The first examples of rhodium-catalyzed 1,4-conjugate addition reactions of arylboronic acids with ethenesulfonamides

Article abstract of DOI:10.1016/j.tetlet.2011.08.108

An unprecedented rhodium-catalyzed 1,4-conjugate addition of arylboronic acids with ethenesulfonamides resulting in the corresponding 2-arylethanesulfonamides is described. The amino substituent, the applied arylboronic acid, the type of Rh-catalyst, and the experimental conditions all affected the reaction outcome.

Full text of DOI:10.1016/j.tetlet.2011.08.108

Tetrahedron Letters 52 (2011) 5934–5939
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Tetrahedron Letters
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The first examples of rhodium-catalyzed 1,4-conjugate addition reactions
of arylboronic acids with ethenesulfonamides
Hicham Zilaout a, Adri van den Hoogenband a,b, , Jelle de Vries a, Jos H. M. Lange a, Jan Willem Terpstra a
⇑
a Abbott Healthcare Products B.V., C. J. van Houtenlaan 36, 1381 CP Weesp, The Netherlands
b Van’t Hoff Institute for Molecular Sciences, PO Box 94157, 1090 GD Amsterdam, The Netherlands
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 7 June 2011
Revised 4 August 2011
Accepted 19 August 2011
Available online 5 September 2011
An unprecedented rhodium-catalyzed 1,4-conjugate addition of arylboronic acids with ethenesulfona-
mides resulting in the corresponding 2-arylethanesulfonamides is described. The amino substituent,
the applied arylboronic acid, the type of Rh-catalyst, and the experimental conditions all affected the
reaction outcome.
Ó 2011 Elsevier Ltd. All rights reserved.
Keywords:
Rhodium
14-Conjugate addition
Boronic acid
Ethenesulfonamide
2-Arylethanesulfonamide
R1
2-Arylethanesulfonamides (Fig. 1) constitute an important class
of compounds in the medicinal chemistry area.1 These compounds
are synthetically accessible from the appropriate 2-aryl-
ethanesulfonyl chloride and amine.2 However, the synthesis of
the required arylethanesulfonyl chlorides generally is not straight-
forward. Different methods have been described, for example,
heating 2-arylethyl bromides with aqueous Na2SO3, followed by
treatment with SOCl2 in benzene.3 Alternatively, in the presence
of a chlorinating reagent such as SO2Cl2 in combination with
KNO3 in acetonitrile,4 NCS in dichloromethane/water5 or dissolved
chlorine gas in methanol/water,6 2-arylethylmercaptans can be
converted into the corresponding sulfonyl chlorides. Treatment of
2-arylethylsulfonic acids or 2-arylethylsulfinyl chlorides with
SOCl2 in benzene3 or with chlorine gas7 is an additional reported
option to obtain arylethanesulfonyl chlorides. Recently, a number
of 2-arylethanesulfonamides were required for one of our research
projects. Based on our interest in metal-catalyzed chemistry,8 we
considered preparing such compounds by Rh-catalyzed 1,4-conju-
gate addition reactions of arylboronic acids with ethenesulfona-
mides (Fig. 2). Although Rh-catalyzed conjugate addition
reactions of arylboronic acids have a broad scope,9 application of
this reaction to ethenesulfonamides has, to the best of our knowl-
edge, not been reported. In this Letter, we disclose our preliminary
results in this area.
O
S
R
N
R'
O
Figure 1. 2-Arylethanesulfonamides.
Rh-catalyzed 1,4-conjugate additions of arylboronic acids with
,b-unsaturated carbonyl derivatives have become an important
a
tool in synthetic organic chemistry. Since the first publication in
1997 by Miyaura et al.,10 a number of other activated vinyl sub-
strates have been applied for conversion into their saturated ana-
logs by the application of this reaction.9 In 1998, Hayashi et al.,11
showed that by running these reactions in the presence of (S)-BIN-
AP, chiral compounds could be obtained in enantiomerically en-
riched form. Rh-catalyzed 1,4-conjugate additions have become a
broad scope conversion which is not only restricted to laboratory
scale. AstraZeneca for example, have demonstrated a conjugate
addition reaction on kilogram-scale for the synthesis of rolipram.12
Our first attempt at the preparation of 2-arylethanesulfona-
mides by a rhodium-catalyzed 1,4-conjugate addition involved
the reaction between 3-chlorophenylboronic acid and ethenesulf-
onamide 1.13 Compound 1 was easily obtained by the reaction of
commercially available 2-chloroethylsulfonyl chloride with trieth-
ylamine in dichloromethane at low temperature to induce b-elim-
ination of the chloride anion followed by reaction with
methylamine (Scheme 1). The conditions described by Willis and
Frost,14 (6 mol % Rh(acac)(C2H4), 6.6 mol % rac-BINAP, 1,4-diox
⇑
Corresponding author. Tel.: +31 (0)205255671; fax: +31 (0)205255604.
E-mail address: A.vandenHoogenband@uva.nl (A. van den Hoogenband).
0040-4039/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2011.08.108

H. Zilaout et al. / Tetrahedron Letters 52 (2011) 5934–5939
5935
O
R
S
N
R'
O
Figure 2. Ethenesulfonamides.
1
6
NRR' = NHCH3
NRR' = N(CH3)2
O
R
O
S
O
(a)
Cl
S
N
Cl
R'
O
11
N
NRR'=
14
NRR' = NHPh
Scheme 1. Reagents and conditions: (a) (i) 2-hloroethylsulfonylchloride (1 mol equiv), Et3N (1.1 mol equiv), CH2Cl, ꢀ60 °C, 2 h; (ii) Et3N (1.1 mol equiv), HNRR0
(1.1 mol equiv), CH2Cl2, ꢀ60 °C to rt.
R1
R1
O
S
O
R
(a) or (b)
O
S
O
R
N
B(OH)2
+
N
R'
R'
Scheme 2. Reagents and conditions: (a) Procedure A15, ethenesulfonamide (1 mmol), arylboronic acid (4 mmol), 6 mol % Rh(acac)(C2H4), 6.6 mol % rac-BINAP, 15 ml 1,4-
dioxane/H2O 10:1 (v/v), 100 °C, 18 h. (b) Procedure B18, ethenesulfonamide (1 mmol), arylboronic acid (4 mmol), 2 mol % [Rh(cod)OH]2, 6 mol % rac-BINAP, 3 ml 1,4-dioxane/
H2O 99:1 (v/v), screw-sealed tube, 120 °C, 18 h.
Table 1
Conjugate addition reactions of arylboronic acids with ethenesulfonamides
R1
R1
A or B
O
S
R
O
S
R
B(OH)2
N
+
N
R'
O
see Scheme 2
R'
O
Entry
1
Ethenesulfonamide
ArB(OH)2
Procedures15,18
Product
Yield (%)a
O
O
S
B(OH)2
S
N
N
A
65
H
H
O
O
Cl
Cl
1
2
O
S
B(OH)2
N
2
3
1
1
A
A
51
28
H
O
3
B(OH)2
O
S
N
H
O
4
B(OH)2
4
5
1
1
B
B
4
40
O
S
B(OH)2
N
55b,c
H
O
5
O
S
O
S
B(OH)2
N
N
6
A
0
O
O
Cl
Cl
7
6
(continued on next page)

5936
H. Zilaout et al. / Tetrahedron Letters 52 (2011) 5934–5939
Table 1 (continued)
Entry
Ethenesulfonamide
ArB(OH)2
Procedures15,18
Product
Yield (%)a
64
B(OH)2
7
6
6
B
7
Cl
O
S
B(OH)2
N
8
9
B
B
B
48
46
33
O
8
B(OH)2
O
S
N
6
6
O
9
O
S
B(OH)2
N
10
O
10
O
S
O
B(OH)2
N
N
S
11
B
40
O
O
12
11
O
S
B(OH)2
B(OH)2
N
12
13
11
11
B
B
19
O
13
O
N
S
<10d
Cl
O
Cl
14
O
S
B(OH)2
N
14
15
16
11
B
B
B
10
61
47
O
15
O
S
O
S
B(OH)2
N
H
N
H
O
Cl
O
Cl
14
16
O
S
B(OH)2
N
H
14
O
17
a
b
c
Isolated yields of pure compounds.
Yield with the phenylboronpinacol ester: 17% (see text).
Yield with the potassium phenyltrifluoroborate: 24% (see text).
No spectral data available due to the presence of impurities.
d
ane/water, 10:1 (v/v), 100 °C) were applied for the Rh-catalyzed
conjugate addition. On a 1 mmol scale, compound 1 was reacted
with 4 M equiv of 3-chlorophenylboronic acid in 15 ml of solvent
(Scheme 2, procedure A, Table 1, entry 1).15 A fair yield (65%) of
sulfonamide 2 was obtained after purification by flash chromatog-
raphy. It should be noted that the isolation of 2 by flash chroma-
tography was troublesome due to the small difference in Rf
values with 1 in combination with the low UV absorption rate of
both 1 and 2. Interestingly, the presence of chlorine atom on 2 al-
lows further functionalization by Pd cross-coupling chemistry.16
Encouraged by this result, 4-biphenylboronic acid was analogously
reacted with 1 to produce 3 in an acceptable yield of 51% (Table 1,
entry 2). However, in the case of 2-naphthaleneboronic acid, only a
modest yield of 28% of 4 was isolated (Table 1, entry 3). After a
thorough survey of the reaction procedure, it was found that the
yield of this particular reaction could be raised to 40% by adapting
Lautens17 conditions in Rh-catalyzed reactions of arylboronic acids
on allyl sulfones, viz. 2 mol % [Rh(cod)OH]2, 6 mol % rac-BINAP,
3 ml 1,4-dioxane/water, 99:1 (v/v), 1 mmol of 1, 4 M equiv of the
applied boronic acid, and heating in a screw-sealed tube at

H. Zilaout et al. / Tetrahedron Letters 52 (2011) 5934–5939
5937
N
O
S O
O
S
B(OH)2
Procedure B
N
+
+
+
+
O
11
15
Scheme 3. Reagents and conditions: Procedure B18, ethenesulfonamide 11 (1 mmol), 2-naphthaleneboronic acid (4 mmol), 2 mol % [Rh(cod)OH]2, 6 mol % rac-BINAP, 3 ml
1,4-dioxane/H2O 99:1 (v/v), screw-sealed tube, 120 °C, 18 h.
120 °C (Scheme 2, procedure B, Table 1, entry 4).18 Deborylation
and homo-coupling of 2-naphthaleneboronic acid constituted ma-
jor side reactions. Compound 52 was obtained in a yield of 55% by
using procedure B (Scheme 2)18 (Table 1, entry 5).
ysis of the crude material revealed the absence of 11, the presence
of a trace product, and the expected presence of naphthalene and
2,20-binaphthalene. Unexpectedly, the presence of 2-vinylnaphtha-
lene in the crude reaction mixture was demonstrated (Scheme 3).
After flash chromatography, 15 was isolated in a low yield of 10%.
Due to the small difference in Rf values, naphthalene, 2,20-binaph-
thalene and 2-vinylnaphthalene were isolated in one fraction. The
overall mass balance of the isolated fractions was almost quantita-
tive. Based on the outcome of the stability experiments on 11, it
can be assumed that 15 partly decomposed under these experi-
mental conditions. Further indications of this decomposition were
found in the 1H NMR spectrum of crude 12 wherein the presence of
4-vinylbiphenyl was observed. Apparently, elimination of the sul-
fonylpiperidine group from the formed product is a significant side
reaction.
To investigate the scope of ethenesulfonamide substrates, com-
pound 619 was prepared in the same way as compound 1 (Scheme
1), followed by Rh-catalyzed conjugate addition with 3-chloro-
phenylboronic acid according to the procedure of Willis and Frost
(Scheme 2, procedure A).15 In contrast with the result obtained
with 1, no product was detected (Table 1, entry 6). After purifica-
tion, only sulfonamide 6 was isolated together with deborylation
and homo-coupling products of 3-chlorophenylboronic acid. Based
on literature reports from Carrerero and Lautens,20 it can be spec-
ulated that the lack of reactivity is caused by decreased coordina-
tion of the initially formed Ar-Rh(I) species to 6. An analogous
finding was reported in the Cu-catalyzed 1,4-conjugate additions
The N-phenylethenesulfonamide (14)24 was prepared (Scheme
1) in order to complete the investigation on the scope of ethene-
sulfonamides. Compound 14 was briefly investigated in Rh-cata-
lyzed conjugate additions with 3-chlorophenylboronic acid and
4-biphenylboronic acid, respectively, which furnished 16 and 17
in reasonable yields (Table 1, entries 15 and 16). Heteroarylboronic
acids, such as the pyridylboronic acids, form a difficult class for Rh-
catalyzed 1,4-conjugate additions on activated alkenes. Neverthe-
less, the reaction between 3-pyridylboronic acid and 1 and with
6 using procedure B18 was attempted (Scheme 2) but led only to
isolation of the starting ethenesulfonamides. Indole-4-boronic acid
as another heteroarylboronic acid example, gave the same unsatis-
factory result, in line with reports in the literature25 that suggested
poisoning of Rh-catalysts by complexation with the N atoms of
pyridine and indole, respectively.
Finally, the potential differences in reactivity between phenyl-
boronic acid, phenylboronic acid pinacol ester, and potassium phe-
nyltrifluoroborate in the rhodium-catalyzed 1,4-conjugated
addition reaction on ethenesulfonamides were briefly explored. It
was established that the conversion of the boron pinacol ester
was incomplete on reaction with 1 according to procedure B18
(Scheme 2) since compound 5 was isolated in a low yield (17%)
and a substantial amount of starting material was present. Applica-
tion of the same procedure to potassium phenyltrifluoroborate also
resulted in a low yield of 24%. It can be concluded that for this type
of Rh-catalyzed addition reaction the boronic acid moiety is supe-
rior in comparison with pinacol ester and potassium trifluorobo-
rate moieties (see Table 1, entry 5)
of Grignard reagents21 and dialkylzinc reagents22 to
rated pyridylsulfones.
a,b-unsatu-
Gratifyingly, using procedure B18 (Scheme 2), the reaction suc-
ceeded and the addition product 7 was isolated in a yield of 64%
(Table 1, entry 7). The reaction of 6 with phenylboronic acid and
with 2-naphthaleneboronic acid also resulted in the desired prod-
ucts (Table 1, compounds 8 and 9, entries 8 and 9). The observed
yield with 4-biphenylboronic acid was somewhat lower, primarily
due to a tedious purification (Table 1, compound 10, entry 10).
So far, only ethenesulfonamides were used that contained an
acyclic aliphatic amino group. In order to verify the reactivity of
ethenesulfonamides containing a cyclic aliphatic amino group,
compound 1123 was prepared (Scheme 1) and subjected to our
Rh-catalyzed conversion using procedure B18 (Scheme 2).
Compound 12 was furnished in 40% yield (Table 1, entry 11). The
reaction yields (<20%) of 11 with phenylboronic acid, 3-chloro-
phenylboronic acid, and 2-naphthaleneboronic acid were very
disappointing. (Table 1, entries 12–14). It was verified that all of
the starting material 11 was converted during these reactions
(entries 11–14). Decreasing the reaction temperature and
extending the reaction time had no positive effect on the yields.
These results prompted us to verify the chemical stability of 11.
Two experiments were initiated for clarification of this point. First,
11 was heated at 100 °C in a screw-sealed tube without boronic
acid in 1,4-dioxane/water, 99:1 (v/v) in the presence of [Rh(co-
d)OH]2 and rac-BINAP. Second, both the boronic acid and rhodium
catalyst/rac-BINAP were omitted. In both cases, after prolonged
heating for 72 h, compound 11 was still present and no decompo-
sition products were detected, that is, 11 remained stable under
these conditions. The experiment between 11 and 2-naphthalen-
eboronic acid was repeated according to procedure B18 (Scheme
2). The reaction mixture was evaporated after 20 h. 1H NMR anal-
In conclusion, a novel one-step conversion is presented for the
synthesis of 2-arylethanesulfonamides via Rh-catalyzed 1,4-conju-
gate additions of arylboronic acids with ethenesulfonamides. The
yields appear to depend strongly on the specific substituent pat-
terns of the applied reagents. Although the scope of the reaction

5938
H. Zilaout et al. / Tetrahedron Letters 52 (2011) 5934–5939
14. Chapman, C. J.; Matsuno, A.; Frost, C. G.; Willis, M. C. Chem. Commun. 2007,
3903–3905.
15. General procedure for the Rh-catalyzed 1,4-conjugate addition according to
procedure A (Scheme 2): A dried 25 ml, three-necked reaction vessel was
charged with degassed [1,4-dioxane/water,15 ml, 10:1 (v/v)] followed by the
needs to be explored in more detail, this straightforward method
should allow fast access to the 2-arylethanesulfonamide chemo-
type. Despite their relatively simple chemical structures, all the re-
ported 2-arylethanesulfonamides in Table 1, except for 52 are, to
the best of our knowledge, novel compounds. Unfortunately, we
are in the future unable to optimize or extend the scope of this
methodology due to the cessation of the research activities at our
site.
addition of
1 (121 mg, 1 mmol) and 3-chlorophenylboronic acid (624 mg,
4 mmol). After addition of Rh(acac)(C2H4)2 (6 mol %, 17 mg, 0.06 mol) and rac-
BINAP (6.6 mol %, 41 mg, 0.066 mol), the stirred mixture was heated in a pre-
heated oil bath at 100 °C for 18 h. After cooling to room temperature, the
resulting mixture was diluted with EtOAc (10 ml) and extracted with 5%
aqueous NaHCO3 solution (10 ml). The organic layer was dried over Na2SO4
and concentrated in vacuo. The crude obtained material was further purified
by flash chromatography [silica gel 60 (0.040–0.063 nm, Merck)], eluent Et2O –
petroleum ether (40–60), 3:1 (v/v) or CH2Cl2 – EtOAc, 9:1 (v/v), to give 150 mg
Acknowledgments
of pure
2 (65%). Spectral data for the compounds described in Table 1,
according to procedure A (Scheme 2): 2: 1H NMR (400 MHz, CDCl3): d 2.76 (d,
J = 8 Hz, 3H), 3.07–3.12 (m, 2H), 3.25–3.30 (m, 2H), 4.18 (br d, J = 4 Hz, 1H),
7.12 (br d, J = 4 Hz, 1H), 7.24 (t, J = 8 Hz, 3H). 13C NMR (100 MHz, CDCl3): d
29.34, 29.57, 52.19, 126.61, 127.25, 128.49, 130.18, 134.64, 139.89. HRMS
(ES+): calcd for C9H12NClO2S (M)+: 233.0277; found: 233.0253. 3: 1H NMR
(400 MHz, CDCl3): d 2.75 (d, J = 8 Hz, 3H), 3.14–3.20 (m, 2H), 3.30–3.36 (m, 2H),
3.93–3.99 (m, 1H), 7.29–7.38 (m, 3H), 7.44 (t, J = 8 Hz, 2H), 7.55–7.60 (m, 4H).
13C NMR (100 MHz, CDCl3): d 29.40, 29.61, 52.35, 127.01, 127.43, 127.62,
128.82, 128.85, 136.89, 140.05, 140.51. HRMS (ES+): calcd for C15H17NO2S (M)+:
275.0980; found: 275.1068. 4: 1H NMR (400 MHz, CDCl3): d 2.72 (d, J = 8 Hz,
3H), 3.27–3.31 (m, 2H), 3.38–3.40 (m, 2H), 3.92 (br d, J = 4 Hz, 1H), 7.35 (dd,
J = 4 and 2 Hz, 1H), 7.46–7.50 (m, 2H), 7.69 (s, 1H), 7.78–7.84 (m, 3H). 13C NMR
The authors wish to thank Hugo Morren for his analytical sup-
port, Marjolein Gaillard-Bosch for performing literature surveys
and Professor Dr. A. J. Minnaard (Stratingh Institute for Chemistry,
University of Groningen) for stimulating discussions. Finally, the
authors are grateful to Professors Dr. H. Hiemstra and Dr. J. H.
van Maarseveen (Biomolecular Synthesis Group Van ’t Hoff Insti-
tute for Molecular Science, University of Amsterdam) for allowing
us the opportunity to publish this manuscript.
(100 MHz, CDCl3):
127.57, 127.77, 128.73, 132.35, 133.52, 135.27. HRMS (ES+): calcd for
13H15NO2S (M)+: 249.0824; found: 249.0898.
d 29.39, 30.14, 52.26, 125.91, 126.40, 126.52, 126.87,
References and notes
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18. General procedure for the Rh-catalyzed 1,4-conjugate addition according to
procedure B, (Scheme 2): A dried 25 ml, screw-sealed tube was charged with
degassed [1,4 dioxane/water, 3 ml, 99:1 (v/v)], followed by the addition of 6
(140 mg, 1 mmol) and 3-chlorophenylboronic acid (624 mg, 4 mmol). After
addition of [RhOH(cod)]2 (2 mol %, 9.1 mg, 0.02 mol) and rac-BINAP (6 mol %,
37 mg, 0.06 mol), the tube was closed. After removing air by vacuum the tube
was back-filled with nitrogen and heated in a pre-heated oil bath at 120 °C for
18 h. After cooling to room temperature, the resulting mixture was diluted
with EtOAc (5 ml) and extracted with 5% aqueous NaHCO3 solution (5 ml). The
organic layer was dried over Na2SO4 and concentrated in vacuo. The crude
obtained 7 was further purified by flash chromatography [silica gel 60 (0.040–
0.063 nm, Merck)] eluent, Et2O-petroleum ether (40–60), 3:1 (v/v) or CH2Cl2
–
EtOAc,, 95:5 (v/v), to give 158 mg of pure 7 (64%). Spectral data are given for
the compounds described in Table 1, according to procedure B, (Scheme 2): 7:
1H NMR (400 MHz, CDCl3): d 2.88 (s, 6H), 3.08–3.17 (m, 4H), 7.09–7.13 (m, 1H),
7.24 (br t, J = 8 Hz, 3H). 13C NMR (100 MHz, CDCl3): d 29.00, 37.45, 49.27,
126.62, 127.18, 128.52, 130.14, 134.59, 140.13. HRMS (ES+): calcd for
C
10H14ClNO2S (M)+: 247.0248; found: 247.0317. 8: 1H NMR (400 MHz,
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CDCl3): d 2.88 (s, 6H), 3.10–3.20 (m, 4H), 7.22 (br d, J = 8 Hz, 2H), 7.26 (br t,
J = 4 Hz, 1H), 7.33 (br t, J = 8 Hz, 2H). 13C NMR (100 MHz, CDCl3): d 29.31, 37.47,
49.65, 126.95, 128.37, 128.87, 138.16. HRMS (ES+): calcd for C10H15NO2S (M)+:
213.0667; found: 213.0708. 9: 1H NMR (400 MHz, CDCl3): d 2.89 (s, 6H), 3.23–
3.32 (m, 4H), 7.34 (dd, J = 8 and 2 Hz, 1H), 7.44–7.50 (m, 2H), 7.67 (s, 1H), 7.78–
7.84 (m, 3H). 13C NMR (100 MHz, CDCl3): d 29.49, 37.49, 49.60, 125.84, 126.40,
126.55, 126.84, 127.49, 127.70, 128.62, 132.33, 133.56, 135.57. HRMS (ES+):
calcd for C14H17NO2S (M)+: 263.0980; found: 263.0929. 10: 1H NMR (400 MHz,
CDCl3): d 2.89 (s, 6H), 3.16–3.21 (m, 4H), 7.30 (br d, J = 8 Hz, 2H), 7.35 (br t,
J = 8 Hz, 1H), 7.44 (br t, J = 8 Hz, 2H), 7.56 (br t, J = 8 Hz, 4H). 13C NMR
(100 MHz, CDCl3):
d 28.95, 37.49, 49.57, 127.02, 127.37, 127.57, 128.82,
128.85, 137.19, 139.95, 140.62. HRMS (ES+): calcd for C16H19NO2S (M)+:
289.1137; found: 289.1155. 12: 1H NMR (400 MHz, CDCl3): d 1.55–1.70 (m,
6H), 3.23–3.33 (m, 6H), 3.53–3.58 (m, 2H), 7.44–7.53 (m, 3H), 7.62 (d, J = 4 Hz,
2H), 7.80 (d, J = 4 Hz, 2H), 7.98 (d, J = 4 Hz, 2H). 13C NMR (100 MHz, CDCl3): d
23.62, 25.59, 42.34, 46.74, 50.43, 127.46, 128.29, 128.58, 128.93, 129.19,
136.73, 139.10, 147.55. HRMS (ES+): calcd for C19H23NO2S (M)+: 329.4647;
found 329.4532. 13: 1H NMR (400 MHz, CDCl3): d 1.43–1.51 (m, 4H), 1.56–1.64
(m, 4H), 3.06 (s, 2H), 3.11 (t, J = 8 Hz, 2H), 3.18 (t, J = 8 Hz, 2H), 7.16 (t, J = 8 Hz,
2H), 7.26 (t, J = 8 Hz, 1H), 7.32–7.44 (m, 2H). 13C NMR (100 MHz, CDCl3): d
22.76, 24.64, 28.33, 45.58, 49.62, 127.35, 128.60, 129.78, 137.23. HRMS (ES+):
calcd for C13H19NO2S (M)+: 253.1137; found: 253.1068. 15: 1H NMR (400 MHz,
CDCl3): d 1.51–1.68 (m, 6H), 3.18–3.31 (m, 8H), 7.32 (br d, J = 8 Hz, 1H), 7.44–
7,48 (m, 2H), 7.65 (s, 1H), 7.77–7.82 (m, 3H). 13C NMR (100 MHz, CDCl3): d
23.95, 25.91, 29.59, 46.85, 50.75, 128.90, 126.42, 126.60, 126.98, 127.58,
127.95, 128.88, 132.38, 133.40, 135.65. HRMS (ES+): calcd for C17H21NO2S (M)+:
303.1293; found: 303.1262. 16: 1H NMR (400 MHz, CDCl3): d 3.08–3.11 (m,
2H), 3.32–3.37 (m, 2H), 6.41 (br s, 1H), 7.02–7.05 (m, 1H), 7.09–7.23 (m, 6H),
7.31–7.37 (m, 2H). 13C NMR (100 MHz, CDCl3): d 29.50, 52.31, 120.55, 125.48,
126.68, 127.35, 128.59, 129.76, 130.19, 134.70, 136.33, 139.41. HRMS (ES+):
calcd for
C
14H14ClNO2S (M)+: 295.0434; found: 295.0182. 17: 1H NMR
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(400 MHz, CDCl3): d 3.16–3.21 (m, 2H), 3.37–3.42 (m, 2H), 6.16 (br s, 1H),
7.07 (d, J = 8 Hz, 2H), 7.14–7.25 (m, 3H), 7.28–7.38 (m, 3H), 7.44 (t, J = 8 Hz,
2H), 7.51–7.57 (m, 4H). 13C NMR (100 MHz, CDCl3): d 29.58, 52.57, 120.51,

H. Zilaout et al. / Tetrahedron Letters 52 (2011) 5934–5939
5939
125.36, 127.01, 127.45, 127.68, 128.85, 128.93, 129.66, 136.41, 136.49, 140.18,
140.50. HRMS (ES+): calcd for C20H19NO2S (M)+: 337.4439; found 337.4328.
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