The first method synthesis of 1-p-chlorobenzyl-2-methylbenzimidazole:
26.4 g of 2-methylbenzimidazole are dissolved in 350 ml of dioxane, 10 g of
sodium amide are added there to. After about 5 min 41,2 g of pchlorobenzylbromide are added to the resulting mixture which is then boiled
under reflux for 6 hours. Dioxane is removed by distillation. The residue is
triturated with dilute hydrochloric acid. The resulting crystalline mass
representing the crude hydrochloride of 1-p-chlorobenzyl-2-
methylbenzimidazole is filtered off by suction and recrystallized from water.
On cooling, colorless crystals are obtained which are dissolved in hot water.
Dilute ammonia solution is added to the resulting aqueous solution to render
it weakly alkaline. The base of 1-p-chloro-benzyl-2-methylbenzimidazole
precipitates, first in liquid form, and gradually solidifies to a white mass of its
hydrate. After recyrstallization from aqueous ethanol, the product has a
melting point of 67-68°C. The base of 1-p-chlorobenzyl-2-
methylbenzimidazole distills in the form of a colorless oil at 240-242°C/12
mm. Its hydrate of the melting point 67-68°C is obtained by trituration with
water.
The second method of synthesis of 1-p-chlorobenzyl-2-methylbenzimidazole:
23.3 g of p-chlorobenzyl-o-phenylenediamine are boiled under reflux with 75
ml of glacial acetic acid for 3 hours. Most of the acetic acid is then removed
by distillation. Dilute sodium hydroxide solution is added to the residue to
render it weakly alkaline. The resulting base of 1-p-chlorobenzyl-2-
methylbenzunidazole is purified as such by recrystallization from aqueous
ethanol. It may also be converted into its hydrochloride which is then worked
up as described hereinabove in the first method of synthesis.
