Acetic Acid → 4-(1H-benzimidazol-2-yl)phenol

Participants

Reaction Steps

A mixture of 324 g (0.3 mol) of o-phenylenediamine, 67.5 g (0.36 mol) of benzene carboximidoic acid, 4 hydroxy-, methyl ester hydrochloride and 450 ml of glacial acetic acid was stirred at reflux for two hours. After standing overnight at room temperature the hydrochloride salt of the benzimidazole was collected by filtration, washed with acetic acid, and finally ether. The hydrochloride salt of the product was suspended in 450 ml of dilute ammonium hydroxide, stirred for one hour at room temperature, and chilled briefly. The product was collected and the filter cake was treated with charcoal during recrystallization from a 2:1 water-alcohol mixture. Filtration gave 45.9 g (73%) of 4-(1H-benzimidazol-2-yl)phenol (mp 286°-289° C.) and a second crop of 2.8 g on standing.

Provenance & Evidence