A convenient route to functionalized derivatives of pyrrolo[2,1-b][1,3] benzothiazole

Full text of DOI:10.1134/S1070363206020332

ISSN 1070-3632, Russian Journal of General Chemistry, 2006, Vol. 76, No. 2, pp. 333 334.
Pleiades Publishing, Inc., 2006.
Original Russian Text
V.N. Sviripa, V.S. Brovarets, B.S. Drach, 2006, published in Zhurnal Obshchei Khimii, 2006, Vol. 76, No. 2, pp. 349 350.
LETTERS
TO THE EDITOR
A Convenient Route to Functionalized Derivatives
of Pyrrolo[2,1-b][1,3]benzothiazole
V. N. Sviripa, V. S. Brovarets, and B. S. Drach
Institute of Bioorganic Chemistry and Oil Chemistry, National Academy of Sciences of Ukraine,
ul. Murmanskaya 1, Kiev, 02094 Ukraine
Received August 26, 2005
DOI: 10.1134/S1070363206020332
Accessible products of cyclocondensation of o-ami-
nothiophenol I with chlorine-containing unsaturated
azlactones II [1] can be readily subjected to
nitrogen atom of the thiazoline fragment, because the
IR spectra indicate that the azlactone ring in the reac-
tion products IV is preserved. This ring is capable of
further opening with methanol in the presence of
sodium methylate. The possibility of easy annelation
interesting transformations III IV
V
VI VII
presented in the Scheme 1.
V
VI evidently arises from the formation of Z
Cyanomethylation of compound III occurs at the
isomers of the intermediate products V in which the
Scheme 1.
H
N
O
O
NH2
2Et3N
Cl
+
O
O
SH
Cl
N
S
N
Ar
Ar
I
IIa, IIb
IIIa, IIIb
ClCH2CN, K2CO3,
CN
CN
O
OMe
N
S
N
MeOH, MeONa
MeOH, MeONa
O
O
O
N
S
N
H
Ar
Ar
IVa, IVb
Va, Vb
CN
CN
OH
O
OMe
O
MeI, K2CO3
Ar = Ph
N
N
Ar
Ph
S
S
N
N
H
H
VIa, VIb
VII
Ar = Ph (a), 4-MeC6H4 (b).
333

334
SVIRIPA et al.
active methylene group and methoxycarbonyl residue
are sterically proximate. Numerous examples of such
intramolecular cyclizations were reported previously
(see, e.g., [2]). Elimination of methanol from inter-
mediates V may probably lead to the corresponding
keto nitriles with the characteristic COCHCN group,
but we failed to identify this group by comparative
was added to a suspension of 0.015 mol of IVa or
IVb in 50 ml of absolute methanol, and the mixture
was refluxed for 10 h. The hot solution was quickly
filtered to remove a small amount of a precipitate, the
solvent was removed in a vacuum, and the residue
was treated with 5 ml of 2% hydrochloric acid. The
precipitate thus obtained was filtered off and recrystal-
lized from acetic acid. Yield of VIa 73%, mp 308
1
analysis of the IR and H NMR spectra of related
1
compounds VI and VII. In this case, formation of
enol group is favorable because it does not distort the
aromaticity of the pyrrole fragment. Finally, it should
be noted that accessible condensed substrates VI
appeared to be suitable for preparing not only
O-methylation products VII, but also a series of other
functional derivatives of pyrrolo[2,1-b][1,3]benzothia-
zole which will be considered in further papers.
310 C. IR spectrum, , cm : 1630 (C=O), 2220
1
(C N), 3000 3350 (N H, O Hass). H NMR spec-
trum, , ppm: 7.29 8.02 m (9H, C6H5, C6H4), 9.91 s
(1H, NH), 10.67 br.s (1H, OH). Found, %: C 64.78;
H 3.39; N 12.35; S 9.50. C18H11N3O2S. Calculated, %:
C 64.85; H 3.33; N 12.60; S 9.62. Yield of VIb 79%,
mp 259 261 C. Found, %: N 12.01; S 9.19. C19H13
N3O2S. Calculated, %: N 12.10; S 9.23.
2-[5(4H)-Oxo-2-phenyl-1,3-oxazol-4-ylidene]-2,3-
dihydrobenzo[1,3]thiazole (IIIa) was prepared as
described previously [1] for IIIb and was recrystal-
lized from DMF. Yield 78%, mp 270 272 C. IR spec-
trum, , cm : 1715 (C=O), 3100 3280 (NHass).
Found, %: N 9.47; S 10.85. C16H10N2O2S. Calcu-
lated, %: N 9.51; S 10.89.
3-Benzoylamino-2-methoxypyrrolo[2,1-b][1,3]-
benzothiazole-1-carbonitrile (VIII). To a suspension
of 0.003 mol of VIa in 25 ml of acetone, 0.004 mol
of anhydrous potassium carbonate and 0.004 mol of
methyl iodide were added, and the mixture was re-
fluxed with stirring for 10 h. After cooling, 100 ml of
water was added, and the precipitate thus formed was
1
filtered off, dried, and recrystallized from acetonitrile;
2-[2-Aryl-5(4H)-oxo-1,3-oxazol-4-ylidene]-2,3-di-
hydrobenzo[1,3]thiazol-3-ylacetonitriles IVa and
IVb. To a suspension of 0.03 mol of IIIa or IIIb in
80 ml of DMF, 0.04 mol of anhydrous potassium
carbonate and 0.04 mol of chloroacetonitrile were
added, and the mixture was heated at 100 110 C with
stirring for 5 h. After cooling, 200 ml of water was
added. The precipitate was filtered off, dried, and
purified by crystallization from DMF. Yield of IVa
1
yield 82%, mp 243 244 C. H NMR spectrum,
,
ppm: 4.15 s (3H, CH3O), 7.35 8.02 m (9H, C6H5,
C6H4), 10.06 s (1H, NH). Found, %: N 11.99; S 9.18.
C10H13N3O2S. Calculated, %: N 12.10; S 9.23.
The IR spectra were recorded on a Specord M-80
1
spectrometer in KBr pellets. The H NMR spectra
were taken on a Varian VXR-300 spectrometer (solu-
tions in DMSO-d6, internal reference TMS).
1
89%, mp 283 285 C. IR spectrum, , cm : 1730
(C=O). Found, %: N 12.34; S 9.57. C18H11N3O2S.
Calculated, %: N 12.60; S 9.62. Yield of IVb 89%,
mp 273 275 C. Found, %: N 11.99; S 9.20, C19H13
N3O2S. Calculated, %: N 12.10; H 9.23.
REFERENCES
1. Sviripa, V.N., Brovarets, V.S., and Drach, B.S., Zh.
Obshch. Khim., 2004, vol. 74, no. 4, p. 699.
3-Acylamino-2-hydroxypyrrolo[2,1-b][1,3]benzo-
thiazole-1-carbonitriles VIa and VIb. A solution of
0.019 mol of sodium methylate in 7 ml of methanol
2. El-Shafei, A.K., Soliman, A.M., Sultan, A.A.-R., and
El-Saghier, A.M.M., Gazz. Chim. Ital., 1995, vol. 125,
no. 3, p. 115.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 76 No. 2 2006