1
benzimidazole-2-thione 1. H NMR spectrum, δ, ppm: 2.63 (8Н, m, 2CH2NCH2); 3.52 (8Н, m, 2CH2ОCH2);
5.11 (4Н, s, 2NСН2N); 7.23-7.29 (2Н, AA'XX' system, Н-5,6); 7.49-7.55 (2Н, AA'XX' system, Н-4,7).
13C NMR spectrum, δ, ppm: 51.0 (CH2NCH2); 65.4 (NСН2N); 66.0 (СН2ОCH2); 110.7 (C-4,7); 122.9 (C-5,6);
132.1 (C-3a,7a); 171.4 (C-2).
1-(Morpholin-4-ylmethyl)-1,3-dihydro-2H-benzimidazole-2-thione (3). Colorless crystals, mp 215-
216°С. IR spectrum, ν, cm-1: 3463 (br.), 3146, 3096, 3055, 2989, 2949, 2933, 2869, 2830, 2804, 2748, 2709,
1
1516, 1470, 1438, 1110, 1000, 739. H NMR spectrum of the obtained compound is presented in Figure 1.
1H NMR spectrum, δ, ppm: 2.63 (4Н, m, CH2NCH2); 3.52 (4Н, m, CH2ОCH2); 5.02 (2Н, s, NСН2N); 7.14-7.20
(3Н, m, Н-4,5,6); 7.42-7.48 (1Н, m, Н-7); 12.80 (1Н, br. s, NH). 13C NMR spectrum, δ, ppm: 51.0 (CH2NCH2);
64.5 (NСН2N); 66.0 (CH2ОCH2); 109.5 and 110.7 (C-4,7); 122.2 and 123.0 (C-5,6); 130.6 and 133.1 (C-3a,7a);
169.7 (C-2). Found, m/z: 250.1009 [M+H]+. C12H16N3ОS. Calculated, m/z: 250.1009.
Reaction of benzimidazole-2-thione 1 with 2 equiv. of morpholine was performed analogously to the
aminomethylation procedure described above, using one half the amount of benzimidazole-2-thione 1 (0.75 g,
5 mmol). Yield 0.75 g (60%), white crystals, mp 215-216°С. The 1H NMR spectrum of the obtained compound
was identical to the spectrum of product obtained by reaction with 1 equiv. of morpholine.
2-(Ethylsulfanyl)-1Н-benzimidazole (6a). Sodium hydroxide (1.2 g, 30 mmol) was dissolved in
2-PrOH (30 ml); benzimidazole-2-thione 1 (4.5 g, 30 mmol) was added, followed by treatment of the stirred and
cooled mixture with bromoethane (2.3 ml, 3.3 g, 30 mmol). The reaction mixture was then heated for 1 h at
40°С (precipitate formed almost immediately). The suspension was cooled, the precipitate was filtered off,
washed with Н2О, and dried. Yield 5.0 g (94%), colorless crystals, mp 175-177°С (mp 168-170°С [41],
1
mp 170°С [42]). H NMR spectrum, δ, ppm (J, Hz): 1.38 (3Н, t, J = 7.3, СН2СН3); 3.26 (2Н, q, J = 7.3,
CH2CH3); 7.06-7.10 (2Н, m, Н-5,6); 7.40 (2Н, br. s, Н-4,7); 12.43 (1Н, br. s, NH). 13C NMR spectrum, δ, ppm:
15.2 (СН3); 25.5 (CH2); 113.7 (br. s, C-4,7); 121.2 (C-5,6); 139.0 (br. s, C-3a,7a); 150.0 (C-2). Found, m/z:
179.0636 [M+H]+. C9H11N2S. Calculated, m/z: 179.0639.
(1H-Benzimidazol-2-ylsulfanyl)acetic Acid (6b). Sodium hydroxide (1.2 g, 30 mmol) was dissolved in
H2O (30 ml); benzimidazole-2-thione 1 (4.5 g, 30 mmol) was added followed by sodium chloroacetate (3.5 g,
30 mmol). The mixture was refluxed for 3 h, cooled, and acidified with dilute HCl to weakly acidic pH. The
obtained precipitate was filtered off, dried, and recrystallized from МеОН. Yield 5.05 g (81%), colorless
1
crystals, mp 214-216°С (mp 214°С [42], mp 212-213°С [43]). H NMR spectrum, δ, ppm: 4.11 (2Н, s, СН2);
7.07-7.13 (2Н, m, Н-5,6); 7.38-7.44 (2Н, m, Н-4,7). 13C NMR spectrum, δ, ppm: 33.6 (CH2); 113.8 (br. s,
C-4,7); 121.4 (C-5,6); 139.5 (br. s, C-3a,7a); 149.6 (C-2); 169.8 (С=О). Found, m/z: 209.0378 [M+H]+.
C9H9N2О2S. Calculated, m/z: 209.0379.
Ethyl (1H-Benzimidazol-2-ylsulfanyl)acetate (6c). Sodium hydroxide (1.6 g, 40 mmol) was dissolved
in 2-PrOH (40 ml); benzimidazole-2-thione 1 (6.0 g, 40 mmol) was added followed by ethyl chloroacetate
(4.3 ml, 4.9 g, 40 mmol). The reaction mixture was refluxed for 5 h, cooled, and poured into water. The
precipitate formed was filtered off, washed with water, dried, and recrystallized from CCl4. Yield 7.2 g (76%),
1
colorless crystals, mp 94-96°С (mp 92-93°С [43], mp 105°С [46]). H NMR spectrum, δ, ppm (J, Hz): 1.21
(3Н, t, J = 7.0, ОСН2СН3); 4.13 (2Н, q, J = 7.2, ОСН2СН3); 4.18 (2Н, s, SСН2); 7.08-7.13 (2Н, m, Н-5,6); 7.41
(2Н, br. s, Н-4,7); 12.55 (1H, br. s, NH). 13C NMR spectrum, δ, ppm: 13.9 (СН3); 33.3 (SCH2); 61.1 (OCH2);
110.3 (br. s) and 117.3 (br. s, C-4,7); 121.4 (br. s, C-5,6); 136.6 (br. s) and 143.4 (br. s, C-3a,7a); 149.1 (C-2);
168.5 (С=О). The spectra contained also some signals due to an impurity, possibly a double alkylation product
at the nitrogen atom. 1H NMR spectrum, δ, ppm (J, Hz): 4.55 (2Н, s); 7.28-7.36 (with a broad signal of the main
product in the background, ~2H, m); 7.57 (1Н, d, J = 7.8); 7.87 (1Н, d, J = 7.3). 13C NMR spectrum, δ, ppm:
111.8; 118.5; 123.4; 125.4. Found, m/z: 237.0694. C11H13N2О2S [M+H]+. Calculated, m/z: 237.0692.
Amide of (1H-Benzimidazol-2-ylsulfanyl)acetic Acid (6d). Sodium hydroxide (1.60 g, 40 mmol) was
dissolved in 2-PrOH (70 ml), benzimidazole-2-thione 1 (6.00 g, 40 mmol) was added followed by portionwise
addition of chloroacetamide (3.75 g, 40 mmol). The reaction mixture was refluxed for 3 h, cooled, the
precipitate was filtered off, washed with water, and dried. Yield 6.75 g (81%), colorless crystals, mp 206-208°С
1554