Highly efficient one-pot synthesis of N-acylsulfonamides using cyanuric chloride at room temperature

Article abstract of DOI:10.1055/s-0029-1218819

A highly efficient and very mild one-pot synthesis of N-acylsulfonamides is described using cyanuric chloride. In this synthesis, structurally diverse carboxylic acids and sulfonamides are reacted in the presence of cyanuric chloride, triethylamine, and alumina in anhydrous acetonitrile at room temperature to afford various N-acylsulfonamides in excellent yields. Georg Thieme Verlag Stuttgart New York.

Full text of DOI:10.1055/s-0029-1218819

PAPER
2599
Highly Efficient One-Pot Synthesis of N-Acylsulfonamides Using Cyanuric
Chloride at Room Temperature
One-PotSynthesisof
N
o
-
Acylsulfon
h
amides ammad Navid Soltani Rad,*a Ali Khalafi-Nezhad,*b Zeinab Asrari,b Somayeh Behrouzb
a
Department of Chemistry, Faculty of Basic Sciences, Shiraz University of Technology, Shiraz 71555-313, Iran
Fax +98(711)7354523; E-mail: soltani@sutech.ac.ir; E-mail: nsoltanirad@gmail.com
b
Department of Chemistry, College of Sciences, Shiraz University, Shiraz 71454, Iran
Received 5 March 2010
dichloromethane and then a solution was added at room
temperature containing benzenesulfonamide (2a, 3 equiv)
and triethylamine (3 equiv) in dichloromethane. The reac-
tion was terminated after 12 hours and N-benzoylben-
Abstract: A highly efficient and very mild one-pot synthesis of N-
acylsulfonamides is described using cyanuric chloride. In this syn-
thesis, structurally diverse carboxylic acids and sulfonamides are
reacted in the presence of cyanuric chloride, triethylamine, and alu-
mina in anhydrous acetonitrile at room temperature to afford vari-
ous N-acylsulfonamides in excellent yields.
O
O
R1
O
S
O
S
TCT, Et3N, alumina
MeCN, r.t.
Key words: one-pot, N-acylsulfonamide, sulfonamide, carboxylic
acid, cyanuric chloride
+
H2N
R2
R1
OH
HN
R2
O
O
1
2
3
R1 = aryl, alkyl...
R2 = H, Me
Cl
Cyanuric chloride (2,4,6-trichloro-1,3,5-triazine, TCT) is
a stable, nonvolatile, inexpensive, and safe reagent that
has long been used in various organic transformations.1
Cyanuric chloride and its derivatives have been widely
employed for the dehydration of amides to nitriles,2 deoxy-
genation of sulfoxides,3 Swern-type oxidation,4 lactoniza-
tion of hydroxy-carboxylic acides,5 Friedel–Crafts
acylation,6 conversion of carboxylic acids into acyl chlo-
rides,7a acyl azides,7b amides,7c–e ketones,7f Weinreb
amides, hydroxamates,7g diazo ketones,7h and alcohols,7i
sulfonic acids to sulfonyl chloride,8 formamides to isoni-
triles,9 ketoximes to amides (Beckmann rearrangement),10
preparation of b-chlorohydrins from epoxides in water,11
conversion of alcohols into the alkyl chloride and formate
esters12 and preparation of sulfonamides from sulfonic
acid.13 Furthermore, cyanuric chloride has been used as an
in situ source of HCl to catalyze various organic reactions
and synthesis.14
N
N
TCT:
Cl
N
Cl
Scheme 1 Preparation of N-acylsulfonamides from carboxylic
acids and sulfonamides using cyanuric chloride
Table 1 Effect of Various Metal Oxide Catalysts on the Reaction of
Benzoic Acid and Benzenesulfonamide Using Cyanuric Chloride
O
O
S
O
TCT, Et3N, catalyst
CH2Cl2, r.t.
O
S
+
OH
H2N
HN
O
O
1a
2a
3a
Entry
1
Catalyst
–
Time (h)
Yielda (%)
12
1
2
5
2
5
3
2
4
7
5
6
45
90
80
73
63
70
60
65
59
63
55
60
2
aluminab
aluminac
aluminad
MgO
3
Recently, we reported that cyanuric chloride is a useful re-
agent for the synthesis of sulfonamides from amine-
derived sulfonate salts in this journal.13a We now report a
highly efficient one-pot synthesis of N-acylsulfonamides
3 from sulfonamides 2 and carboxylic acids 1 under very
mild reaction conditions using cyanuric chloride in the
presence of triethylamine as the base, alumina as a reus-
able heterogeneous catalyst, and acetonitrile as the solvent
(Scheme 1).
4
5
6
montmorillonite K-10
ZnO
7
8
silica gel
SnO2
9
In order to establish the optimized reaction conditions, we
chose the reaction of benzenesulfonamide (2a) and readi-
ly available benzoic acid as a model reaction. Thus, ben-
zoic acid (3 equiv) was treated with triethylamine (3
equiv) and cyanuric chloride (1 equiv) in anhydrous
10
11
12
TiO2
ZrO2
CdO
a Isolated yield.
b 1 equiv used.
c 0.5 equiv used.
d 0.25 equiv used.
SYNTHESIS 2010, No. 15, pp 2599–2603
Advanced online publication: 17.06.2010
DOI: 10.1055/s-0029-1218819; Art ID: P03510SS
x
x.
x
x
.
2
0
1
0
© Georg Thieme Verlag Stuttgart · New York

2600
M. N. Soltani Rad et al.
PAPER
zenesulfonamide (3a) was isolated in 45% yield
(Table 1). Subsequently, we attempted to shorten the reac-
tion time and increase the chemical yield. Thus, we stud-
ied the influence of metal oxides as heterogeneous
catalysts (Table 1).
Table 3 Effect of Various Organic and Inorganic Bases on Reaction
of Benzoic Acid and Benzene Sulfonamide Using Cyanuric Chloride
O
O
O
TCT, base, alumina
MeCN, r.t.
OH
+ H2N
S
O
S
O
HN
O
As the data in Table 1 indicate, applying a metal oxide as
a heterogeneous catalyst dramatically increases the yield
as well as shortening the reaction time for the formation
of N-benzoylbenzenesulfonamide (3a). Among these cat-
alysts, one equivalent of neutral alumina (entry 2) gave
the best result. Furthermore, using smaller amounts of alu-
mina provided good yields of 3a but in longer reaction
times (entries 3 and 4). Applying other metal oxides also
afforded reasonable to good yields of N-acylsulfonamide,
but the reactions required longer times.
1a
2a
3a
Entry
Base
Time (h)
Yielda (%)
1
2
3
4
5
6
7
8
Et3N
1
3
92
15
20
32
K2CO3
Cs2CO3
DABCO
DBN
5
6
b
12
12
12
12
–
We also investigated the effect of various aprotic solvents
on the model reaction (Table 2). Anhydrous acetonitrile
and dichloromethane gave the best result (entries 1 and 2);
however, acetonitrile was preferred over dichloromethane
because it provided better solubility for polar reactants.
Acetone and chloroform (entries 3 and 4) also afforded
good yields of 3a, but other solvents were not as efficient
for this purpose (entries 5–8).
b
DBU
–
b
pyridine
DIPEA
–
b
–
a Isolated yield.
b No reaction.
and sulfonamides were capable of undergoing acylation to
give the corresponding N-acylsulfonamides using cyanu-
ric chloride. Hence, we studied the N-acylation reactions
of diverse carboxylic acids 1 and sulfonamides 2a–c.
We then evaluated the effect of various organic and inor-
ganic bases on the reaction model (Table 3).
The results in Table 3 demonstrate that, of the bases ex-
amined, triethylamine (entry 1) was the most appropriate
base in terms of yield. Potassium and cesium carbonates
(entries 2 and 3) as well as DABCO (entry 4) also afforded
3a in low yield; however, other bases were ineffective
(entries 5–8).
As shown by the data in Table 4, by employing different
carboxylic acids 1 and sulfonamides 2a–c, good to excel-
lent yields as well as short reaction times were attained us-
ing this method. Both aromatic and aliphatic carboxylic
acids and sulfonamides were successfully condensed to
afford the corresponding N-acylsulfonamides 3a–p. Elec-
tron-releasing or electron-withdrawing substituents on the
arylcarboxylic acids had little effect on the efficiency of
the reaction; however, longer reaction times were required
for arylcarboxylic acids with electron-withdrawing
groups (entries 3, 4, and 16). We studied the reaction of N-
benzoylglycine with both aliphatic (entry 14) and aromat-
ic sulfonamides (entries 6 and 11); interestingly, good
yields of the corresponding N-acylsulfonamides 3f,k,n
were attained under mild reaction condition.
Having obtained the optimized reaction condition, it was
of interest to determine whether other carboxylic acids
Table 2 Effect of Various Aprotic Solvents on Reaction of Benzoic
Acid and Benzenesulfonamide Using Cyanuric Chloride
O
O
O
TCT, Et3N, alumina
O
S
+
H2N
S
OH
solvent, r.t.
HN
O
O
1a
2a
3a
Entry
Solventa
CH2Cl2
MeCN
Time (h)
Yieldb (%)
Mechanistically, we suggest that, this reaction proceeds
via an initial SnAr-type reaction between the carboxylate
anion and cyanuric chloride which affords the active car-
boxylate-cyanuric ester (Scheme 2). Indeed, in agreement
with the literature,7a–e the ready formation of the corre-
sponding active ester was observed at early stage of the re-
action. Interestingly, the sulfonamides were inert to
cyanuric chloride, which reacted exclusively with the car-
boxylic acids as the carboxylic anions possess higher nu-
cleophilic strength than the sulfonamides. The active
carboxylate-cyanuric esters then react with the sulfon-
amides to provide the corresponding N-acylsulfonamides.
1
2
3
4
5
6
7
8
1
1
90
92
60
50
acetone
CHCl3
4
3
c
DMF
12
12
12
12
–
c
DMSO
1,4-dioxane
HMPA
–
c
–
c
–
In summary, we have developed a mild, one-pot synthetic
method for the preparation of N-acylsulfonamides from
carboxylic acids and sulfonamides using readily available
a Anhydrous solvent.
b Isolated yield.
c No reaction.
Synthesis 2010, No. 15, 2599–2603 © Thieme Stuttgart · New York

PAPER
One-Pot Synthesis of N-Acylsulfonamides
2601
Table 4 One-Pot Synthesis of N-Acylsulfonamide from Carboxylic Acid and Sulfonamide Using Cyanuric Chloride at Room Temperaturea
O
TCT, Et3N
alumina, MeCN
O
O
O
O
S
R1 CO2H
+
S
R2
R1
R2
NH2
N
H
2a R2 = Ph
1
3a–p
2b R2 = 4-MeC6H4
2c R2 = Me
Entry
116
2
R1
R2
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Time (h)
60
Productb
3a
Yieldc (%)
Mp (°C)
149
164
143
254
145
191
157
123
foam
149
175
140
75
Ph
92
85
75
70
86
60
62
74
65
85
55
70
65
60
68
76
4-ClC6H4
4-O2NC6H4
3-pyridyl
4-MeOC6H4
CH2NHBz
(E)-CH=CHPh
Me
50
3b
3c
3
90
4
120
50
3d
3e
5
6
75
3f
717
816
9
120
80
3g
3h
3i
4-MeOC6H4CH2
90
1013
11
1216
1316
14
1513
16
Ph
4-MeC6H4
4-MeC6H4
4-MeC6H4
Me
40
3j
CH2NHBz
Me
70
3k
3l
75
Ph
60
3m
3n
3o
CH2NHBz
Me
Me
70
122
72
Me
75
4-ClC6H4
Me
100
3p
116
a Reaction conditions: TCT (1 equiv), Et3N (6 equiv), alumina (1 equiv), MeCN (50 mL), r.t.
b All products were characterized by 1H and 13 C NMR, IR, CHN, and MS analysis.
c Yield of isolated product.
O
All chemicals were purchased from commercial sources. Solvents
were purified and dried using reported methods15 and stored over
3 Å molecular sieves. The reaction progress was monitored by TLC
using SILG/UV 254 silica gel plates. Column chromatography was
carried out on silica gel 60, (0.063–0.200 mm, 70–230 mesh,
ASTM). IR spectra were run on a Shimadzu FTIR-8300 spectro-
photometer. 1H (250 MHz) and 13C NMR (62.5 MHz) were record-
ed using a Brüker Avance DPX-250, FT-NMR spectrometer. Mass
spectra were recorded on a Shimadzu GC MS-QP 1000 EX appara-
tus. Microanalyses were performed on a Perkin-Elmer 240-B mi-
croanalyzer. Melting points were recorded on a Büchi 510
apparatus in open capillary tubes and are uncorrected. Full analyti-
cal data are provided for novel products and references are given for
known compounds (see Table 4).
Cl
N
O
N
R1
O
O
N
N
Et3N
3
+
O
N
N
O
R1
OH
– Et3NHCl
Cl
Cl
O
R1
O
R1
O
O
OH
3
S
O
O
R2
3
H2N
S
+
N
N
R2
N
H
R1
Et3N
HO
N
OH
R1, R2 = alkyl, aryl...
Scheme 2 A plausible mechanism for N-acylation of sulfonamide
using cyanuric chloride
N-Acylsulfonamides 3; General Procedure
cyanuric chloride, triethylamine, and alumina in anhy-
drous acetonitrile. This method provided structurally di-
verse N-acylsulfonamides in good to excellent yields.
Furthermore, the cyanuric acid byproduct can be removed
from the reaction mixture using an aqueous workup.
To a stirred soln of carboxylic acid (3 mmol) and Et3N (3 mmol) in
anhyd MeCN (40 mL) was added TCT (1 mmol) followed by the
addition of alumina (1 mmol) and the mixture was stirred at r.t. for
5 min. A soln of sulfonamide (3 mmol) and Et3N (3 mmol) in anhyd
MeCN (10 mL) was added and the soln stirred for a further 40–120
min (TLC indicated completion of the reaction, see Table 4). The
reaction was filtered and the filtrate was concentrated under vacuum
and the residue was dissolved in CHCl3 (150 mL). The organic layer
Synthesis 2010, No. 15, 2599–2603 © Thieme Stuttgart · New York

2602
M. N. Soltani Rad et al.
PAPER
2-(4-Methoxyphenyl)-N-(phenylsulfonyl)acetamide (3i)
was washed with H2O (2 × 100 mL), dried (anhyd Na2SO4), and
evaporated in vacuo. The residue was purified by short column
chromatography (silica gel, n-hexane–EtOAc).
IR (KBr): 3227, 1690, 1474, 1425, 1348, 1232, 1158, 1090, 776,
531 cm–1.
1H NMR (250 MHz, DMSO-d6): d = 3.26 (s, 2 H, CH2), 3.48 (s, 3
H, CH3), 6.58–6.97 (m, 4 H, ArH), 7.33–7.71 (m, 5 H, ArH), 12.08
(s, 1 H, NH, exchangeable with D2O).
13C NMR (62.5 MHz, DMSO-d6): d = 40.23, 55.41, 116.87, 129.21,
129.86, 130.31, 130.3, 132.13, 144.21, 162.26, 170.43.
N-(4-Chlorobenzoyl)benzenesulfonamide (3b)
IR (KBr): 3247, 2945, 1753, 1458, 1365, 1146, 765, 539 cm–1.
1H NMR (250 MHz, DMSO-d6): d = 7.35–8.19 (m, 9 H, ArH),
11.85 (s, 1 H, NH, exchangeable with D2O).
13C NMR (62.5 MHz, DMSO-d6): d = 125.51, 127.20, 127.65,
130.21, 132.54, 140.80, 144.05, 148.44, 166.79.
MS (EI): m/z (%) = 305.1 (22.4) [M+].
Anal. Calcd for C15H15NO4S: C, 59.00; H, 4.95; N, 4.59; S, 10.50.
Found: C, 59.06; H, 4.98; N, 5.03; S, 10.48.
MS (EI): m/z (%) = 295.0 (32.8) [M+].
Anal. Calcd for C13H10ClNO3S: C, 52.80; H, 3.41; Cl, 11.99; N,
4.74; S, 10.84. Found: C, 52.83; H, 3.38; Cl, 12.03; N, 4.68; S,
10.80.
N-[2-(4-Methylphenylsulfonamido)-2-oxoethyl]benzamide (3k)
IR (KBr): 3458, 3132, 2884, 2780, 1728, 1640, 1524, 1458, 1355,
1146, 1088, 861, 711, 662, 554 cm–1.
N-(4-Nitrobenzoyl)benzenesulfonamide (3c)
IR (KBr): 3350, 3256, 3050, 1694, 1542, 1333, 1159, 1090, 755,
688, 536 cm–1.
1H NMR (250 MHz, DMSO-d6): d = 7.38–8.29 (m, 9 H, ArH),
11.45 (s, 1 H, NH, exchangeable with D2O).
13C NMR (62.5 MHz, DMSO-d6): d = 123.42, 125.25, 128.87,
130.64, 131.34, 135.8, 144.05, 148.44, 165.78.
MS (EI): m/z (%) = 306.0 (28.6) [M+].
1H NMR (250 MHz, DMSO-d6): d = 2.36 (s, 3 H, CH3), 3.98 (s, 2
H, CH2), 7.38–7.53 (m, 5 H, ArH), 7.78–7.82 (m, 4 H, ArH), 11.17
(s, 1 H, NH, exchangeable with D2O), 12.27 (s, 1 H, NH, exchange-
able with D2O).
13C NMR (62.5 MHz, DMSO-d6): d = 20.99, 48.28, 127.17, 128.28,
129.51, 131.46, 133.44, 136.34, 144.28, 149.88, 166.47, 168.14.
MS (EI): m/z (%) = 332.1 (43.4) [M+].
Anal. Calcd for C16H16N2O4S: C, 57.82; H, 4.85; N, 8.43; S, 9.65.
Found: C, 57.85; H, 4.80; N, 8.46; S, 9.60.
Anal. Calcd for C13H10N2O5S: C, 50.98; H, 3.29; N, 9.15; S, 10.47.
Found: C, 60.01; H, 3.34; N, 9.10; S, 10.51.
N-[2-(Methylsulfonamido)-2-oxoethyl]benzamide (3n)
IR (KBr): 3340, 3211, 3084, 1718, 1638, 1600, 1555, 1463, 1415,
1400, 1317, 1144, 989, 779, 691, 533 cm–1.
1H NMR (250 MHz, DMSO-d6): d = 2.89 (s, 3 H, CH3), 3.90 (s, 2
H, CH2), 7.42–7.49 (m, 3 H, ArH), 7.83–7.86 (m, 2 H, ArH), 11.14
(s, 1 H, NH, exchangeable with D2O), 12.61 (s, 1 H, NH, exchange-
able with D2O).
N-Nicotinoylbenzenesulfonamide (3d)
IR (KBr): 3355, 3071, 2449, 1923, 1712, 1596, 1488, 1417, 1322,
1300, 1185, 1040, 811, 747, 693, 641, 537 cm–1.
1H NMR (250 MHz, DMSO-d6): d = 7.50–7.54 (m, 3 H, ArH),
8.22–8.26 (m, 2 H, ArH), 8.74–8.77 (m, 3 H, ArH), 9.04–9.41 (m,
1 H, ArH), 13.18 (s, 1 H, NH, exchangeable with D2O).
13C NMR (62.5 MHz, DMSO-d6): d = 123.43, 123.71, 126.50,
128.83, 135.98, 136.86, 140.01, 150.14, 153.20, 166.21.
13C NMR (62.5 MHz, DMSO-d6): d = 41.03, 43.05, 127.16, 128.29,
131.37, 133.72, 166.44, 171.31.
MS (EI): m/z (%) = 262.0 (24.2) [M+].
MS (EI): m/z (%) = 256.1 (41.3) [M+].
Anal. Calcd for C12H10N2O3S: C, 54.95; H, 3.84; N, 10.68; S, 12.23.
Found: C, 54.98; H, 3.79; N, 10.71; S, 12.25.
Anal. Calcd for C10H12N2O4S: C, 46.87; H, 4.72; N, 10.93; S, 12.51.
Found: C, 46.81; H, 4.75; N, 10.99; S, 12.57.
N-(4-Methoxybenzoyl)benzenesulfonamide (3e)
IR (KBr): 3325, 2885, 1686, 1465, 1446, 1356, 1237, 1158, 1090,
756, 533 cm–1.
N-(Methylsulfonyl)-4-nitrobenzamide (3p)
IR (KBr): 3358, 3248, 1708, 1545, 1330, 1238, 1139, 775, 533
cm–1.
1H NMR (250 MHz, DMSO-d6): d = 3.79 (s, 3 H, OCH3), 6.98–7.97
(m, 9 H, ArH), 12.60 (s, 1 H, NH, exchangeable with D2O).
1H NMR (250 MHz, DMSO-d6): d = 2.96 (s, 3 H, CH3), 7.90–8.51
(m, 4 H, ArH), 10.47 (s, 1 H, NH, exchangeable with D2O).
13C NMR (62.5 MHz, DMSO-d6): d = 55.36, 113.75, 125.51,
127.54, 128.88, 130.58, 131.74, 144.06, 162.78, 166.98.
13C NMR (62.5 MHz, DMSO-d6): d = 40.24, 122.79, 129.43,
144.48, 148.45, 168.46.
MS (EI): m/z (%) = 291.1 (48.7) [M+].
MS (EI): m/z (%) = 244.0 (26.7) [M+].
Anal. Calcd for C14H13NO4S: C, 57.72; H, 4.50; N, 4.81; S, 11.01.
Found: C, 57.70; H, 4.55; N, 4.79; S, 11.07.
Anal. Calcd for C8H8N2O5S: C, 39.34; H, 3.30; N, 11.47; S, 13.13.
Found: C, 39.30; H, 3.36; N, 11.51; S, 13.17.
N-[2-Oxo-2-(phenylsulfonamido)ethyl]benzamide (3f)
IR (KBr): 3458, 3132, 2780, 1728, 1640, 1524, 1458, 1355, 1146,
1088, 861, 711, 662, 554 cm–1.
1H NMR (250 MHz, DMSO-d6): d = 4.02 (s, 2 H, CH2), 7.25–7.49
(m, 5 H, ArH), 7.83–7.97 (m, 5 H, ArH), 11.37 (s, 1 H, NH, ex-
changeable with D2O), 12.64 (s, 1 H, NH, exchangeable with D2O).
13C NMR (62.5 MHz, DMSO-d6): d = 47.37, 129.33, 129.49,
130.22, 130.30, 130.41, 131.25, 133.62, 135.81, 168.57, 170.39.
MS (EI): m/z (%) = 318.1 (42.8) [M+].
Acknowledgment
We thank Shiraz University of Technology and Shiraz University
Research Councils for partial support of this work.
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Found: C, 56.63; H, 4.39; N, 8.82; S, 10.11.
Synthesis 2010, No. 15, 2599–2603 © Thieme Stuttgart · New York

PAPER
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Synthesis 2010, No. 15, 2599–2603 © Thieme Stuttgart · New York