Hydrochloric Acid → 2-chloro-1-ethyl-1H-1,3-benzodiazole

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Reaction Steps

1-Ethyl-2-benzimidazolinone (100 g, 0.62 mol) was dissolved in phosphorus oxychloride (475 mL) with stirring and heated to reflux temperature. Hydrogen chloride gas was passed into the refluxing solution for 4 h. Excess phosphorous oxychloride was removed on a rotary evaporator at 70° C. The residue was poured into a stirred mixture of aqueous potassium carbonate solution and methylene chloride. The mixture was basified with 50% sodium hydroxide solution and the methylene chloride layer was separated, dried (Na2SO4), concentrated, and distilled to obtain 86 g (77%) of oil, bp 110°-115° C./2-0.3 mmHg, which crystallized on standing; mp 50°-52° C.

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