A convenient preparation of 2-aroyl-3,3-bis(alkylsulfanyl)acrylaldehydes and their application in the synthesis of 5-aroyl-2-oxo-1,2-dihydro-2- pyridinecarbonitriles

Article abstract of DOI:10.1055/s-2005-918491

The reaction of aroylketene dithioacetals 1 with Vilsmeier-Haack reagent, prepared from POCl₃ and DMF, under mild conditions gave 2-aroyl-3,3-bis(alkylsulfanyl)acrylaldehydes 2 in excellent yields. Cyclization of 2-[2-aroyl-3,3-bis(methylsulfan

Full text of DOI:10.1055/s-2005-918491

PAPER
151
A Convenient Preparation of 2-Aroyl-3,3-bis(alkylsulfanyl)acrylaldehydes
and Their Application in the Synthesis of 5-Aroyl-2-oxo-1,2-dihydro-2-
pyridinecarbonitriles
P
reparation and
n
A
pplication
g
of 2-Aroyl-
3
o
,3-bis(alkyls
o
ulfanyl)acry
r
laldehydes R. Anabha, Chittoorthekkathil V. Asokan*
School of Chemical Sciences, Mahatma Gandhi University, Priyadarshini Hills P. O., Kottayam 686 560, India
Fax +91(481)2731009; E-mail: asokancv@yahoo.com
Received 2 April 2005; revised 4 July 2005
erally, a-formyl derivatives of ketene dithioacetals are
obtained indirectly from the corresponding bis(methylsul-
fanyl)ethylene carboxylates via a reduction–oxidation
process.7 Rudorf et al. reported the synthesis of 2 from
Abstract: The reaction of aroylketene dithioacetals 1 with Vilsmei-
er–Haack reagent, prepared from POCl3 and DMF, under mild con-
ditions gave 2-aroyl-3,3-bis(alkylsulfanyl)acrylaldehydes 2 in
excellent yields. Cyclization of 2-[2-aroyl-3,3-bis(methylsulfanyl)-
2-propylidene]malononitriles 3, derived from 2 and malononitrile, aroylacetaldehydes by treating them with carbon disulfide
in the presence of base, followed by alkylation.8 Most of
in the presence of concentrated hydrochloric acid in tertiary butanol
afforded 2-pyridone derivatives 4.
the 2-aroyl-3,3-bis(alkylsulfanyl)acrylaldehydes 2 have
Key words: ketene dithioacetals, Knoevenagel condensations, cy-
clizations, Vilsmeier–Haack reactions, 2-pyridones
already been reported and were characterized by compar-
ison of their spectral and physical properties with the re-
ported data.
O
The Vilsmeier–Haack reaction is a widely used method
for the formylation of electron-rich aromatic compounds
and alkenes.1 The versatile reactivity of carbonyl com-
pounds with chloromethylene iminium salts and a variety
of cyclization reactions leading to heterocyclic com-
pounds induced by this reagent have been investigated.2
In our earlier reports, we demonstrated the utility of this
reagent in the synthesis of functionalized heterocycles,3
enaldehydes and polyenaldehydes.4 As part of our con-
tinuing interest in the synthetic transformations of a-oxo-
ketene dithioacetals,5 we examined their reactivity
towards the Vilsmeier–Haack reagent. We observed that
acylketene dithioacetals lead to a facile formylation at the
a-position. While these studies were in progress, Dong et
al. reported their findings on the reactions of the
acylketene dithioacetals with the Vilsmeier reagent.6 Here
we report a convenient preparation of 2-aroyl-3,3-
bis(alkylsulfanyl)acrylaldehydes 2 via the formylation of
aroylketene dithioacetals 1 and their application in the
synthesis of 2-pyridone derivatives 4.
O
CHO
1. DMF/POCl3
2. aq K2CO3
Ar
Ar
RS
SR
RS
SR
2
1
Scheme 1
Table 1 2-Aroyl-3,3-bis(alkylsulfanyl)acrylaldehydes 2
2
a
b
c
d
e
f
Ar
R
Yield (%)
98
C6H5
CH3
4-CH3OC6H4
4-CH3C6H4
4-NO2C6H4
4-ClC6H4
4-BrC6H4
2-naphthyl
2-thienyl
C6H5
CH3
96
CH3
83
CH3
92
CH3
90
CH3
98
Dimethyl aroylketene dithioacetals 1a–h were treated
with 1.5 equivalents of the Vilsmeier–Haack reagent pre-
pared from POCl3 and DMF for 12–16 hours at room tem-
perature followed by treatment with a saturated aqueous
solution of K2CO3 to afford 2-aroyl-3,3-bis(methylsulfa-
nyl)acrylaldehydes 2a–h in 62–98% yield. The reactions
of 1-aryl-2-(1,3-dithiolan-2-yliden)-1-ethanone 1i–m and
dibenzylketene dithioacetal 1n with the Vilsmeier–Haack
reagent also resulted in the formation of the corresponding
substituted aldehydes 2i–m and 2n, respectively, in good
yields under similar conditions (Scheme 1, Table 1). Gen-
g
h
i
CH3
98
CH3
62
(CH2)2
(CH2)2
(CH2)2
(CH2)2
(CH2)2
CH2Ph
95
j
4-CH3C6H4
4-ClC6H4
4-BrC6H4
4-CH3OC6H4
C6H5
89
k
l
95
92
m
n
92
62
SYNTHESIS 2006, No. 1, pp 0151–0155
x
x
.
x
x
.2
0
0
5
Advanced online publication: 24.11.2005
DOI: 10.1055/s-2005-918491; Art ID: T04405SS
© Georg Thieme Verlag Stuttgart · New York

152
E. R. Anabha, C. V. Asokan
PAPER
The 2-aroyl-3,3-bis(alkylsulfanyl)acrylaldehydes 2 are along with the 6-methoxy substituted pyridones. The py-
stable at room temperature but easily undergo a deformyl- ridone derivatives 4 could be obtained exclusively when
ation reaction in the presence of bases. We noticed that the the reaction was carried out in the presence of concentrat-
2-benzoyl-3,3-bis(methylsulfanyl)acrylaldehyde 2a is ed hydrochloric acid in tertiary butanol (Scheme 2,
completely converted to benzoylketene dithioacetal 1a on Table 2).
treatment with one equivalent of sodium tertiary butoxide
In conclusion, we have developed a high-yielding proto-
for four hours at room temperature. The preparation of 2-
col for the synthesis of pharmaceutically important 2-py-
aroyl-3,3-bis(alkylsulfanyl)acrylaldehydes from aroyl-
ridone derivatives from readily available starting
materials. The 3-cyano-2-pyridone derivatives 4 are ap-
acetaldehydes could lead to lower yields as a result of the
possible deformylation of the product under the basic re-
action conditions.
propriately functionalized for further aromatic
annulations16 and are potential precursors for the synthe-
Having developed a simple procedure for the preparation sis of a variety of fused heterocycles.
of 2-aroyl-3,3-bis(alkylsulfanyl)acrylaldehydes 2, we be-
came interested in exploring their synthetic potential fur-
ther. Rudorf and co-workers reported applications of
functionalized ketene dithioacetals analogous to 2 in the
Table 2 Yields of 2-[2-Aroyl-3,3-bis(methylsulfanyl)-2-propyl-
idene]malononitrile 3 and 5-Aroyl-6-(methylsulfanyl)-2-oxo-1,2-di-
hydro-3-pyridinecarbonitrile 4
synthesis
of
substituted
thiophenes
and
Product
Ar
Yield (%)
thienothiophenes.9 They have also reported the condensa-
tion of ketene dithioacetals 2 with thiocyanoacetamide
leading to the formation of substituted thiopyridones.10
We have treated 2-aroyl-3,3-bis(alkylsulfanyl)acrylalde-
hydes 2 with malononitrile in the presence of ammonium
acetate in acetic acid and the corresponding Knoevenagel
adducts 3 were formed in 82–91% yields (Table 2).11 The
reaction did not proceed to form the 2-amino pyridines
under these conditions, even after heating for longer peri-
ods.12 Ketene dithioacetals having a push–pull butadiene
moiety similar to 3 are known to undergo cyclization re-
actions under a variety of conditions.13 The conversion of
3 to 2-pyridone derivatives was of interest due to the pres-
ence of this moiety in a number of biologically active mol-
ecules.14 Mosti and co-workers reported that substituted
1,2-dihydro-2-oxo-3-pyridinecarbonitriles show better
cardiac activity compared to the common amrinone- and
milrinone-based drugs used in therapy for congestive
heart failure.15
3, 4
a
3
4
C6H5
82
83
88
84
91
96
94
95
70
94
b
4-CH3OC6H4
4-CH3C6H4
4-NO2C6H4
4-ClC6H4
c
d
e
Melting points were determined on a Büchi 530 melting point appa-
ratus and were not corrected. The IR spectra were recorded from
KBr pellets on a Shimadzu IR-470 spectrometer, and the frequen-
cies are reported in cm–1. 1H NMR spectra were recorded on a Bruk-
er WM 300 (300 MHz) using TMS as internal standard and CDCl3
as solvent. 13C NMR spectra were recorded on a Bruker WM 300
(75.47 MHz) spectrometer using CDCl3 as solvent. Electron impact
mass spectra were obtained on a Finnigan-Mat 312 instrument or a
Shimadzu model GCMS 5050 instrument. CHN analyses were done
on an Elementar Vario EL III Carlo Erba 1108 instrument.
The treatment of 2-[2-aroyl-3,3-bis(methylsulfanyl)-2-
propylidene]malononitrile 3 with concentrated hydro-
chloric acid in refluxing methanol gave 5-aroyl-6-(meth-
All reagents were commercially available and were purified before
use. The previously reported aroylketene dithioacetals were pre-
pared via a known procedure.5 Anhydrous Na2SO4 was used as dry-
ing agent.
ylsulfanyl)-2-oxo-1,2-dihydro-3-pyridinecarbonitrile
4
O
O
2-Aroyl-3,3-bis(alkylsulfanyl)acrylaldehydes 2; General Proce-
dure
CHO
CN
NCCH2CN
Ar
H3CS
Ar
H3CS
The Vilsmeier–Haack reagent was prepared by adding POCl3 (0.67
mL, 7 mmol) to DMF (6 mL, 70 mmol) at 0 °C and stirring the mix-
ture for 20 min at r.t. The appropriate a-oxoketene dithioacetal (4.7
mmol) was added to this mixture, and the solution was stirred well
for 10–16 h (monitored by TLC). The reaction mixture was poured
into cold sat. K2CO3 soln (70 mL) and was extracted with Et2O
(3 × 25 mL). The combined organic layers were washed with H2O
then dried, and the solvent was evaporated. The crude product ob-
tained was filtered through a column with silica gel (EtOAc–hex-
ane, 1:50).
NH4OAc
AcOH
CN
SCH3
SCH3
70 °C
3a–e
2a–e
HCl
t-BuOH
O
CN
Ar
H3CS
N
H
O
2-Benzoyl-3,3-bis(methylsulfanyl)acrylaldehyde (2a)
Pale yellow oil; yield: 1.16 g (98%). The analytical data are in ac-
cord with literature values.8
4a–e
Scheme 2
Synthesis 2006, No. 1, 151–155 © Thieme Stuttgart · New York

PAPER
Preparation and Application of 2-Aroyl-3,3-bis(alkylsulfanyl)acrylaldehydes
153
2-(4-Methoxybenzoyl)-3,3-bis(methylsulfanyl)acrylaldehyde
2-[2-Aroyl-3,3-bis(methylsulfanyl)-2-propylidene]malononi-
triles 3; General Procedure
(2b)
Yellow crystalline solid; yield: 1.27 g (96%); mp 91–92 °C (lit.8 91–
93 °C).
To a mixture of malononitrile (500 mg, 7.5 mmol), NH4OAc (1.5 g,
20 mmol), and AcOH (5 mL) at 70 °C, 2-aroyl-3,3-bis(methylsulfa-
nyl)acrylaldehyde 2 (5 mmol) was added, stirred for 5 min at the
same temperature and then cooled to attain r.t. The reaction mixture
was poured into ice-cold water, extracted with CHCl3 (3 × 25 mL)
then dried, and the solvent was evaporated. The crude product ob-
tained was recrystallized from hexane–EtOAc, 95:5.
2-(4-Methylbenzoyl)-3,3-bis(methylsulfanyl)acrylaldehyde (2c)
Pale yellow oil; yield: 1.04 g (83%). The analytical data are in ac-
cord with literature values.8
3,3-Bis(methylsulfanyl)-2-(4-nitrobenzoyl)acrylaldehyde (2d)
Pale yellow oil; yield: 1.29 g (92%). The analytical data are in ac-
cord with literature values.8
2-[2-Benzoyl-3,3-bis(methylsulfanyl)-2-propenylidene]malono-
nitrile (3a)
Deep yellow crystals; yield: 1.23 g (82%); mp 112–114 °C.
2-(4-Chlorobenzoyl)-3,3-bis(methylsulfanyl)acrylaldehyde (2e)
Pale yellow oil; yield: 1.20 g (90%). The analytical data are in ac-
cord with literature values.8
IR (KBr): 2223, 1667, 1548, 1456, 1306, 1091 cm–1.
1H NMR (300 MHz, CDCl3): d = 2.39 (s, 6 H, SCH3), 7.46–7.52 (m,
2 H, ArH), 7.58–7.65 (m, 1 H, ArH), 7.75–7.82 (m, 2 H, ArH), 8.03
(s, 1 H, vinylic).
13C NMR (75.47 MHz, CDCl3): d = 18.7, 81.6, 111.2, 114.4, 128.6,
129.2, 134.2, 136.4, 144.8, 151.2, 166.4, 192.1.
2-(4-Bromobenzoyl)-3,3-bis(methylsulfanyl)acrylaldehyde (2f)
Pale yellow oil; yield: 1.52 g (98%). The analytical data are in ac-
cord with literature values.8
MS (EI, 70 eV): m/z (%) = 300 (15) [M+], 286 (6), 256 (5), 183 (12),
149 (25), 137 (23), 123 (32), 105 (100).
3,3-Bis(methylsulfanyl)-2-(2-naphthoyl)acrylaldehyde (2g)
Yellow crystalline solid; yield: 1.39 g (98%); mp 78–79 °C.
Anal. Calcd for C15H12N2OS2: C, 59.97; H, 4.03; N, 9.33. Found: C,
60.17; H, 4.05; N, 9.38.
IR (KBr): 3055, 2925, 1670, 1624, 1513, 1287, 1169, 1119, 923,
750 cm–1.
1H NMR (300 MHz, CDCl3): d = 2.37 (s, 6 H, SCH3), 7.42–7.55 (m,
2 H, ArH), 7.78–7.90 (m, 4 H, ArH), 8.27 (s, 1 H, ArH), 10.15 (s, 1
H, CHO).
MS (EI, 70 eV): m/z (%) = 302 (12) [M+], 255 (24), 227 (32), 207
(18), 155 (100), 127 (98), 99 (82), 77 (43).
2-[2-(4-Methoxybenzoyl)-3,3-bis(methylsulfanyl)-2-propenyl-
idene]malononitrile (3b)
Deep yellow crystals; yield: 1.37 g (83%); mp 114–116 °C.
IR (KBr): 2227, 1661, 1601, 1508, 1460, 1299, 1259, 1166, 1024
cm–1.
1H NMR (300 MHz, CDCl3): d = 2.47 (s, 6 H, SCH3), 3.89 (s, 3 H,
OCH3), 6.97 (d, 2 H, J = 8.3 Hz, ArH), 7.83 (d, 2 H, J = 8.3 Hz,
ArH), 8.11 (s, 1 H, vinylic).
13C NMR (75.47 MHz, CDCl3): d = 18.8, 55.6, 81.3, 111.2, 114.4,
114.6, 129.4, 131.8, 136.5, 151.1, 164.6, 165.7, 190.7.
Anal. Calcd for C16H14O2S2: C, 63.55; H, 4.67. Found: C, 63.30; H,
4.69.
3,3-Bis(methylsulfanyl)-2-(2-thienylcarbonyl)acrylaldehyde
(2h)
Yellow crystalline solid; yield:750 mg (62%); mp 60–61 °C (lit.8
61.5–63.5 °C).
MS (EI, 70 eV): m/z (%) = 330 (29) [M+], 205 (5) 135 (100), 107
(9), 77 (19).
2-(1,3-Dithiolane-2-ylidene)-3-oxo-3-phenylpropanal (2i)
Yellow crystalline solid; yield: 1.16 g (95%); mp 103–104 °C (lit.8
100–102 °C).
Anal. Calcd for C16H14N2O2S2: C, 58.16; H, 4.27; N, 8.48. Found:
C, 58.32; H, 4.29; N, 8.51.
2-[2-(4-Methylbenzoyl)-3,3-bis(methylsulfanyl)-2-propenyl-
idene]malononitrile (3c)
Deep yellow crystals; yield: 1.38 g (88%); mp 120–122 °C.
IR (KBr): 2214, 1663, 1594, 1532, 1463, 1287, 1200 cm–1.
2-(1,3-Dithiolane-2-ylidene)-3-(4-methylphenyl)-3-oxopropa-
nal (2j)
Yellow crystalline solid; yield: 1.10 g (89%); mp 152–153 °C (lit.8
152–153 °C).
1H NMR (300 MHz, CDCl3): d = 2.43 (s, 3 H, CH3), 2.46 (s, 6 H,
SCH3), 7.29 (d, 2 H, J = 8.7 Hz, ArH), 7.75 (d, 2 H, J = 8.7 Hz,
ArH), 8.10 (s, 1 H, vinylic).
13C NMR (75.47 MHz, CDCl3): d = 18.8, 21.9, 81.3, 111.3, 114.6,
129.4, 129.8, 133.9, 136.3, 145.5, 151.3, 166.3, 191.8.
3-(4-Chlorophenyl)-2-(1,3-dithiolane-2-ylidene)-3-oxopropa-
nal (2k)
Yellow crystalline solid; yield: 1.27 g (95%); mp 146–147 °C (lit.8
144–146 °C).
MS (EI, 70 eV): m/z (%) = 314 (32) [M+], 297 (6), 133 (9), 119
(100), 91 (48), 65 (27).
3-(4-Bromophenyl)-2-(1,3-dithiolane-2-ylidene)-3-oxopropa-
nal (2l)
Yellow crystalline solid; yield: 1.41 g (92%); mp 144–145 °C (lit.8
144 °C).
Anal. Calcd for C16H14N2OS2: C, 61.12; H, 4.49; N, 8.91. Found: C,
60.92; H, 4.51; N, 8.96.
(1,3-Dithiolane-2-ylidene)-3-(4-methoxyphenyl)-3-oxopropa-
2-[3,3-Bis(methylsulfanyl)-2-(4-nitrobenzoyl)-2-propenyl-
idene]malononitrile (3d)
Deep yellow crystals; yield: 1.4 g (84%); mp 128–130 °C.
IR (KBr): 2219, 1667, 1548, 1524, 1463, 1342, 1290, 1195 cm–1.
nal (2m)
Yellow crystalline solid; yield: 1.17 g (92%); mp 131–132 °C (lit.8
132–133 °C).
1H NMR (300 MHz, CDCl3): d = 2.48 (s, 6 H, SCH3), 8.03 (d, 2 H,
J = 8.3 Hz, ArH), 8.10 (d, 2 H, J = 8.3 Hz, ArH), 8.34 (s, 1 H, vi-
nylic).
2-Benzoyl-3,3-bis(benzylsulfanyl)acrylaldehyde (2n)
Yellow crystalline solid; yield 1.17 g (62%); mp 108–109 °C (lit.8
106–108 °C).
Synthesis 2006, No. 1, 151–155 © Thieme Stuttgart · New York

154
E. R. Anabha, C. V. Asokan
PAPER
13C NMR (75.47 MHz, CDCl3): d = 18.9, 82.3, 111.6, 114.0, 124.2,
130.0, 134.6, 141.3, 150.6, 151.8, 168.1, 190.3.
5-(4-Methylbenzoyl)-6-(methylsulfanyl)-2-oxo-1,2-dihydro-3-
pyridinecarbonitrile (4c)
Colorless crystals; yield: 460 mg (95%); mp 208–210 °C.
IR (KBr): 2365, 2236, 1662, 1568, 1196, 1118 cm–1.
MS (EI, 70 eV): m/z (%) = 345 (17) [M+], 150 (69), 139 (27), 120
(100), 104 (42), 76 (63).
Anal. Calcd for C15H11N3O3S2: C, 52.16; H, 3.21; N, 12.17. Found:
C, 52.31; H, 3.24; N, 12.21.
1H NMR (300 MHz, CDCl3): d = 2.35 (s, 3 H, SCH3), 2.45 (s, 3 H,
CH3), 7.34–7.41 (br m, 4 H, ArH), 8.28 (s, 1 H, H-4), 12.10 (s, 1 H,
NH).
2-[2-(4-Chlorobenzoyl)-3,3-bis(methylsulfanyl)-2-propenyl-
idene]malononitrile (3e)
Deep yellow crystals; yield: 1.52 g (91%); mp 132–134 °C.
IR (KBr): 2220, 1657, 1581, 1544, 1450, 1294, 1206, 1093 cm–1.
1H NMR (300 MHz, CDCl3): d = 2.46 (s, 6 H, SCH3), 7.47 (d, 2 H,
J = 8.3 Hz, ArH), 7.79 (d, 2 H, J = 8.3 Hz, ArH), 8.09 (s, 1 H, vi-
nylic).
13C NMR (75.47 MHz, CDCl3): d = 18.8, 81.5, 111.4, 114.4, 129.4,
130.5, 134.9, 135.3, 140.7, 151.4, 167.2, 190.9.
13C NMR (75.47 MHz, CDCl3): d = 12.7, 21.6, 102.0, 114.3, 117.8,
128.7, 129.3, 129.8, 142.8, 147.8, 154.1, 161.1, 189.4.
MS (EI, 70 eV): m/z (%) = 284 (3) [M+], 268 (17), 253 (18), 237
(100), 219 (4), 209 (6), 194 (19), 179 (12), 153 (14), 127 (14), 118
(33), 91 (30), 77 (9).
Anal. Calcd for C15H12N2O2S: C, 63.36; H, 4.25; N, 9.85. Found: C,
63.60; H, 4.27; N, 9.89.
6-(Methylsulfanyl)-5-(4-nitrobenzoyl)-2-oxo-1,2-dihydro-3-
pyridinecarbonitrile (4d)
Yellow crystals; yield: 440 mg (70%); mp 222–224 °C.
MS (EI, 70 eV): m/z (%) = 336 (7) [M+ + 2], 334 (17) [M+], 319 (4),
142 (28), 139 (100), 110 (30), 75 (18).
IR (KBr): 3425, 2952, 2364, 2227, 1654, 1569, 1521, 1350, 1284
cm–1.
1H NMR (300 MHz, CDCl3): d = 2.61 (s, 3 H, SCH3), 7.78 (s, 1 H,
H-4), 7.86 (d, 2 H, J = 8.8 Hz, ArH), 8.37 (d, 2 H, J = 8.8 Hz, ArH).
MS (EI, 70 eV): m/z (%) = 316 (4) [M+], 230 (4), 193 (6), 165 (11),
149 (12), 129 (18), 120 (24), 95 (32), 81 (63), 69 (100).
Anal. Calcd for C15H11ClN2OS2: C, 53.80; H, 3.31; N, 8.37. Found:
C, 54.07; H, 3.34; N, 8.41.
5-Aroyl-6-(methylsulfanyl)-2-oxo-1,2-dihydro-3-pyridinecar-
bonitriles 4; General Procedure
2-Aroyl-2-[3,3-bis(methylsulfanyl)-2-propylidene]malononitrile 3
(1.7 mmol) was dissolved in t-BuOH (10 mL) and concd HCl (1
mL) was added. The reaction mixture was refluxed for 30 min and
cooled to r.t. Then it was poured into ice-cold water, extracted with
CHCl3, dried, and the solvent was evaporated off. The crude prod-
uct obtained was recrystallized from hexane–EtOAc, 4:1.
Anal. Calcd for C14H9N3O4S: C, 53.33; H, 2.88; N, 13.33. Found:
C, 53.64; H, 2.91; N, 13.39.
5-(4-Chlorobenzoyl)-6-(methylsulfanyl)-2-oxo-1,2-dihydro-3-
pyridinecarbonitrile (4e)
Colorless crystals; yield: 490 mg (94%); mp 210–212 °C.
5-Benzoyl-6-(methylsulfanyl)-2-oxo-1,2-dihydro-3-pyridine-
carbonitrile (4a)
Colorless crystals; yield: 440 mg (96%); mp 224–226 °C.
IR (KBr): 3178, 2364, 2227, 1680, 1643, 1546, 1191 cm–1.
1H NMR (300 MHz, CDCl3): d = 2.35 (s, 3 H, SCH3), 7.25–7.58 (m,
5 H, ArH), 8.45 (s, 1 H, H-4), 13.15 (s, 1 H, NH).
13C NMR (75.47 MHz, CDCl3): d = 12.2, 102.6, 115.0, 127.9,
128.2, 130.7, 131.3, 148.6, 150.3, 154.3, 166.7, 188.6.
IR (KBr): 3405, 3054, 2896, 2226, 1727, 1656, 1485, 1187, 1092
cm–1.
1H NMR (300 MHz, CDCl3): d = 2.73 (s, 3 H, SCH3), 7.40 (d, 2 H,
J = 8 Hz, ArH), 7.46 (d, 2 H, J = 8 Hz, ArH), 8.32 (s, 1 H, H-4).
13C NMR (75.47 MHz, CDCl3): d = 12.1, 102.6, 114.7, 116.4,
127.8, 128.2, 130.1, 136.5, 146.6, 153.2, 159.8, 188.3.
MS (EI, 70 eV): m/z (%) = 304 (9) [M+], 288 (18), 273 (24), 257
(100), 232 (13), 222 (33), 194 (19), 174 (29), 138 (43), 111 (29), 75
(35).
MS (EI, 70 eV): m/z (%) = 270 (6) [M+], 229 (15), 223 (100), 198
(8), 180 (22), 140 (38), 104 (52), 95 (51), 83 (76).
Anal. Calcd for C14H9ClN2O2S: C, 55.18; H, 2.98; N, 9.19. Found:
C, 55.39; H, 3.01; N, 9.26.
Anal. Calcd for C14H10N2O2S: C, 62.21; H, 3.73; N, 10.36. Found:
C, 62.40; H, 3.75; N, 10.41.
5-(4-Methoxybenzoyl)-6-(methylsulfanyl)-2-oxo-1,2-dihydro-3-
pyridinecarbonitrile (4b)
Acknowledgment
Yellow crystals; yield: 480 mg (94%); mp 194–196 °C.
This work was supported by Kerala State CSTE and CSIR New
Delhi [Project No. 01(1954)/04/EMR-II]. We thank CDRI, Luck-
now and SIF, IISc, Bangalore for spectral and elemental analyses.
E.R.A. thanks CSIR for a research fellowship.
IR (KBr): 2965, 2365, 2225, 1646, 1610, 1310, 1263, 1186, 1025
cm–1.
1H NMR (300 MHz, CDCl3): d = 2.39 (s, 3 H, SCH3), 3.87 (s, 3 H,
OCH3), 7.15 (d, 2 H, J = 8.8 Hz, ArH), 7.47 (d, 2 H, J = 8.8 Hz,
ArH), 8.26 (s, 1 H, H-4), 12.18 (br s, 1 H, NH).
13C NMR (75.47 MHz, CDCl3): d = 12.7, 55.5, 102.0, 114.5, 117.7,
122.8, 130.5, 130.8, 147.8, 153.8, 161.3, 162.7, 189.7.
MS (EI, 70 eV): m/z (%) = 301 (11) [M+], 284 (19), 269 (18), 253
(100), 238 (10), 210 (18), 182 (12), 170 (13), 127 (23), 119 (15), 91
(13), 77 (13).
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