solution, and then the precipitate was filtered out. To purify the precipitate, it was dissolved in a 10% aqueous
solution of sodium hydroxide, boiled with activated charcoal, and neutralized with hydrochloric acid to pH 8;
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compound 3 precipitated as cream-colored flakes. Yield 2.07 g (76%); mp 239-241°C. H NMR spectrum,
δ, ppm (J, Hz): 6.45 (2H, s, NH2); 7.14 (1H, d, J = 8.3, H-7); 7.40 (1H, d, J = 8.3, H-6); 7.52 (1H, s, H-4); 7.64
(3H, m, H-3,4,5 arom.); 7.82 (2H, d, J = 6.8, H-2,6 arom.); 10.92 (1H, br. s, NH). Found, %: C 56.85; H 4.19;
N 15.60. C13H11N3O2S. Calculated, %: C 57.13; H 4.06; N 15.37.
2-Amino-5(6)-tosylbenzimidazole (3) was obtained as for compound 2, from compound 1 (1.33 g,
10 mmol) and p-toluenesulfonic acid (1.72 g, 10 mmol). Yield 2.35 g (82%); mp 259-261°C. 1H NMR spectrum,
δ, ppm (J, Hz): 2.36 (3H, s, CH3); 6.48 (2H, s, NH2); 7.15 (1H, d, J = 8.3, H-7); 7.30 (2H, d, J =8.7, H-3,4
arom.); 7.38 (1H, d, J = 8.3, H-6); 7.57 (1H, s, H-4); 7.72 (2H, d, J = 8.7, H-2,5 arom.); 10.94 (1H, br. s, NH).
Found, %: C 58.87; H 4.69; N 14.35. C14H13N3O2S. Calculated, %: C 58.52; H 4.56; N 14.62.
2-Amino-5(6)-sulfonylbenzimidazole Hydrosulfate (4) was obtained as for compound 2, from
compound 1 (1.33 g, 10 mmol) and sulfuric acid (d 1.84) (1.47 g, 15 mmol), but the sulfonic acid was separated
in a different way. The reaction mass was poured into water (100 ml). Upon cooling with ice, colorless crystals
1
of compound 4 precipitated, which were crystallized from water. Yield 1.96 g (63%); mp >350°C. H NMR
spectrum, δ, ppm (J, Hz): 7.25 (1H, d, J = 8.2, H-7); 7.48 (1H, d, J = 8.2, H-6); 7.58 (1H, s, H-4); 8.40 (2H, s,
NH2); 12.38 (2H, br. s, NH). Found, %: N 13.88. C7H9N3O7S2. Calculated, %: N 13.50.
2-Acetylaminobenzimidazole (5) was obtained as for compound 2, from compound 1 (1.33 g, 10 mmol)
and acetic acid (1.2 g, 20 mmol) at 140°C. The crude reaction product was crystallized from 2-propanol. Yield
1
1.52 g (87%); mp 310-311°C. H NMR spectrum, δ, ppm (J, Hz): 2.15 (3H, s, CH3); 7.00 (2H, m, H-6,7); 7.40
(2H, m, H-4,5); 11.78 (1H, br. s, NH); 11.48 (1H, br. s, NH). Found, %: C 62.02; H 4.97. C9H9N3O. Calculated,
%: C 61.70; H 5.18.
2-Benzoylaminobenzimidazole (6) was obtained as for compound 5, from compound 1 (1.33 g,
1
10 mmol) and benzoic acid (2.44 g, 20 mmol) at 160-180°C. Yield 1.82 g (77%); mp 287-288°C. H NMR
spectrum, δ, ppm (J, Hz): 7.03 (2H, dd, J = 6.4, H-6,7); 7.40 (2H, dd, J = 6.4, H-4,5); 7.52 (3H, m, H-3,4,5
arom.); 8.18 (2H, d, J = 6.8, H-2,6 arom.); 12.12 (2H, br. s, NH). Found, %: C 71.13; H 4.32. C14H11N3O.
Calculated, %: C 70.87; H 4.67.
This work was carried out with the financial support of grant 04-03-32485 of the Russian Foundation for
Basic Research.
REFERENCES
1.
2.
Ch. C. Price and R. H. Reitsema, J. Org. Chem., 12, 269 (1947).
N. I. Leonard, D. Y. Curtin, and K. M. Beck, J. Am. Chem. Soc., 69, 2459 (1947).
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