STRUCTURE OF THE REACTION PRODUCT OF ANTHRANILIC ACID HYDRAZIDE
1335
amino group and oxadiazole ring in the ortho positions
of the benzene ring. On the other hand, the alklylation
of IV with acetic anhydride readily occurred to give
5-(2-acetylaminophenyl)-2-methylsulfanyl-1,3,4-oxa-
diazole (XI).
C 49.58; H 3.79; N 22.03; S 16.52. C8H7N3OS. Cal-
culated, %: C 49.73; H 3.65; N 21.75; S 16.59.
3-Benzylideneamino-2-thioxo-1,2,3,4-tetrahydro-
quinazolin-4-one (V). A solution of 10 mmol of
quinazolin-4-one III and 15 mmol of benzaldehyde in
15 ml of acetic acid was heated for 4 h. The mixture
was cooled, and the precipitate was filtered off,
washed with diethyl ether (5 ml), and dried. Yield
2.10 g (75%), mp 272–274°C. IR spectrum, ν, cm–1:
1420, 1500, 1550, 1630 (C=N), 1690 (C=O), 3260.
1H NMR spectrum, δ, ppm: 7.32–7.40 m (2H, Harom),
7.59 m (3H, Harom), 7.74 m (1H, Harom), 7.95–8.01 m
(4H, Harom), 8.67 s (1H, N=CH), 13.09 s (1H, NH).
Found, %: C 63.98; H 4.19; N 15.03. C15H11N3OS.
Calculated, %: C 64.04; H 3.94; N 14.94.
Thus we have revised the assignment given in [8]
1
and unambiguously proved by H and 13C NMR and
IR spectroscopy and chemical transformations that the
reaction of anthranilic acid hydrazide with carbon di-
sulfide in alkaline medium yields 5-(2-aminophenyl)-
2,3-dihydro-1,3,4-oxadiazole-2-thione rather than
3-amino-2-thioxo-1,2,3,4-tetrahydroquinazolin-4-one.
EXPERIMENTAL
The NMR spectra were recorded from solutions in
DMSO-d6 on a Varian-300 spectrometer (300 MHz for
1H and 75 MHz for 13C) using tetramethylsilane as
internal reference. The IR spectra were measured in
KBr on a UR-20 spectrometer.
Thermal decomposition of 3-benzylideneamino-
2-thioxo-1,2,3,4-tetrahydroquinazolin-4-one (V).
Compound V, 10 mmol, was heated for 30 min at
180°C, cooled, and treated with diethyl ether (2×
5 ml). The precipitate of 2-thioxo-1,2,3,4-tetrahydro-
quinazolin-4-one (VI) was filtered off and dried. Yield
1.48 g (83%), mp 299–302°C; published data [13]:
mp 304–305°C. IR spectrum, ν, cm–1: 1440, 1480,
3-Amino-2-thioxo-1,2,3,4-tetrahydroquinazolin-
4-one (III) was synthesized according to the procedure
described in [10] by reaction of methyl 2-isothio-
cyanatobenzoate (I) with hydrazine in diethyl ether.
Yield 83%, mp 255–257°C (from DMSO); published
data [10]: mp 227–230°C. IR spectrum, ν, cm–1: 1410,
1440, 1495, 1570, 1650 (C=N), 1695 (C=O), 3200,
1
1580, 1640 (C=N), 1720 (C=O), 3150. H NMR spec-
trum, δ, ppm: 7.32 m (2H, Harom), 7.73 d.d (1H, Harom
,
J1 = 8.1, J2 = 0.6 Hz), 7.92 d (1H, Harom, J = 7.8 Hz),
12.48 s (1H, N3H), 12.71 s (1H, N1H). Found, %:
C 54.15; H 3.20; N 16.00. C8H6N2OS. Calculated, %:
C 53.92; H 3.39; N 15.72. The ether solution was
evaporated, and benzonitrile (VII) was distilled under
reduced pressure (water-jet pump). Yield 0.66 g (64%),
bp 185–188°C; published data [14]: bp 191°C. Found,
%: C 81.76; H 5.16; N 13.40. C7H5N. Calculated, %:
C 81.53; H 4.89; N 13.58.
1
3300. H NMR spectrum, δ, ppm: 6.40 s (2H, NH2),
7.23 m (1H, Harom), 7.34 d (1H, Harom, J = 8.4 Hz),
7.62 d.d (1H, Harom, J1 = 8.4, J2 = 0.8 Hz), 7.91 d (1H,
H
arom, J = 7.2 Hz), 12.50 br.s (1H, NH). 13C NMR
spectrum, δC, ppm: 115.8 (C4a), 119.1 (C8), 123.1 (C6),
126.2 (C7), 133.8 (C5), 141.9 (C8a), 155.9 (C4), 169.5
(C2). Found, %: C 50.01; H 3.58; N 21.54; S 16.73.
C8H7N3OS. Calculated, %: C 49.73; H 3.65; N 21.75;
S 16.59.
3-(4-Fluorophenyl)-2H,6H-[1,3,4]thiadiazino-
[2,3-b]quinazolin-6-one (VIII). A solution of
10 mmol of 4-fluorophenacyl bromide in 5 ml of
ethanol was added to a solution of 10 mmol of
quinazolin-4-one III and 10 mmol of KOH in 20 ml of
ethanol, and the mixture was heated for 30 min under
reflux. The mixture was cooled and diluted with 50 ml
of water, and the precipitate of compound VIII was
filtered off. Yield 2.11 g (68%), mp 215–218°C (from
nitromethane). IR spectrum, ν, cm–1: 1480, 1530, 1570,
1620 (C=N), 1700 (C=O), 3100. 1H NMR spectrum, δ,
ppm: 4.33 s (2H, CH2), 7.37 m (2H, Harom), 7.55 m
(2H, Harom), 7.80 m (1H, Harom), 8.14 m (3H, Harom).
Found, %: C 62.01; H 3.19; N 13.33. C16H10FN3OS.
Calculated, %: C 61.73; H 3.24; N 13.50.
5-(2-Aminophenyl)-2,3-dihydro-1,3,4-oxadi-
azole-2-thione (IV) was synthesized according to the
procedure described in [8] by reaction of anthranilic
acid hydrazide with carbon disulfide and potassium
hydroxide in ethanol. Yield 69%, mp 199–201°C (from
ethanol); published data [12]: mp 185–186°C. IR spec-
trum, ν, cm–1: 1460, 1500, 1580, 1640 (C=N), 3000,
1
3100, 3300. H NMR spectrum, δ, ppm: 6.38 s (2H,
NH2), 6.68 m (1H, Harom), 6.89 d (1H, Harom, J =
8.7 Hz), 7.28 d.d (1H, Harom, J1 = 8.7, J2 = 1.3 Hz),
7.54 d (1H, Harom, J = 7.2 Hz), 13.50 br.s (1H, NH).
13C NMR spectrum, δ, ppm: 103.3 (C2), 115.7 (C5),
116.0 (C3), 127.3 (C4), 132.5 (C6), 147.3 (C1), 160.9
(C5, oxadiazole), 175.9 (C2, oxadiazole). Found, %:
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 41 No. 9 2005