ISSN 1070-3632, Russian Journal of General Chemistry, 2011, Vol. 81, No. 10, pp. 2209–2211. © Pleiades Publishing, Ltd., 2011.
Original Russian Text © V.S. Zyabrev, M.A. Renskii, 2011, published in Zhurnal Obshchei Khimii, 2011, Vol. 81, No. 10, pp. 1757–1758.
LETTERS
TO THE EDITOR
Recyclization of 5-[Methyl(phenyl)amino]-2-(4-nitrobenzyl)-
3-p-tolyl-1,2,4-thiadiazolium Perchlorate
into 9-Methyl-3a-(4-nitrophenyl)-2-p-tolyl-3a,9-dihydrobenzo[b]-
imidazo[4,5-e][1,4]thiazine
V. S. Zyabrev and M. A. Renskii
Institute of Bioorganic Chemistry and Petrochemistry, National Academy of Sciences of Ukraine,
ul. Murmanskaya 1, Kiev, 02660 Ukraine
e-mail: zyabrev@bpci.kiev.ua
Received April 12, 2011
DOI: 10.1134/S107036321110032X
Previously was shown that 5-[methyl(phenyl)amino]-
3-p-tolyl-2-phenyl-1,2,4-thiadiazolium perchlorates iso-
merize under heating into the benzothiazole derivatives
[1]. Using the well-known approaches [2, 3], we syn-
thesized an analog of 1,2,4-tiadiazolium salt containing
p-nitrobenzyl substituent in position 2 (transformation
I → II) and obtained the corresponding benzothiazole
derivatives: salt III and base IV (see the scheme
bellow).
5-[Methyl(phenyl)amino]-2-(4-nitrobenzyl)-3-p-
tolyl-1,2,4-thiadiazolium perchlorate (II). To a solu-
tion of 68 mmol imidoylthiocarbamide I [4] and
68 mmol of pyridine in 140 ml of dichloromethane
was added a solution of 68 mmol of bromine in 40 ml
of dichloromethane for 1 h. The mixture was stirred for
4 h, then was added 100 ml of water. The organic layer
was separated and concentrated in a vacuum. The oily
residue was dissolved in 80 ml of ethanol and added to
40 ml of 3 M. aqueous solution of sodium perchlorate,
the resulting precipitate was filtered off. Yield 88%,
In DMSO-d6 solution, the compound IV exists as a
1
mixture of stereoisomers in 1:1.3 ratio, as seen from
mp 195–198ºС (EtOH). Н NMR spectrum (CDCl3,
1
the signals doubling in the H NMR spectrum. This is
200 MHz), δ, ppm: 2.44 s (СН3), 3.78 s (СН3), 5.49 s
(СН2), 7.36 d (2Н aromatic, JHH 7.6 Hz), 7.49–7.54 m
(7H aromatic), 7.77 d (2Н aromatic, JHH 8.0 Hz), 8.18
d (2Н aromatic, JHH 8.8 Hz). Found, %: N 11.10, S
6.32. C23H21ClN4O6S. Calculated, %: N 10.84, S 6.20.
due obviously to the hindered syn-anti-isomerization at
the nitrogen and (or) the hindered rotation around the
C–N bond in 1,3-diazadiene fragment. This isomers
ratio does not change at raising temperature to 90ºC or
at replacing the solvent by CDCl3. However, adding
trifluoroacetic acid simplifies spectrum: in the region
of 2.9 ppm it becomes identical to the spectrum of the
salt III.
4-Methyl-N1-(3-methylbenzyl[d]thiazol-2(3H)-
ylidene)-N2-(4-nitrobenzyl)benzamidine hydroper-
chlorate (III). 0.135 mmol of compound II was
slowly heated to 190ºC and maintained at this tem-
perature for 40 min. The melt was cooled to 20ºC and
recrystalled from 5 ml of ethanol. The precipitate was
We found that at heating and due to the catalytic
effect of triethylamine the compound IV undergo an
unexpected rearrangement into benzo[b]imidazo[4,5-
e]-1,4-thiazine derivative V, structure of which was
determined by the X-ray diffraction study. In such
transformation occurring with the hydrogen molecule
eliminating the p-nitrophenyl substituent plays im-
portant role. It activates the methylene group and
promotes the intermediate cyclization.
1
filtered off. Yield 86%, mp 111–114ºС (EtOH). Н
NMR spectrum (DMSO-d6, 400 MHz), δ, ppm: 2.41 s
(СН3), 3.86 s (СН3), 5.01 s (СН2), 7.40-7.46 m (3Н
aromatic), 7.61 t (1Н aromatic, JHH 7.8 Hz), 7.66 d (2Н
aromatic, JHH 8.0 Hz), 7.76 d (2Н aromatic, JHH
8.4 Hz), 7.82 d (1Н aromatic, JHH 8.4 Hz), 7.88 d (1Н
aromatic, JHH 7.6 Hz), 8.29 d (2Н aromatic, JHH
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Zyabrev
