(compound 5) instruments in DMSO-d6, internal standard was TMS. The EI mass spectra were obtained on a
MX-1321 (70 eV) (compound 3) with direct insertion of substance into the ion source (70 eV) and on a
Chrommas GC/MS Hewlett-Packard 5890/5972 with HP-5MS column (compound 5).
The melting points of compounds were determined on a Kofler block. A check on the progress of
reactions and the homogeneity of compounds was carried out by TLC on Silufol UV 254 plates in the system
acetone–hexane, 3:5, visualization was with iodine vapor and in UV light.
2-cyano-N-(2-methoxyphenyl)-3,3-bis(methylsulfanyl)acrylamide (2) was obtained by the procedure
of [3].
1-Amino-4-cyano-3-methylthio-N-(2-methoxyphenyl)pyrido[1,2-a]benzimidazole-2-carboxamide (3).
2-(Benzimidazol-2-yl)acetonitrile (1) (1.57 g, 10 mmol) was added to a suspension of KOH (0.56 g, 10 mmol)
in DMSO (10 ml) and the mixture stirred for 15 min. 2-cyano-N-(2-methoxyphenyl)-3,3-bis(methylsulfanyl)-
acrylamide (2) (2.94 g, 10 mmol) was then added to the reaction mixture, which was stirred for 1 h, and heated
at 80oC for 15 min. The mixture was then left for 2 h, poured into cold water, the mixture was acidified with an
equimolar quantity of 30% HCl solution, the resulting solid was filtered off, and washed with water. Yield 2.41
g (60%); mp 126-130oC (butanol). IR spectrum, , cm-1: 1556 (NH2, NH), 1643 (C=O), 2216 (C≡N), 3234,
3334. 1H NMR spectrum, δ, ppm (J, Hz): 9.63 (1H, br. s, NH); 8.45 (1H, d, J = 8.1, H benzimidazole); 8.20 (1H,
d, J = 8.1, H arom); 7.89 (2H, br. s, NH2); 7.80 (1H, d, J = 8.1, H benzimidazole); 7.53 (1H, t, J = 7.7,
H benzimidazole); 7.34 (1H, t, J = 7.7, H benzimidazole); 7.11 (1H, t, J = 7.7, H arom); 7.02 (1H, d, J = 8.1,
H arom); 6.96 (1H, t, J = 7.7, H arom); 3.88 (3H, s, OCH3); 2.63 (3H, s, SCH3). Mass spectrum, m/z (Irel, %):
108 [M]+ (24), 206 (9), 281 (7), 403 (13). Found, %: C 62.52; H 4.25; N 17.36. C21H17N5O2S. Calculated, %:
C 62.59; H 4.09; N 17.36.
1-Hydroxy-3-methylsulfanylpyrido[1,2-a]benzimidazole-2,4-dicarbonitrile (5) was obtained
analogously to compound 3 using as ketenedithioacetal the diethyl ester of 2-cyano-3,3-bis(methylsulfanyl)-
acrylic acid (4) or 2-cyano-3,3-bis(methylsulfanyl)acrylamide (6). Yield 2.02 g (72%) and 2.24 g (80%)
respectively, mp 290-297oC (butanol). IR spectrum, , cm-1: 2215 (C≡N), 3450 (OH). 1H NMR spectrum, δ,
ppm, (J, Hz): 8.45 (1H, d, J = 8.0, H arom); 7.64 (1H, d, J = 7.8, H arom.); 7.45 (1H, t, J = 7.6, H arom); 7.30
(1H, t, J = 7.6, H arom.); 2.74 (3H, s, SCH3). The signal of the OH group proton was not displayed, probably as
a result of rapid deuterium exchange. Mass spectrum, m/z (Irel, %): 279 [M-1]+ (100). Found, %: C 59.99;
H 2.88; N 19.99. C14H8N4OS. Calculated, %: C 60.05; H 2.97; N 19.86.
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