Iron-catalyzed sulfonylimine synthesis under neutral conditions

Article abstract of DOI:10.1016/j.tet.2009.07.029

A convenient FeCl₃-catalyzed synthesis of N-sulfonylimines via the condensation of aldehydes with N-sulfonylamides in mild and neutral conditions (in ethanol at room temperature) is reported. This procedure constitutes the first iron-catalyzed

Full text of DOI:10.1016/j.tet.2009.07.029

Tetrahedron 65 (2009) 7380–7384
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Iron-catalyzed sulfonylimine synthesis under neutral conditions
*
´
Xiao-Feng Wu, Chloe Vovard-Le Bray, Lazhar Bechki, Christophe Darcel
UMR 6226 CNRS-Universite´ de Rennes 1 ‘Sciences Chimiques de Rennes’, Equipe ‘Catalyse et Organome´talliques’, Campus de Beaulieu,
Bat 10C, Avenue du Ge´ne´ral Leclerc, 35042 Rennes Cedex, France
a r t i c l e i n f o
a b s t r a c t
Article history:
A convenient FeCl3-catalyzed synthesis of N-sulfonylimines via the condensation of aldehydes with
N-sulfonylamides in mild and neutral conditions (in ethanol at room temperature) is reported. This
procedure constitutes the first iron-catalyzed synthesis of N-sulfonylimines and is adapted to the con-
densation of both aromatic and aliphatic aldehydes.
Received 15 April 2009
Received in revised form 7 July 2009
Accepted 9 July 2009
Available online 14 July 2009
Ó 2009 Elsevier Ltd. All rights reserved.
1. Introduction
hydrosilylation,14 oxidation,15 epoxidation,16 even hydrogenation
areas.17
N-Sulfonylimines have been increasing in importance during
the two last decades because they are one of the few types of im-
ines bearing electron-withdrawing N-substituents that are stable
enough to be isolated but also enough reactive to be useful in-
termediates1 in organic synthesis and industrial applications. They
were used in numerous reactions such as nucleophilic addition,2
hetero Diels–Alder,3 or ene reactions.4 In addition, they were ex-
cellent precursors for the preparation of aziridines5 and
oxaziridines.6
In continuing our work on the use of iron as catalyst18, we de-
scribed herein the first iron-catalyzed synthesis of N-sulfonylaldi-
mines using an efficient and simple procedure for the direct
condensation of aldehydes with N-sulfonamides (Scheme 1).
SO2R2
O
[Fe]
N
+ R2-SO2-NH2
R1
H
R1
H
A lot of synthetic routes7 toward N-sulfonylaldimines have al-
ready been developed based on Lewis acid catalyzed reactions8 of
sulfonamides with aldehyde precursors, rearrangement of oxime
O-sulfinates,9 tellurium mediated reaction of aldehydes with
chloramine-T,10 via the reaction of N-trimethylsilylaldimine with
various sulfonyl chlorides.11
The straightforward route is still the direct condensation of
carbonyl compounds with sulfonamides.12 Due to the weak nu-
cleophilicity of sulfonamide derivatives, harsh acidic conditions
and high temperatures were usually required and dehydrating
agents or apparatus were oftenly used. In a synthetic point of view,
those drastic conditions were not compatible with the resulting
imine derivatives. Furthermore, some other procedures needed
cumbersome experimental and multi-step procedure.
Scheme 1. Iron-catalyzed N-sulfonylimine synthesis from aldehydes and
sulfonylamides.
2. Results and discussion
In an initial attempt to synthesize N-sulfonylimine using iron-
catalyzed procedure, we have investigated the condensation re-
action of benzaldehyde 1a (1 mmol) with N-tosylamide 2 (1 mmol)
in ethanol as solvent. Our catalytic system consisted on commer-
cially available iron salt such as dry FeCl3. A systematic study was
first undertaken to define the best reaction conditions, and Table 1
lists the representative data obtained for the synthesis of N-tosyl-
benzylimine 3a with various commercially available iron salts.
In general, 10 mol % of iron salt was applied as catalyst precursor
in ethanol and the reaction mixture was stirred at room tempera-
ture for 1 h.
First of all, when iron(II) salts were employed as catalyst, low to
moderate GC-yields ranging from 4 to 50% were observed. Among
the different iron(II) salt precursors tested, the best result was
achieved when the reaction was performed in presence of FeCl2,
furnishing the N-tosylbenzylimine 3a in 50% GC-yield (Table 1,
entry 2). Interestingly, the use of iron(III) salts, and more especially
FeCl3 is crucial for the success of this reaction as a promising GC-
yield of 75% was obtained (Table 1, entry 11). Interestingly, the
In another hand, iron, one of the most abundant metals on the
earth, and consequently one of the most inexpensive and envi-
ronmentally friendly ones, has seen a rise of its use as catalyst. Very
efficient processes, which are now able to compete with other
metal-catalyzed ones have emerged in the C–C bond formation,13
* Corresponding author. Tel.: þ33 2 23 23 62 71; fax: þ33 2 23 23 69 39
E-mail address: Christophe.darcel@univ-rennes1.fr (C. Darcel).
0040-4020/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2009.07.029

X.-F. Wu et al. / Tetrahedron 65 (2009) 7380–7384
7381
Table 1
Iron salt screening for the addition of p-tosylamide to benzaldehyde
Table 3
Investigation of benzaldehyde and catalyst amount on the model reaction
SO2-p-Tol
SO2-p-Tol
O
O
FeCl3
[Fe] (10 mol-%)
EtOH, rt, 1 h
N
N
+ p-Tol-SO2-NH2
+ p-Tol-SO2-NH2
Ph
H
Ph
H
EtOH, rt, 1 h
Ph
H
Ph
H
1a
2
3a
1a
2
3a
FeCl3 (mol %)a
Benzaldehyde (equiv)
GC-yield(%)b
Entry
Iron salt 10 mol %a
GC-yield (%)b
Entry
1
2
3
4
5
6
7
8
d
0
50
46
5
4
28
7
44
1
60
75
5
1
2
3
4
5
10
10
10
4
1
1.5
2
2
2
75
76
85
FeCl2
FeBr2
100 (92c)
80
Fe(acac)2
Fe(OAc)2
FeSO4$7H2O
(NH4)2Fe(SO4)2$6H2O
Fe(ClO4)3$xH2O
Fe2O3
FeCl3$6H2O
FeCl3
Fe(acac)3
1
a
Experimental conditions: benzaldehyde, p-tosylamide (1 mmol), iron salt in
3 mL of ethanol for 1 h.
b
GC-yield of tosylamide, determined by GC.
Isolated yield.
9
c
10
11
12
4). But when the lower amount of FeCl3 was used (1 mol %), the GC-
yield decreased to 80%.
a
Experimental conditions: benzaldehyde (1 mmol), p-tosylamide (1 mmol), iron
salt (10 mol %) in 3 mL of ethanol for 1 h.
Hence, the optimized conditions found for the synthesis of N-
tosylaldimines starting from aldehyde and N-tosylamide are the
use of 2 equiv of aldehyde, 1 equiv of N-tosylamide in the presence
of 4 mol % of dry FeCl3 in ethanol at room temperature for 1 h.
The substrate scope was then investigated. A variety of alde-
hydes and N-sulfonylamides were tested under the optimized
conditions using FeCl3 as catalyst (Table 4).
b
Determined by GC.
conversion was moderate (61%) when FeCl3$6H2O was used, which
shows the far better Lewis acid ability of FeCl3.
periments in absence of iron salt (Table 1, entry 1) confirmed the
crucial role, which the iron catalyst plays in the described con-
densation reaction as it did not occur.
18b,19
Control ex-
To get more information on the optimal catalytic conditions, we
carried out also intensive investigations to define the best solvent
for this transformation. Eight different solvents were tested at room
temperature for 1 h using 10 mol % of dry FeCl3 as catalyst. Table 2
lists representative data collected for the synthesis of N-tosylben-
zylimine 3a as model reaction.
Table 4
Scope of the reactiona
SO2R2
O
FeCl3 (4 mol-%)
EtOH, rt, 1 h
N
+ R2-SO2-NH2
R1
H
R1
H
1
2
3
Ethanol has been found to be a far better solvent than other
classical organic ones tested: N-tosylbenzylimine 3a was obtained
with rather good GC-yield (75%) (Table 2, entry 8). In other classical
solvents, the GC-yields were moderate and surprisingly, no reaction
occurred in DMF and N-methylpyrrolidone (NMP) (Table 2, entries
3 and 4).
Entry R1
R2
Time (h)
GC-yield Isolated yield
3a 100 92
1
Ph
p-Tol
1
1
1
1
1
1
1
1
2
3
4
4-CF3–C6H4
4-OMe–C6H4
4-Br–C6H4
p-Tol
p-Tol
p-Tol
p-Tol
p-Tol
p-Tol
p-Tol
3b
3c
3d 100
3e
3f
3g
3h
96
90
83
72
80
70
67
74
30
45
71
30
62
71
70
48
66
57
54
d
5
4-Cl–C6H4
95
86
87
56
80
100
57
80
Table 2
6
Furan-2-yl
Investigation of solvents on the model reaction
7
8
Thiophen-2-yl
Thiophen-3-yl
SO2-p-Tol
O
FeCl3
N
9
2
+ p-Tol-SO2-NH2
2
10
11
12
13
14
15
16
17
18
19
20
4b
4
solvent, rt, 1 h
Ph
H
Ph
H
5-Methylthio-phen-2-yl p-Tol
3i
3j
1a
3a
4b
48
5-Ethylthio-phen-2-yl
4-Br–C6H4
4-Cl–C6H4
4-Br–C6H4
4-Cl–C6H4
4-Br–C6H4
Cyclohexyl
Propyl
p-Tol
p-ClC6H4 16
p-ClC6H4 16
Ph
Ph
Me
p-Tol
p-Tol
100
Entry
FeCl3 (mol %)a
Solvent
GC-yield (%)b
3k 100
3l
1
2
3
4
5
6
7
8
10
10
10
10
10
10
10
10
DCE
THF
NMP
DMF
Toluene
Acetone
AcOEt
EtOH
58
65
0
100
90
86
16
16
3m
3n
3o
3p 100
3q >90
0
16
95
16b
16b
50
54
41
75
d
a
Experimental conditions: aldehyde (2 mmol), p-tosylamide (1 mmol), FeCl3
(0.04 mmol, 4 mol %) in 3 mL of ethanol for 1 h.
a
b
The reaction was performed at 60 ꢀC.
Experimental conditions: benzaldehyde (1 mmol), p-tosylamide (1 mmol), iron
salt (10 mol %) in 3 mL of solvent for 1 h.
b
Determined by GC.
In general, all reactions were clean, and the N-sulfonylimines 3
were obtained in moderate to good yields under the previously
optimized conditions. The purification of the desired compound
was made by simple recrystallization. It turned out that our iron-
catalyzed condensation could adapt to various aldehydes. For
aromatic aldehydes such as benzaldehyde or p-substituted benz-
aldehydes, the reaction proceeded smoothly and gave rise to the
aromatic N-tosylimines 3a–e in moderate to good GC-yields
reaching 100% and isolated yields ranging from 70 to 92% (Table 4,
entries 1–5). When 2-furaldehyde and 2-thiophenecarboxaldehyde
were used, good GC-yields were observed (86 and 87%,
Variation of the ratio of aldehyde to N-tosylamide had signifi-
cant impact on the conversion. With a 1:1 ratio, the GC-yield was
75% (Table 3, entry 1). When we increased the amount of aldehyde
to a ratio 1.5:1, the GC-yield didn’t increase significantly (76%)
(Table 3, entry 2). But when the ratio reached 2:1, a good and
promising GC-yield of 85% was observed (Table 3, entry 3).
At this stage, we studied the variation of the amount of catalyst
on the conversion of the reaction. By changing the amount of iron
from 10 mol % to 4 mol %, the yield increased to 92% (Table 3, entry

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X.-F. Wu et al. / Tetrahedron 65 (2009) 7380–7384
respectively) and good isolated yields were obtained (3f, 67% and
3g, 74%) (Table 4, entries 6 and 7). Using the same reaction condi-
tions (room temperature, 1 h), 3-thiophenecarboxaldehyde gave
only a moderate GC-yield of 56% and an isolated yield of 30% (Table
4, entry 8). Increasing the reaction time to 2 h had a beneficial effect
(GC-yield¼80%, isolated yield¼45%, entry 9). However, enhancing
the temperature to 60 ꢀC for 4 h improved both GC-yield (100%)
and isolated yield (71%) (Table 4, entry 10). In like manner, the 5-
methylthiophen-2-yltosylimine 3i was obtained in 62% yield when
the reaction mixture was warmed at 60 ꢀC for 4 h instead of 30%
after 4 h at room temperature (Table 4, entries 11and 12). The 5-
ethylthiophen-2-yltosylimine 3j was obtained with 71% isolated
yield after 48 h at room temperature (Table 4, entry 13).
We were successful in extending the procedure to include other
sulfonamides such as p-chlorophenylsulfonamide (entries 14 and
15), phenylsulfonamide (entries 16 and 17) and methylsulfonamide
(entry 18). In those cases, the reactions proceeded at room tem-
perature for 16 h and led to the corresponding sulfonaldimines
with moderate to good isolated yields (48–70%).
(room temperature in ethanol as solvent). Its increased efficiency
and enlargement of the substrate scope are currently under in-
vestigation by our research group.
4. Experimental section
4.1. General information
All reagents and solvents were used as received. Reactions were
performed under ambient atmosphere. Technical grade solvents
were used. 1H and 13C NMR spectra were recorded on a Bruker DPX
200 and AM300WB spectrometers at ambient temperature in
CDCl3. Chemical shifts are given in parts per million (ppm) relative
to CDCl3 (1H: 7.26 ppm, 13C: 77.00 ppm). Coupling constants are
given in hertz (Hz). High resolution mass spectra (HRMS) were
recorded by the HRMS unit of the CMRPO (Rennes) using EI
(Electron ionization, 70 eV) or electrospray ionization (ESI). Gas
chromatography (GC) was performed on a GC-2014 (Shimadzu) Gas
Chromatograph equipped with a 30-m capillary column (Supelco,
We must underline that the conversion rate of p-toluenesulfo-
namide with aldehydes was higher than the other sulfonamides
used, certainly due to a difference of nucleophilicity of the amino
part.
EquityÔ-5, fused silica capillary column, 30 Mꢁ0.25 mmꢁ0.25
mm
film thickness), using N2/air as vector gas. GC–MS were measured
by GCMS-QP2010S (Shimadzu) with GC-2010 equipped with a 30-
m capillary column (Supelco, SLBÔ-5ms, fused silica capillary col-
Due to mild and neutral condensation reaction conditions, eno-
lizable aliphatic aldehydes were also good candidates for the re-
action (Table 4, entries 19 and 20) and gave the desired N-tosylimines
3p,q with good GC-yields ranging from 90 to 100%. Those two ali-
phatic N-Ts imines were not purified because of their instability.
At this stage of the project, although the mechanism of the
present reaction has not been studied in details and if any mech-
anistic discussion is speculative, we believe that the catalyzed
transformation proceeds via an iron Lewis acid activation of the
carbonyl group of the aldehyde. Therefore, iron-coordinated car-
bonyl increases its electrophilicity to trigger the nucleophilic attack
by the sulfonylamide (Scheme 2).
umn, 30 Mꢁ0.25 mmꢁ0,25
mm film thickness), using helium as
vector gas. The following GC conditions were used: initial tem-
perature 100 ꢀC, for 2 min, then rate 10 ꢀC/min until 250 ꢀC and
kept at 250 ꢀC for 15 min.
4.2. General procedure
In a 10 mL vial equipped with a magnetic stirring bar, 4 mol % of
commercially available dry FeCl3 was added to the solution of sul-
fonylamide (1 mmol) in ethanol (3 mL). Aldehyde (2 mmol) was
then added.
The solution was stirred at room temperature for 1 h. Volatile
components were then removed under reduced pressure and the
residue was recrystallized in a mixture of 2 mL of hot AcOEt and
6 mL of hexane. After 5 h in fridge, the solid was filtered, washed,
SO2R2
N
O
R1
H
and dried.
R1
O
H
FeCl3
Compounds 3a,2c,12b,g,h 3b,20 3c,2c,12g,20 3d,21 3e,
3f,12c
8a,12b,g
H2O
3g,8a,12b 3h,8a 3l22, 3m,23 and 3n23 were characterized by compar-
ing their NMR spectra with the literature data.
FeCl3
H
FeCl3
H
H
4.2.1. N-Benzylidene-4-methylbenzenesulfonamide 3a
R1
O
The compound was prepared as described in the general pro-
cedure (92% isolated yield). GC: tR¼19.4 min. MS (EI): m/z 259 (Mþ,
80), 195 (40), 155 (100), 104 (90), 91 (90), 77 (90), 65 (90), 51 (90).
R1
H
N
SO2R2
H2N-SO2R2
1H NMR (200.13 MHz, CDCl3):
d
ppm 2.46 (s, 3H), 7.37 (d, 2H, J¼8),
7.45–7.55 (m, 2H), 7.60–7.75 (m, 1H), 7.85–8.00 (m, 4H), 9.06 (s, 1H).
13C NMR (50.75 MHz, CDCl3):
ppm 170.6, 145.1, 135.4, 132.8, 131.8,
130.3, 129.6, 128.5, 126.9, 22.1.
d
FeCl3
O
SO2R2
R1
N
H2
H
4.2.2. N-(4-Trifluoromethylbenzylidene)-4-methylbenzene-
sulfonamide 3b
Scheme 2. Plausible mechanism for iron-catalyzed sulfonylimine synthesis.
The compound was prepared as described in the general pro-
cedure (83% isolated yield). GC: tR¼18.4 min. MS (EI): m/z 327 (Mþ,
60), 155 (100), 145 (30), 91 (100), 65 (100), 51 (30). 1H NMR
3. Conclusion
(200.13 MHz, CDCl3):
d
ppm 2.48 (s, 3H), 7.39 (d, 2H, J¼8.4), 7.77 (d,
In conclusion, we have developed the first iron-catalyzed ad-
dition of N-sulfonylamides on aldehydes, which involves a com-
mercially available catalyst, FeCl3. This efficient and simple method
provides in most cases the desired N-sulfonylimines in moderate to
good yields. Overall the novel iron-catalyzed N-sulfonylimines
synthesis reported here constitutes a promising process because of
its operational simplicity: it must be pointed out that this N-sul-
fonylimine synthesis is conducted in mild and neutral conditions
2H, J¼8.0), 7.92 (d, 2H, J¼7.8), 8.07 (d, 2H, J¼8.0), 9.10 (s, 1H). 13C
NMR (50.75 MHz, CDCl3):
d ppm 169.3, 144.9, 125.5–143.7 (m),
129.3 (q, 1JC–F¼260), 22.3.
4.2.3. N-(4-Methoxybenzylidene)-4-methylbenzenesulfonamide 3c
The compound was prepared as described in the general pro-
cedure (72% isolated yield). GC: tR¼26.9 min. MS (EI): m/z 289 (Mþ,
15), 155 (15), 134 (70), 91 (80), 77 (15), 65 (30). 1H NMR

X.-F. Wu et al. / Tetrahedron 65 (2009) 7380–7384
7383
(200.13 MHz, CDCl3):
J¼8.8), 7.35 (d, 2H, J¼8.0), 7.91 (d, 2H, J¼8.8), 7.90 (d, 2H, J¼8.2),
8.96 (s, 1H). 13C NMR (50.75 MHz, CDCl3):
ppm 169.7, 165.7, 144.7,
d
ppm 2.45 (s, 3H), 3.91 (s, 3H), 6.98 (d, 2H,
126.0, 24.2, 21.5, 15.2. HRMS (EI, 70 eV): calcd for C14H15NO2S2 [Mþ]
293.0544, found 293.0534.
d
136.1, 134.2, 130.2, 128.3, 125.6, 115.1, 56.1, 22.1.
4.2.11. N-(4-Bromobenzylidene)-4-chlorobenzenesulfonamide 3k
The compound was prepared as described in the general pro-
cedure (70% isolated yield). GC: tR¼21.7 min. MS (EI): m/z 359 (Mþ,
10), 357 (Mþ, 8), 184 (20), 182 (20), 177 (25), 175 (65), 113 (35), 111
(100), 76 (25), 75 (55), 51 (20), 50 (10).1H NMR (300.13 MHz, CDCl3):
4.2.4. N-(4-Bromobenzylidene)-4-methylbenzenesulfonamide 3d
The compound was prepared as described in the general pro-
cedure (80% isolated yield). GC: tR¼21.4 min. MS (EI): m/z 339 (Mþ,
10), 337 (Mþ, 10), 184 (10), 182 (10), 155 (60), 91 (100), 65 (25). 1H
d
ppm 7.52 (d, 2H, J¼8.7), 7.66 (d, 2H, J¼8.5), 7.79 (d, 2H, J¼8.6), 7.96
NMR (200.13 MHz, CDCl3):
7.64 (d, 2H, J¼7.7), 7.80 (d, 2H, J¼8.0), 7.90 (d, 2H, J¼7.7), 8.99 (s,
1H). 13C NMR (50.75 MHz, CDCl3):
ppm 169.3, 145.3, 135.3, 133.0,
132.8, 131.6, 130.7, 130.3, 128.6, 22.1.
d
ppm 2.46 (s, 3H), 7.37 (d, 2H, J¼8.0),
(d, 2H, J¼8.8), 9.02 (s, 1H). 13C NMR (75.46 MHz, CDCl3):
d ppm
169.6,140.4,136.5,132.7,132.5,131.0,130.7,129.5,129.5. HRMS (ESI):
d
calcd for C13H9NO2SClBrNa [MþNa]þ 379.9124, found 379.9122.
4.2.12. N-(4-Chlorobenzylidene)-4-chlorobenzenesulfonamide 3l
The compound was prepared as described in the general pro-
cedure (48% isolated yield). GC: tR¼20.6 min. MS (EI): m/z 315 (Mþ,
8), 313 (Mþ, 10), 177 (15), 175 (45), 140 (10), 138 (25), 113 (35), 111
(100), 76 (10), 75 (45), 51 (10), 50 (15). 1H NMR (300.13 MHz,
4.2.5. N-(4-Chlorobenzylidene)-4-methylbenzenesulfonamide 3e
The compound was prepared as described in the general pro-
cedure (70% isolated yield). GC: tR¼20.4 min. MS (EI): m/z 295 (Mþ,
5), 293 (Mþ, 10), 155 (50), 91 (100), 65 (25). 1H NMR (200.13 MHz,
CDCl3):
7.88 (m, 4H), 9.02 (s,1H). 13C NMR (50.75 MHz, CDCl3):
145.3, 141.9, 135.3, 132.8, 131.2, 130.3, 130.2, 128.6, 22.1.
d
ppm 2.47 (s, 3H), 7.37 (d, 2H, J¼6.9), 7.49 (d, 2H, J¼7.2),
CDCl3):
d
ppm 7.50 (d, 2H, J¼8.4), 7.55 (d, 2H, J¼8.5), 7.89 (d, 2H,
d
ppm 169.2,
J¼8.3), 7.96 (d, 2H, J¼8.4), 9.04 (s, 1H). 13C NMR (75.46 MHz, CDCl3):
d
ppm 169.4, 141.9, 140.4, 136.5, 132.5, 130.6, 129.7, 129.6, 129.5.
4.2.6. N-(2-Furylmethylene)-4-methylbenzenesulfonamide 3f
The compound was prepared as described in the general pro-
cedure (67% isolated yield). GC: tR¼17.8 min. MS (EI): m/z 249 (Mþ,
80), 155 (100), 139 (40), 91 (100), 65 (100), 51 (30). 1H NMR
4.2.13. N-(4-Bromobenzylidene)-benzenesulfonamide 3m
The compound was prepared as described in the general pro-
cedure (66% isolated yield). GC: tR¼20.3 min. MS (EI): m/z 325 (Mþ,
5), 323 (Mþ, 5),184 (15),182 (15), 141 (45), 77 (100), 51 (25), 50 (10).
(200.13 MHz, CDCl3):
7.70–8.00 (m, 4H), 9.13 (s, 1H). 13C NMR (50.75 MHz, CDCl3):
162.7, 144.9, 139.6, 138.6, 137.2, 135.8, 130.2, 129.3, 128.4, 22.1.
d
ppm 2.45 (s, 3H, CH3), 7.10–7.50 (m, 3H),
1H NMR (300.13 MHz, CDCl3):
d ppm 7.61 (m, 5H), 7.79 (m, 2H), 8.00
d
ppm
(m, 2H), 9.03 (s, 1H). 13C NMR (75.46 MHz, CDCl3):
140.4, 136.4, 132.7, 132.5, 130.9, 130.7, 129.52, 129.50.
d ppm 169.6,
4.2.7. 4-Methyl-N-(2-thienylmethylene)-benzenesulfonamide 3g
The compound was prepared as described in the general pro-
cedure (74% isolated yield). GC: tR¼20.8 min. MS (EI): m/z 265 (Mþ,
80), 174 (60), 155 (100), 110 (100), 91 (100), 83 (30), 65 (100), 51
4.2.14. N-(4-Chlorobenzylidene)-benzenesulfonamide 3n
The compound was prepared as described in the general pro-
cedure (57% isolated yield). GC: tR¼19.3 min. MS (EI): m/z 281 (Mþ,
4), 279 (Mþ, 10), 141 (45), 138 (25), 113 (12), 111 (4), 77 (100), 51
(30). 1H NMR (200.13 MHz, CDCl3):
d
ppm 2.45 (s, 3H), 7.18–7.30 (m,
1H), 7.36 (d, 2H, J¼8.2), 7.80 (d, 2H, J¼4.2), 7.88 (d, 2H, J¼8.4), 9.13
(s, 1H). 13C NMR (50.75 MHz, CDCl3):
ppm 162.7, 144.0, 139.5,
(25), 50 (10). 1H NMR (300.13 MHz, CDCl3):
d ppm 7.49 (d, 2H,
J¼7.7), 7.57 (m, 3H), 7.89 (d, 2H, J¼7.8), 8.02 (d, 2H, J¼7.0), 9.04 (s,
d
1H). 13C NMR (75.46 MHz, CDCl3):
132.4, 130.7, 129.6, 129.2, 128.0.
d ppm 169.1, 141.6, 137.9, 133.7,
138.6, 135.8, 130.2, 129.3, 128.4, 126.9, 22.1.
4.2.8. 4-Methyl-N-(thiophen-3-ylmethylene)-benzenesulfonamide 3h
The compound was prepared as described in the general pro-
cedure (71% isolated yield). GC: tR¼20 min. MS (EI): m/z 265 (Mþ,
10), 210 (100), 174 (90), 155 (100), 110 (45), 91 (100), 83 (35), 65
4.2.15. N-(4-bromobenzylidene)-methanesulfonamide 3o
The compound was prepared as described in the general pro-
cedure (54% isolated yield). GC: tR¼14.9 min. MS (EI): m/z 263 (Mþ,
25), 261 (Mþ, 25), 184 (100), 182 (100), 157 (45), 155 (45), 102 (30),
101 (20), 80 (50), 79 (55), 76 (75), 75 (75), 65 (20), 51 (15), 50 (50).
(100). 1H NMR (200.13 MHz, CDCl3):
d
ppm 2.46 (s, 3H), 7.25–7.35
(m, 2H), 7.62 (d, 1H, J¼5.0), 7.89 (d, 2H, J¼8.2), 8.16 (m, 2H), 9.02 (s,
1H). 13C NMR (50.75 MHz, CDCl3):
ppm 163.5, 145.0, 138.6, 137.5,
135.7, 130.2, 128.5, 128.2, 126.9, 22.1.
1H NMR (200.13 MHz, CDCl3):
d
ppm 3.15 (s, 3H), 7.67 (d, 2H, J¼7.7),
d
7.84 (d, 2H, J¼8.0), 9.00 (s, 1H). 13C NMR (75.46 MHz, CDCl3):
d
ppm170.4, 132.7, 132.4, 130.9, 130.5, 40.2. HRMS (EI, 70 eV): calcd
for C8H8NO279BrS [Mþ] 260.9459, found 260.9473.
4.2.9. 4-Methyl-N-((5-methylthiophen-2-yl)methylene)-
benzenesulfonamide 3i
4.2.16. N-(Cyclohexylmethylene)-4-methylbenzenesulfonamide 3p
The compound was prepared as described in the general pro-
cedure. It was not purified because of its instability. GC:
tR¼18.4 min. MS (EI): m/z 265 (Mþ, 35), 210 (40), 197 (70), 155 (85),
133 (80), 110 (100), 91 (100), 83 (40), 65 (100), 55 (100).
The compound was prepared as described in the general pro-
cedure (62% isolated yield). GC: tR¼20.7 min. MS (EI): m/z 281 (Mþ,
8), 279 (20), 207 (25), 155 (20), 124 (55), 91 (100), 65 (30), 53 (20).
1H NMR (300.13 MHz, CDCl3):
d
ppm 2.44 (s, 3H), 2.58 (s, 3H), 6.89–
7.88 (m, 6H), 9.00 (s, 1H). 13C NMR (75.47 MHz, CDCl3):
d
ppm 161.9,
153.7, 144.2, 140.1, 136.0, 135.8, 129.7, 127.8, 21.6, 16.5. HRMS (EI,
70 eV): calcd for C13H13NO2S2 [Mþ] 279.0388, found 279.0388.
4.2.17. N-Butylidene-4-methylbenzenesulfonamide 3q
The compound was prepared as described in the general pro-
cedure. It was not purified because of its instability. GC: tR¼14 min.
MS (EI): m/z 225 (Mþ, 10), 197 (100), 155 (100), 133 (100), 106 (60),
91 (100), 70 (100), 65 (100), 51 (30).
4.2.10. N-((5-Ethylthiophen-2-yl)methylene)-4-
methylbenzenesulfonamide 3j
The compound was prepared as described in the general pro-
cedure (71% isolated yield). GC: tR¼21.2 min. MS (EI): m/z 293 (Mþ,
20), 155 (15), 138 (75), 122 (15), 91 (100), 65 (30). 1H NMR
Acknowledgements
`
(300.13 MHz, CDCl3):
d
ppm 1.30 (t, 3H, J¼7.5), 2.41 (s, 3H), 2.88 (q,
We thank the Ministere de la Recherche and the CNRS for pro-
2H, J¼7.5), 6.90–7.85 (m, 6H), 9.00 (s, 1H). 13C NMR (50.75 MHz,
viding financial support. L.B. is grateful to the French-algerian
PROFAS program for financial support.
CDCl3):
d ppm 162.0, 161.3, 144.1, 140.1, 135.7, 135.3, 129.6, 127.6,

7384
X.-F. Wu et al. / Tetrahedron 65 (2009) 7380–7384
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