Formic Acid → 5-Benzimidazolecarboxylic acid

Participants

Reaction Steps

3,4-Diaminobenzoic acid (20 g, 0.13 mol) was suspended in formic acid (120 ml) while cooling. After that hydrochloric acid (12 ml) was added. An obtained reaction mass was agitated for 24 hours at a room temperature. Reaction mixture was filtered through fiber glass filter. Then filter cake was dissolved in water (400 ml), pH was adjusted to 2.0 with ammonia solution and reaction mass was agitated overnight. Resulting suspension was filtered, pH of filtrate was adjusted to 3.0 with ammonia solution and reaction mass was agitated for two hours. Precipitate was filtered and dried at ˜100° C. H1NMR (Brucker Avance-300, DMSO-d6, δ, ppm): 7.695 (d, H, CHAr(7)); 7.877 (dd, H, CHAr(6)); 8.25 (d, H, CHAr(4)); 8.44 (s, H, (s, H, CHAr(2)); 12.82 (s, 2H, NH, COOH). Yield was 11.3 g (54%).

Provenance & Evidence