Merging cross-metathesis and radical cyclization: A straightforward access to 4-substituted benzosultams

Article abstract of DOI:10.1055/s-0032-1318147

N-Alkyl-N-allyl-2-bromobenzenesulfonamides were functionalized by selective E-cross-metathesis with various alkenes. Subsequent radical cyclization initiated by 2,2′-azobis(isobutyronitrile) and tris(trimethylsilyl)silane gave the corresponding 4-substituted benzosultams directly in moderate-to-good yields.

Full text of DOI:10.1055/s-0032-1318147

810▌
PAPER
paper
Merging Cross-Metathesis and Radical Cyclization: A Straightforward Access
to 4-Substituted Benzosultams
4-Substituted Benzosultams
Sophie Feuillastre, Béatrice Pelotier, Olivier Piva*
Université de Lyon, Université Lyon 1, Institut de Chimie et de Biochimie Moléculaire et Supramoléculaire (ICBMS), UMR 5246 CNRS,
Bat Raulin, 43 Bd. du 11 novembre 1918, 69622 Villeurbanne cedex, France
Fax +33(0)472448136; E-mail: piva@univ-lyon1.fr
Received: 17.12.2012 ; Accepted after revision: 11.01.2013
the corresponding bromosulfonamide 6 (Scheme 1).7
Abstract: N-Alkyl-N-allyl-2-bromobenzenesulfonamides were
Evans’s group used a similar Heck cyclization to synthe-
functionalized by selective E-cross-metathesis with various al-
size the parent structures.9 More recently, benzosultams
kenes. Subsequent radical cyclization initiated by 2,2′-azobis(iso-
have been prepared from less-densely functionalized sub-
strates through processes involving C–H activation,10,11
mainly promoted by palladium salts,10 or through intra-
molecular hydroamination initiated by copper(II), sil-
ver(I), or gold(I) catalysts.12,13 Ring enlargement of
saccharin is another suitable route, and this strategy has
been used in a synthesis of sultam 2 and its analogues by
a relative lengthy route.3
butyronitrile) and tris(trimethylsilyl)silane gave the corresponding
4-substituted benzosultams directly in moderate-to-good yields.
Key words: metathesis, cyclizations, radical reactions, sulfon-
amides, heterocycles
Sulfonamides and sultams are important classes of phar-
macologically active compounds.1 For example, sultam 1
(Figure 1) is implicated in the inhibition of calpain I, a cal-
cium-activated cysteine protease involved in the degener-
ation of neurons.2 Sultam 2 has been recently reported to
be a potential inhibitor of aldolase reductase, and might be
useful for treatment of complications arising from diabe-
tes.3 Sultam 3 exhibits activities against HIV,4 whereas
piroxicam (4) is a nonsteroidal antiinflammatory drug.5
Because of these activities, a wide range of synthetic
methods have been devised for the synthesis of sultams
and related structures.6
O
O
N
O
O
S
R1
S
R1
R2
N
R2
+
H
Br
O
6
O
5
Scheme 1 Hanson’s approach to benzosultams 5 by sequential Heck
reaction and aza-Michael addition
In the last three decades, radical cyclizations have
emerged as powerful methods for building heterocyclic
structures from unsaturated substrates,14,15 and these reac-
tions have found a number of direct applications in syn-
theses of complex natural products. Metathesis is
currently the process of choice for the direct functional-
ization of terminal alkenes or alkynes.16–18 Therefore,
combinations of cross-metathesis and radical cyclization
would appear to have potential for developing attractive
routes to new heterocyclic structures from readily avail-
able compounds in small numbers of steps. To date, how-
ever, this combination has been not widely examined.19,20
O
O
O O
O
O
S
Et
O
S
N
H
N
O
N
Ph
H
Ph
CO2H
1
2
O
O
O
O
S
Me
S
Me
N
H
N
N
N
OH
OH
O
In 2005, we reported a one-pot synthesis of tricyclic fused
structures by combining a ring-closing metathesis/isomer-
ization process with a radical cyclization.21 We have now
extended this process by investigating the reactivity of
more-flexible structures, such as the N-alkyl-N-allyl-2-
bromobenzenesulfonamides 7.
Radical cyclizations are governed by Baldwin’s rules.22
We therefore expected that the cyclization mode might be
strongly dependent of the substitution of the double bond
(Scheme 2). It is important to point out that, even before
our first attempts to perform this reaction, the plausibility
of the radical process was supported by a result obtained
by Ganguly and co-workers,23 who found that the diallylic
3
4
Figure 1 Some representative pharmacologically active sultams
Hanson’s group have been very active in this field and
they have developed several strategies for preparing li-
braries of new sultams.7,8 In particular, they have reported
a one-pot procedure that combines a Heck reaction with
an aza-Michael cyclization to give benzosultams 5 from
SYNTHESIS 2013, 45, 0810–0816
Advanced online publication: 08.02.2013
0
0
3
9
-
7
8
8
1
1
4
3
7
-
2
1
0
X
DOI: 10.1055/s-0032-1318147; Art ID: SS-2012-T0962-OP
© Georg Thieme Verlag Stuttgart · New York

PAPER
4-Substituted Benzosultams
811
As pointed out above, substitution of the alkene moiety
should have a marked effect on the regioselectivity of the
cyclization reaction. Because cross-metathesis usually re-
quires an excess of the alkene partner, it is not possible to
perform the cross-metathesis and the radical cyclization
as a one-pot process, as this would result in the production
of side products from polycondensation reactions. We
therefore performed an initial cross-metathesis between
sulfonamide 7b and but-3-en-2-one (10a) in the presence
of the Grubbs II catalyst (GBII; Scheme 4). The reaction
proceeded smoothly and gave the N-alkenyl sulfonamide
11a as a single E-isomer. The E-configuration of the new-
ly created double bond was assigned from the coupling
constant in the 1 H NMR spectrum (typical J value = 15.0
Hz). We also tested microwave activation,26 and the reac-
tion occurred faster but without a significant increase in
the chemical yield. With microwave activation, the
Hoveyda–Grubbs reagent efficiently catalyzed the reac-
tion to give sulfonamide 11a in 57% yield and 85% selec-
tivity. We then subjected the functionalized 2-
bromosulfonamide 11a to radical cyclization in toluene,
and we obtained sultam 12a in a reasonable yield.
O
O
S
R1
N
6-exo-trig
cyclization
O
O
O
O
S
R1
S
R1
R2
O
N
N
O
R1
Br
Br
S
N
7-endo-trig
cyclization
R2
7
R2
Scheme 2 Cyclization strategy based on a cross-metathesis and a
radical cyclization
sulfonamide 7a24 underwent an initial 7-endo-trig cycliza-
tion to give products 8 and 9a/9b. This preliminary study
was based on the use of tributylstannane as a radical-chain
promoter. However, to facilitate workup of the reaction
mixture, we chose to replace tributylstannane with tris(tri-
methylsilyl)silane, also known also as Chatgilialoglu’s re-
agent.25 This reagent is easily removed under vacuum
during workup, and it eliminates the need to use lipophilic
toxic organostannanes derivatives. Interestingly, when we
applied our new conditions to substrate 7a, we obtained
compounds 8 and 9a/9b in 50% overall yield, but in a ratio
of 15:35, which is significantly different from the value of
56:3 obtained by Ganguly et al. This preliminary result es-
tablished the feasibility of our intended process (Scheme
3).
N
N
O
O
O O
Mes
Ph
Mes
Cl
Cl
S
Me
S
Me
Ru
PCy3
(5 mol%)
N
N
+
Br
Br
R
10a–e
(3 equiv)
7b
CH2Cl2, 40 °C
R
(E)-11a–e
O
O
S
O
O
O
O
N
S
Me
S
Me
AIBN
(0.4 equiv)
N
N
O
O
H
O
O
S
Allyl
(TMS)3SiH
N
S
AIBN
H
N
toluene, Δ
•
(TMS)3SiH
9a
R
R
H
+
Br
7a
12a–e
toluene
reflux
O
S
O
8
Scheme 4 Cross-metathesis between 7b and alkenes 10a–e and sub-
sequent radical cyclization
N
H
H
Next, we examined the cross-metathesis of various al-
kenes 10b–e in the presence of the Grubbs II catalyst, and
we obtained the corresponding N-alkenylsulfonamides
11b–e in moderate-to-good yields as single isomers in
9b
Scheme 3 Radical cyclization of substrate 7a
Table 1 Preparation of Cross-Adducts 11 and Their Subsequent Radical Cyclization
Alkene reactant
Intermediate product
Yielda (%) of 11
Product
Yielda (%) of 12
10a
10b
10c
10d
10e
CH2=CHCOMe
11a
11b
11c
11d
11e
76b
12a
63
73
51
61
–
CH2=CHCO2Me
CH=CH2CO-4-Tol
CH2=CHCON(Me)OMe
CH2=CHPh
96
12b
21 (31% conv.)
43 (81% conv.)
53 (95% conv.)
12c
12d
polymers
a Isolated yields.
b Yield was 46% (82% conv.) when performed for 4 h with microwave activation (110 °C) in the presence of the Grubbs II catalyst (5 mol%),
and 57% (65% conv.) when performed for 2 h under microwave activation (110 °C) with the Hoveyda–Grubbs catalyst (5 mol%).
© Georg Thieme Verlag Stuttgart · New York
Synthesis 2013, 45, 810–816

812
S. Feuillastre et al.
PAPER
each case (Scheme 4, Table 1). The lower yields observed straction at the benzylic center, followed by intensive po-
in some cases were the result of the homodimerization of lymerization, as reflected by the base line on the thin-layer
7b. Radical cyclization of 11b–d gave acceptable yields chromatogram of the reaction mixture. The diastereose-
of sultams 12a–d, whereas the styrene derivative 11e gave lectivity was also poor, probably as a result of insufficient
only polymers.
1,5-asymmetric induction between the (1-phenyl-
ethyl)amine moiety and the prochiral sp2 carbon center.
We also performed the cross-metathesis of 7b with allyl
phenyl sulfide (10f) to give the corresponding sulfon-
amide 11f in 72% yield. Subsequent radical cyclization–
fragmentation reaction of 11f gave the sensitive 4-vinyl-
benzosultam 13 in 40% yield (Scheme 5).
O
O
O O
GBII
+
(5 mol%)
10b
S
S
N
Ph
N
Ph
CH2Cl2, 40 °C
Br
(S)-7c
Br
O
O
CO2Me
N
N
(E)-15 (60%)
Mes
Cl
Cl
Mes
Ph
S
Me
O
O
N
S
Me
Ru
PCy3
(5 mol%)
CH2Cl2, 40 °C
N
Br
O
O
O O
+
AIBN
(0.4 equiv)
Br
7b
S
S
N
Ph
N
Ph
PhS
+
10f
(TMS)3SiH
toluene, Δ
11f (72%) PhS
*
*
CO2Me
16a,b (27%; 55:45 dr)
CO2Me
O
O
O
O
S
Me
S
Me
AIBN
N
N
(0.4 equiv)
Si(TMS)3
Scheme 7 Diastereoselectivity in the reaction of sulfonamide 7c
+
(TMS)3SiH
Ph-Me, Δ
SH-Ph
•
In conclusion, we have developed a route for the synthesis
of 4-substituted benzosultams in moderate-to-high yields
through a combination of a cross-metathesis and a radical
cyclization reaction. In comparison with alternative path-
ways, this sequence is straightforward and requires only
two steps from readily available substrates. Work is un-
derway to apply this strategy to other important building
blocks for drug design.
13 (40%)
SPh
Scheme 5 Synthesis of vinylsultam 13 by cyclization–fragmentation
To enhance the functional diversity of our reaction, we re-
acted the Weinreb amide 12d with allylmagnesium bro-
mide. Selective 1,2-addition occurred to give the β,γ-
unsaturated ketone 14a together with isomer 14b, formed
as a result of migration of the terminal carbon–carbon
double bond under the basic conditions (Scheme 6).
All commercially available compounds were used without further
purification. Solvents were dried by standard procedures. Hexanes
refers to a hydrocarbon mixture with a boiling range of 40–60 °C.
Column chromatography was performed with silica gel (0.040–
0.063 mm). NMR spectra were recorded at 293 K by using a 300-
MHz spectrometer (Bruker AMX 300) or a 500-MHz spectrometer
(Bruker DRX 500). Shifts are referenced to the residual peaks of the
deuterated solvent. Low- and high-resolution mass spectra were re-
corded in the positive mode by using a Bruker MicrOTOF-Q II XL
spectrometer. IR spectra were recorded on a Nicolet IS 100 spec-
trometer.
O
O
S
Me
N
O
O
S
Me
N
O
MgBr
Et2O, r.t.
14a (48%)
OMe
N
O
O
2-Bromobenzenesulfonamides 7b and 7c; General Procedure
Et3N (3 equiv ) was added to a 0.2 M soln of alkyl(allyl)amine (1
equiv) in anhyd CH2Cl2, and the mixture was stirred at r.t. for 15
min, then being cooled to 0 °C. 2-BrC6H4SO2Cl (1 equiv) was add-
ed dropwise, and the mixture was warmed to r.t., stirred for 2 h, and
concentrated under reduced pressure. The residue was purified by
flash chromatography (silica, hexanes–EtOAc).
S
Me
Me
N
O
12d
O
14b (11%)
N-Allyl-2-bromo-N-methylbenzenesulfonamide (7b)
Colorless oil; yield: 2.01 g (99%) from 2-BrC6H4SO2Cl (1.80 g).
Scheme 6 Formation of ketones 14a and 14b from amide 12d
IR: 3085, 2918, 1446, 1329, 1154, 919 cm–1.
In an attempt to control the configuration of the new chiral
center that was formed, we developed a diastereoselective
approach with (1-phenylethyl)amine as a chiral auxiliary
(Scheme 7). Radical cyclization gave an inseparable mix-
ture of sultams 16a and 16b in only 27% yield. This low
efficiency might be the result of competitive hydrogen ab-
1H NMR (300 MHz, CDCl3): δ = 8.09 (dd, J = 2.0, 7.7 Hz, 1 H),
7.72 (dd, J = 1.5, 7.7 Hz, 1 H), 7.46–7.33 (m, 2 H), 5.82–5.65 (m,
1 H), 5.27–5.17 (m, 2 H), 3.85 (d, J = 6.3 Hz, 2 H), 2.80 (s, 3 H).
13C NMR (75 MHz, CDCl3): δ = 138.6, 135.7, 133.6, 132.8, 132.4,
127.6, 120.3, 119.2, 52.8, 34.0.
Synthesis 2013, 45, 810–816
© Georg Thieme Verlag Stuttgart · New York

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4-Substituted Benzosultams
813
HRMS (ESI): m/z [M + Na]+ calcd for C10H12BrNNaO2S 311.9664;
found: 311.9668.
1H NMR (300 MHz, CDCl3): δ = 8.16 (dd, J = 1.9, 7.7 Hz, 1 H),
7.85 (d, J = 8.2 Hz, 2 H), 7.76 (dd, J = 1.4, 7.7 Hz, 1 H), 7.51–7.35
(m, 2 H), 7.28 (d, J = 8.2 Hz, 2 H), 7.12 (dt, J = 15.4, 1.5 Hz, 1 H),
6.90 (dt, J = 15.4, 5.1 Hz, 1 H), 4.20 (dd, J = 1.3, 5.1 Hz, 2 H), 2.90
(s, 3 H), 2.43 (s, 3 H).
13C NMR (75 MHz, CDCl3): δ = 189.4, 144.2, 141.5, 138.3, 135.9,
134.9, 134.0, 132.7, 129.5, 129.0, 127.8, 127.6, 120.5, 51.6, 34.9,
21.9.
N-Allyl-2-bromo-N-[(1S)-1-phenylethyl]benzenesulfonamide
(7c)
Yellow oil; yield: 1.00 g (84%) from allyl[(1S)-1-phenyleth-
yl]amine (505 mg);27 Rf = 0.62 (hexanes–EtOAc, 7:3); [α]D20 –5.1
(c = 1.4, CHCl3).
IR: 3057, 1448, 1330, 1265, 1164, 1028, 924 cm–1.
HRMS (ESI): m/z [M + Na]+ calcd for C18H18BrNNaO3S: 430.0083;
found: 430.0083.
1H NMR (300 MHz, CDCl3): δ = 8.17 (dd, J = 2.2, 7.4 Hz, 1 H),
7.75 (dd, J = 1.8, 7.3 Hz, 1 H), 7.40 (dquint, J = 1.8, 7.4 Hz, 2 H),
7.32–7.19 (m, 5 H), 5.70–5.49 (m, 1 H), 5.17 (q, J = 7.1 Hz, 1 H),
5.01–4.85 (m, 2 H), 4.05 (dd, J = 5.6, 16.6 Hz, 1 H), 3.70 (dd, J =
6.9, 16.6 Hz, 1 H), 1.60 (d, J = 7.1 Hz, 3 H).
13C NMR (75 MHz, CDCl3): δ = 140.1, 139.5, 136.0, 135.6, 133.5,
132.8, 128.4, 128.0, 127.9, 127.6, 120.5, 116.9, 56.1, 47.6, 18.3.
(2E)-4-{[(2-Bromophenyl)sulfonyl](methyl)amino}-N-meth-
oxy-N-methylbut-2-enamide (11d)
Light-brown oil; yield: 145 mg (43%; 81% conversion) from 7b
(345 mg); Rf = 0.35 (hexanes–EtOAc, 5:5).
IR: 2938, 1666, 1634, 1421, 1332, 1266, 978, 922 cm–1.
HRMS (ESI): m/z [M + Na]+ calcd for C17H18BrNNaO2S: 402.0134;
found: 402.0128.
1H NMR (300 MHz, CDCl3): δ = 8.13 (dd, J = 1.9, 7.7 Hz, 1 H),
7.75 (dd, J = 1.5, 7.6 Hz, 1 H), 7.50–7.35 (m, 2 H), 6.84 (dt, J =
15.5, 5.3 Hz, 1 H), 6.64 (d, J = 15.5 Hz, 1 H), 4.11 (dd, J = 1.4, 5.3
Hz, 2 H), 3.71 (s, 3 H), 3.24 (s, 3 H), 2.85 (s, 3 H).
13C NMR (75 MHz, CDCl3): δ = 165.9, 140.5, 138.4, 135.9, 133.9,
132.6, 127.8, 121.6, 120.5, 62.1, 51.4, 34.6, 32.5.
N-Allyl-N-alkenyl-2-bromobenzenesulfonamides 11a–e;
General Procedure
A 0.1 M soln of the appropriate benzenesulfonamide derivative (1
equiv) and alkene derivative (3 equiv) in anhyd CH2Cl2 was treated
with the Grubbs II catalyst (5 mol%) under argon. The mixture was
stirred at reflux under argon atmosphere for 3 h and then a second
portion of Grubbs II catalyst (2 mol%) was added and the mixture
was stirred at the reflux overnight. The solvent was removed in
vacuo, and the residue was purified by flash chromatography [silica
gel, hexanes–EtOAc].
HRMS (ESI): m/z [M + Na]+ calcd for C13H17BrN2NaO4S:
398.9985; found: 398.9982.
2-Bromo-N-methyl-N-[(2E)-3-phenylprop-2-en-1-yl]benzene-
sulfonamide (11e)
Pale-yellow oil; yield: 168 mg (53%; 95% conversion) from 7b
(250 mg); Rf = 0.17 (hexanes–EtOAc, 9:1).
2-Bromo-N-methyl-N-[(2E)-4-oxopent-2-en-1-yl]benzenesul-
fonamide (11a)
Light-brown oil; yield: 217 mg (76%) from 7b (250 mg); Rf = 0.17
(hexanes–EtOAc, 7:3).
IR: 3059, 1575, 1448, 1331, 1265, 1159, 1026, 967, 926 cm–1.
1H NMR (300 MHz, CDCl3): δ = 8.15 (dd, J = 1.9, 7.7 Hz, 1 H),
7.76 (dd, J = 1.5, 7.7 Hz, 1 H), 7.46 (td, J = 7.6, 1.5 Hz, 1 H), 7.40
(dd, J = 1.9, 7.6 Hz, 1 H), 7.38–7.24 (m, 5 H), 6.54 (d, J = 15.8 Hz,
1 H), 6.14 (dt, J = 15.8, 6.7 Hz, 1 H), 4.08–3.99 (m, 2 H), 2.87 (s, 3
H).
13C NMR (75 MHz, CDCl3): δ = 138.8, 136.3, 135.8, 134.3, 133.7,
132.6, 128.7, 128.1, 127.7, 126.6, 124.1, 120.5, 52.4, 34.2.
IR: 2907, 1661, 1325, 1255, 1158, 933 cm–1.
1H NMR (300 MHz, CDCl3): δ = 8.13 (dd, J = 2.0, 7.6 Hz, 1 H),
7.75 (dd, J = 1.5, 7.6 Hz, 1 H), 7.52–7.34 (m, 2 H), 6.67 (dt, J =
16.0, 5.7 Hz, 1 H), 6.22 (dt, J = 16.0, 1.5 Hz, 1 H), 4.09 (dd, J = 1.3,
5.7 Hz, 2 H), 2.83 (s, 3 H), 2.26 (s, 3 H).
13C NMR (75 MHz, CDCl3): δ = 197.9, 141.0, 138.1, 135.9, 134.0,
133.0, 132.7, 127.8, 120.4, 51.4, 34.8, 27.5.
HRMS (ESI): m/z [M + Na]+ calcd for C16H16BrNNaO2S: 387.9977;
found: 387.9973.
HRMS (ESI): m/z [M + Na]+ calcd for C12H14BrNNaO3S: 353.9770;
found: 353.9760.
2-Bromo-N-methyl-N-[(2E)-4-(phenylsulfanyl)but-2-en-1-
yl]benzenesulfonamide (11f)
Pale-yellow oil; yield: 255 mg (72%; 76% conversion) from 7b
(250 mg); Rf = 0.26 (hexanes–EtOAc, 8:2).
Methyl (2E)-4-{[(2-Bromophenyl)sulfonyl](methyl)amino}but-
2-enoate (11b)
Light-brown oil; yield: 346 mg (96%) from 7b (300 mg); Rf = 0.30
(hexanes–EtOAc, 7:3).
IR: 2010, 1575, 1438, 1331, 1265, 1157, 1025, 964 cm–1.
1H NMR (300 MHz, CDCl3): δ = 8.07 (dd, J = 2.0, 7.6 Hz, 1 H),
7.72 (dd, J = 1.5, 7.6 Hz, 1 H), 7.51–7.05 (m, 7 H), 5.77–5.59 (m,
1 H), 5.46 (dt, J = 15.2, 6.5 Hz, 1 H), 3.77 (d, J = 6.5 Hz, 2 H), 3.51
(d, J = 6.9 Hz, 2 H), 2.59 (s, 3 H).
13C NMR (75 MHz, CDCl3): δ = 138.6, 135.8, 135.3, 133.6, 132.4,
130.6, 130.4, 129.0, 127.9, 127.6, 126.6, 120.4, 51.5, 35.9, 33.6.
IR: 2951, 1720, 1435, 1332, 1273, 1159, 1025, 929 cm–1.
1H NMR (300 MHz, CDCl3): δ = 8.13 (dd, J = 2.1, 7.5 Hz, 1 H),
7.75 (dd, J = 1.5, 7.7 Hz, 1 H), 7.52–7.34 (m, 2 H), 6.85 (dt, J =
15.7, 5.6 Hz, 1 H), 6.04 (dt, J = 15.7, 1.7 Hz, 1 H), 4.07 (dd, J = 1.7,
5.6 Hz, 2 H), 3.74 (s, 3 H), 2.82 (s, 3 H).
13C NMR (75 MHz, CDCl3): δ = 166.2, 142.5, 138.2, 135.9, 133.9,
132.7, 127.8, 123.8, 120.4, 51.9, 51.1, 34.6.
HRMS (ESI): m/z [M + Na]+ calcd for C17H18BrNNaO2S2:
433.9855; found: 433.9848.
HRMS (ESI): m/z [M + Na]+ calcd for C12H14BrNNaO4S: 369.9719;
found: 369.9720.
Methyl (2E)-4-{[(2-Bromophenyl)sulfonyl][(1S)-1-phenyl-
ethyl]amino}but-2-enoate (15)
White viscous liquid; yield: 96 mg (60%; 81% conversion) from 7c
20
2-Bromo-N-methyl-N-[(2E)-4-(4-tolyl)-4-oxobut-2-en-1-yl]ben-
zenesulfonamide (11c)
Light-brown oil; yield: 88 mg (21%; 31% conversion) from 7b (300
mg); Rf = 0.26 (hexanes–EtOAc, 7:3).
(140 mg); Rf = 0.30 (hexanes–EtOAc, 8:2); [α]D +1.5 (c = 0.9,
CHCl3).
IR: 2950, 2360, 1720, 1448, 1434, 1333, 1267, 1163, 1026, 899
cm–1.
1H NMR (300 MHz, CDCl3): δ = 8.20 (dd, J = 2.0, 7.4 Hz, 1 H),
7.77 (dd, J = 1.5, 7.3 Hz, 1 H), 7.50–7.35 (m, 2 H), 7.32–7.17 (m,
5 H), 6.63 (dt, J = 15.8, 6.0 Hz, 1 H), 5.66 (d, J = 15.8 Hz, 1 H),
IR: 2925, 1671, 1625, 1605, 1448, 1332, 1265, 1162, 1026, 924
cm–1.
© Georg Thieme Verlag Stuttgart · New York
Synthesis 2013, 45, 810–816

814
S. Feuillastre et al.
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5.15 (q, J = 7.0 Hz, 1 H), 4.14 (ddd, J = 1.4, 6.0, 17.6 Hz, 1 H), 3.89
(dd, J = 6.8, 17.6 Hz, 1 H), 3.67 (s, 3 H), 1.55 (d, J = 7.0 Hz, 3 H).
13C NMR (75 MHz, CDCl3): δ = 206.2, 138.5, 135.7, 132.6, 128.5,
127.8, 124.9, 53.3, 48.9, 35.3, 30.4, 29.8.
13C NMR (75 MHz, CDCl3): δ = 166.2, 145.5, 139.8, 139.0, 135.8,
133.8, 133.0, 128.7, 128.3, 127.9, 127.8, 122.2, 120.6, 56.1, 51.7,
45.6, 18.0.
HRMS (ESI): m/z [M + Na]+ calcd for C19H20BrNNaO4S: 460.0189;
found: 460.0189.
HRMS (ESI): m/z [M + Na]+ calcd for C12H15NNaO3S: 276.0665;
found: 276.0668.
Methyl (2-Methyl-1,1-dioxido-3,4-dihydro-2H-1,2-benzothi-
azin-4-yl)acetate (12b)
Yellow oil; yield: 90 mg (73%) from 11b (160 mg); Rf = 0.16
(hexanes–EtOAc, 7:3).
Sultams 8, 9a/9b, 12a–d, and 16a/16b; General Procedure
A 0.1 M soln of the appropriate benzene sulfonamide 11 (1 equiv)
in toluene was bubbled with a dried stream of N2 for 10 min. AIBN
(0.4 equiv) was then added and the reaction mixture was bubbled
again for 10 min. (TMS)3SiH (1.6 equiv) was added dropwise and
the mixture was refluxed for 5 h. The solvent was removed in vacuo
and the crude mixture was purified by flash chromatography (silica,
hexanes–EtOAc).
IR: 2953, 1732, 1438, 1331, 1160 cm–1.
1H NMR (300 MHz, CDCl3): δ = 7.87 (dd, J = 1.3, 7.8 Hz, 1 H),
7.51 (td, J = 7.6, 1.3 Hz, 1 H), 7.46–7.38 (m, 1 H), 7.29 (d, J = 7.8
Hz, 1 H), 3.82 (dd, J = 5.1, 14.0 Hz, 1 H), 3.73 (s, 3 H), 3.72–3.69
(m, 1 H), 3.66–3.56 (m, 1 H), 2.89 (s, 3 H), 2.79–2.74 (m, 2 H).
13C NMR (75 MHz, CDCl3): δ = 172.0, 137.7, 136.0, 132.6, 128.5,
128.1, 125.0, 53.1, 52.2, 39.2, 35.3, 31.7.
2-Allyl-2,3,4,5-tetrahydro-1,2-benzothiazepine 1,1-Dioxide (8)23
Yellow oil; yield: 22 mg (15%) from 7a (200 mg).
1H NMR (300 MHz, DMSO-d6, 75 °C): δ = 7.79 (d, J = 7.8 Hz, 1
H), 7.58–7.49 (m, 1 H), 7.42 (d, J = 7.8 Hz, 2 H), 5.72 (ddt, J =
10.1, 17.0, 6.0 Hz, 1 H), 5.23 (dq, J = 17.0, 1.6 Hz, 1 H), 5.15 (dq,
J = 10.1, 1.6 Hz, 1 H), 3.64–3.54 (m, 2 H), 3.42 (d, J = 6.0 Hz, 2
H), 3.28–3.16 (m, 2 H), 1.83–1.69 (m, 2 H).
HRMS (ESI): m/z [M + Na]+ calcd for C12H15NNaO4S: 292.0614;
found: 292.0616.
2-(2-Methyl-1,1-dioxido-3,4-dihydro-2H-1,2-benzothiazin-4-
yl)-1-(4-tolyl)ethanone (12c)
Yellow oil; yield: 31 mg (51%) from 11c (75 mg); Rf = 0.33
(hexanes–EtOAc, 3:7).
IR: 2923, 1678, 1477, 1331, 1165, 979 cm–1.
MS (ESI): m/z (%) = 238.1 [M + H]+ (100).
1H NMR (300 MHz, CDCl3): δ = 7.92–7.82 (m, 3 H), 7.50 (td, J =
7.6, 1.5 Hz, 1 H), 7.41 (td, J = 7.6, 1.2 Hz, 1 H), 7.29 (m, 3 H), 3.97–
3.90 (m, 1 H), 3.86 (dd, J = 3.8, 15.1 Hz, 1 H), 3.71–3.56 (m, 1 H),
3.53 (dd, J = 9.0, 18.1 Hz, 1 H), 3.38–3.23 (m, 1 H), 2.87 (s, 3 H),
2.42 (s, 3 H).
(10R*,11R*)-11-Methyl-2-thia-1-azatricyclo[8.2.1.03,8]trideca-
3,5,7-triene 2,2-Dioxide (9a) and (10R*,11S*)-11-Methyl-2-thia-
1-azatricyclo[8.2.1.03,8]trideca-3,5,7-triene 2,2-Dioxide (9b)23
Obtained as a 7:3 mixture of 9a and 9b.
13C NMR (75 MHz, CDCl3): δ = 197.3, 144.9, 139.0, 136.0, 134.0,
132.7, 129.6, 128.8, 128.3, 127.9, 125.0, 53.5, 44.1, 35.3, 30.7,
21.8.
HRMS (ESI): m/z [M + Na]+ calcd for C18H19NNaO3S: 352.0978;
found: 352.0980.
9a
Orange oil; yield: 53 mg (35%).
1H NMR (500 MHz, DMSO-d6): δ = 7.89 (dd, J = 1.3, 7.8 Hz, 1 H),
7.57–7.52 (m, 1 H), 7.45 (t, J = 7.8 Hz, 1 H), 7.40 (t, J = 7.6 Hz, 1
H), 3.90 (d, J = 12.9 Hz, 1 H), 3.32 (ddd, J = 1.6, 4.7, 12.9 Hz, 1
H), 3.24–3.16 (m, 2 H), 3.09 (d, J = 15.8 Hz, 1 H), 2.59 (dd, J = 5.1,
13.7 Hz, 1 H), 2.18 (dd, J = 4.7, 7.5 Hz, 1 H), 1.83–1.75 (m, 1 H),
0.92 (d, J = 7.1 Hz, 3 H).
13C NMR (125 MHz, DMSO-d6): δ = 138.8, 136.8, 133.5, 132.7,
129.6, 127.1, 56.2, 55.2, 42.9, 40.9, 34.0, 20.2.
MS (ESI): m/z (%): C12H16NO2S: 238.1 [M + H]+ (100), 185.2 (12).
N-Methoxy-N-methyl-2-(2-methyl-1,1-dioxido-3,4-dihydro-2H-
1,2-benzothiazin-4-yl)acetamide (12d)
Yellow oil: yield: 94 mg (61%) from 11d (194 mg); Rf = 0.24
(hexanes–EtOAc, 4:6).
IR: 2939, 1655, 1421, 1332, 1266, 1169, 997, 944 cm–1.
1H NMR (400 MHz, CDCl3): δ = 7.87 (d, J = 7.6 Hz, 1 H), 7.51 (t,
J = 7.6 Hz, 1 H), 7.41 (t, J = 7.6 Hz, 1 H), 7.32 (d, J = 7.6 Hz, 1 H),
3.83 (dd, J = 4.5, 13.4 Hz, 1 H), 3.76–3.66 (m, 2 H), 3.65 (s, 3 H),
3.22 (s, 3 H), 2.88 (m, 5 H).
13C NMR (100 MHz, CDCl3): δ = 172.0, 138.7, 135.9, 132.6, 128.8,
127.9, 125.0, 61.5, 53.4, 37.6, 35.3, 32.4, 31.0.
9b
Orange oil: yield: 23 mg (15%).
1H NMR (500 MHz, DMSO-d6): δ = 7.72 (dd, J = 1.1, 7.9 Hz, 1 H),
7.57–7.52 (m, 1 H), 7.45 (td, J = 7.6, 1.1 Hz, 1 H), 7.40 (t, J = 7.6
Hz, 1 H), 4.05 (dd, J = 1.9, 14.4 Hz, 1 H), 3.67–3.60 (m, 1 H), 3.56
(dd, J = 1.8, 14.4 Hz, 1 H), 3.00 (s, 1 H), 2.85 (dd, J = 12.3, 14.1
Hz, 1 H), 1.75–1.66 (m, 2 H), 1.52 (tt, J = 6.5, 11.8 Hz, 1 H), 0.70
(d, J = 6.5 Hz, 3 H).
HRMS (ESI): m/z [M + Na]+ calcd for C13H18N2NaO4S: 321.0879;
found: 321.0875.
13C NMR (125 MHz, DMSO-d6): δ = 139.5, 139.4, 132.3, 129.2,
127.7, 123.3, 54.8, 50.3, 39.7, 32.0, 22.7, 18.1.
MS (ESI): m/z (%): C12H16NO2S: 238.1 [M + H]+ (100), 185.2 (12).
2-Methyl-4-vinyl-3,4-dihydro-2H-1,2-benzothiazine 1,1-Diox-
ide (13)
Pale-yellow oil; yield: 50 mg (46%) from 11f (200 mg); Rf = 0.29
(PE–EtOAc, 8:2).
IR: 2924, 1473, 1330, 1161, 923 cm–1.
1-(2-Methyl-1,1-dioxido-3,4-dihydro-2H-1,2-benzothiazin-4-
yl)acetone (12a)
Orange oil: yield: 72 mg (63%) from 11a (150 mg); Rf = 0.11
(hexanes–EtOAc, 7:3).
1H NMR (300 MHz, CDCl3): δ = 7.86 (dd, J = 1.3, 7.7 Hz, 1 H),
7.49 (dd, J = 1.3, 7.6 Hz, 1 H), 7.40 (t, J = 7.6 Hz, 1 H), 7.30 (d, J =
7.7 Hz, 1 H), 5.85–5.67 (m, 1 H), 5.41–5.26 (m, 2 H), 3.98 (dd, J =
10.4, 14.3 Hz, 1 H), 3.90–3.76 (m, 1 H), 3.56 (dd, J = 5.6, 14.3 Hz,
1 H), 2.93 (s, 3 H).
13C NMR (75 MHz, CDCl3): δ = 136.9, 136.8, 135.3, 132.3, 129.9,
128.1, 125.1, 119.9, 53.8, 38.7, 35.9.
IR: 2926, 1715, 1330, 1267, 1162, 1139 cm–1.
1H NMR (300 MHz, CDCl3): δ = 7.82 (d, J = 7.8 Hz, 1 H), 7.47 (td,
J = 7.6, 1.4 Hz, 1 H), 7.38 (t, J = 7.6 Hz, 1 H), 7.21 (d, J = 7.8 Hz,
1 H), 3.72 (ddd, J = 6.4, 13.2, 17.6 Hz, 2 H), 3.56 (dd, J = 6.4, 13.2
Hz, 1 H), 2.95–2.85 (m, 2 H), 2.83 (s, 3 H), 2.18 (s, 3 H).
HRMS (ESI): m/z [M + Na]+ calcd for C11H13NNaO2S: 246.0559;
found: 246.0563.
Synthesis 2013, 45, 810–816
© Georg Thieme Verlag Stuttgart · New York

PAPER
4-Substituted Benzosultams
815
Methyl {(4S/4R)-1,1-Dioxido-2-[(1S)-1-phenylethyl]-3,4-di-
hydro-2H-1,2-benzothiazin-4-yl}acetate (16a,16b)
Yellow oil; yield: 19 mg (27%; dr 55:45) from 11f (87 mg); Rf =
0.18 (hexanes–EtOAc, 2:8).
Acknowledgment
S.F. thanks the Région Rhône-Alpes for a doctoral fellowship and
financial support (Programme Cible 2011-2014). Additional finan-
cial support from Université de Lyon and CNRS is warmly acknow-
ledged. We are indebted to Prof. Ganguly and Dr. Biswas for copies
of spectra of compounds 9.
1H NMR (500 MHz, CDCl3): δ (major) = 7.95–7.81 (m, 1 H), 7.50–
7.38 (m, 3 H), 7.38–7.32 (m, 2 H), 7.31–7.21 (m, 2 H), 7.20–7.05
(m, 1 H), 5.53 (q, J = 7.0 Hz, 1 H), 3.84 (ddd, J = 1.1, 3.7, 14.0 Hz,
1 H), 3.41 (s, 3 H), 3.33 (dd, J = 2.9, 14.0 Hz, 1 H), 3.28 (dq, J =
10.0, 3.7 Hz, 1 H), 2.23 (dd, J = 10.0, 17.7 Hz, 1 H), 2.21–2.12 (m,
1 H), 1.67 (d, J = 7.0 Hz, 3 H). δ (minor) = 7.95–7.81 (m, 1 H),
7.50–7.38 (m, 3 H), 7.38–7.32 (m, 2 H), 7.31–7.21 (m, 2 H), 7.20–
7.05 (m, 1 H,), 5.41 (q, J = 7.0 Hz, 1 H), 3.68 (s, 3 H), 3.53 (dd, J
= 5.4, 14.4 Hz, 1 H), 3.45–3.41 (m, 1 H), 3.14 (dq, J = 10.2, 5.4 Hz,
1 H), 2.71 (dd, J = 9.7, 16.6 Hz, 1 H) and 2.61 (dd, J = 4.4, 16.6 Hz,
1 H), 1.62 (d, J = 7.0 Hz, 3 H).
13C NMR (125 MHz, CDCl3): δ = 171.9 and 171.8, 139.4 and 139.0,
138.5 and 138.3, 138.0 and 137.9, 132.4 and 132.2, 128.9, 128.6
and 128.5, 128.3 and 128.10, 128.05 and 127.97, 127.7, 124.0 and
123.9, 53.8 and 52.0 52.1 and 51.6, 45.2 and 43.0, 39.0 and 37.8,
34.4 and 33.9, 18.3 and 15.5.
Supporting Information for this article is available online at
http://www.thieme-connect.com/ejournals/toc/synthesis.SnoIufproi
m
tgioSrantnugIifoop
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IR: 3058, 1715, 1477, 1331, 1302, 1265, 1168, 929 cm–1.
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7.49 (td, J = 7.6, 1.4 Hz, 1 H), 7.40 (t, J = 7.6 Hz, 1 H), 7.21 (d, J =
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7.49 (td, J = 7.6, 1.4 Hz, 1 H), 7.40 (t, J = 7.6 Hz, 1 H), 7.21 (d, J =
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3.84–3.69 (m, 2 H), 3.65–3.50 (m, J = 6.2 Hz, 1 H), 3.07 (dd, J =
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