SYNTHESIS AND PROPERTIES OF SUBSTITUTED 1-(2-BENZOTHIAZOLYL)-2-PYRIDONES

Article abstract of DOI:10.1135/cccc19950999

The studied 1-(2-benzothiazolyl)-2-pyridones Va-Vf were prepared from N-(2-benzothiazolyl)cyanoacetamide (II) which on reaction with 4-substituted benzaldehydes afforded 3-aryl-N-(2-benzothiazolyl)-2-cyano-2-propenamides IVa-IVg.Compounds IVa-IVf were cyclized with malonodinitrile in the presence of piperidine to give the corresponding pyridones Va-Vf.

Full text of DOI:10.1135/cccc19950999

1-(2-Benzothiazolyl)-2-pyridones
999
SYNTHESIS AND PROPERTIES OF SUBSTITUTED
1-(2-BENZOTHIAZOLYL)-2-PYRIDONES
a
a
b
c
a
Jarmila STETINOVA , Rudolf KADA , Jan LESKO , Lubomir ZALIBERA , Dusan ILAVSKY
a
and Alexander BARTOVIC
a Department of Organic Chemistry,
Slovak Technical University, 812 37 Bratislava, The Slovak Republic
b Mass Spectrometry Laboratory,
Slovak Technical University, 812 37 Bratislava, The Slovak Republic
c Department of Physical Chemistry,
Slovak Technical University, 812 37 Bratislava, The Slovak Republic
Received January 19, 1995
Accepted March 9, 1995
The studied 1-(2-benzothiazolyl)-2-pyridones Va–Vf were prepared from N-(2-benzothiazolyl)-
cyanoacetamide (II) which on reaction with 4-substituted benzaldehydes afforded 3-aryl-N-(2-benzo-
thiazolyl)-2-cyano-2-propenamides IVa–IVg. Compounds IVa–IVf were cyclized with malonodinitrile
in the presence of piperidine to give the corresponding pyridones Va–Vf.
The significant biological properties and utilization of various benzothiazoles1,2 on the
one hand and pyridones3,4 on the other have influenced the research in these two re-
gions. In this context, derivatives containing both the mentioned moieties in the mole-
cule are also of interest.
The present communication concerns the synthesis and study of properties of some
substituted 1-(2-benzothiazolyl)-2-pyridones Va–Vf which were synthesized starting
from 2-aminobenzothiazole5 (I).
1-Cyanoacetyl-3,5-dimethylpyrazole6 (III), an effective reagent for cyanoacetylation
of various amino derivatives7, reacted with amine I in boiling toluene to give the corre-
sponding cyanoacetamide II in 91% yield.
Collect. Czech. Chem. Commun. (Vol. 60) (1995)

1000
Stetinova, Kada, Lesko, Zalibera, Ilavsky, Bartovic:
3-Aryl-N-(2-benzothiazolyl)-2-cyano-2-propenamides IVa–IVg were obtained in
very good yields (75–95%; see Table I) by Knoevenagel reaction of the C-acid II with
4-substituted benzaldehydes. The condensation was performed at elevated temperature
in 10% ethanolic sodium hydroxide or in boiling solution of potassium acetate in acetic
acid.
As shown below, 2-propenamides of general formula IV are suitable precursors for
the synthesis of polysubstituted 2-pyridones V. Although many authors prepared 2-pyri-
dones in various ways8–10, a synthesis starting from derivatives IV has not been de-
scribed so far.
The desired 6-amino-4-aryl-1-(2-benzothiazolyl)-3,5-dicyano-2-pyridones Va–Vf
were prepared by treatment of N-(2-benzothiazolyl)-2-propenamides IVa–IVf with ma-
lonodinitrile in boiling ethanol in the presence of piperidine (yields 17–34%). The reac-
Collect. Czech. Chem. Commun. (Vol. 60) (1995)

1-(2-Benzothiazolyl)-2-pyridones
1001
TABLE I
Melting points, yields and analytical data for compounds IVa–IVg and Va–Vf
Calculated/Found
M.p., °C
Yield, %
Formula
(M.w.)
Compound
% C
% H
% N
% S
IVa
IVb
IVc
IVd
IVe
IVf
IVg
Va
221–223a
C17H11N3OS
(305.3)
66.87
67.67
3.63
3.47
13.76
13.98
10.50
10.71
95
235–236a
C18H13N3OS
(319.4)
67.69
66.96
4.10
4.24
13.16
13.18
10.04
10.20
75
236–237a
C18H13N3O2S
(335.4)
64.46
63.70
3.91
3.96
12.53
12.50
9.56
9.22
90
239–241b
C17H10ClN3OS
(339.8)
60.09
59.52
2.97
3.02
12.37
12.47
9.44
9.34
77
280–282b
C17H10N4O3S
(350.3)
58.28
58.53
2.88
2.85
15.99
16.23
9.15
9.39
91
280–282a
C18H10N4OS
(330.4)
65.44
64.67
3.05
3.12
16.96
17.00
9.71
9.99
91
292–294c
C19H16N4OS
(348.4)
65.49
64.85
4.63
4.72
16.08
16.31
9.20
9.33
86
299–302b
C20H11N5OS
(369.4)
65.03
65.46
3.00
3.12
18.96
19.05
8.68
8.63
34
Vb
299–301b
C21H13N5OS
(383.4)
65.78
65.52
3.42
3.41
18.27
18.42
8.36
8.47
17
Vc
308–311b
C21H13N5O2S
(399.4)
64.15
63.59
3.28
3.28
17.53
17.80
8.03
8.13
17
315–317c
59.48
59.49
57.96
57.79
63.92
64.28
2.50
2.76
2.43
2.54
2.56
2.68
17.34
17.57
20.28
20.38
21.31
21.52
7.94
7.60
7.74
7.79
8.13
8.00
Vd
C20H10ClN5OS
(403.8)
25
306–309c
32
Ve
C20H10N6O3S
(414.4)
306–311c
Vf
C21H10N6OS
(394.4)
33
Crystallized from: a ethanol, b acetic acid, c N,N-dimethylformamide.
Collect. Czech. Chem. Commun. (Vol. 60) (1995)

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Stetinova, Kada, Lesko, Zalibera, Ilavsky, Bartovic:
TABLE II
Infrared (in KBr) and UV spectra (in dioxane, c 1 . 10−4 mol l−1) of compounds II, IVa–IVg and
Va–Vf
IR spectrum, cm−1
ν(C≡N)
UV spectrum
Compound
ν(NH)a
ν(C=O)
λmax, nm
log ε
II
3 293
2 261
1 690
220
275
298
3.30
3.14
2.94
IVa
IVb
IVc
IVd
IVe
3 177
3 320
3 248
3 290
3 175
2 226
2 218
2 220
2 218
2 238
1 669
1 688
1 676
1 684
1 690b
222
334
3.40
3.30
222
340
3.39
3.44
218
360
3.42
3.60
223
335
3.40
3.40
217
321
363
3.31
3.13
3.14
IVf
3 351
3 274
2 231
2 228
1 688b
1 673
217
306
358
3.46
3.40
3.34
IVg
2 216
2 210
2 209
2 215
218
263
321
434
3.40
3.09
2.80
3.67
Va
Vb
Vc
Vd
3 319
3 318
3 312
3 326
1 676
1 676
1 676
1 678
216
276
305c
381
3.58
3.51
3.11
3.08
217
279
308c
381
3.59
3.48
3.28
3.05
217
278
331
375c
3.61
3.44
3.35
3.06
2 224
2 210
217
278
310c
379
3.58
3.50
3.14
3.05
Collect. Czech. Chem. Commun. (Vol. 60) (1995)

1-(2-Benzothiazolyl)-2-pyridones
1003
TABLE II
(Continued)
IR spectrum, cm−1
ν(C≡N)
UV spectrum
Compound
ν(NH)a
ν(C=O)
λmax, nm
log ε
Ve
Vf
3 304
2 218
1 680
217
273
305c
382
3.62
3.60
3.25
3.09
3 301
2 218
1 678
217
268
310c
381
3.57
3.49
3.03
3.03
a For compounds Va–Vf ν(NH2); b significantly lower band intensity; c shoulder.
TABLE III
1H NMR data (δ, ppm; J, Hz) of compounds IVa–IVg in (CD3)2SO
Com-
pound
H-4′
J(4′,5′)
H-5′
J(5′,6′) J(6′,7′)
H-6′
NH
H-3
H-7′
Other signals
a
IVa
9.96 s 8.49 s 7.96 d
7.9
7.48 t 7.34 t 8.06–7.98 m and 7.70–7.55 m, 2 H and 4
7.8
7.3
H (phenyl and H-7′ of 2-benzo-
thiazolyl)
IVb
IVc
IVd
IVe
IVf
9.90 s 8.37 s 7.88 d 7.61
8.3
7.46 t 7.32 t 7.88 d and 7.36 d, 2 H and 2 H, J = 8.3
8.3 8.3 (4-methylphenyl); 2.36 s, 3 H (CH3)
9.81 s 8.40 s 7.90 d 7.63 d 7.45 t 7.31 t 8.03 d and 7.12 d, 2 H and 2 H, J = 8.9
7.9 7.4 7.9 (4-methoxyphenyl); 3.08 s, 3 H (OCH3)
9.95 s 8.47 s 7.98 d 7.62 d 7.50 t 7.36 t 8.05 d and 7.69 d, 2 H and 2 H, J = 8.6
8.1 7.2 7.7 (4-chlorophenyl)
–
8.57 s 7.96 d 7.64 d 7.51 t 7.37 t 8.39 d and 8.22 d, 2 H and 2 H, J = 8.9
7.9 7.3 7.7 (4-nitrophenyl)
–
8.52 s 7.98 d 7.61 d 7.50 t 7.35 t 8.16 d and 8.06 d, 2 H and 2 H, J = 8.2
7.7 7.1 7.7 (4-cyanophenyl)
IVg
9.63 s 8.24 s 7.89 d 7.64 d 7.44 t 7.30 t 7.91 and 6.83 d, 2 H and 2 H, J = 9.1
7.9
7.0
7.7
(4-dimethylaminophenyl); 3.06 s, 3 H
((CH3)2N)
a Multiplet 7.70–7.55, 4 H (H-3″, H-4″, H-5″ of phenyl and H-7′ of 2-benzothiazolyl).
Collect. Czech. Chem. Commun. (Vol. 60) (1995)

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Stetinova, Kada, Lesko, Zalibera, Ilavsky, Bartovic:
tion proceeds probably as the Michael addition of malonodinitrile to the α,β-unsatu-
rated system followed by cyclization.
The structure of N-(2-benzothiazolyl)cyanoacetamide (II), substituted 2-propen-
amides IVa–IVg and 1-(2-benzothiazolyl)-2-pyridones Va–Vf was confirmed by their
spectral data and elemental analyses (Tables I–VI). In addition to the characteristic
bands, the infrared spectra of compounds IVa–IVg show also a weak band at 1 591–1 614 cm−1
due to C=C bond (Table II). The amide hydrogen in derivatives IVe and IVf is appa-
rently more acidic and the compounds are partly enolized; this results in the observed
lower intensity of the ν(C=O) band.
The extended conjugated system in compounds IVa–IVg (as compared with N-(2-
benzothiazolyl)cyanoacetamide (II)) manifests itself in the UV spectra (Table II) not
only by a bathochromic shift of the maxima (36–136 nm, according to the substituent)
but also by increased intensity of the bands. The pyridone grouping in derivatives Va–Vf is
characterized by an absorption maximum in the region 375–382 nm (shifted to the
visible region only by 15–49 nm relative to the corresponding derivatives IVa–IVf).
1
The H NMR data confirm unequivocally the structure of the synthesized com-
pounds. In the spectra of substituted 2-propenamides IVa–IVg (Table III) the olefinic
TABLE IV
1H NMR data (δ, ppm; J, Hz) of compounds Va–Vf in (CD3)2SO
H-4′
J(4′,5′)
H-7′
J(6′,7′)
Compound
NH2
Other signals
Va
Vb
8.71 bs
8.70 bs
8.22 d
7.4
8.12 d
7.8
7.70–7.55 m, 7 H (H-5′ and H-6′
of 2-benzothiazolyl and phenyl)
8.22 d
8.0
8.12 d
7.3
7.68–7.55 m, 2 H (H-5′ and H-6′
of 2-benzothiazolyl); 7.48 d and 7.40 d, 2 H and 2 H,
J = 7.9 (4-methylphenyl); 2.43 s, 3 H (CH3)
Vc
Vd
Ve
Vf
8.69 bs
8.79 bs
8.82 bs
8.82 bs
8.22 d
8.2
8.12 d
7.7
7.67–7.58 m, 2 H (H-5′ and H-6′
of 2-benzothiazolyl); 7.56 d and 7.15 d, 2 H and 2 H,
J = 8.7 (4-methylphenyl); 3.88 s, 3 H (OCH3)
8.22 d
8.12 d
7.6
7.73 d and 7.65 d, 2 H and 2 H, J = 8.7
(4-chlorophenyl); 7.65–7.56 m, 2 H (H-5′ and H-6′ of
2-benzothiazolyl)
8.23 d
7.1
8.12 d
7.2
8.43 d and 7.88 d, 2 H and 2 H, J = 8.7
(4-nitrophenyl); 7.68–7.56 m, 2 H (H-5′ and H-6′
of 2-benzothiazolyl)
8.22 d
7.1
8.13 d
7.5
8.07 d and 7.79 d, 2 H and 2 H, J = 7.7
(4-cyanophenyl); 7.72–7.52 m, 2 H (H-5′ and H-6′ of
2-benzothiazolyl)
Collect. Czech. Chem. Commun. (Vol. 60) (1995)

1-(2-Benzothiazolyl)-2-pyridones
1005
proton H-3 appears as a singlet at δ 8.57–8.24. Proton spectra of 1-(2-benzothiazolyl)-
2-pyridones Va–Vf (Table IV) exhibit a broad signal at δ 8.82–8.69 due to protons of
the amino group. As expected, the highest effect of the substituent R was on the signals
of phenyl protons H-2″, H-6″ and H-3″, H-5″ at δ 7.88–7.48 and 8.64–7.15, respec-
tively. Practically no change was observed for the benzothiazole protons H-4′ and H-7′
(δ 8.23–8.22 and 8.13–8.12, respectively). Analogously, in the 13C NMR spectra of
compounds Va–Vf (Table V) the highest effect of substituent R was observed on carbon
atoms of the ring to which the substituent was attached.
The principal fragmentation pattern in the mass spectra of compounds IVa–IVg
(Table VI) are depicted in Scheme 1.
The molecular ion peaks in the mass spectra of pyridones Va–Vf (Table VI) belong
to the most intensive ones. For most of these derivatives (except Vc and Ve), ions
•
[M − H ]+ represent the base peaks. On the other hand, the loss of water from the
molecular ions contributes only very little (less than 10%) to the fragmentation pattern.
The relative abundance of fragment ions formed by loss of carbon monoxide from M+•
ions amounts to 10–20%. Within this range of relative intensities are present also the
benzothiazole ions m/z 135, arising by fission of the C−N bond and hydrogen transfer.
Mass spectra of all the pyridone derivatives exhibit also fragment ions of m/z 177 and
m/z 150, formed by fission of bonds in the pyridine ring. The loss of the substituent R
from the molecular ion is marked only in the case of the nitro group (Vf) where it gives
rise to the ion of m/z 369 (49%).
SCHEME 1
Collect. Czech. Chem. Commun. (Vol. 60) (1995)

1006
Stetinova, Kada, Lesko, Zalibera, Ilavsky, Bartovic:
EXPERIMENTAL
The melting points were determined on a Kofler block. IR spectra were recorded on a FTIR PU9800
(Philips) spectrometer, UV spectra (λ in nm, ε in m2 mol−1) on a Specord UV-VIS M-40 (Zeiss,
Jena) instrument. Proton and 13C NMR spectra were measured on a Varian VXR-300 spectrometer
1
(300 MHz for H and 60 MHz for 13C) in hexadeuteriodimethyl sulfoxide with tetramethylsilane as
internal standard. Chemical shifts are given in ppm (δ-scale), coupling constants J in Hz). The 13C NMR
spectra were assigned using the SINEPT and HETCOR techniques and a set of CHEM3WIND pro-
grams. Mass spectra (EI) were taken on an MS 902 S (A.E.I. Manchester) spectrometer; direct
inlet, electron energy 70 eV, trap current 100 µA, ion source temperature 220–240 °C (for Va–Vf) or
150–200 °C (for II, IVa–IVg).
N-(2-Benzothiazolyl)cyanoacetamide (II)
A solution of 1-cyanoacetyl-3,5-dimethylpyrazole6 (III; 16.3 g, 100 mmol) in anhydrous toluene (150 ml)
was added to a solution of 2-aminobenzothiazole5 (I; 15.0 g, 100 mmol) in toluene (200 ml) and the
mixture was refluxed for 4 h. After cooling, the deposited solid was collected and crystallized from
acetic acid, yield 19.7 g (91%), m.p. 246–248 °C. For IR, UV and mass spectra see Tables II and VI.
1H NMR spectrum: 7.93 d, 1 H (H-4, J(4,5) = 7.9, J(4,6) = 1.3); 7.73 d, 1 H (H-7, J(7,6) = 7.9,
TABLE V
13C NMR data (δ, ppm; J, Hz) of compounds Va–Vc, Ve–Vf in (CD3)2SO
13C NMR spectum
Compounda
C-2
C-3
C3-CN
C-4
C-5
C5-CN
C-6
C-2
C-3′a
Va
Vb
Vc
Ve
Vf
156.5
156.5
156.5
156.6
156.6
75.8
75.8
75.8
75.6
75.6
114.6
114.8
114.9
114.3
114.3
162.1
162.1
160.8
160.1
160.4
88.0
87.6
87.4
87.6
87.6
115.0
115.2
115.3
114.7
114.8
154.1
154.1
154.2
153.8
153.9
158.7
158.8
158.8
158.5
158.5
149.2
149.2
149.2
149.4
149.4
C-2″
C-6″
C-3″
C-5″
C-4′
C-5′
C-6′
C-7′
C-7′a
C-1″
C-4″
Va
Vb
Vc
Ve
Vf
122.2
122.2
122.2
122.3
122.2
126.0
126.0
126.0
126.0
126.0
126.1
126.1
126.1
126.1
126.2
123.3
123.3
123.3
123.3
123.7
136.5
136.5
136.4
136.6
136.6
134.2
131.3
126.1
140.5
138.8
127.4b
128.8b
129.4
129.2
128.6
128.2b
127.5b
113.8
123.5
123.3
130.0
140.0
161.7
148.5
113.0
a
b
Additional signals: for Vb 20.3 (CH3), for Vc 55.1 (OCH3), for Vf 117.6 (C4″-CN); the signals
may be interchanged.
Collect. Czech. Chem. Commun. (Vol. 60) (1995)

1-(2-Benzothiazolyl)-2-pyridones
1007
J(7,5) = 1.3); 7.44 dt, 1 H (H-5, J(5,6) = 7.6); 7.31 dt, 1 H (H-6); 4.02 s, 2 H (CH2). 13C NMR
spectrum: 163.1 (C=O); 26.38 (CH2); 115.1 (CN); 157.9 (C-2); 148.2 (C-3a); 120.8 (C-4); 124.2 (C-5);
126.6 (C-6); 121.9 (C-7); 131.6 (C-7a). For C10H7N2OS (217.2) calculated: 55.28% C, 3.25% H,
19.34% N, 14.76% S; found: 55.44% C, 3.24% H, 19.40% N, 14.32% S.
General Procedure for Preparation of 3-Aryl-N-(2-benzothiazolyl)-2-cyano-2-propenamides IVa–IVc
and IVg
A stirred mixture of 4-substituted benzaldehyde (5 mmol), N-(2-benzothiazolyl)cyanoacetamide (II;
1.08 g, 5 mmol), anhydrous potassium acetate (1.96 g, 20 mmol) and acetic acid (20 ml) was re-
fluxed for 3 h. After pouring on ice, the crude product was filtered, washed with water, dried and
crystallized from an appropriate solvent. For yields, melting points and elemental analyses see Table I.
TABLE VI
Mass spectra (EI) of derivatives II, IVa–IVg and Va–Vf. For each compound 10 most abundant peaks
are given.
Compound
m/z (relat. abundance, %)
II
217(M+•, 37), 178(8), 151(7), 150(100), 149(9), 123(10), 115(8), 108(7), 69(6), 45(6)
IVa
305(M+•, 76), 304(21), 277(20), 276(26), 200(24), 156(100), 150(64), 128(87),
101(33), 77(42)
IVb
IVc
IVd
IVe
IVf
IVg
Va
320(19), 319(M+•, 76), 318(17), 291(14), 290(15), 170(100), 150(35), 142(26),
116(16), 115(64)
336(15), 335(M+•, 63), 334(21), 187(19), 186(100), 158(37), 150(15), 143(12),
115(11), 77(10)
341(29), 339(M+•, 73), 338(21), 310(25), 192(33), 190(100), 162(53),150(47),
127(49), 126(37)
350(M+•, 100), 322(34), 321(34), 228(43), 201(29), 200(62), 177(35), 155(86),
150(52), 127(44)
330(M+•, 95), 329(35), 302(31), 301(44), 228(30), 200(47), 181(69), 153(100),
150(81), 126(40)
349(6), 348(M+•, 25), 347(12), 200(16), 199(100), 172(5), 171(35), 156(7), 155(5),
134(8)
370(25), 369(M+•, 98), 368(100), 341(14), 303(11), 177(12), 165(11), 150(24),
135(17), 96(12)
Vb
384(27), 383(M+•, 98), 382(100), 355(16), 177(18), 150(34), 149(10), 135(15),
108(11), 96(11)
Vc
400(26), 399(M+•, 100), 398(90), 371(11), 355(9), 333(8), 177(14), 150(37), 149(9),
135(11)
Vd
405(36), 404(59), 403(M+•, 93), 402(100), 375(13), 177(17), 150(33), 135(20),
123(14), 96(14)
Ve
415(27), 414(M+•, 100), 413(81), 383(19), 367(49), 177(27), 176(32), 150(42),
149(17), 135(19)
Vf
395(23), 394(M+•, 80), 393(100), 366(14), 177(15), 150(29), 149(19), 135(24),
108(15), 96(18)
Collect. Czech. Chem. Commun. (Vol. 60) (1995)

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Stetinova, Kada, Lesko, Zalibera, Ilavsky, Bartovic:
General Procedure for Preparation of 3-Aryl-N-(2-benzothiazolyl)-2-cyano-2-propenamides IVd–IVf
A solution of 4-substituted benzaldehyde (5 mmol) in ethanol (20 ml) and 10% aqueous sodium hy-
droxide (5 drops) were added to a stirred boiling solution of N-(2-benzothiazolyl)cyanoacetamide (II;
1.08 g, 5 mmol) in ethanol (50 ml). The reaction mixture was kept at reflux for 2 h (compound IVd)
or 15 min (compounds IVe and IVf) and then gradually cooled to ambient temperature (5 h) with
stirring. The crude product was purified by crystallization from an appropriate solvent. For yields,
melting points and elemental analyses see Table I.
General Procedure for Preparation of 6-Amino-4-aryl-1-(2-benzothiazolyl)-3,5-dicyano-2-pyridones
Va–Vf
A mixture of 3-aryl-N-(2-benzothiazolyl)-2-cyano-2-propenamide IVa–IVf (3 mmol), malonodinitrile
(0.26 g, 4 mmol), piperidine (4 drops) and anhydrous ethanol (60 ml) was refluxed for 6 h. After
cooling, the solid was filtered and crystallized from an appropriate solvent. For yields, melting points
and elemental analyses see Table I.
The authors are indebted to Mrs K. Wiesingerova for the technical assistance, to Mrs M. Hrobonova
for measurement of the UV spectra and Mrs S. Markusova for recording the IR spectra. This work was
supported by the Grant Agency of Ministery of Education of the Slovak Republic (grant No. 1/1415/94).
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Collect. Czech. Chem. Commun. (Vol. 60) (1995)