Phosphorus oxychloride → 2-chloro-6-methyl-1H-1,3-benzodiazole

Beteiligte Stoffe

Reaktionsschritte

5-Methyl-1,3-dihydro-2H-benzimidazol-2-one (13.1 g, 88.5 mmol) and phosphorus oxychloride (130 ml, freshly distillated) was charged into three-neck round-bottom flask. The mixture was heated up to boiling point till homogeneous solution was formed. After that the dried hydrogen chloride was bubbled through inlet gas-pipe into the reaction mixture. The mixture was boiled for 15 hours. Excess of phosphorus oxychloride was distillated in vacuo. Mixture of ice and water (250 ml) was added to residue. The obtained suspension was cooled to the room temperature and filtered. Filtrate was alkalinized by aqueous ammonia solution till pH 8, cooled by cold water and filtered crude 2-chloro-6-methyl-1H-benzimidazole. White powder was crystallized from aqueous methanol (water-methanol: 1:1, 200 ml), washed by aqueous methanol and dried in a desiccator under phosphorous oxide in vacuo. Yield: 8.17 g (55%).

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