Synthesis of a new heterocyclic system: 3-phenylbenzimidazo[1,2-c]-[1,2,3] selenadiazole

Full text of DOI:10.1007/s10593-009-0391-7

Chemistry of Heterocyclic Compounds, Vol. 45, No. 9, 2009
SYNTHESIS OF A NEW HETEROCYCLIC
SYSTEM: 3-PHENYLBENZIMIDAZO[1,2-c]-
[1,2,3]SELENADIAZOLE
L. Labanauskas,1,2* V. Dudutiene3, D. Matulis3, and G. Urbelis2,4
Keywords: benzimidazo[1,2-c]selenadiazole, benzimidazo[1,2-c][1,2,3]thiadiazole, selenium oxide,
condensation.
The unexpected formation of benzimidazo[1,2-c][1,2,3]thiadiazole system as the result of the cyclization
of amines 1a or 1b with thionyl chloride [1] has led to interest in the further study of the scope of this reaction.
Amines 1 containing an active methylene group due to the presence of a phenyl, phenylamino, phenoxy, or
phenylthio substituent were treated with thionyl chloride or selenium oxide. Amines 1e,f underwent tar
formation in all cases, while amines 1a,b underwent tar formation only with selenium oxide. Amines 1c,d were
converted to benzimidazo[1,2-c][1,2,3]thiadiazoles 2c [2] and 2d and also a new heterocyclic system, namely,
benzimidazo[1,2-c][1,2,3]selenadiazoles 3c,d.
N
X
N
N
X
SOCl2 (SeO2)
N
Y
N
NH2
1a–f
2c,d, 3c,d
1 a X = OH, b X = Cl, c X = Ph, d X = SPh, e X = OPh, f X = NHPh; 2 Y = S; 3 Y = Se
1
The H and 13C NMR spectra were taken on a Varian Unity Inova spectrometer at 300 and 75 MHz,
respectively, in DMSO-d6. The residual solvent signal at δ 2.50 ppm served as the standard reference.
2-Phenylthiomethyl-1H-benzimidazole-1-amine (1d). 2-Chloromethyl-1H-benzimidazole-1-amine (1b)
(0.32 g, 1.76 mmol) was added to a solution of sodium thiophenolate (1.8 mmol) in methanol (10 ml) and stirred
for 3 h without heating. The precipitate formed was filtered off, washed with water, and recrystallized from
1
methanol to give 0.32 g (71%) 1d; mp 133-134°C. H NMR spectrum, δ, ppm (J, Hz): 4.52 (2H, s, CH2);
_______
* To whom correspondence should be addressed, e-mail: linas.labanskaus@chf.vu.lt.
1Institute of Chemistry, Vilnius 01108, Lithuania.
2Institute of Biotechnology, Vilnius 02241, Lithuania.
3Institute of Biochemistry, Vilnius 08662, Lithuania.
4Vilnius University, Vilnius 03225, Lithuania.
__________________________________________________________________________________________
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1435-1436, September, 2009.
Original article submitted April 24, 2009.
0009-3122/09/4509-1153©2009 Springer Science+Business Media, Inc.
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6.06 (2H, s, NH2); 7.10-7.30 (3H, m, ArH); 7.35 (2H, t, J = 8, ArH); 7.45-7.60 (4H, m, ArH). Found, %:
C 65.74; H 4.94; N 16.30. C14H13N3S. Calculated, %: C 65.85; H 5.13; N 16.46.
3-Phenylthiobenzimidazo[1,2-c][1,2,3]thiadiazole (2d) was synthesized in 54% yield by heating
amine 1d in thionyl chloride at reflux for 15 min according to our previous procedure [1] and recrystallized from
octane; mp 96-97°C. 1H NMR spectrum, δ, ppm (J, Hz): 7.29 (1H, t, J = 8, ArH); 7.40-7.50 (3H, m, ArH); 7.54
(1H, t, J = 8, ArH); 7.62-7.71 (2H, m, ArH); 7.81 (1H, d, J = 8, H-5); 8.12 (1H, d, J = 8, H-8). 13C NMR
spectrum, δ, ppm: 113.3, 120.6, 121.3, 128.1, 128.6, 129.6, 130.0, 130.5, 131.8, 132.8, 153.2, 154.3. Found, %:
C 59.28; H 2.99; N 14.56. C14H9N3S2. Calculated, %: C 59.34; H 3.20; N 14.83.
3-Phenylbenzimidazo[1,2-c][1,2,3]selenadiazole (3c). A mixture of 2-benzyl-1H-benzimidazole-1-amine
(0.2 g, 0.89 mmol) [3], acetic acid (5 ml), and SeO2 (0.09 g, 0.89 mmol) was heated at 65-75°C for 5 h and
evaporated. Then, 10 ml water was added and the mixture was neutralized by adding sodium bicarbonate.
Chromatographic separation, collecting the fraction with Rf 0.5 (1:4 ethyl acetate–toluene as eluent), gave 0.13 g
(46%) 3c; mp 146-148°C. 1H NMR spectrum, δ, ppm (J, Hz): 7.25 (1H, t, J = 8, ArH); 7.48-7.62 (4H, m, ArH);
13
7.82 (1H, d, J = 8, H-5); 8.15 (1H, d, J = 8, H-8); 8.44 (2H, d, J = 8, ArH). C NMR spectrum, δ, ppm: 113.8,
120.1, 121.1, 128.7, 128.8, 129.4, 130.1, 130.7, 132.0, 144.6, 155.2, 155.3. Found, %: C 56.68; H 3.13;
N 14.15. C14H9N3Se. Calculated, %: C 56.39; H 3.04; N 14.09.
3-Phenylthiobenzimidazo[1,2-c][1,2,3]selenadiazole (3d) was synthesized in 66% yield analogously to
1
3c and recrystallized from octane; mp 146-147°C. H NMR spectrum, δ, ppm (J, Hz): 7.18 (1H, t, J = 8, H-7);
7.49 (1H, t, J = 8, H-6); 7.45-7.58 (3H, m, ArH); 7.69 (1H, d, J = 8, H-5); 7.72-7.78 (2H, m, ArH); 8.05 (1H, d,
13
J = 8, H-8). C NMR spectrum, δ, ppm: 113.6, 119.6, 121.2, 128.2, 129.0, 130.3, 131.0, 132.2. 134.1, 141.8,
155.0, 155.4. Found, %: C 51.13; H 2.49; N 12.61. C14H9N3SSe. Calculated, %: C 50.91; H 2.75; N 12.72.
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