Dimethylformamide dimethyl acetal in heterocyclic synthesis: Synthesis of polyfunctionally substituted pyridine derivatives as precursors to bicycles and polycycles [1,2]

Article abstract of DOI:10.1002/jhet.5570440406

(Chemical Equation Presented) Polysubstituted pyridines 11a,c and 12 were prepared by the reaction of benzoylacetone with dimethylformamide dimethyl acetal followed by treatment with cyanothioacetamide 9a, cyanoacetamide 9b and the anion of malononitrile dimmer 9c in dry DMF. When the reaction was carried out in ethanol as a solvent and piperidine as a base afforded 14a,b. Thienopyridines 16a,b were prepared by the reaction of pyridinethiones 11a and 14a with 2-chloro-N-p-tolyl-acetamide (15). Further reaction of thienopyridines 16a,b with either DMFDMA or nitrous acid to gave 17a,b and 18a,b respectively. The reaction of pyridine derivative 11c with hydrazine and phenylhydrazine afforded the tricyclic compounds 19a,b.

Full text of DOI:10.1002/jhet.5570440406

Jul-Aug 2007
787
Dimethylformamide Dimethyl Acetal in Heterocyclic Synthesis:
Synthesis of Polyfunctionally Substituted Pyridine Derivatives as
Precursors to Bicycles and Polycycles [1,2]
Fathi A. Abu-Shanab*, A. M. Hessen, and S. A. S. Mousa
Chemistry Department, Faculty of Science, Al-Azhar University, Assiut 71524, Egypt.
e-mail: fathorg82@hotmail.com
Received April 29, 2006
O
O
CH3
X
X
O
O
Y
X
CN
X
CN
CN
Ph
H2N
H2N
EtOH/Et3N
NMe2
H3C
N
H
N
H
H3C
DMF/NaH
X = S, Y = CN
X = O, Y = CONH2
X = C(CN)2 , Y = CN
X = S
X = C(CN)2
Polysubstituted pyridines 11a,c and 12 were prepared by the reaction of benzoylacetone with dimethyl-
formamide dimethyl acetal followed by treatment with cyanothioacetamide 9a, cyanoacetamide 9b and the
anion of malononitrile dimmer 9c in dry DMF. When the reaction was carried out in ethanol as a solvent
and piperidine as a base afforded 14a,b. Thienopyridines 16a,b were prepared by the reaction of
pyridinethiones 11a and 14a with 2-chloro-N-p-tolyl-acetamide (15). Further reaction of thienopyridines
16a,b with either DMFDMA or nitrous acid to gave 17a,b and 18a,b respectively. The reaction of pyridine
derivative 11c with hydrazine and phenylhydrazine afforded the tricyclic compounds 19a,b.
J. Heterocyclic Chem., 44, 787 (2007).
Formamide acetals are useful reagents; [3,4] their main
(3-6) [6,7]. The structures of these compounds have been
confirmed by X-ray crystallography [6,7].
application has been used for functional group transfor-
mations [5], but they may also be regarded as one-carbon
synthons in the construction of carbon skeletons. One type
of reaction, which is potentially valuable for the future
purpose, is with 1,3-dicarbonyl compounds (1) to give
enamines (2) [4].
In conjunction with our studies aimed at exploring the
synthetic potential of enamine (2) we report here the
reaction of benzoylacetone (7) with N,N-dimethylform-
amide dimethyl acetal (1:1) to give the corresponding
enamine (8) [8].
O
O
O
O
R1
R2
R1
R2
Me2NCH(OMe)2
Me2NCH(OMe)2
Ph
Ph
NMe2
NMe2
H3C
H3C
O
O
O
O
(2)
(1)
(7)
(8)
R1
R2
This intermediate need not be isolated but can be
reacted directly with cyanothioacetamide, cyanoacetamide
or anion of malononitrile dimer in dry DMF and sodium
hydride to give 2,3,5,6-tetrasubstituted pyridines (10a-c)
or (11a-c) respectively as outlined in Scheme 1. In the
first, initial Michael addition with elimination of
dimethylamine followed by cyclization of the amino
CH3
CH3
CH3
OCH3
OC2H5
OC2H5
OC2H5
CH3
C2H5
CH2CO2C2H5
-(CH2)3-
We have reported that these enamines (2) were used as
precursors in the synthesis of pentasubstituted pyridines
R1
O
R1
O
O
O
CN
X
CONH2
X
CN
X
CONH2
X
R2
R2
R2
R2
R1
N
H
N
H
N
H
R1
N
H
(3)
(4)
(5)
(6)
X = S
X = O
X = C(CN)2

788
F. A. Abu-Shanab, A. M. Hessen, and S. A. S. Mousa
Vol 44
group with the carbonyl of the benzoyl moiety to give
2,3,5,6-tetrasubstituted pyridines (10a-c), whereas in the
second initial Michael addition with elimination of
dimethylamine followed by cyclization of the amino
group with the carbonyl of the acetyl moiety gave 2,3,5,6-
tetrasubstituted pyridines (11a-c). In practice, only one
isomer was isolated in each case, but the 1H NMR spectra
show a singlet signal for the ring proton at ꢀH 8.41, 7.51
and 8.3 ppm for compounds 11a, 11c and 12 respectively,
did not enable the compounds to be identified
unequivocally.
the cyano group so that the structure of (11a) becomes
(12) up on hydrolysis.
On the other hand, reactions analogous to those
reported above, but with ethanol as solvent and pepridine
as a base [4], gave either (13a,b) or (14a,b) as outlined in
Scheme 2.
The mass spectra of the isolated products show two
peaks, one at m/z 105 corresponding to the benzoyl
moiety and the other at m/z 77 corresponding to the
benzene ring. This indicates that the molecule must
contain the benzoyl moiety which corresponds to
Scheme (1)
O
O
O
CN
X
H3C
CH3
CN
- H2O
N
H
X
H2N
Me2
H
(10)
- N
O
O
N
a, X = S
b, X = O
c, X = C(CN)2
CN
CH3
CH3
+
X
- N
H
H2N
M
e
2
CH3
O
O
O
(8)
(9)
CN
- H2O
CH3
a, X = S
b, X = O
c, X = C(CN)2
NH2
H3C
N
H
X
X
(11)
CN
a, X = S
b, X = O
c, X = C(CN)2
The mass spectra of the isolated products show two
peaks at m/z 105 corresponding to the benzoyl moiety and
at m/z 77 corresponding to the benzene ring. This
indicates that the molecule must contain the benzoyl
moiety which corresponding to structure (11a-c) not (10a-
c). Hence, the isolated products have structures 11a-c.
The mass spectra of 11a and 11c show the molecular ions
(m/z 254 and m/z 286) that fit to the structures 11a and
11c respectively, while the mass spectrum of 11b shows a
molecular ion peak (m/z 256) that is greater than the
expected (m/z 238) by 18 units corresponding to a
molecule of water. This confirms that the reaction was
carried out with hydrolysis of the cyano group to amide
group. Also the IR spectrum shows the disappearance of
structures (14a,b) not (13a,b). Hence, the isolated
products have structures 14a,b. Also the H NMR spectra
of these compounds show a singlet signal at ꢀ 7.78 and
7.27 ppm corresponding to the ring proton.
1
Some illustrative reactions, designed to demonstrate the
potential usefulness of the products described above for
further heterocyclic synthesis, are represented in Scheme
3 and Scheme 4. Thus, reaction of 5-benzoyl-6-methyl-2-
thioxo-1,2-dihydropyridine-3-carbonitrile (11a), and
5-benzoyl-4-methyl-2-thioxo-1,2-dihydropyridine-3-carbo-
nitrile (14a) with 2-chloro-N-p-tolyl-acetamide (15) and
potassium carbonate in ethanol afforded 3-amino-5-
benzoyl-6-methylthieno[2,3-b]pyridine-2-carboxylic acid
p-tolylamide (16a) and 3-amino-5-benzoyl-4-methylthieno-
O
O
O
OH
NH
CN
O
CONH2
O
H2O
H3C
N
H
H3C
N
H
H3C
N
H
O
(11b)
(12)

Jul-Aug 2007
Dimethylformamide Dimethyl Acetal in Heterocyclic Synthesis
789
Scheme (2)
O
CN
X
O
H3C
NC
e
HM
- N
2
CH3
NMe2
N
H
X
NH2
(13)
O
2
O
O
N
- H
CN
a, X = S
b, X = C(CN)2
CH3
CH3
+
X
H2N
- H
2
O
CH3
(9)
(8)
O
CH3
CN
CH3
NH2
O
e
M
H
- N
2
a, X = S
c, X = C(CN)2
NC
X
N
H
X
NMe2
(14)
a, X = S
b, X = C(CN)2
[2,3-b]pyridine-2-carboxylic acid p-tolylamide (16b)
respectively. These compounds (16a) and (16b) upon
treatment with dimethylformamide dimethyl acetal afforded
3-benzoyl-2-methyl-7-p-tolyl-7H-9-thia-1,5,7-triaza-fluoren-
8-one (17a) and 3-benzoyl-4-methyl-7-p-tolyl-7H-9-thia-
1,5,7-triaza-fluoren-8-one (17b) respectively. While on
treatment of (16a,b) with sodium nitrite in acetic acid
afforded 3-benzoyl-2-methyl-7-p-tolyl-7H-9-thia-1,5,6,7-
tetraaza-fluoren-8-one (18a) and 3-benzoyl-4-methyl-7-
p-tolyl-7H-9-thia-1,5,6,7-tetraaza-fluoren-8-one (18b)
respectively as shown in Scheme 3. The structure of the
isolated compounds was confirmed by elemental analysis
as well as spectral analysis.
Further reaction of 5-benzoyl-2-dicyanomethyl-
idene-6-methyl-1,2-dihydropyridin-3-carbonitrile (11c)
with hydrazine and phenylhydrazine to give 3-
(hydrazono-phenyl-methyl)-2-methyl-1H-pyrazolo[3,
4-h][1,6]-naphthyridine-5,9-diamine (19a) and
9-imino-2-methyl-8-phenyl-3-[phenyl-(phenyl-hydra-
zono)-methyl]-8,9-dihydro-1H-pyrazolo[3,4-h][1,6]-
naphthyridine-5-ylamine (19b) respectively as out-
lined in Scheme 4. IR spectra show the disappear-
ance of the cyano groups and the carbonyl group and
the appearance of amino groups. Also the mass
spectra show the molecular mass corresponds to the
proposed structures.
Scheme (3)
O
X
Y
O
O
X
Y
N
NH2
H
CN
S
H
Cl
N
CH3
N
EtOH
+
S
K2CO3
O
N
H
CH3
11a, X = CH3, Y = H
14a, X = H, Y= CH3
16a, X = CH3, Y = H
a, X = H, Y= CH3
15
A
NaNO
AcOH
M
D
F
DM
2
Dioxane
CH3
CH3
O
X
Y
N
O
X
Y
N
N
N
N
S
N
N
O
O
S
17a, X = CH3, Y = H
a, X = H, Y= CH3
18a, X = CH3, Y = H
a, X = H, Y= CH3

790
F. A. Abu-Shanab, A. M. Hessen, and S. A. S. Mousa
Vol 44
Scheme (4)
H
H
N
N
R
R
N
NH2
N
NH2
O
CN
CN
H2NNHR
N
N
CN
R = H
R = Ph
H3C
N
H3C
N
H3C
N
H
N
N
H
N
N
HN
H2N
R
R
19a, R = H
b, R = Ph
(11C)
solid obtained in yield (1.7 g, 71.43%) as yellow crystals
(DMF/EtOH), m.p. 292-294˚C, ir: NH 3368,3215; C=O 1668
cm-1,1H nmr (DMSO-d6) ꢀ 2.49 (s, 3H, CH3), 7.52-7.71 (m, 6H,
phenyl protons + NH), 8.3 (s, 1H, ring-H), 8.80 (s, 1H, exch.,
NH), 12.86 ppm (br., 1H, exch., NH), ms: m/z 256 (M+).
Anal.Calcd. for C14H12N2O3: C, 65.62; H, 4.72; N, 10.93. Found:
C, 65.4; H, 4.6; N, 10.8.
General Procedure for the Preparation of 2,3,4,5-
Tetrasubstituted pyridines (14a,b). In a dry flask a mixture of
benzoylacetone (7) (1.62 g, 10 mmol), dry toluene (20 mL) and
N,N-dimethylformamide dimethyl acetal (DMFDMA) (1.19 g,
10 mmol) was left stirring at room temperature for 24 h, and
then refluxed for 2 h, cooled and evaporated to yield red oil
which dissolved in absolute ethanol. A solution of active
methylene (9a,c) (10 mmol) in absolute ethanol (30 mL) was
added followed by piperidine (0.5 mL), and the reaction mixture
was left under reflux temperature for about 4 h. The reaction
mixture was poured into ice cold water and acidified with
concentrated HCl. The solid product was recovered by filtration
and recrystallized from the proper solvent.
5-Benzoyl-4-methyl-2-thioxo-1,2-dihydropyridine-3-carbo-
nitrile (14a). The title compound was prepared by the method
described above using cyanothioacetamide (1.0 g, 10 mmol).
The solid obtained in yield (1.92 g, 75.59%) as yellow crystals,
m.p. 238-240˚C (EtOH). ir: NH 3169, CN 2218 cm-1. 1H nmr
(DMSO-d6) d 2.43 (s, 3H, CH3), 7.50-7.76 (m, 5H, phenyl
protons), 7.78 (s, 1H, ring-H), 14.08 ppm (br., 1H, exch., NH),
ms: m/z 254 (M+). Anal. Calcd. for C14H10N2OS, C, 66.12; H,
3.96; N, 11.02, Found , C, 65.9; H, 3.8; N, 10.9.
5-Benzoyl-2-dicyanomethylidene-4-methyl-1,2-dihydro-
pyridine-3-carbonitrile (14b). The title compound was
prepared by the method described above using sodium salt
of malononitrile dimer (1.54 g, 10 mmol). The solid
obtained in yield (2.03 g, 70.98%) as gray crystals, m.p.
145-147˚C (EtOH), ir: NH 3337, CN 2190, 2156, C=O
1638 cm-1. 1H nmr (DMSO-d6) ꢀ 2.12 (s, 3H, CH3), 4.16
(br., 1H, exch., NH) 7.05-7.24 (m, 5H, phenyl protons),
7.27 ppm (s, 1H, ring-H). ms: m/z 286(M+). Anal. Calcd.
for C17H10N4O, C, 71.32; H, 3.52; N, 19.57. Found, C, 71.0;
H, 3.40; N, 19.3.
EXPERIMENTAL
Melting points are uncorrected. IR spectra were recorded on a
Perkin-Elmer 1710 FTIR spectrometer as KBr disks. NMR
spectra were recorded on Bruker AC300 spectrometer at 300
MHz for solutions of [2H6]dimethyl sulfoxide with tetramethyl-
silane (TMS) as an internal standard unless otherwise recorded.
Mass spectra were obtained on Finnigan 4500 (low resolution)
spectrometer using electron impact (EI). 2-Chloro-N-p-tolyl-
acetamide (15) was prepared by literature method [9].
General Procedure for the Preparation of 2,3,5,6-
Tetrasubstituted pyridines (11a,c and 12). In a dry flask a
mixture of benzoylacetone (7) (1.62 g, 10 mmol), dry toluene
(20 mL) and N,N-dimethylformamide dimethyl acetal
(DMFDMA) (1.19 g, 10 mmol) was left stirring at room
temperature for 24 h, and then refluxed for 2 h, the solvent
evaporated to yield red oil which dissolved in dry DMF. In a
second flask a mixture of anhydrous N,N-dimethylformamide
(DMF) (10 mL), sodium hydride (0.24 g, 10 mmol) and
active methylene (9a-c) (10 mmol) was allowed to stir at
room temperature for 10 min. The contents of the second
flask were transferred into the first flask and left stirring at
room temperature overnight. The resulting mixture was
poured into ice cold water and acidified with concentrated
HCl. The solid product was recovered by filtration and
recrystallized from the proper solvent.
5-Benzoyl-6-methyl-2-thioxo-1,2-dihydropyridine-3-carbo-
nitrile (11a). This compound was prepared by the method
described above using cyanothioacetamide (9a) (1.0g, 10mmol).
The solid obtained in yield (1.85g, 72.83%) as greenish brown
crystals (DMF/EtOH), m.p. 270-272˚C, ir: NH 3170, CN 2227,
1
and C=O 1662 cm-1, H nmr (DMSO-d6) ꢀ 2.46 (s, 3H, CH3),
7.50-8.04 (m, 5H, phenyl protons), 8.41 (s, 1H, ring-H), 14.39
ppm (br., 1H, exch., NH), ms: m/z 254 (M+). Anal. Calcd. for
C14H10N2OS: C, 66.12; H, 3.96; N, 11.02. Found: C, 65.9; H,
3.8; N, 10.9.
5-Benzoyl-2-dicyanomethylidene-6-methyl-1,2-dihyropyri-
dine-3-carbonitrile (11c). The title compound was prepared by
the method described above using sodium salt of malononitrile
dimer (1.54g, 10 mmol). The solid was obtained in yield (2.2 g,
76.92%) as brown crystals, m.p. 206-208˚C (EtOH), ir: NH
3-Amino-5-benzoyl-6-methyl-thieno[2,3-b]pyridine-2-car-
boxylic acid p-tolylamide (16a). A mixture of pyridine-2(1H)-
thione (11a) (2.54 g, 10 mmol), 2-chloro-N-p-tolyl-acetamide
(15) (1.83 g, 10 mmol) and sodium ethoxide (30 mL, 0.5 g
sodium metal) was heated under reflux for about 2 h. The
reaction mixture was poured on cold water, the solid product
was recovered by filtration to give the title compound (16a) in
yield (3.25, 81.05%) as reddish brown, m.p. 195-197ºC (EtOH),
ir: NH, NH2 3435, 3317, 3203, C=O 1666, 1643 cm-1, ms: m/z
1
3250, CN 2212, 2188, C=O 1660 cm-1. H nmr (DMSO-d6): ꢀ
2.22 (s, 3H, CH3), 4.36 (br., 1H, exch., NH) 7.18-7.36 (m, 5H,
phenyl protons), 7.51 ppm (s, 1H, ring-H), ms: m/z 286(M+).
Anal.Calcd. for C17H10N4O, C, 71.32; H, 3.52; N, 19.57. Found,
C, 71.1; H, 3.4; N, 19.3.
5-Benzoyl-6-methyl-2-oxo-1,2-dihydropyridine-3-carbox-
amide (12). This compound was prepared by the method
described above using cyanoacetamide (0.84 g, 10 mmol). The

Jul-Aug 2007
Dimethylformamide Dimethyl Acetal in Heterocyclic Synthesis
791
401(M+). Anal. Calcd. for C23H19N3O2S, C, 68.81; H, 4.77; N,
10.47. Found, C, 68.5; H, 4.6; N, 10.2.
C23H16N4O2S, C, 66.98; H, 3.91; N, 13.58. Found, C, 66.7; H,
3.8; N, 13.4.
3-Amino-5-benzoyl-4-methyl-thieno[2,3-b]pyridine-2-car-
boxylic acid p-tolylamide (16b). The reaction was carried out
by the method described above using pyridine-2(1H)-thione
(14a) (2.54 g, 10 mmol) instead of (11a). The reaction was
worked up as usual, and the solid obtained in yield (2.9 g,
72.32%) as yellow crystals, m.p. 230-232ºC (EtOH), ir: NH,
NH2 3489, 3401, 3341, C=O 1638 cm-1, ms: m/z 401(M+). Anal.
Calcd. for C23H19N3O2S, C, 68.81; H, 4.77; N, 10.47. Found, C,
68.6; H, 4.5; N, 10.3.
3-(Hydrazono-phenyl-methyl)-2-methyl-1H-pyrazolo[3,4-
h][1,6]-naphthyridine-5,9-diamine (19a). A mixture of
pyridine (11c) (2.86 g, 10 mmol), and hydrazine hydrate
(1.5mL) in ethanol (30 mL) was heated under reflux for 2 h. The
solvent was evaporated and the residue was recrystallized from
ethanol to give 3-(hydrazono-phenyl-methyl)-2-methyl-1H-
pyrazolo[3,4-h][1,6]naphthyridine-5,9-diamine (19a), (2.13 g,
64.16%) as brown crystals, m.p. 260-262ºC (DMF/EtOH), ir:
1
NH, NH2 3443, 3326, 3208 cm-1, H nmr (DMSO-d6) ꢀ 2.49 (s,
3-Benzoyl-2-methyl-7-p-tolyl-7H-9-thia-1,5,7-triaza-fluoren-
8-one (17a). 3-Amino-5-benzoyl-6-methyl-thieno[2,3-b]-
pyridine-2-carboxylic acid p-tolylamide (16a) (0.40 g, 1 mmol)
in dry DMF (10 mL) was treated with DMFDMA (0.13 g, 1
mmol) portionwise with stirring at room temperature, and left
stirring further 12 h. The solid obtained (0.33 g, 82.29%) as
gray, m.p. 100-102ºC (EtOH), ir: C=O 1684 cm-1, 1H nmr
(DMSO-d6) ꢀ 2.39 (s, 3H, CH3), 2.47 (s, 3H, CH3), 7.32-7.78
(m, 9H, phenyl protons), 8.62 (s, 1H, pyridine-H) and 8.77 ppm
(s, 1H, pyrimidine-H), ms: m/z 411(M+). Anal. Calcd. for
C24H17N3O2S, C, 70.06; H, 4.16; N, 10.21. Found, C, 69.8; H,
4.0; N, 10.0.
3H, CH3), 2.92 (s, 2H, exch., NH2), 5.48 (s, 2H, exch., NH2),
6.58 (s, 2H, exch., NH2), 7.55-7.95 (m, 5H, phenyl protons),
8.22 (s, 1H, ring-H), 11.64 ppm (br., 1H, exch., NH), ms: m/z
332 (M+). Anal. Calcd. for C17H16N8, C, 61.43; H, 4.85; N,
33.71. Found, C, 61.2; H, 4.7; N, 33.5.
9-Imino-2-methyl-8-phenyl-3-[phenyl-(phenylhydrazono)-
methyl]-8,9-dihydro-1H-pyrazolo[3,4-h][1,6]naphthyridine-
5-ylamine (19b). A mixture of pyridine (11c) (2.86 g, 10
mmol), and phenylhydrazine (2.5mL) in ethanol (30 mL) was
heated under reflux for 2 h. The solvent was evaporated and the
residue was recrystallized from ethanol to give 9-imino-2-
methyl-8-phenyl-3-[phenyl-(phenylhydrazono)-methyl]-8,9-di-
hydro-1H-pyrazolo[3,4-h][1,6]naphthyridin-5-ylamine in yield
(19b) (2.54g, 52.48%) as gray crystals, m.p. 296-298ºC
(DMF/EtOH), ir: NH, NH2 3430, 3330, 3245 cm-1, 1H
nmr(DMSO-d6) ꢀ 2.09 (s, 3H, CH3), 3.37 (br., 2H, exch., NH2),
6.36 (br., 1H, exch., NH), 6.65-7.32 (m, 17H, phenyl protons +
2NH), and 7.64 ppm (s, 1H, ring-H), ms: m/z 484 (M+). Anal.
Calcd. for C29H24N8, C, 71.88; H, 4.99; N, 23.12. Found, C,
71.6; H, 4.8; N, 22.9.
3-Benzoyl-4-methyl-7-p-tolyl-7H-9-thia-1,5,7-triaza-fluoren-
8-one (17b). The reaction was carried out by the method
described above using 3-amino-5-benzoyl-4-methyl-thieno[2,3-
b]pyridine-2-carboxylic acid p-tolylamide (16b) (0.40 g, 1
mmol) instead of (16a). The reaction was worked up as usual,
and the solid obtained (0.3 g, 74.81%) as yellow crystals, m.p.
1
200-202ºC (EtOH), ir: C=O 1669, 1640 cm-1, H nmr ꢀ 2.26 (s,
3H, CH3), 2.84 (s, 3H, CH3), 7.10,7.13 (d, 2H, phenyl-AB),
7.38-7.55 (m, 5H, phenyl protons), 7.77 (s, 1H, pyridine-H),
8.12,8.15 (d, 2H, phenyl-AB) and 9.36 ppm (s, 1H, pyrimidine-
H), ms: m/z 411(M+). Anal. Calcd. for C24H17N3O2S, C, 70.06;
H, 4.16; N, 10.21. Found, C, 69.7; H, 3.9; N, 10.1.
3-Benzoyl-2-methyl-7-p-tolyl-7H-9-thia-1,5,6,7-tetraaza-
fluoren-8-one (18a). 3-Amino-5-benzoyl-6-methyl-thieno[2,3-
b]pyridine-2-carboxylic acid p-tolylamide (16a) (0.4 g, 1 mmol)
in acetic acid (25 mL) was treated with sodium nitrite (0.14, 2
mmol) portionwise with stirring at room temperature, and left
stirring further 1 h. The solid obtained (0.31 g, 77.31%) as gray,
m.p. 135-137ºC (EtOH), ir: C=O 1692 cm-1, ms: (M+) at m/z
412. Anal. Calcd. for C23H16N4O2S, C, 66.98; H, 3.91; N, 13.58.
Found, C, 66.6; H, 3.8; N, 13.3.
3-Benzoyl-4-methyl-7-p-tolyl-7H-9-thia-1,5,6,7-tetraaza-
fluoren-8-one (18b). The reaction was carried out by the
method described above using 3-amino-5-benzoyl-4-methyl-
thieno[2,3-b]pyridine-2-carboxylic acid p-tolylamide (16b)
(0.40 g, 1 mmol) instead of (16a). The reaction was worked up
as usual, and the solid obtained (0.28g, 69.83%) as gray, m.p.
265-267ºC (EtOH), ir: C=O 1675 cm-1. Anal. Calcd. for
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