A Route to O-Aminosulfonates and Sulfonamides through Insertion of Sulfur Dioxide and Hydrogen Atom Transfer

Article abstract of DOI:10.1002/adsc.201700501

A three-component reaction of aryldiazonium tetrafluoroborates, the 1,4-diazabicyclo[2.2.2]octane?bis(sulfur dioxide) adduct [DABCO?(SO₂)₂] and hydroxylamines under catalyst-free and additive-free conditions has been developed, providing aryl O-aminosulfonates in good yields. Sulfonamides could also be obtained via a one-pot process through the reaction of aryldiazonium tetrafluoroborates, DABCO?(SO₂)₂ and amines in the presence of N-hydroxybenzotriazole. A mechanism involving the insertion of sulfur dioxide and hydrogen atom transfer is proposed and supported by theoretical calculations. (Figure presented.).

Full text of DOI:10.1002/adsc.201700501

Title: Route to O-aminosulfonates and Sulfonamides through Insertion
of Sulfur Dioxide and Hydrogen Atom Transfer
Authors: Tong Liu, Danqing Zheng, Zhenhua Li, and Jie Wu
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10.1002/adsc.201700501
Advanced Synthesis & Catalysis
FULL PAPER
DOI: 10.1002/adsc.201((will be filled in by the editorial staff))
Route to O-aminosulfonates and Sulfonamides through
Insertion of Sulfur Dioxide and Hydrogen Atom Transfer
Tong Liu,a Danqing Zheng,a Zhenhua Li,a,* and Jie Wua,b,*
a
Department of Chemistry, Fudan University, 220 Handan Road, Shanghai 200433, China. E-mail:
jie_wu@fudan.edu.cn
b
State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of
Sciences, 345 Lingling Road, Shanghai 200032, China
Received: ((will be filled in by the editorial staff))
Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/adsc.201######.((Please
delete if not appropriate))
Abstract. A three-component reaction of aryldiazonium
tetrafluoroborates, DABCO•(SO2)2 and hydroxylamines
under catalyst-free and additive-free conditions is developed,
providing aryl O-aminosulfonates in good yields.
Sulfonamides could also be obtained via a one-pot process
through a reaction of aryldiazonium tetrafluoroborates,
Keywords: aryldiazonium tetrafluoroborate; amine;
hydrogen atom transfer; hydroxylamine; sulfur dioxide
DABCO·(SO2)2
and amines in the presence of N-
hydroxybenzotriazole. A mechanism involved with the
insertion of sulfur dioxide and hydrogen atom transfer is
proposed, supported by theoretical calculations.
cation. In this mechanism, the hydrazine participated
in the production of sulfonyl radicals and this might
explain why the nucleophile was restricted to
hydrazines. Very recently, our group reported a
surprising discovery that the treatment of
Introduction
The sulfonyl group is widely existed in
pharmaceuticals, argrochemicals, materials and
synthetic intermediates.[1-4] In the past few years,
sulfur dioxide insertion has been recognized as an
efficient strategy for the generation of sulfonyl-
containing compounds. The introduction of sulfonyl
moiety from simple sources into small molecules is
attractive and promising.[5-7] Early reports centered on
the transition metal catalysis for the synthesis of N-
aminosulfonamides and related compounds via the
insertion of sulfur dioxide starting from aryl halides,
arylboronic acids, or arylsilanes (Scheme 1a).[6a-b,6f,7a-b]
Although various electrophiles have been employed,
the nucleophile was limited to hydrazines and hydride.
Other nucleophiles were examined in the above
transformations, which were all unsuccessful. This
drawback hampered the applications for the
generation of sulfonyl compounds. In 2014, our
group reported a metal-free coupling reaction of
aryldiazonium salts, DABCO.(SO2)2 and hydrazines
(Scheme 1b).[7c] This process opened a window to the
radical-based transformations of sulfur dioxide,
although the substrate scope was also limited,
similarly to the transition-metal catalysis. We
proposed that the hydrazine-SO2 complex (generated
through sulfur dioxide exchange) would proceed
through a single electron transfer to produce the aryl
radical, sulfur dioxide and the hydrazine radical
aryldiazonium
tetrafluoroborates
with
Scheme 1. Proposed synthetic route via hydrogen atom
transfer
(a) transition-metal catalysis
R'
N
R'
O2
S
[M] (cat.)
Ar
X
+
+
H2N N
"SO2"
Ar
N
R
R
H
X = I, Br, Si(OR)3, B(OH)2
(b) radical process
R'
R'
O2
S
metal-free
Ar N2BF4
+ "SO2"
H2N
N
N
+
Ar
N
R
R
H
ArSO2
R
ArN2BF4
O
R
- H+
R
S
N
NH2
N
O
N NH
R'
R'
NH2
R'
ArSO2
hydrazine-SO2
(c) our proposed strategy
ArN2BF4
O
H
N
R
R
N
S
R
R
N
O
R
R
HAT
R
R
R
ArSO2
O
O
ArSO2
DABCO.(SO2)2
S
Nu
Nu
H
Ar
Nu
breaking the restriction of nucleophiles
1
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10.1002/adsc.201700501
Advanced Synthesis & Catalysis
DABCO·(SO2)2 would directly generate sulfonyl
radicals and tertiary amine radical cations without the
participation of hydrazines.[8] The sulfonyl radicals
could be trapped by aryl propiolates leading to 3-
sulfonated coumarins.
Table 1. Initial studies for the reaction of
phenyldiazonium tetrafluoroborate 1a, DABCO•(SO2)2
and 2-hydroxyisoindoline-1,3-dione 2a[a]
O
O
Ph N2BF4 1a
O
O
solvent
temp.
S
HO
N
+
Ph
O
N
In the meantime, hydrogen atom transfer (HAT) is
a fundamental mechanistic step and provides an
efficient route to radical intermediates in organic
chemistry.[9] We noticed that recently, the MacMillan
group demonstrated the tertiary amine radical cation
DABCO (SO2)2
O
3a
O
2a
[b]
Entry
1
2
3
4
5
6
7
8
Solvent
DCE
DCE
toluene
1,4-dioxane
DMF
T (oC) DABCO·(SO2)2 Yield
rt
1.0 equiv
1.0 equiv
1.0 equiv
1.0 equiv
1.0 equiv
1.0 equiv
1.0 equiv
1.0 equiv
0.8 equiv
1.2 equiv
1.0 equiv
n.d.
75
16
21
n.d.
42
80
48
61
81
51
80
80
80
80
80
60
40
60
60
60
(generated via
a
photoredox process) would
accomplish H-atom abstraction from a range of Csp3-
H bonds.[10] The resulting radical intermediate would
participate with a nickel catalysis to generate the
arylated products. Moreover, the Murphy group
reported that the DABCO radical cation would
mediate a H-atom transfer from N-CH3 groups.[11]
According to these new discoveries, we supposed that
the tertiary amine radical cation generated from the
reaction of aryldiazonium tetrafluoroborates with
MeCN
DCE
DCE
DCE
DCE
9
10
11[c]
DCE
DABCO·(SO2)2
would
accomplish
H-atom
[a]
Reaction conditions: phenyldiazonium tetrafluoroborate 1a
abstraction from the latent nucleophile, giving rise to
the radical intermediates (Scheme 1c). The radical
intermediates would be subsequently trapped by
sulfonyl radicals to generate the sulfonated products.
This proposed strategy took advantage of the in situ
generated tertiary amine radical cation and the
nucleophile might not be restricted to hydrazines. A
variety of C, O or N nucleophiles were employed to
this transformation but most of them were
unsuccessful. It seemed that the HAT process might
not be compatible with the existence of sulfur dioxide.
Pleasingly, we were finally able to establish the
construction of C-SO2-O bonds by using N-
hydroxyphthalimide as nucleophile. To the best of
our knowledge, this represents the first successful
example of oxygen nucleophiles applied in sulfur
dioxide insertion reactions.
(0.3 mmol), DABCO•(SO2)2, 2-hydroxyisoindoline-1,3-dione 2a
[b]
(0.2 mmol), solvent (2.0 mL), under N2 protection, 8 h.
Isolated yield based on 2-hydroxyisoindoline-1,3-dione 2a.
[c]
Under air atmosphere
transformation was lower when the reaction occurred
under air atmosphere (Table 1, entry 11).
Under the above optimized reaction conditions as
shown in Table 1, scope of the catalyst-free three-
component
reaction
of
aryldiazonium
tetrafluoroborates,
DABCO·(SO2)2,
with
was
2-
hydroxyisoindoline-1,3-dione
2a
next
investigated. The result is presented in Table 2.
Various aryldiazonium tetrafluoroborates were used
as the reaction partners, giving rise to the desired
sulfonated compounds in good to excellent yields
(Table 2, 3a-m). A minimal influence of electronic
effects on the aromatic ring of aryldiazonium
tetrafluoroborates was observed. Different functional
groups including methyl, methoxyl, chloro, bromo,
trifluoromethyl, nitro, and ester were all compatible
in this transformation. Additionally, reaction of
ortho-substituted phenyldiazonium tetrafluoroborate
was workable as well, although the yield was lower
(3j, 50% yield). Reactions of N-hydroxy-N-
Results and Discussion
Initially, the reaction of
phenyldiazonium
tetrafluoroborate 1a, DABCO·(SO2)2, with 2-
hydroxyisoindoline-1,3-dione 2a was examined in
1,2-dichloroethane (DCE) at room temperature. No
desired product was observed (Table 1, entry 1). To
our delight, the sulfonated product was isolated in 75%
yield when the reaction temperature was increased to
phenylbenzamide
2b,
aryldiazonium
tetrafluoroborates with DABCO·(SO2)2 were then
examined. As expected, all reactions proceeded
efficiently to provide the corresponding products in
good yields. Again, all substituents appended to the
aromatic ring of aryldiazonium tetrafluoroborates.
were tolerated under the conditions. Phenyldiazonium
tetrafluoroborate 1a reacted with DABCO·(SO2)2 and
N-hydroxybenzamide at room temperature, leading to
the desired product 3u in 56% yield.[12] It is notable
that the substrate scope could be further extended to
o
80 C (Table 1, entry 2). We further explored this
reaction in different solvents. It was found that no
better yields were obtained in other solvents, and
DCE was demonstrated as the best choice (Table 1,
entries 3-6). Gratifyingly, the yield of compound 3a
(80%) could be improved when the reaction took
place at 60 °C (Table 1, entry 7). An inferior result
was observed when the reaction was performed at
40 °C (Table 1, entry 8). The yield was lower when
the amount of DABCO·(SO2)2 was reduced to 0.8
equiv. (Table 1, entry 9). A similar result was
obtained when 1.2 equiv. of DABCO·(SO2)2 was
utilized (Table 1, entry 10). The efficiency of this
1H-benzo[d][1,2,3]triazol-1-ol,
hydroxybenzo[d][1,2,3]triazin-4(3H)-one and N-
hydroxy-N,4-dimethylbenzenesulfonamide. For
example, reaction of phenyldiazonium
3-
tetrafluoroborate 1a, DABCO·(SO2)2, and 1H-
2
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10.1002/adsc.201700501
Advanced Synthesis & Catalysis
temperature,
tolyloxy)carbonyl)amino)benzoate 5 in 80% yield.[14]
Treatment of 1,3-dioxoisoindolin-2-yl
affording
p-tolyl
2-(((p-
Table 2. Scope investigation for the reaction of
aryldiazonium tetrafluoroborates 1, DABCO·(SO2)2, and
compound 2 [a,b]
benzenesulfonate 3a with hydrazine under reflux
conditions gave rise to 3-aminoquinazoline-
2,4(1H,3H)-dione 6 in 90% yield.[15] Rhodium-
catalyzed C-H bond activation of 2-phenylpyridine
with 1,3-dioxoisoindolin-2-yl benzenesulfonate 3a
could be performed as well, leading to compound 7 in
80% yield (Scheme 2, eq. c).[16]
Several control experiments were subsequently
carried out to gain more insights of the reaction
mechanism (Scheme 3). The reaction was completely
terminated when 2.0 equivalent of 2,2,6,6-
tetramethyl-1-piperidinyloxy (TEMPO) was added to
the reaction system, suggesting this reaction
proceeded through a radical process (Scheme 3, eq. a).
No desired product 3a was observed as well when 3.0
equivalent of 1,1-diphenylethylene was added to the
standard reaction (Scheme 3, eq. b). Ethene-1,1,2-
triyltribenzene 8 and (2-(phenylsulfonyl) dibenzene 9
R2
R1
N
DCE
60 o
O
O
Ar N2BF4
+
DABCO (SO2)2
+
HO
N
R1
S
C
Ar
O
R2
1
2
3
O
3a: R = H, 80% yield
3h: R = 4-CO2Et, 80% yield
3i: R = 4-NO2, 86% yield
3j: R = 2-Cl, 50% yield
3k: R = 3-OMe, 65% yield
3l: R = 3-Cl, 90% yield
O
O
3b: R = 4-Me, 68% yield
3c: R = 4-tBu, 72% yield
3d: R = 4-OMe, 57% yield
3e: R = 4-Cl, 72% yield
3f: R = 4-Br, 77% yield
3g: R = 4-CF3, 90% yield
S
O
N
R
O
3m: R = 3-CO2Me, 93% yield
3n: R = H, 78% yield
Ph
N
O
O
H
O
O
3o: R = 4-Me, 72% yield
3p: R = 4-OMe, 80% yield
3q: R = 4-Cl, 77% yield
3r: R = 4-CO2Et, 68% yield
3s: R = 2-Cl, 61% yield
3t: R = 3-CO2Me, 77% yield
S
N
Ph
S
Ph
O
O
R
O
O
3u, 56% yield
O
Ts
O
OSO2Ph
N
N
O
OSO2Ph
N
S
N
O
CH3
N
N
N
3v, 91% yield
3w, 50% yield
3x, 90% yield
Table 3. One-pot synthesis of sulfonamides[a,b]
[a]
Reaction conditions: aryldiazonium tetrafluoroborate 1 (0.3
DABCO (SO2)2
O
O
N-hydroxybenzotrizole
mmol), DABCO•(SO2)2 (0.2 mmol), substrate 2 (0.2 mmol),
R1 R2
R1
S
+
N
H
DCE (2.0 mL), under N2 protection, 60 C, 8 h. [b] Isolated yield
o
Ar
N
R2
iPr2NEt, DCE
Ar-N2BF4
based on compound 2.
4
1
O
O
4a: R = H, 83% yield
O
O
S
S
4b: R = 3-Me, 73% yield
4c: R = 4-OMe, 77% yield
4d: R = 4-NO2, 81% yield
N
benzo[d][1,2,3]triazol-1-ol afforded the expected
product 3v in 91% yield.
N
R
(
)
n
O
To further extend the practicability of this process,
we next explored the transformation of O-
4e: 86% yield (n=1)
4f: 80% yield (n=2)
aminosulfonates
sulfonamides.
to
We
biologically
found that
important
the N-
O
O
N
O
O
O
O
O
O
S
S
Bn
S
nBu
S
Bn
nPr
N
N
N
H
H
nPr
Me
hydroxybenzotriazole sulfonate could act as a
replacement of sulfonyl chloride in amidation
reactions, and react with amines in the presence of
diisopropylethyl amine at room temperature to
produce the corresponding sulfonamides.[13] Thus, we
established a one-pot, two-step process for the
synthesis of sulphonamides through the insertion of
sulfur dioxide. After completion of the three-
4g, 76% yield
4h, 82% yield
4i, 64% yield
4j, 76% yield
OMe
MeO2C
O
O
O
O
S
S
N
N
S
H
O
4k, 46% yield
4l, 44% yield
[a]
Reaction conditions: aryldiazonium tetrafluoroborate 1 (0.36
component
reaction
of
aryldiazonium
with N-
mmol), DABCO•(SO2)2 (0.2 mmol), N-hydroxybenzotriazole
(0.24 mmol), DCE (2.0 mL), under N2 protection, 60 oC, 1 h, then
ethyldiisopropylamine (0.24 mmol), amine (0.2 mmol) was added
at room temperature. [b] Isolated yield based on amine.
tetrafluoroborates,
DABCO•(SO2)2,
hydroxybenzotriazole, amines and diisopropylethyl
amine were added subsequently at room temperature.
A variety of sulfonamides could be produced under
the reaction conditions (Table 3). Both primary and
secondary aliphatic amines were capable for this
transformation, affording the desired products in
moderate to good yields. Aromatic amines such as p-
methoxyaniline gave a lower yield of 46% (4k). The
heterocyclic thiophenediazonium tetrafluoroborates
could also deliver the desired product 4l. This
procedure presents an efficient and general route for
the synthesis of sulfonamides through the insertion of
sulfur dioxide.
O
O
O
O
OH
OC6H4p-Me
DBU
S
+
(a)
Ph
O
N
H
DCE, rt
80% yield
N
5
3a
O
O
OC6H4p-Me
O
H
O
O
N
O
toluene
S
+
N2H4 H2O
(b)
Ph
O
N
reflux
NNH2
90% yield
3a
6
O
O
O
O
O
O
[Rh(Cp*Cl2)]2
N
N
S
+
(c)
Ph
O
N
AgSbF6, DCE
80% yield
N
O
The O-aminosulfonate 3a could also react with
other nucleophiles to produce diverse compounds
(Scheme 2, eq. a and b). For instance, 1,3-
dioxoisoindolin-2-yl benzenesulfonate 3a reacted
with p-cresol in the presence of DBU at room
3a
O
7
Scheme 2. Transformation of compound 3a
3
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10.1002/adsc.201700501
Advanced Synthesis & Catalysis
O
O
nucleophilicity. According to the theoretical
calculations, the HAT process was also reasonable
for the hydrazine. In spite of this, we still thought that
the previous proposed mechanism (presented in
Scheme 1b) could not be excluded, considering the
SO2 exchange between hydrazine and DABCO.(SO2)2
was feasible (the hydrazine-SO2 complex was
accessible in previous report).[6b] Apparently, the
electron deficient N-acyl hydroxylamines were
unfavourable for the SO2 exchange, suggesting that
the hydrazine and hydroxylamine might undergo two
different reaction routes.
Based on the above experimental observations and
theoretical calculations, a plausible mechanism was
proposed in Scheme 4. As mentioned in our previous
report,[7c] arydiazonium cation 1a would react with
DABCO·(SO2)2 to generate complex A through
electrostatic interaction.[7c] The homolytic cleavage of
N-S bond[17] and a single electron transfer would
occur subsequently, leading to the tertiary amine
radical cation B, SO2 and phenyl radical C with the
release of N2. Then phenylsulfonyl radical D would
be produced through the addition of phenyl radical C
to sulfur dioxide. In the meantime, the hydrogen atom
transfer (HAT) between the tertiary amine radical
cation B and 2-hydroxyisoindoline-1,3-dione 2a
would give rise to the O-radical intermediate E,
which would be trapped by the phenylsulfonyl radical
Ph N2BF4 1a
O
O
DCE, 60 o
TEMPO
C
a)
S
HO
N
+
Ph
O
N
DABCO (SO2)2
(2.0 equiv.)
O
O
3a, n.d.
2a
O
Ph N2BF4 1a
Ph
b)
Ph
Ph PhO2S
+
Ph
DCE
60 o
HO
N
+
+
C
Ph
DABCO (SO2)2
Ph
Ph
O
2a
3a, n.d.
8, 9% yield
9, 24% yield
Ph N2BF4 1a
PhO2S
Ph
Ph
Ph
Ph
Ph
Ph
+
c)
d)
DCE
60 o
+
C
Ph
DABCO (SO2)2
8, 11% yield
9, 26% yield
O
Ph
Ph
Ph
Ph
DCE
Ph N2BF4
HO
N
+
+
60 o
C
Ph
1a
O
2a
8, n.d.
O
Ph
Ph
e)
DCE
60 o
DABCO (SO2)2
+
HO
N
+
NR
C
O
2a
Scheme 3. Investigation of mechanism
could be isolated in 9% and 24% yields, respectively.
This result indicated that this transformation
experienced both aryl radical and arylsulfonyl radical
as reaction intermediates. Compounds 8 and 9 could
also be produced in 11% and 26% yields via the
treatment of phenyldiazonium tetrafluoroborate 1a,
DABCO·(SO2)2 and 1,1-diphenylethylene in DCE
(Scheme 3, eq. c). However, ethene-1,1,2-
triyltribenzene 8 was not observed in the absence of
DABCO·(SO2)2, which showed that DABCO·(SO2)2
was essential for the introduction of aryl radical
(Scheme 3, eq. d). Furthermore, no reaction took
place with the treatment of DABCO·(SO2)2, 2-
Table 4. Free-energy barrier and free-energy change (in
kcal/mol) at 298.15 K for the proton exchange between
various substrates with the R3N+ radical.
O
O
NH2
NH2
HO
N
N
hydroxyisoindoline-1,3-dione
diphenylethylene (Scheme 3, eq. e).
2a
and
1,1-
OH
N
nC6H13 OH
Ph
N
O
OH
H
O
To explain the unique success of N-acyl
hydroxylamines in this transformation, the free-
energy barrier and free-energy change for the
hydrogen atom transfer between several O and N
nucleophiles with the DABCO+ radical cation were
calculated through theoretical calculations. The
results were presented in Table 4. In most cases, the
Gibbs free-energy barrier and free-energy change
were reasonable for this transformation except the
aliphatic alcohol. Comparison with the three
hydroxylamines showed that the electron-rich
substrate which owned a bigger free-energy change
might be more reactive. The reaction of 2-
hydroxyisoindoline-1,3-dione took place efficiently at
Substrate
Free-Energy Free-Energy
Barrier
NA[a]
-0.7[b]
NA[a]
28.2
NA[a]
NA[a]
Change
-17.4
-1.4
-12.6
8.2
morpholin-4-amine
aniline
2-hydroxyisoindoline-1,3-dione
n-hexanol
N,N-diethylhydroxylamine
N-hydroxybenzamide
[a] The potential energy surface is so flat that no transitions state
could be optimized. [b] There is a complex between R3N+ and the
substrate before the transition state.
-24.4
-15.8
N2
N
O
N
O
S
Ph N2
1a
O
Ph
N
R
60
oC,
while
the
reactions
of
N,N-
O
S
N
R
R
A
R
R
O
N
R
B
diethylhydroxylamine and N-hydroxybenzamide
(5.5)
R
R
R
(0.0)
DABCO (SO2)2
SO2
HO
N
became complex at the same temperature. When the
Ph
(12.3)
C
o
reaction temperature was decreased to 25 C, we
2a
O
barrierless
could isolate the sulfonated product of the N-
monoacyl substituted hydroxylamine in a moderate
yield while the N-dialkyl hydroxylamine still failed in
this process. The thermodynamic calculations and
experimental results suggested that excessively
reactive substrates might also be unfavourable in this
transformation. Aniline was not a good partner as
well in the reaction system, since aniline would react
with aryldiazonium salt directly due to its strong
TS(5.4)
(-5.8)
O
(12.3)
HNR3
S
Ph
O
O
O
N
D
O
O
TS(5.4)
S
Ph
O
N
O
E
3a (-44.9)
O
O
(-0.3)
Scheme 4. Proposed mechanism. The numbers in brackets
are the changes in Gibbs free energy relative to those of the
initial reactants at 298 K. TS=transition state.
4
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10.1002/adsc.201700501
Advanced Synthesis & Catalysis
D leading to the desired product 3a. The overall
Gibbs free energy barrier of this transformation is
17.7 kcal mol-1 according to theoretical calculations,
indicating this route is feasible from the perspective
of thermodynamics.
Med. Chem. 2010, 53, 6560; b) D. A. Smith, R. M.
Jones, Curr. Opin. Drug Discovery Dev. 2008, 11, 72;
c) Y. Noutoshi, M. Ikeda, T. Saito, H. Osada, K.
Shirasu, Front Plant Sci. 2012, 3, 245.
[2] a) M. Bartholow, Top 200 Drugs of 2011. Pharmacy
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http://www.pharmacytimes.com/publications/issue/201
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Conclusion
In summary, we have realized a catalyst-free three-
component
tetrafluoroborates,
reaction
of
aryldiazonium
and
DABCO·(SO2)2
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hydroxylamines under mild conditions. This
transformation provides aryl O-aminosulfonates in
good yields under catalyst-free and additive-free
conditions. More importantly, this transformation
could provide an efficient and convenient route to
sulfonamides via a one-pot process of aryldiazonium
tetrafluoroborates, DABCO·(SO2)2 and amines in the
presence of N-hydroxybenzotrizole. A radical process
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sulfur dioxide and hydrogen atom transfer, supported
by theoretical calculations.
Experimental Section
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General experimental procedure for the reaction of
aryldiazonium tetrafluoroborates 1, DABCO·(SO2)2, and
compound 2: Hydroxylamine 2 (0.2 mmol) was added to a
solution of DABCO·(SO2)2 (0.4 mmol) and aryldiazonium
tetrafluoroborate 1 (0.24 mmol) in DCE (2.0 mL) under N2
protection. The mixture was stirred at 60 C for 8 hours.
After completion of reaction as indicated by TLC, the
mixture was evaporated under reduced pressure and
purified directly by flash column chromatography
(EtOAc/n-hexane, 1:2) to give the desired product 3.
General experimental procedure for the synthesis of
sulfonamides 4:
A
solution of aryldiazonium
tetrafluoroborate 1 (0.36 mmol), DABCO•(SO2)2 (0.2
mmol), N-hydroxybenzotriazole (0.24 mmol) in DCE (2.0
o
mL) under N2 protection was stirred at 60 C for 1 h. Then
the reaction was cooled to room temperature and
ethyldiisopropylamine (0.24 mmol) and amine (0.2 mmol)
was added and stirred for additional 2 h. After completion
of reaction as indicated by TLC, the solvent was
evaporated under reduced pressure and the residue was
purified directly by flash column chromatography
(EtOAc/n-hexane, 1:4) to give the desired product 4.
Acknowledgements
Financial support from National Natural Science
Foundation of China (Nos. 21372046, 21532001) is
gratefully acknowledged.
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6
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10.1002/adsc.201700501
Advanced Synthesis & Catalysis
FULL PAPER
Route to O-aminosulfonates and Sulfonamides
through Insertion of Sulfur Dioxide and Hydrogen
Atom Transfer
R2
R1 R2
HO
N
R1
N
H
R1
N
O
O
Ar N2BF4
+
O
O
R1
Adv. Synth. Catal. Year, Volume, Page – Page
S
S
Ar
N
R2
Ar
O
R2
DCE
N-hydroxybenzotrizole
DABCO (SO2)2
iPr2NEt, DCE
Tong Liua, Danqing Zheng,a Zhenhua Li,a,* and Jie
Wua,b,*
7
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