An one-pot approach to the synthesis of triazolobenzothiadiazepine 1,1-dioxide derivatives by basic alumina-supported azide-alkyne [3+2] cycloaddition

Article abstract of DOI:10.1016/j.tet.2012.07.040

An efficient one-pot strategy for the synthesis of triazolobenzothiadiazepine 1,1-dioxide derivatives has been developed by the reaction of 2-azido-N-substituted benzenesulfonamides and propargyl bromide in basic alumina under microwave condition via [3+2] azide-alkyne cycloaddition reaction. This protocol has synthetic advantages in terms of low environmental impact and short reaction time.

Full text of DOI:10.1016/j.tet.2012.07.040

Tetrahedron 68 (2012) 7806e7811
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An one-pot approach to the synthesis of triazolobenzothiadiazepine 1,1-dioxide
derivatives by basic alumina-supported azideealkyne [3þ2] cycloaddition
*
K.C. Majumdar , Sintu Ganai, Biswajit Sinha
Department of Chemistry, University of Kalyani, Kalyani 741235, West Bengal, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 31 May 2012
Received in revised form 7 July 2012
Accepted 10 July 2012
Available online 17 July 2012
An efficient one-pot strategy for the synthesis of triazolobenzothiadiazepine 1,1-dioxide derivatives has
been developed by the reaction of 2-azido-N-substituted benzenesulfonamides and propargyl bromide
in basic alumina under microwave condition via [3þ2] azideealkyne cycloaddition reaction. This pro-
tocol has synthetic advantages in terms of low environmental impact and short reaction time.
Ó 2012 Elsevier Ltd. All rights reserved.
Keywords:
Basic alumina
Microwave
Fused triazole
Sultam
Triazolobenzothiadiazepine 1,1-dioxides
[3þ2] Cycloaddition
1. Introduction
organic solvents, stepwise synthesis, use of catalyst or expensive
reagents, requirement of inert atmosphere and stringent reaction
Over the last decade, design of the sultam scaffold has attracted
the attention of synthetic organic chemists due to their biological
and pharmacological potency.1 The ability to serve as amide sur-
rogates, with unique physical properties, have made them ideal
condition. Development of mild and simple method to synthesize
benzothiadiazepine 1,1-oxide derivatives is still desirable because
of their biological significance. Huisgen’s 1,3-dipolar cycloaddi-
tion reaction11 of an azide with an alkyne may be useful for the
above purpose. We employed the possibility of using a solid-
supported reaction using alumina12 or silica because organic
compounds can get adsorbed on the surface of the inorganic
oxide that itself does not absorb or restrict the transmission of
microwave irradiation.13 In continuation of our efforts on sus-
tainable synthesis development,14 we synthesized benzothiadia-
zepine 1,1-oxide derivatives via a microwave-assisted, one-pot
reaction of 2-azido-N-substituted benzenesulfonamide and
propargyl bromide in basic alumina. Herein we report the results
of our investigation.
functionalities for the development of novel peptidomimetics.2
A
number of benzo-fused thiadiazepines have recently appeared that
display potent activities including selective tumour necrosis factor
inhibitor3 and antidepressant agent.4 In particular, benzothiadia-
zepine 1,1-oxides are a pivotal structural entity and possess a re-
markable range of biological properties such as antiblastic,
antitumour, apoptotic and antihypertensive activities.5 On the
other hand, the 1,2,3-triazole moiety and fused triazole have their
own importance in synthetic, medicinal as well as materials
chemistry.6,7 Especially, fused triazolobenzothiadiazepines have
gained much attention due to their important characteristics as
antimicrobial and antibacterial agents.8
A large number of reports have appeared in the literature on
the synthesis of 1,2,3-triazoles6,9 and fused triazoles.10 Although
various approaches to the preparation of benzothiadiazepine 1,1-
oxide derivatives have been reported,5 most of them are associ-
ated with a number of drawbacks like the use of hazardous
2. Results and discussion
At first we prepared 2-azido-N-phenylbenzenesulfonamides
(1aei) required for our study, using the standard protocol.15 Ini-
tially, we treated 2-azido-N-phenylbenzenesulfonamide (1a) and
propargyl bromide (2a) in DMF at room temperature using K2CO3
as base and obtained a solid product in 56% yield (Scheme 1). The
spectral and analytical data of the compound revealed the for-
mation of the desired product triazolobenzothiadiazepine
1,1-dioxide 3a.
* Corresponding author. Tel.: þ91 33 2582 7521; fax: þ91 33 2582 8282; e-mail
address: kcm@klyuniv.ac.in (K.C. Majumdar).
0040-4020/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2012.07.040

K.C. Majumdar et al. / Tetrahedron 68 (2012) 7806e7811
7807
Table 2
O
O
N
Optimization of solid-supported intramolecular azideealkyne [3þ2] cycloaddition
S
Ph
reaction under microwave irradiationa
O
O
Ph
S
DMF, K2CO3
r.t., 9h
O
O
N
N
Br
+
N
N
H
S
Ph
O
O
N3
Ph
S
N
N
Br
+
3a
2a
N
N
H
1a
MW
N3
Scheme 1. Synthesis of triazolothiadiazepine 1,1-dioxide 3a in DMF.
N
3a
2a
1a
Application of heat increased the yield to 65% (entry 2, Table 1).
Change in bases by Cs2CO3 and Et3N did not give any better yield
(entries 3 and 4, Table 1). Next we have performed a series of re-
actions with the replacement of the solvent by other solvents like
CH3CN, acetone, EMK, toluene, MeOH, EtOH and tBuOH, but none of
them afforded any better result (entries 3e11, Table 1). The obser-
vations are summarized in Table 1. We became interested to ex-
plore the reaction using solid supports like silica and alumina
because of the fact that organic groups can robustly anchor to their
surface.16 Minimization of energy consumption is an important
factor for developing technologies. In this respect the microwave
irradiation technique is well known for achieving energy efficiency
and enhancing the rate of reaction.17
Entry
Solid supportebase
Neutral aluminaeEt3Nb
Neutral aluminaeK2CO3
Temp (ꢀC)
Time
Yieldd (%)
1
2
3
4
5
6
7
8
80
90
90
90
90
80
rt
100
80
80
90
90
90
15 min
20 min
20 min
20 min
20 min
10 min
14 h
10 min
15 min
20 min
20 min
20 min
20 min
68
56
52
54
0
92
32
85
89
45
42
37
40
b
b
Neutral aluminaeNa2CO3
Neutral aluminaeKFb
Neutral alumina
Basic alumina
Basic aluminac
Basic alumina
b
9
Basic aluminaeK2CO3
10
11
12
13
Silica geleEt3Nb
Silica geleK2CO3
b
b
Silica geleNa2CO3
Silica geleKFb
a
All the reactions were carried out using 1 equiv 1a and 1.5 equiv 2a under mi-
Table 1
crowave irradiation techniques.
b
Summary of intramolecular azideealkyne [3þ2] cycloaddition using different
Bases (2 equiv) were added.
Reaction was stirred at room temperature without MW.
Isolated yields.
solventsa
c
d
O
O
N
S
Ph
O
O
Ph
S
Solvent
Temp
N
was decreased when the reaction was carried out at 100 ꢀC. The
decomposition of azide at higher temperature18 may be responsible
for this lower yield of the product. However, lower yields were
obtained when the reactions were performed by changing the re-
action condition by using the combination of bases and silica gel as
solid supports (entries 10e13, Table 2). It is notable that basic
alumina appears to be the most effective solid support for this
reaction.
Br
+
H
N
3a
N
2a
N3
1a
N
Entry
Solvent
Base
Temp (ꢀC)
Time (h)
Yieldb (%)
1
2
3
4
5
6
7
8
DMF
DMF
DMF
DMF
CH3CN
CH3CN
Acetone
Acetone
EMK
Toluene
MeOH
EtOH
K2CO3
K2CO3
Cs2CO3
Et3N
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
rt
9
6
6
8
12
8
12
10
8
8
10
7
56
65
59
52
46
80 ꢀ
80 ꢀ
80 ꢀ
rt
C
C
C
From the above set of experiments the optimized condition
developed so far is treatment of 1 equiv 2-azido-N-substituted
benzenesulfonamide (1a) with 1.5 equiv propargyl bromide (2a) in
basic alumina under microwave irradiation at 80 ꢀC for 10 min. We
then carried out the reactions of a variety of substrates under the
optimized condition and the results are summarized in Table 3.
The formation of products 3 may be rationalized by considering
two alternative pathways (path-a or path-b). Path-a may involve N-
alkylation of eSO2NH2 by the reaction of nucleophilic sulfonamide
1 with propargyl bromides 2 in the presence of basic alumina to
form the intermediates IA that may then undergo 1,3-dipolar azi-
deealkyne cycloaddition leading to simultaneous formation of
seven-membered sultam fused with five-membered triazole rings.
An alternative pathway (path-b) may occur via the early formation
of bromomethyl-1,2,3-triazole intermediates IB from the in-
termolecular azideealkyne cycloaddition reaction of propargyl
bromides with the azido group of nucleophilic sulfonamide 1, fol-
lowed by intramolecular coupling of bromomethyl group of triazole
with eSO2NH. It is well known that here the reaction is exclusively
1,4-directing and momentaneous. It should therefore follow the
path-a rather than path-b. If the reaction would have followed
path-b then that should have afforded some di- and oligomerized
product along with the desired product followed by the formation
of 1,5-regioisomer (IB/) directing the arrangement of the tethering
group (Scheme 2).
Reflux
Reflux
Reflux
80 ꢀ
80 ꢀ
Reflux
Reflux
80 ꢀ
58
<10
36
9
C
C
43
10
11
12
13
<20
30
26
37
t-BuOH
C
8
a
All the reactions were carried out using 1 equiv 1a and 1.5 equiv 2a and 2 equiv
base used.
b
Isolated yields.
Initially, reaction of 2-azido-N-phenylbenzenesulfonamide (1a)
with 1.5 equiv propargyl bromide (2a) was investigated with neu-
tral alumina using 2 equiv Et3N as a base under microwave irradi-
ation. After 15 min of stirring at 80 ꢀC the desired product 3a was
obtained in 68% yield (entry 1, Table 2). We then tried to modify the
reaction condition varying the bases by K2CO3, Na2CO3 and KF but
they did not give any better result (entries 2e4, Table 2). The re-
action in neutral alumina did not occur in absence of any bases
(entry 5, Table 2). To further tune the reaction condition we per-
formed the reaction replacing the solid support by basic alumina
with a view to increase the yield of the product 3a.
Pleasingly, the reaction in basic alumina without any external
base improved the yield of the reaction to 92% at 80 ꢀC under mi-
crowave heating for only 10 min (entry 6, Table 2). But the reaction
in basic alumina at room temperature gave only 32% product after
stirring for 14 h (entry 7, Table 2). However, the yield of the product
It is now evident that the microwave-assisted cyclization pro-
tocol is quite useful for the synthesis of triazolobenzothiadiazepine
1,1-dioxide derivatives as this procedure can effectively avoid the
use of environmentally hazardous solvents as well as externally

7808
K.C. Majumdar et al. / Tetrahedron 68 (2012) 7806e7811
Table 3
Intramolecular azideealkyne cycloaddition with variety of substrates under microwave irradiationa
O
N
O
S
R1
O
O
R1
S
Basic alumina
MW
Br
N
R2
N
+
H
N
N3
3
2
1
R2
N
Entry
Azidosulphonamide
Alkyne
Time (min)
Product
Yieldb (%)
1
2
3
4
5
6
7
8
9
1a, R1¼C6H5
2a, R2¼H
10
10
10
10
10
10
10
10
10
3a, R1¼C6H5, R2¼H
92
94
90
89
86
91
87
95
88
1b, R1¼4-CleC6H4
1b, R1¼4-CleC6H4
1c, R1¼4-MeeC6H4
1c, R1¼4-MeeC6H4
1d, R1¼4-OMeeC6H4
1e, R1¼eCH2C6H5
1f, R1¼Me
2a, R2¼H
3b, R1¼4-CleC6H4, R2¼H
3c, R1¼4-CleC6H4, R2¼Me
3d, R1¼4-MeeC6H4, R2¼H
3e, R1¼4-MeeC6H4, R2¼Me
3f , R1¼4-OMeeC6H4, R2¼H
3g, R1¼eCH2C6H5, R2¼H
3h, R1¼Me, R2¼H
2b, R2¼Me
2a, R2¼H
2b, R2¼Me
2a, R2¼H
2a, R2¼H
2a, R2¼H
2a, R2¼H
1g, R1¼H
3i, R1¼H2CeC^CH, R2¼H
10
2a, R2¼H
2a, R2¼H
10
10
83
85
1h, R1 =
3j, R1 =
, R2 = H
O
O
O O
11
1
1
, R =
, R2 = H
1i
, R =
3k
a
Reaction conditions: 1 (1 mmol), 2 (1.5 mmol) were microwave irradiated at 80 ꢀC in basic alumina.
Isolated yields.
b
Scheme 2. Rationalization for the formation of compound 3.
added bases. Moreover, the reaction condition developed can also
avoid the separation problems and use of expensive reagents. Re-
cently Barange and his co-workers19 have reported the synthesis of
triazole-fused sultams via [3þ2] cycloaddition followed by CeN
bond formation using Cu catalyst and DMF solvent, which provides
relatively low yields of the products. It should also be noted that we
have achieved the triazolobenzothiadiazepine derivatives in
a much simpler manner whereas Hemming et al.20 have reported
the synthesis of triazolobenzodiazepines and pyrrolobenzodiaze-
pines using intramolecular 1,3-dipolar cycloaddition reaction in
a multistep process.
3. Conclusions
In conclusion, we have developed a simple and efficient one-pot
method for the synthesis of potentially bioactive triazol-

K.C. Majumdar et al. / Tetrahedron 68 (2012) 7806e7811
7809
obenzothiadiazepine 1,1-dioxide derivatives via [3þ2] azideealkyne
cycloaddition reaction avoiding the use of hazardous solvent, addi-
tional bases as well as costly reagents etc. The process affords con-
siderable synthetic advantages in terms of shorter reaction time,
product diversity, simplicity of the reaction procedure and good to
excellent yields. This may be suitable for generation of library of
relevant compounds.
ArH), 7.22 (s, 1H, NH), 7.27 (d, J¼8.0 Hz, 1H, ArH), 7.56 (t, J¼7.6 Hz,
1H, ArH), 7.88 (d, J¼8.0 Hz, 1H, ArH); 13C NMR (100 MHz, CDCl3):
dC¼118.5, 121.8, 124.8, 125.4, 129.0, 129.1, 129.5, 132.5, 133.0, 136.5.
136.9; HRMS-ESI m/z found 331.0042 (MNaþ), C12H9ClN4O2SNa
requires 331.0032.
4.2.3. 2-Azido-N-p-tolylbenzenesulfonamide (1c). Using the general
procedure (as 1a) starting from 500 mg of 2-azidobenzenesulfonic
acid and 403 mg of p-methylaniline, 637 mg of compound 1c was
isolated as white solid (88%); [Found: C, 53.91; H, 4.12; N, 19.61%.
C13H12N4O2S requires C, 54.15; H, 4.20; N, 19.43%]. Rf (15% EtOAc/
4. Experimental section
4.1. General information
Pet) 0.47; mp 138e140 ꢀC; IR (KBr): 1159, 1331, 2134, 3263 cmꢁ1
;
Melting points were determined in open capillaries and are un-
corrected. Silica gel [(60e120 mesh) was used for chromatographic
separation. Silica gel G was used for TLC. Petroleum ether (Pet) refers
to the fraction boiling between 60 ꢀC and 80 ꢀC. IR spectra were
recorded on a PerkineElmer L 120-000A spectrometer (nmax in
cmꢁ1) on KBr disks. 1H NMR and 13C spectra were recorded in CDCl3
1H NMR (400 MHz, CDCl3): dH¼2.23 (s, 3H, CH3), 6.98e7.02 (m, 5H,
NH and ArH overlapped), 7.14 (dt, J¼8.4, 0.8 Hz, 1H, ArH), 7.26 (d,
J¼8.8 Hz, 1H, ArH), 7.52 (dt, J¼8.4, 1.6 Hz, 1H, ArH), 7.86 (dd, J¼8.0,
1.2 Hz, 1H, ArH); 13C NMR (100 MHz, CDCl3): dC¼20.8, 119.4, 121.9,
124.8, 129.0, 129.9, 131.3, 133.4, 134.3, 135.6, 137.6.
and DMSO (chemical shift in
d
) with TMS as internal standard. MS
4.2.4. 2-Azido-N-(4-methoxyphenyl)benzenesulfonamide (1d). Using
the general procedure (as 1a) starting from 500 mg of 2-
azidobenzenesulfonic acid and 463 mg of p-methoxyaniline,
649 mg of compound 1d was isolated as grey solid (85%); [Found: C,
51.03; H, 4.10; N, 18.57%. C13H12N4O3S requires C, 51.31; H, 3.97; N,
18.41%]. Rf (15% EtOAc/Pet) 0.48; mp 116e118 ꢀC; IR (KBr): 1163,1511,
2139, 3277 cmꢁ1; 1H NMR (400 MHz, CDCl3): dH¼3.72 (s, 3H, OCH3),
6.72 (dd, J¼6.8, 2.0 Hz, 2H, ArH), 6.87 (s, 1H, NH), 7.01 (dd, J¼7.6,
2.0 Hz, 2H, ArH), 7.14 (t, J¼7.6 Hz,1H, ArH), 7.29 (d, J¼8.0 Hz,1H, ArH),
7.54 (dt, J¼8.0, 1.6 Hz, 1H, ArH), 7.80 (dd, J¼8.0, 1.6 Hz, 1H, ArH); 13C
NMR (100 MHz, CDCl3): dC¼55.4, 114.5, 119.3, 124.7, 124.8, 124.9,
128.6, 129.0, 131.3, 134.2, 137.6.
were recorded on a Q-TOF microÔ instrument at the Indian Institute
of Chemical Biology (Kolkata). CHN analyses were recorded on
a PerkineElmer 2400 series II CHN analyser from University of
Kalyani. HRMS were recorded on a Q-TOF Micro YA263 instrument at
Indian Association for the Cultivation of Science (Kolkata). The MW
reactor used for the reaction was a CEM, Discover, USA.
4.2. General procedure for the preparation of 2-azidobenze-
nesulfonic acid15a
2-Amino-benzenesulfonic acid (11.57 g, 66.8 mmol) was taken
in water (45 mL) and concd H2SO4 (15 mL) mixture and cooled to
0 ꢀC. A solution of NaNO2 (6 g, 86.8 mmol) in water (30 mL) was
added dropwise to it and the reaction mixture was stirred at 0 ꢀC
for 30 min. A cooled solution of NaN3 (8.68 g, 133.6 mmol) in water
(30 mL) was added and the reaction mixture was stirred over
a period of 12 h. The resulting precipitate was collected, washed
with cold water (10 mL) and dried under vacuo to give 2-
azidobenzenesulfonic acid (6.64 g, 50%).
4.2.5. 2-Azido-N-benzylbenzenesulfonamide (1e). Using the general
procedure (as 1a) starting from 500 mg of 2-azidobenzenesulfonic
acid and 403 mg of benzylamine, 579 mg of compound 1e was
isolated as light tan solid (80%); [Found: C, 53.81; H, 4.06; N,19.65%.
C13H12N4O2S requires C, 54.15; H, 4.20; N, 19.43%]. Rf (15% EtOAc/
Pet) 0.50; mp 80e82 ꢀC; IR (KBr): 1165, 1327, 2142, 3292 cmꢁ1; 1H
NMR (400 MHz, CDCl3): dH¼4.10 (d, J¼6.0 Hz, 2H, NCH2), 5.28 (br s,
1H, NH), 7.16e7.23 (m, 7H, ArH), 7.55 (t, J¼7.2 Hz, 1H, ArH), 7.98 (d,
J¼7.6 Hz, 1H, ArH); 13C NMR (100 MHz, CDCl3): dC¼47.6, 119.3,
124.8, 127.9, 128.0, 128.4, 128.5, 130.0, 130.6, 134.0, 136.0, 137.5.
4.2.1. 2-Azido-N-phenylbenzenesulfonamide (1a). To a suspension
of 2-azidobenzenesulfonic acid (500 mg, 2.510 mmol) in dichloro-
methane (30 mL) were added 2 M oxalyl chloride in CH2Cl2
(6.280 mmol) and four drops of DMF. The resulting mixture was
heated under reflux for 3 h and then evaporated under reduced
pressure. Then this 2-azidobenzenesulfonyl chloride was added in
small portions to a vigorously stirred mixture of the aniline
(350 mg, 3.760 mmol) and NaOAc (312 mg, 3.760 mmol) in 50% aq
MeOH (15 mL) over a period of 30 min. The mixture was then
stirred at 60 ꢀC for 1 h, cooled to room temperature, diluted with
water (30 mL) and acidified to pH 2 with concd HCl. The precipitate
was filtered off, washed thoroughly with water and recrystallized
from EtOAc to afford 571 mg of grey solid product 1a (83%) [Found:
C, 52.71; H, 3.86; N, 20.18%. C12H10N4O2S requires C, 52.54; H, 3.67;
N, 20.43%]. Rf (15% EtOAc/Pet) 0.48; mp 255e257 ꢀC; IR (KBr): 1155,
4.2.6. 2-Azido-N-methylbenzenesulfonamide (1f). Using the general
procedure (as 1a) starting from 500 mg of 2-azidobenzenesulfonic
acid and 10 mL methylamine solution, 442 mg of compound 1f was
isolated as colourless solid (83%); [Found: C, 39.86; H, 4.05; N, 26.17%.
C7H8N4O2S requires C, 39.62; H, 3.80; N, 26.40%]. Rf (15% EtOAc/Pet)
0.53; mp 136e138 ꢀC; IR (KBr): 1161,1326, 2142, 3305 cmꢁ1; 1H NMR
(400 MHz, CDCl3): dH¼2.61 (d, J¼5.2 Hz, 3H, CH3), 4.94 (d, J¼4.8 Hz,
1H, NH), 7.27 (d, J¼8.0 Hz, 1H, ArH), 7.31 (d, J¼8.4 Hz, 1H, ArH), 7.60
(dt, J¼8.8, 0.8 Hz, 1H, ArH), 7.99 (d, J¼7.6 Hz, 1H, ArH); 13C NMR
(100 MHz, CDCl3): dC¼29.4, 119.4, 124.9, 128.4, 131.1, 134.1, 137.6.
4.2.7. 2-Azidobenzenesulfonamide (1g). Using the general procedure
(as 1a) starting from 500 mg of 2-azidobenzenesulfonic acid and
10 mL liquor ammonia, 398 mg of compound 1g was isolated as grey
solid (80%); [Found: C, 36.58; H, 3.37; N, 28.10%. C6H6N4O2S requires
C, 36.36; H, 3.05; N, 28.27%]. Rf (20% EtOAc/Pet) 0.48; mp 176 ꢀC
decomposed; IR (KBr): 1163, 1385, 2133, 3360, 3364 cmꢁ1; 1H NMR
(400 MHz, CDCl3): dH¼5.12 (s, 2H, NH), 7.28e7.33 (m, 2H, ArH), 7.60
(dt, J¼8.8, 1.2 Hz, 1H, ArH), 7.99 (dd, J¼9.2, 1.2 Hz, 1H, ArH); 13C NMR
(100 MHz, CDCl3): dC¼118.5, 124.1, 125.2, 132.6, 133.0, 137.6.
1472, 2130, 3254 cmꢁ1
;
1H NMR (400 MHz, CDCl3): dH¼7.05e7.12
(m, 4H, ArH), 7.16e7.24 (m, 3H, ArH), 7.28 (s, 1H, NH), 7.53 (t,
J¼8.0 Hz, 1H, ArH), 7.90 (d, J¼8.0 Hz, 1H, ArH); 13C NMR (100 MHz,
CDCl3): dC¼119.4, 121.2, 124.8, 125.5, 128.9, 129.3, 131.3, 134.4, 136.1,
137.7; MS (ESI): m/z found 275 (MHþ), C12H10N4O2S requires 274.
4.2.2. 2-Azido-N-(4-chlorophenyl)benzenesulfonamide (1b). Using
the general procedure (as 1a) starting from 500 mg of 2-
azidobenzenesulfonic acid and 450 mg of p-chloroaniline, 627 mg
of compound 1b was isolated as gummy liquid (81%). Rf (15% EtOAc/
4.2.8. 2-Azido-N-(naphthalen-1-yl)benzenesulfonamide (1h). Using
the general procedure (as 1a) starting from 500 mg of
2-azidobenzenesulfonic acid and 538 mg of 1-napthylamine,
Pet) 0.51; IR (neat): 1160, 1331, 2136, 3251 cmꢁ1
;
1H NMR
(400 MHz, CDCl3): dH¼7.04e7.07 (m, 3H, ArH), 7.17e7.19 (m, 2H,

7810
K.C. Majumdar et al. / Tetrahedron 68 (2012) 7806e7811
643 mg of compound 1h was isolated as grey solid (79%); [Found:
C, 59.41; H, 3.55; N, 16.99%. C16H12N4O2S requires C, 59.25; H,
3.73; N, 17.27%]. Rf (15% EtOAc/Pet) 0.60; mp 128e130 ꢀC; IR (KBr):
(MHþþ2), C15H11ClN4O2S requires 347.0361 (MHþ), 349.0361
(MHþþ2).
1163, 1319, 2132, 3340 cmꢁ1
;
1H NMR (400 MHz, DMSO): dH¼7.13
4.3.3. Compound 3c. Using the general procedure starting from
150 mg (0.486 mmol) of 1b and 97 mg (0.729 mmol) of 2b, 157 mg
of title compound 3c was isolated as colourless solid (90%). Rf (50%
(t, J¼7.6 Hz, 1H, ArH), 7.21e7.30 (m, 3H, ArH), 7.33 (s, 1H, NH),
7.48e7.58 (m, 3H, ArH), 7.66 (d, J¼7.6 Hz, 1H, ArH), 7.80 (d,
J¼8.0 Hz, 1H, ArH), 7.85 (d, J¼8.0 Hz, 1H, ArH), 8.15 (d, J¼8.4 Hz,
1H, ArH); 13C NMR (100 MHz, CDCl3): dC¼119.5, 120.8, 121.7, 124.8,
125.3, 126.5, 126.7, 127.0, 128.4, 128.8, 129.5, 131.1, 131.4, 134.2,
134.3, 137.9.
EtOAc/Pet) 0.57; mp 160e162 ꢀC; IR (KBr): 1175, 1350, 1483 cmꢁ1
;
1H NMR (200 MHz, CDCl3): dH¼2.40 (s, 3H, CH3), 4.91 (s, 2H, NCH2),
7.04 (d, J¼8.6 Hz, 2H, ArH), 7.24 (dd, J¼8.8, 3.0 Hz, 2H, ArH), 7.46 (t,
J¼7.6 Hz, 1H, ArH), 7.74e7.87 (m, 2H, ArH), 8.30 (d, J¼8.0 Hz, 1H,
ArH); 13C NMR (50 MHz, CDCl3): dC¼10.4, 46.4, 125.1, 127.8, 128.5,
128.8, 129.0, 129.8, 130.9, 133.6, 134.2, 134.8, 138.9, 141.8; HRMS-ESI
m/z found 361.0532 (MHþ), 363.0532 (MHþþ2), C16H13ClN4O2S
requires 361.0518 (MHþ), 363.0518 (MHþþ2).
4.2.9. 2-Azido-N-(2-oxo-2H-chromen-6-yl)benzenesulfonamide
(1i). Using the general procedure (as 1a) starting from 500 mg of 2-
azidobenzenesulfonic acid and 605 mg of 6-aminocoumarine,
773 mg of compound 1i was isolated as brown solid (90%); [Found:
C, 52.78; H, 3.15; N, 16.11%. C15H10N4O4S requires C, 52.63; H, 2.94;
N,16.37%]. Rf (30% EtOAc/Pet) 0.50; mp 194e196 ꢀC decomposed; IR
4.3.4. Compound 3d. Using the general procedure starting from
150 mg (0.520 mmol) of 1c and 93 mg (0.780 mmol) of 2a, 151 mg
of title compound 3d was isolated as grey solid (89%). Rf (50%
(KBr):1160, 1310, 2128, 1711, 3282 cmꢁ1
;
1H NMR (400 MHz,
DMSO): dH¼6.43 (d, J¼9.6 Hz, 1H, ]CH of coumarin), 7.26e7.35 (m,
3H, ArH), 7.43 (d, J¼2.4 Hz,1H, ArH), 7.52 (d, J¼8.0 Hz,1H, ArH), 7.64
(t, J¼7.6 Hz, 1H, ArH), 7.84 (d, J¼8.0 Hz, 1H, ArH), 8.00 (d, J¼9.6 Hz,
1H, ]CH of coumarin), 10.48 (s, 1H, NH); 13C NMR (100 MHz,
CDCl3þDMSO): dC¼116.9, 117.3, 118.7, 119.0, 119.8, 124.4, 124.6,
129.0, 131.0, 133.8, 134.3, 137.8, 143.2, 150.6, 160.4.
EtOAc/Pet) 0.54; mp 196e198 ꢀC; IR (KBr): 1169, 1346, 1487 cmꢁ1
;
1H NMR (400 MHz, CDCl3): dH¼2.30 (s, 3H, CH3), 4.98 (s, 2H, NCH2),
6.98 (d, J¼8.0 Hz, 2H, ArH), 7.09 (d, J¼8.0 Hz, 2H, ArH), 7.53 (dt,
J¼7.6, 0.8 Hz,1H, ArH), 7.72e7.77 (s,1H, ArH), 7.80 (dd, J¼8.0,1.6 Hz,
1H, ArH), 7.87 (dd, J¼8.0, 1.6 Hz, 1H, ArH), 8.28 (dd, J¼8.0, 0.4 Hz,
1H, ArH); 13C NMR (100 MHz, CDCl3): dC¼21.1, 46.5, 125.2, 126.5,
128.6, 129.0, 130.3, 131.7, 133.3, 133.4, 134.5, 137.7, 138.8; HRMS-ESI
m/z found 327.0926 (MHþ), C16H14N4O2S requires 327.0916 (MHþ).
4.3. General procedure for the preparation of compound
3aek
4.3.5. Compound 3e. Using the general procedure starting from
150 mg (0.520 mmol) of 1c and 104 mg (0.780 mmol) of 2b, 152 mg
of title compound 3e was isolated as colourless solid (86%). Rf (50%
The substrate, 2-azidosulfonamide 1 (1 equiv) was dissolved in
a minimum amount of chloroform, added to a sealed tube and basic
alumina (500 mg) was added to it. The organic solvent was evap-
orated to dryness under reduced pressure. To the residue, propargyl
bromide 2 (1.5 equiv) was added. The solid mixture was then stir-
red at room temperature for an additional 10e15 min to ensure
efficient mixing. The sealed tube was then fitted with a stopper, and
the mixture was subjected to irradiation in a microwave reactor
(CEM, Discover, USA) at 80 ꢀC (external sensor type, 150 W) for
10 min (as monitored by TLC). After cooling, ethyl acetate was
added and the slurry stirred at room temperature for 10 min. The
mixture was then vacuum filtered through a sintered glass funnel.
The filtrate was evaporated to dryness under reduced pressure and
the residue was passed through a column to obtain the solid
product 3.
EtOAc/Pet) 0.58; mp 108e110 ꢀC; IR (KBr): 1171, 1350, 1486 cmꢁ1
;
1H NMR (200 MHz, CDCl3): dH¼2.30 (s, 3H, CH3), 2.39 (s, 3H, CH3),
4.90 (s, 2H, NCH2), 6.97 (d, J¼6.4 Hz, 2H, ArH), 7.07 (d, J¼8.2 Hz, 2H,
ArH), 7.45 (dt, J¼7.6, 1.0 Hz, 1H, ArH), 7.72 (dt, J¼8.4, 1.6 Hz, 1H,
ArH), 7.84 (dd, J¼7.8, 1.4 Hz, 1H, ArH), 8.31 (d, J¼8.2 Hz, 1H, ArH);
13C NMR (100 MHz, CDCl3): dC¼10.4, 21.0, 46.7, 125.0, 126.4, 128.6,
128.7, 129.4, 130.2, 131.3, 133.7, 134.4, 137.8, 138.7, 141.6; HRMS-ESI
m/z found 341.1074 (MHþ), C17H16N4O2S requires 341.1072 (MHþ).
4.3.6. Compound 3f. Using the general procedure starting from
150 mg (0.493 mmol) of 1d and 88 mg (0.739 mmol) of 2a,153 mg of
title compound 3f was isolated as colourless solid (91%). Rf (50%
EtOAc/Pet) 0.56; mp 152e154 ꢀC; IR (KBr): 1168,1352,1487 cmꢁ1; 1H
NMR (200 MHz, CDCl3): dH¼3.77 (s, 3H, OCH3), 4.97 (s, 2H, NCH2),
6.78 (dd, J¼6.6, 2.2 Hz, 2H, ArH), 7.00 (dd, J¼6.8, 2.2 Hz, 2H, ArH), 7.50
(dt, J¼7.6,1.0 Hz,1H, ArH), 7.77 (s,1H, ArH), 7.80 (dd, J¼7.8, 1.6 Hz, 1H,
ArH),7.87 (dd, J¼7.8,1.4 Hz,1H, ArH), 8.29 (dd, J¼8.2,1.0 Hz,1H, ArH);
13C NMR (50 MHz, CDCl3): dC¼46.8, 55.7, 115.0, 125.5, 128.4, 128.7,
129.3, 132.0, 133.2, 133.4, 133.6, 134.7, 159.8; HRMS-ESI m/z found
343.0858 (MHþ), C16H14N4O3S requires 343.0865 (MHþ).
4.3.1. Compound 3a. Using the general procedure starting from
150 mg (0.547 mmol) of 1a and 98 mg (0.820 mmol) of 2a, 157 mg
of title compound 3a was isolated as colourless solid (92%). Rf (50%
EtOAc/Pet) 0.48; mp 222e224 ꢀC; IR (KBr): 1172, 1347, 1488 cmꢁ1
;
1H NMR (400 MHz, DMSO): dH¼5.06 (s, 2H, NCH2), 7.23 (d, J¼7.2 Hz,
2H, ArH), 7.36e7.41 (m, 3H, ArH), 7.75 (t, J¼7.6 Hz, 1H, ArH), 7.85
(dd, J¼8.0, 0.8 Hz, 1H, ArH), 7.98e8.02 (m, 2H, ArH), 8.20 (d,
J¼8.0 Hz, 1H, ArH); 13C NMR (100 MHz, CDCl3þDMSO): dC¼44.2,
125.5, 127.0, 127.6, 128.3, 129.5, 129.9, 131.2, 133.0, 133.2, 134.1,
135.2, 140.6; HRMS-ESI m/z found 313.0753 (MHþ), C15H12N4O2S
requires 313.0751 (MHþ).
4.3.7. Compound 3g. Using the general procedure starting from
150 mg (0.520 mmol) of 1e and 93 mg (0.780 mmol) of 2a, 148 mg
of title compound 3g was isolated as colourless solid (87%). Rf (50%
EtOAc/Pet) 0.60; mp 126e128 ꢀC; IR (KBr): 1163, 1334, 1474 cmꢁ1
;
1H NMR (400 MHz, CDCl3): dH¼4.33 (s, 2H, NCH2), 4.34 (s, 2H,
NCH2), 7.28e7.30 (m, 2H, ArH), 7.32e7.35 (m, 3H, ArH), 7.60e7.64
(m, 2H, ArH), 7.79 (dt, J¼8.4, 0.8 Hz, 1H, ArH), 8.09 (dd, J¼8.0,
0.8 Hz, 1H, ArH), 8.22 (dd, J¼8.0 Hz, 1H, ArH); 13C NMR (100 MHz,
CDCl3): dC¼41.2, 54.2, 125.0, 128.3, 128.6, 128.6, 129.0, 129.2, 131.6,
132.8, 133.0, 133.9, 134.0, 134.4; HRMS-ESI m/z found 327.0924
(MHþ), C16H14N4O2S requires 327.0916 (MHþ).
4.3.2. Compound 3b. Using the general procedure starting from
150 mg (0.486 mmol) of 1b and 87 mg (0.729 mmol) of 2a, 158 mg
of title compound 3b was isolated as colourless solid (94%). Rf (50%
EtOAc/Pet) 0.52; mp 154e156 ꢀC; IR (KBr): 1177, 1350, 1487 cmꢁ1
;
1H NMR (200 MHz, CDCl3): dH¼4.98 (s, 2H, NCH2), 7.01 (dd, J¼6.6,
2.0 Hz, 2H, ArH), 7.21e7.27 (m, 1H, ArH), 7.43 (dt, J¼7.6, 1.2 Hz, 1H,
ArH), 7.74e7.78 (m, 2H, ArH), 7.82 (dd, J¼7.8, 1.6 Hz, 2H, ArH), 8.27
(dd, J¼8.2, 1.2 Hz, 1H, ArH); 13C NMR (100 MHz, CDCl3): dC¼46.3,
125.4, 127.9, 128.6, 129.2, 129.9, 131.2, 132.9, 133.3, 133.4, 134.4,
134.8, 138.8; HRMS-ESI m/z found 347.0376 (MHþ), 349.0340
4.3.8. Compound 3h. Using the general procedure starting from
150 mg (0.707 mmol) of 1f and 126 mg (1.060 mmol) of 2a, 168 mg
of title compound 3h was isolated as colourless solid (95%). Rf (50%

K.C. Majumdar et al. / Tetrahedron 68 (2012) 7806e7811
7811
EtOAc/Pet) 0.55; mp 110e112oC; IR (KBr): 1166, 1342, 1488 cmꢁ1
;
Roush, W. R.; Gwaltney, S. L., II; Cheng, J.; Scheidt, K. A.; McKerrow, J. H.;
Hansell, E. J. Am. Chem. Soc. 1998, 120, 10994e10995.
3. Cherney, R. J.; Duan, JJ.-W.; Voss, M. E.; Chen, L.; Wang, L.; Meyer, D. T.; Was-
serman, Z. R.; Hardman, K. D.; Li, R.-Q.; Covington, M. B.; Qian, M.; Mandlekar,
S.; Christ, D. D.; Trzaskos, J. M.; Newton, R. C.; Magnolda, R. L.; Wexler, R. R.;
Decicco, C. P. J. Med. Chem. 2003, 46, 1811e1823.
1H NMR (400 MHz, CDCl3): dH¼2.89 (s, 3H, NCH3), 4.43 (s, 2H,
NCH2), 7.62 (dt, J¼7.6, 0.8 Hz, 1H, ArH), 7.77 (s, 1H, ArH), 7.80 (dt,
J¼8.0, 1.2 Hz, 1H, ArH), 8.06 (dd, J¼8.0, 1.2 Hz, 1H, ArH), 8.23 (d,
J¼8.0 Hz,1H, ArH); 13C NMR (100 MHz, CDCl3): dC¼38.0, 44.0,125.0,
128.8, 129.4, 130.1, 132.6, 133.2, 134.0, 134.6; HRMS-ESI m/z found
251.0609 (MHþ), C10H10N4O2S requires 251.0603 (MHþ).
4. Giannotti, D.; Viti, G.; Sbraci, P.; Pestellini, V.; Volterra, G.; Borsini, F.; Lecci, A.;
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4.3.9. Compound 3i. Using the general procedure starting from
150 mg (0.757 mmol) of 1g and 136 mg (1.135 mmol) of 2a, 182 mg
of title compound 3i was isolated as colourless solid (88%). Rf (50%
EtOAc/Pet) 0.45; mp 180e182 ꢀC; IR (KBr): 1166, 1343, 1488 cmꢁ1
;
1H NMR (400 MHz, DMSO): dH¼3.19 (s, 1H, acetylenic CH), 4.22 (d,
J¼2.0 Hz, 2H, NCHaHb), 4.53 (s, 2H, NCH2), 7.78 (t, J¼7.6 Hz, 1H,
ArH), 7.97 (s, 1H, ArH),7.99 (d, J¼7.6 Hz, 1H, ArH), 8.05 (t, J¼7.6 Hz,
2H, ArH); 13C NMR (100 MHz, DMSO): dC¼30.2, 40.2, 75.8, 77.4,
125.0, 128.0, 129.9, 130.9, 132.6, 132.8, 134.6, 135.2; HRMS-ESI m/z
found 275.0612 (MHþ), C12H10N4O2S requires 275.0603 (MHþ).
6. (a) Chem. Soc. Rev. 2010, 39, 1221e1408; (b) Fan, W.-Q.; Katritzky, A. R. In
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4.3.10. Compound 3j. Using the general procedure starting from
150 mg (0.462 mmol) of 1h and 83 mg (0.693 mmol) of 2a,139 mg of
title compound 3j was isolated as colourless solid (83%). Rf (50%
EtOAc/Pet) 0.50; mp 204e206 ꢀC; IR (KBr): 1180,1360,1484 cmꢁ1; 1H
NMR (400 MHz, CDCl3): dH¼4.69 (d, J¼14.8 Hz, 1H, NCHaHb), 5.20 (d,
J¼14.8 Hz, 1H, NCHaHb), 7.03 (d, J¼7.6 Hz, 1H, ArH), 7.34 (t, J¼7.6 Hz,
1H, ArH), 7.55e7.65 (m, 3H, ArH), 7.80 (s, 1H, ArH), 7.87 (dt, J¼7.6,
0.8 Hz, 3H, ArH), 7.97 (dd, J¼7.6,1.2 Hz,1H, ArH), 8.20 (d, J¼8.0 Hz,1H,
ArH), 8.31 (dd, J¼8.0, 0.8 Hz, 1H, ArH); 13C NMR (100 MHz, DMSO):
dC¼44.2, 122.8, 125.0, 125.6, 125.9, 126.8, 127.3, 127.4, 128.2, 129.2,
130.2, 131.6, 131.7, 132.7, 133.0, 134.1, 134.5, 135.3, 137.3; HRMS-ESI m/z
found 363.0921 (MHþ), C19H14N4O2S requires 363.0916 (MHþ).
4.3.11. Compound 3k. Using the general procedure starting from
150 mg (0.438 mmol) of 1i and 78 mg (0.657 mmol) of 2a, 141 mg
of title compound 3k was isolated as colourless solid (85%). Rf (60%
EtOAc/Pet) 0.48; mp 272e274 ꢀC; IR (KBr): 1174, 1354, 1485,
1724 cmꢁ1; 1H NMR (400 MHz, DMSO): dH¼5.09 (s, 2H, NCH2), 6.54
(d, J¼9.6 Hz, 1H, ]CH of coumarin), 7.45e7.47 (m, 2H, ArH),
7.72e7.78 (m, 2H, ArH), 7.86 (d, J¼8.0 Hz, 1H, ArH), 8.01e8.06 (m,
3H, ArH and ]CH of coumarin overlapped), 8.21 (d, J¼8.0 Hz, 1H,
ArH); 13C NMR (100 MHz, DMSO): dC¼43.9, 117.2, 117.5, 119.2, 125.6,
127.2,127.7,130.1,130.6,130.9,132.8,133.1,134.2,135.4,136.4, 143.4,
152.8, 159.5; HRMS-ESI m/z found 381.0655 (MHþ), C18H12N4O4S
requires 381.0658 (MHþ).
11. (a) Huisgen, R.; Knorr, R.; Moebius, L.; Szeimies, G. Chem. Ber. 1965, 98,
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Acknowledgements
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14. For some of our recent synthesis of heterocycles, see: (a) Majumdar, K. C.;
Ganai, S.; Nandi, R. K. New J. Chem. 2011, 35, 1355e1359; (b) Majumdar, K. C.;
Ponra, S.; Nandi, R. K. Eur. J. Org. Chem. 2011, 6909e6915; (c) Majumdar, K. C.;
Nandi, R. K.; Ganai, S.; Taher, A. Synlett 2011, 116e120; (d) Majumdar, K. C.;
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2010, 51, 1736e1738; (g) Majumdar, K. C.; Ray, K.; Ganai, S.; Ghosh, T. Synthesis
2010, 5, 858e862; (h) Majumdar, K. C.; Ray, K.; Ganai, S. Synthesis 2010, 12,
2101e2105; (i) Majumdar, K. C.; Ray, K.; Ganai, S. Synlett 2010, 2122e2124; (j)
Majumdar, K. C.; Ponra, S.; Ganai, S. Synlett 2010, 2575e2578.
We thank CSIR (New Delhi) and DST (New Delhi) for financial
assistance. Twoofus(S.G. and B.S.)are gratefultoCSIR(New Delhi)for
their research fellowships. We specially thank to Professor B.C. Ranu
of IACS, Kolkata, for providing us the MW instrument facility. We also
thank DST (New Delhi) for providing Bruker NMR (400 MHz), Per-
kineElmer CHN Analyser, FTIR and UVevis spectrometer.
References and notes
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