2-Hydroxy benzimidazole → 2-Chlorobenzimidazole

Participants

Reaction Steps

Benzimidazolin-2-one (13.0 g) was added to phosphoryl chloride and the mixture was heated under reflux for a period of 3.5 hours. The excess phosphoryl chloride was removed by distillation and the residue was treated with water. The acidic solution was cooled, filtered and made basic by the addition of dilute ammonium hydroxide. The solid was collected and recrystallised from aqueous ethanol to give 2-chlorobenzimidazole (11.5 g) as colourless needles, mp 214° C.

Provenance & Evidence