Phosphorus oxychloride → 2-Chloro-5,6-dinitrobenzimidazole

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Reaction Steps

As represented in the following synthesis scheme, 10 g of 2-benzoimidazolone was heated and stirred in 100 mL of nitric acid (1.38) at 70° C. for 1 hour, followed by diluting with cold water, to thereby obtain yellow green 5,6-dinitro-2-benzoimidazolone (yield 76.5%). The thus obtained 5,6-dinitro-2-benzoimidazolone was refluxed in phosphorous oxychloride at 140° C. for 7 hours, followed by evaporating the excessive phosphorous oxychloride under reduced pressure, and neutralizing with an aqueous solution of sodium hydrogen carbonate, to thereby obtain yellow 5,6-dinitro-2-chlorobenzimidazole the 2-position of which was chloridized (yield 64.7%).

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