Russian Journal of Organic Chemistry, Vol. 37, No. 7, 2001, pp. 1056 1057. Translated from Zhurnal Organicheskoi Khimii, Vol. 37, No. 7, 2001,
p. 1102.
Original Russian Text Copyright
2001 by Britsun, Pirozhenko, Lozinskii.
SHORT
COMMUNICATIONS
New Synthesis of 5-Aryl-5,6-dihydro-7H-[1,2,4]triazolo-
[5,1-b][1,3]thiazin-7-ones
V. N. Britsun, V. V. Pirozhenko, and M. O. Lozinskii
Institute of Organic Chemistry, National Academy of Sciences of Ukraine,
ul. Murmanskaya 5, Kiev, 253660 Ukraine
Received October 21, 1999
The acylation of 4,5-dihydro-1,2,4-triazole-5-
thiones with carboxylic acid chlorides is known to
occur at the nitrogen atom in position 1 of the hetero-
ring [1, 2], while compounds having an activated
double bond readily add at the 5-thioxo group at 20 C
[3]. Taking these data into account, we proposed
a new procedure for synthesizing poorly studied
5-aryl-5,6-dihydro-7H-[1,2,4]triazolo[5,1-b][1,3]thia-
zin-7-ones by condensation of triazolethione I with
substituted cinnamoyl chlorides IIa IIc (Scheme 1).
4 ml of pyridine. The mixture was refluxed for 1 h,
cooled, and diluted with 50 ml of water. The precip-
itate was filtered off and dried. Yield 1.62 g (70%),
1
mp 163 C. H NMR spectrum (acetone-d6), , ppm:
3.47 m (1H, 6-H), 3.88 m (1H, 6-H), 5.40 m (1H,
5-H), 7.46 7.58 m (5H, Harom), 8.10 s (1H, 2-H).
Mass spectrum, m/z (Irel, %): M+ 231 (27). Found, %:
C 56.66; H 3.95; N 18.20. C11H9N3OS. Calculated,
%: C 57.14; H 3.89; N 18.18.
Compounds IIIb and IIIc were synthesized in
a similar way.
The heterocyclization occurs under mild conditions,
on heating the reactants in a benzene pyridine mixture
for 1 h under reflux. Products III were formed in
good yields, and no by-products were detected.
5-(4-Methoxyphenyl)-5,6-dihydro-7H-[1,2,4]tri-
azolo[5,1-b][1,3]thiazin-7-one (IIIb). Yield 72%,
1
mp 143 C. H NMR spectrum (acetone-d6), , ppm:
The structure of compounds III was established on
3.41 m (1H, 6-H), 3.78 m (1H, 6-H), 3.83 s (3H,
CH3O), 5.36 m (1H, 5-H), 7.00 d (2H, Harom), 7.53 d
(2H, Harom), 8.06 s (1H, 2-H). Mass spectrum, m/z
(Irel, %): M+ 261 (41). Found, %: C 55.12; H 4.10;
N 16.12. C12H11N3O2S. Calculated, %: C 55.17;
H 4.21; N 16.09.
1
the basis on the H NMR spectra. The double bond of
initial cinnamoyl chloride II (two doublets at 6.80
and 7.50 ppm) is transformed into a single bond
( 3.30 5.50 ppm) which gives rise to an ABX system.
The composition of products III was confirmed by the
data of mass spectrometry and elemental analysis.
5-Phenyl-5,6-dihydro-7H-[1,2,4]triazolo[5,1-b]-
[1,3]thiazin-7-one (IIIa). A solution of 1.66 g
(10 mmol) of cinnamoyl chloride (IIa) in 4 ml of
benzene was added at 20 C to a solution of 1.01 g
(10 mmol) of 4,5-dihydro-1,2,4-triazole-5-thione (I) in
5-(3-Nitrophenyl)-5,6-dihydro-7H-[1,2,4]tri-
azolo[5,1-b][1,3]thiazin-7-one (IIIc). Yield 81%,
1
mp 202 C. H NMR spectrum (DMSO-d6), , ppm:
3.41 m (1H, 6-H), 3.99 m (1H, 6-H), 5.60 m (1H,
5-H), 7.76 d.d (1H, Harom, J = 8.3, J = 8.3 Hz),
7.95 d (1H, Harom, J = 8.3 Hz), 8.25 d (1H, Harom
Scheme 1.
,
Ar = Ph (a), 4-MeOC6H4 (b), 3-O2NC6H4 (c).
1070-4280/01/3707-1056$25.00 2001 MAIK Nauka/Interperiodica