Photoisomerization of sultams derived from saccharin; part 3: Dihydro[1]benzothieno[3,2-b]pyrrole 4,4-dioxides from dihydropyrrolo[1,2-b][1,2]benzisothiazole 5,5-dioxides

Article abstract of DOI:10.1055/s-2001-15073

1-Substituted 2,3-dihydropyrrolo[1,2-b][1,2]benzisothiazole 5,5-dioxides 7a-c,e undergo a smooth and efficient transformation into the 2,3-dihydro[1]benzothieno[3,2-b]pyrrole 4,4-dioxides 8a-c,e upon irradiation at 254 nm in acetonitrile. The structures of the products have been elucidated by spectroscopic methods and a single crystal X-ray structure determination for 8b.

Full text of DOI:10.1055/s-2001-15073

PAPER
1223
Photoisomerization of Sultams Derived from Saccharin; Part 3:1,2
Dihydro[1]benzothieno[3,2-b]pyrrole 4,4-Dioxides from Dihydropyrrolo[1,2-
b][1,2]benzisothiazole 5,5-Dioxides
P
hotoge
n
b
eration of
D
r
ihydro[1
a
]benzothien
h
o[3,2-
b
]pyr
im
-Dioxides Elghamry,a Dietrich Döpp,*a Gerald Henkelb
a
Division of Organic Chemistry, Gerhard-Mercator-University Duisburg, 47048 Duisburg, Germany
Fax +(49)2033794192; E-mail: doepp@uni-duisburg.de
b
Division of Solid State Chemistry, Gerhard-Mercator-University Duisburg, 47048 Duisburg, Germany
Received 8 March 2001; revised 23 April 2001
Dedicated to Prof. Howard E. Zimmerman on the occasion of his 75th birthday
nm, whereby the electrophilic substituent on the nitrogen
Abstract: 1-Substituted 2,3-dihydropyrrolo[1,2-b][1,2]benzisothi-
azole 5,5-dioxides 7a–c,e undergo a smooth and efficient transfor-
mation into the 2,3-dihydro[1]benzothieno[3,2-b]pyrrole 4,4-
dioxides 8a–c,e upon irradiation at 254 nm in acetonitrile. The
atom (H, alkoxymethyl) is attached to this oxygen atom
(Scheme 2).1,2 Product 5 is in fact a sulfine hydroxamic
acid derivative, a functional group not accessible in free
structures of the products have been elucidated by spectroscopic form by treating hydroxylamines with sulfinyl halides or
esters.7,8
methods and a single crystal X-ray structure determination for 8b.
Key words: photoisomerization, sultams, dihydro[1]benzothieno-
[3,2-b]pyrrole 4,4-dioxides
The photoreactivity of sulfonamides and sultams is domi-
nated by S–N bond homolysis.3,4 Among five-membered
sultams, saccharin derivatives have been irradiated in so-
lution.1,2,5,6 For example, upon irradiation, 2,3-dihydro-3-
oxo-2-propyl-[1,2]benzisothiazole 1,1-dioxide (1) in eth-
anol or propanol undergoes extrusion of sulfur dioxide to
form N-propylbenzamide (2) by hydrogen uptake, while
Scheme 2
in benzene as solvent N-propylbiphenyl-2-carboxamide
(3) is formed (Scheme 1).5,6
We wanted to clarify whether a similar oxygen shift as in
the case 4
5 would also be possible with [b]fused
[1,2]benzoisothiazole 5,5-dioxides 7. Compounds 7a–c9
have been obtained by intramolecular condensation of the
oxo group with the activated methylene group adjacent to
R in the side chain (Scheme 3). It soon became apparent,
however, that a similar oxygen shift as outlined above did
not take place. We report here the outcome of this photo-
reaction, which appears to be another type of reaction, be-
ing in fact a skeletal rearrangement of 7.
The amide 7e was obtained from the carboxylic acid de-
rivative 7d (R = CO2H), which was prepared by hydrolyz-
ing the methyl ester 7b or the ethyl ester 7c in acetone
with added 10% aqueous sodium hydroxide solution at
room temperature. Upon neutralization with dilute hydro-
chloric acid the carboxylic acid 7d was obtained in good
yield and converted into the acid chloride by boiling with
excess thionyl chloride. The acid chloride in turn was re-
fluxed with p-toluidine in anhydrous benzene to give the
amide 7e. All the new synthesized compounds were un-
ambiguously characterized by both elemental analyses
and spectroscopic techniques.
Scheme 1
When the 3-oxo group is replaced by either two alkyl (or
phenyl) groups or one hydrogen atom and an alkyl (or
phenyl) group as in 4, a net migration of one oxygen atom
from sulfur to nitrogen is observed upon irradiation at 254
The UV spectrum of the ethyl ester 7c shall be discussed
briefly. In acetonitrile, two distinct structureless bands are
observed: A broad band with an onset of absorption at
Synthesis 2001, No. 8, 18 06 2001. Article Identifier:
1437-210X,E;2001,0,08,1223,1227,ftx,en;C03001SS.pdf.
© Georg Thieme Verlag Stuttgart · New York
ISSN 0039-7881

1224
I. Elghamry et al.
PAPER
oxide derivatives 8a–c,e is observed (Scheme 4). The
same result was obtained using methanol as the solvent.
This photochemical isomerization of 7a–c,e to 8a–c,e
could be rationalized through the biradical A which is
formed via homolytical S–N rupture. This biradical is res-
onance stabilized and, following rotation around the C–C
bond, ring-closure occurs from conformer B producing
8a–c,e (Scheme 4). No attempts have been made to trap
the biradical, since intramolecular combination forming a
five-membered ring seemed highly favourable. Practical-
ly it has been noticed that the more electron-withdrawing
the character of the substituent R, the faster the transfor-
mation of 7 into 8. This observation is in complete agree-
ment with the proposed mechanistic pathway. By
monitoring the reaction with thin layer chromatography it
was found that for R = CN (7a) the shortest time was need-
ed for the appearance of the irradiation product in the re-
action medium, and the rate of conversion and the percent
yield of the product (based on the consumed starting ma-
terial) was higher than that of the esters 7c,b, followed by
the amide derivative 7e, which was photolyzed very slow-
ly. The low yield (22% with 63% recovery of 7e) and the
long time of irradiation required for the amide 7e may be
rationalized not only by the low electron-withdrawing ef-
fect of the amide group (especially, if the N-substituent
was aromatic) but also, by the steric influence of the phe-
nyl group which might have hindered the final ring-clo-
sure. Moreover, the presence of the N-phenyl group may
cause a retardation due to absorption of some of the inci-
dent UV light.
Scheme 3
max = 400 nm and max = 324 nm (log = 4.00), and a sec-
ond band ( max = 250 nm, log = 3.91). In benzene, the
long wavelength band appears at the same wavelength and
shows the same intensity as in acetonitrile. Whereas irra-
diation at the long wavelength absorption using Duran-fil-
tered (
280 nm) UV light slowly gave a complex
mixture of products in low yield, it had been found that se-
lective irradiation into the short wavelength absorption
band (254 nm) gave an efficient transformation (see be-
low), which probably involves an higher excited singlet
state.
The structures of 8a–c,e may be delineated primarily from
the mass spectral and NMR data but are firmly supported
by a single crystal X-ray structure determination for com-
pound 8b10 (Figures 1 and 2, Table 1).
When 1-substituted 2,3-dihydropyrrolo[1,2-b][1,2]benz-
isothiazole 5,5-dioxides 7a–c,e are irradiated with the 254
nm emission of the low-pressure mercury lamp in argon-
purged acetonitrile (through a quartz jacket retaining the
185 nm emission), a smooth and efficient isomerization
into the 2,3-dihydro[1]benzothieno[3,2-b]pyrrole 4,4-di-
Scheme 4
Synthesis 2001, No. 8, 1223–1227 ISSN 0039-7881 © Thieme Stuttgart · New York

PAPER
Photogeneration of Dihydro[1]benzothieno[3,2-b]pyrrole 4,4-Dioxides
1225
Table 1 Selected Bond Lengths and Angles of Compound 8b in the
Crystal (The Crystallographic Numbering does not Reflect Systemat-
ic Numbering)
Bond Lengths (pm)
Bond Angles (°)
C9–C8–S
C8–S
181.93 (16)
119.27 (0.119)
110.72 (0.12)
102.19 (0.10)
100.10 (0.12)
113.67 (0.13)
115.07 (0.14)
105.69 (012)
107.47 (013)
C8–C7
C8–C9
C8–C11
C7–N
152.8 (2)
C7–C8–C11
C7–C8–S
152.8 (2)
153.24 (2)
126.83 (2)
176.46 (16)
148.22 (21)
C9–C8–C7
C6–C7–C8
C8–C7–N
C1–S
C10–N
C9–C10–N
C7–N–C10
Figure 1 ORTEP-plot of molecular structure of 8b in the crystal
(the crystallographic numbering does not reflect the systematic num-
bering)
Due to the formation of a new stereogenic centre (C-3a) in
8, the A2X2 pattern of the CH2–CH2 fragment in the nearly
planar 7 is changed into a complicated pattern in 8 giving
rise to the occurrence of several multiplets, one of which
overlaps with the resonances of the diastereotopic ester
methylene protons (in 8b). An attempt to resolve all mul-
tiplets has not been made. Thus, the 1H NMR spectrum of
7b shows two triplets at = 3.33 and 3.81 for 2 H at C-2
and 2 H at C-3, respectively. These four protons in the
product 8b are all under different environments, thus a
pattern of four multiplets at = 2.62, 2.93, 4.33 and 4.65
is obtained. Also, the 13C NMR of 8b reveals a new sp3
carbon signal at = 82.0 attributable to the new quaterna-
ry stereogenic centre (C-3a). The analogous products
8a,c,e likewise show a quaternary carbon at = 70.1, 82.2,
and 83.5, respectively. In the infrared spectra, the carbon-
yl absorption band in 7b (being an , -unsaturated ester)
at 1706 cm–1 was shifted by 19.0 cm–1 towards higher
wavenumber and appeared at 1725 cm–1 in 8b as a typical
value for normal esters.
In summary, we have found a remarkably clean light-in-
duced transformation of pyrrolo[1,2-b][1,2]benzisothiaz-
ole 5,5-dioxides into [1]benzothieno[3,2-b]pyrrole 4,4-
oxides. The formally related case of formation of 3,4-ben-
zo-2-thia-6-azabicyclo[3,2,0]hepta-3,6-dienes initiated
by [2+2] photocycloaddition of electron-rich alkynes to
1,2-benzisothiazoles,11 has been interpreted in a different
way, however.
The NMR spectra were recorded on Bruker WM 300 and DRX 500
spectrometers (300 MHz and 500 MHz, respectively for 1H, 75 and
125 MHz, respectively, for 13C) using TMS as internal standard and
the deuterated solvent as lock. IR spectra were obtained by using a
Perkin–Elmer 983 spectrophotometer (m: medium intense, s:
strong). Electron impact ionisation mass spectrometry (EIMS) was
performed on a Varian AMD 604 instrument using 70 eV ionization
energy. Melting points (mp) are uncorrected. All the chromato-
graphic separations were performed on 48 20 cm glass plates cov-
ered with an air-dry layer (1 mm thick) of silica gel (Merck
Kieselgel PF254). Reactions were monitored by TLC.
Figure 2 Stereo-view of crystal packing of 8b
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1226
I. Elghamry et al.
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N-Substituted 1,2-benzisothiazol-3(2H)-one 1,1-dioxides 6a–c
washed several times with 10% aq NaHCO3 solution, then with
H2O, and air dried.
were prepared following the literature procedure.9
Pale yellow crystals (0.81 g, 74%); mp 219–220°C (EtOH).
UV (MeCN): max (log ) = 250 (4.21) 340 nm (4.29).
IR (KBr): = 3337s (NH), 1648s (C=O), 1359s, 1173s (SO2) cm–1.
1H NMR (DMSO-d6): = 9.51 (s, 1 H, NH), 8.92 (m, 1 H, aryl-H),
8.12 (m, 1 H, aryl-H), 7.85 (m,1 H, aryl-H), 7.81 (m, 1 H, aryl-H),
7.60 (m, 2 H, aryl-H), 7.15 (m, 2 H), 3.82 (t, 2 H, J = 9.0 Hz, 3-H2),
3.52 (t, 2 H, J = 9.0 Hz, 2-H2), 2.30 (s,3 H, CH3).
2,3-Dihydropyrrolo[1,2-b][1,2]benzisothiazole 5,5-Dioxides 7a–
c; General Procedure
To a solution of NaOt-Bu (0.07mol) in tert-butyl alcohol (100 mL)
at 110°C was added powdered 6a–c (0.035 mol) in one lot. The re-
action mixture was kept at 110°C for 20–25 min, then poured into
concd HCl–ice mixture. The resulting solid was filtered, washed
with H2O, and air-dried.
13C NMR (DMSO-d6): = 162.1, 145.5, 139.3, 136.5, 134.3, 133.3,
132.6, 130.9, 129.2, 125.5, 122.2, 121.5, 114.5, 42.2, 33.0, 20.2.
MS: m/z (%) = 340 (M+, 18), 234 (100), 164 (8), 115 (13).
2,3-Dihydropyrrolo[1,2-b][1,2]benzisothiazole-1-carbonitrile 5,5-
Dioxide (7a)
Colorless solid (2.1 g, 23%); mp 227°C (EtOH) (Lit.9a mp 210°C).
UV (MeCN): max (log ) = 250 (3.67), 280 (3.48), 324 nm (3.65).
Anal.Calcd for C18H16N2O3S (340.1) C, 63.53; H, 4.71; N, 8.23; S,
9.47. Found: C, 63.20; H, 4.64; N, 8.12; S, 9.23.
1H NMR (CDCl3): = 8.13 (m, 1 H, aryl-H), 7.88–7.72 (m, 3 H,
aryl-H), 3.94 (t, 2 H, J = 8.8 Hz, 3-H2), 3.32 (t, 2 H, J = 8.8 Hz, 2-
H2).
13C NMR (CDCl3): = 151.1, 139.9, 134.5, 133.4, 124.9, 123.6,
122.3, 115.2, 83.9, 43.4, 34.8.
Photoconversion of 2,3-Dihydropyrrolo[1,2-b]benzisothiazole
5,5-Dioxides 7a–c,e into Dihydro[1]benzothieno[3,2-b]pyrrole
4,4-Dioxides 8a–c,e; General Procedure
Samples of 7a–c,e (1.1 mmol each) in MeCN (80 mL) were irradi-
ated for the time listed using a quartz immersion well in connection
with a Hanau TNN 15 low pressure mercury lamp (15W input) with
continuous argon purging. After concentration the residue was
chromatographed on two silica gel plates with EtOAc–hexane (1:1).
The Rf values of the appropriate zones are given below.
Methyl 2,3-Dihydropyrrolo[1,2-b][1,2]benzisothiazole-1-carbox-
ylate 5,5-Dioxide (7b)
Colorless crystals (0.95 g, 21%); mp 181°C (MeOH) (Lit.9a mp
176°C).
UV (MeCN): max (log ) = 250 (3.60), 3.24 nm (4.03).
2,3-Dihydro[1]benzothieno[3,2-b]pyrrole-3a-carbonitrile 4,4-
Dioxide (8a)
After 3 h irradiation (from zone with Rf 0.25); colorless solid (0.21
g, 91%), mp 184–185°C.
Ethyl 2,3-Dihydropyrrolo[1,2-b][1,2]benzisothiazole-1-carboxyl-
ate 5,5-Dioxide (7c)
Colorless crystals (2.92 g, 54%); mp 153°C (EtOH) (Lit.9b,c mp
152°C).
IR (KBr): = 2242m (CN), 1653m (C=N), 1337s, 1131s (SO2)
cm–1.
UV (MeOH): max (log ) = 250 (3.91), 324 nm (4.00).
1H NMR (CDCl3) = 8.03 (m, 2 H, aryl-H), 7.85 (m, 2 H, aryl-H),
4.85 (m, 1 H, 2-H), 4.63 (m, 1 H, 2-H), 2.85 (m, 2 H, 3-H2).
13C NMR(CDCl3) = 163.6, 146.7, 135.8, 134.3, 129.5, 125.5,
123.5, 112.5, 70.1, 68.2, 32.1.
MS: m/z (%) = 232 (M+, 100), 176 (10), 168 (47), 152 (15), 140
(66), 129 (24), 114 (22), 103 (18), 90 (18), 76 (9).
2,3-Dihydropyrrolo[1,2-b][1,2]benzisothiazole-1-carboxylic
Acid 5,5-Dioxide (7d)
A 10% aq NaOH solution (0.5 mL) was added to a solution of 1.00
g (3.80 mmol) of the methyl ester 7b (or the ethyl ester 7c) in ace-
tone (5 ml) at 0°C. Then the mixture was stirred at r.t. for 4 h (TLC-
monitoring) and H2O (50 mL) was added. The resulting clear solu-
tion was neutralized with dil. HCl and the precipitate was collected
by filtration and washed with H2O.
Anal. Calcd for C11H8N2O2S (232.1): C, 56.89; H, 3.44; N, 12.06;
S, 13.79. Found: C, 56.74; H, 3.49; N, 12.18; S, 13.78.
Colorless crystals (0.89 g, 89%); mp 227°C (EtOH).
Methyl 2,3-Dihydro-[1]benzothieno[3,2-b]pyrrole-3a-carboxylate
4,4-Dioxide (8b)
IR (KBr): = 3200s–2800s (br, OH), 1676s (C=O) 1318s, 1177s
(SO2) cm–1.
After 6 h of irradiation (from zone with Rf 0.26); colorless solid
(0.13g, 86%); mp 170–171°C (MeOH).
1H NMR (DMSO-d6): = 13.0 (s, 1 H, CO2H); 8.94 (m, 1 H, aryl-
H), 8.10 (m, 1 H, aryl-H), 7.81 (m, 2 H, aryl-H), 3.81 (t, 2 H, J = 9.0
Hz, 3-H2) 3.35 ( t, 2 H, J = 9.0 Hz, 2-H2).
13C NMR (DMSO-d6): = 166.1, 146.2, 140.2, 134.1, 133.1, 128.3,
125.3, 122.1, 110.0, 41.3, 34.2.
MS: m/z (%) = 251 (M+, 100), 206 (43), 186 (36), 142 (32), 115
(50), 103 (17), 89 (18), 77 (12).
IR (KBr): = 1725s (C=O), 1648m (C=N), 1315s, 1153s (SO2)
cm–1.
1H NMR (CDCl3): = 7.91 (m, 1 H, aryl-H), 7.75 (m, 1 H, aryl-H),
7.65 (m, 2 H, aryl-H), 4.65 (m,1 H, 2-H), 4.33 (m, 1 H, 2-H), 3.75
(s, 3 H, OCH3), 2.93 (m, 1 H, 3-H), 2.62 (m, 1 H, 3-H).
13C NMR (CDCl3): = 168.4, 164.6, 148.4, 134.7, 133.8, 132.6,
124.0, 122.5, 82.0, 67.0, 54.1, 30.0.
MS: m/z (%) = 265 (M+, 23), 250 (10), 234 (16), 206 (42), 201 (57),
186 (29), 164 (28), 142 (28), 115 (100), 102 (12), 89 (20), 77 (11),
59 (35).
Anal. Calcd for C11H9NO4S (251.1): C, 52.59; H, 3.59; N, 5.58; S,
12.75. Found: C, 52.55; H, 3.53; N, 5.60; S, 12.61.
2,3-Dihydropyrrolo[1,2-b][1,2]benzisothiazole-1-[N-(4-methyl
phenyl)] carboxamide 5,5-Dioxide (7e)
A mixture of 7d (1.10 g, 4.4 mmol) and excess SOCl2 (5 mL) was
refluxed for 4 h at 85–90°C. Then the unreacted SOCl2 was evapo-
rated in vacuo to give the crude acid chloride as a pale yellow solid
which was used directly in the next step. A mixture of the acid chlo-
ride (0.86 g, 3.2 mmol) and p-toluidine (0.34 g, 3.18 mmol) was re-
fluxed for 4 h (TLC-monitoring) in anhyd benzene (50 mL). The
solvent was evaporated completely in vacuo and the residue was
Anal.Calcd. for C12H11NO4S (265.2): C, 54.34; H, 4.15; N, 5.28; S,
12.08. Found: C, 54.15; H, 4.18; N, 5.30; S, 12.10.
Ethyl 2,3-Dihydro-[1]benzothieno[3,2-b]pyrrole-3a-carboxylate
4,4-Dioxide (8c)
After 5 h of irradiation (from zone at Rf 0.18); colorless solid (0.14
g, 88%); mp 84°C (EtOH).
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Photogeneration of Dihydro[1]benzothieno[3,2-b]pyrrole 4,4-Dioxides
1227
IR (KBr): = 1725s (C=O), 1648m (C=N), 1515s, 1153s (SO2)
cm–1.
1H NMR (CDCl3): = 7.95 (m, 1 H, aryl-H), 7.85 (m, 1 H, aryl-H),
7.75 (m, 2 H, aryl-H), 4.65 (m, 1 H, 2-H), 4.25 (m, 3 H, 2-H and
OCH2CH3 overlap), 2.91 (m, 1 H, 3-H), 2.82 (m, 1 H, 3-H), 1.15 (t,
3 H, J = 7.0 Hz).
13C NMR (CDCl3): = 168.2, 164.1, 148.0, 134.1, 133.0, 132.0,
124.1, 122.5, 82.2, 67.2, 64.1, 30.2, 14.1.
MS: m/z (%) = 279 (M+, 11), 250 (13), 234 (24), 215 (100), 186
(43), 164 (52), 151 (23), 142 (70), 129 (18), 115 (86), 101 (73), 89
(22), 77 (14).
(3) Horspool, W. M. In The Chemistry of Sulphonic Acids,
Esters and their Derivatives; Patai, S.; Rappoport, Z., Eds.;
Wiley: New York, 1991, 501; and references cited therein.
(4) Pincock, J. A. In CRC Handbook of Organic Photochemistry
and Photobiology; Horspool, W. M.; Song, Pill-Soon., Eds.;
CRC Press: Boca Raton, 1995, and references cited therein.
(5) Ono, I.; Sato, S.; Fukuda, K.; Inayoshi, T. Bull. Chem. Soc.
Jpn. 1997, 70, 2051.
(6) Kamigata, N.; Saegusa, T.; Fujie, S.; Kobayashi, M. Chem.
Lett. 1979, 9.
(7) Whalen, A. F.; Jones, L. W. J. Am. Chem. Soc. 1925, 47,
1356.
(8) O-Alkyl-N-sulfinyl hydroxyamines, on the other hand, have
been described:.(a) Zinner, G.; Ritter, W. Arch. Pharm.
(Weinheim, Ger.) 1963, 681..(b) Hovius, K.; Engberts, J. B.
F. N. Tetrahedron Lett. 1972, 181..(c) Maricich, T. J.;
Jourdenais, R. A.; Albright, T. A. J. Am. Chem. Soc. 1973,
95, 5831.
(9) (a) Blanco, M.; Perillo, I. A.; Schapira, C. J. Heterocycl.
Chem. 1995, 32, 145..(b) Schapira, C.; Lorenzo, G.; Perillo,
I. A. An. R. Soc. Esp. Fis. Quim., Ser. B 1992, 88, 265..
(c) Chem. Abstr. 1992, 117, 233998.
Anal. Calcd for C13H13NO4S (279.23): C, 55.91; H, 4.65; N, 5.01;
S, 11.46. Found: C, 55.88; H, 4.65; N, 5.00; S, 11.29.
2,3-Dihydro-[1]benzothieno[3,2-b]pyrrole-3a-[N-(4-methylphen-
yl)]carboxamide 4,4-dioxide (8e)
After 24 h of irradiation (from zone with Rf 0.36) colorless solid
(0.06 g, 22%); mp 217–218°C (EtOH).
IR (KBr): = 3303m (NH), 1672m (C=O), 1611m (C=N) 1149s,
1319s cm–1 (SO2).
(10) Crystal data and structure refinement: Crystal size 0.55
0.24 0.18 mm, from MeOH. C12H11NO4S, formula weight
265.28. Triclinic system, P–1. Unit cell dimensions:
a = 6.923(2), b = 7.126(2), c = 12.471(3) Å; = 82.67(2),
= 78.60(2), = 73.52(2)°; Z = 4, cell volume 576.6(3) Å3,
dC = 1.528 g cm–3, = 0.71073 Å (MoK ), = 0.287 mm–1.
1H NMR (CDCl3): = 8.65 (s, 1 H, NH), 8.0 (m, 1 H, aryl-H), 7.91
(m, 1 H, aryl-H), 7.75 (m, 2 H, aryl-H), 7.35 (m, 2 H, aryl-H), 7.10
(m, 2 H, aryl-H), 4.82 (m, 1 H, 2-H), 4.55 (m, 1 H, 2-H), 3.04 (m, 1
H, 3-H), 2.65 (m, 1 H, 3-H), 2.41 (s, 3 H, CH3).
13C NMR (CDCl3): = 168.2, 162.1, 148.5, 137.5, 137.2, 136.8,
136.5, 135.4, 133.5, 130.3, 125.5, 123.5, 120.3, 83.5, 68.3, 51.2,
31.5, 21.1.
F(000) = 276, = 2.99–27.00°, limiting indices –8
–9 8, –15 15. A Siemens P4RA four-circle
diffractometer with graphite monochromator and
h
0,
k
l
MS: m/z (%) = 340 (M+, 25), 234 (100), 115 (44), 102 (21), 89 (21).
scintillation counter was used to collect 2728 reflections,
2514 of which were unique (Rint = 0.0204). -Scan,
transmission range 0.884 0.794. Refinement method: Full-
matrix least-squares on F2, 2514 data, 165 parameters.
Goodness of fit on F2 1.082, final R indices, all data ( I
2 (I)), R1 = 0.0361 (0.0323), wR2 = 0.0885 (0.0855).
Extinction coefficient: 0.013(3). Residual electron density
between –0.367 and 0.445 eÅ–3. The programs SHELXS-97
for crystal structure solution and SHELXL-97 for crystal
structure refinement by Sheldrick, G. M., University of
Göttingen, Germany, 1997 have been used. All
Anal. Calcd for C18H16N2O3S (340.1) C, 63.53; H, 4.71; N, 8.23; S,
9.47. Found: C, 63.21; H, 4.64; N, 8.12; S, 9.23.
Acknowledgement
Dr. I. Elghamry is deeply indebted to Alexander von Humboldt
Foundation for award of a research fellowship during the period
from Dec. 1999 till June 2001 at Duisburg University (Germany).
Generous support by Fonds der Chemischen Industrie is gratefully
acknowledged.
crystallographic data have been deposited at the Cambridge
Crystallographic Data Centre as supplementary publication
no. CCDC-152473. Copies of the data can be obtained free
of charge on application to CCDC, 12 Union Road,
Cambridge CB2 1EZ, UK.
References
(1) Part 1: Döpp, D.; Krüger, C.; Lauterfeld, P.; Raabe, E.
Angew. Chem., Int. Ed. Engl. 1987, 26, 146.
(2) Part 2: Döpp, D.; Lauterfeld, P.; Schneider, M.; Schneider,
D.; Seidel, U. Phosphorus, Sulfur, and Silicon 1994, 95/96,
481.
(11) Sindler-Kulyk, M.; Neckers, D. C. J. Org. Chem. 1983, 48,
1275.
Synthesis 2001, No. 8, 1223–1227 ISSN 0039-7881 © Thieme Stuttgart · New York