol
ONa
2a
O
S
O
O
S
Tol
O
S
S
Ph
O
Tol
O
O
Tol
Ph
O
3
ab
C
D
Ph
C
1
ab
To gain further insight into the reaction mechanism, several
control experiments were carried out (Scheme 2). Initially, when
,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) was added under the
standard reaction condi-tions, inhibition of the reaction was
observed, and disul-fonylethene 3aa was not obtained (Scheme 2a),
which indicated that a radical pathway may be involved.
2
2
3
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reports,12 a tentative mechanism was proposed (Scheme 2a). First,
the reaction of I(iii) I with sodium p-toluenesulfinate 2a could give
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1
8
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