p-Toluenesulfonic acid monohydrate → 2-Methyl-5-(6-nitrobenzoxazol-2-yl)-1-(tetrahydropyran-4-yl)benzimidazole

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Reaction Steps

5-(2-Hydroxy-4-nitroanilinocarbonyl)-2-methyl-1-(tetrahydropyran-4-yl)benzimidazole (see Working Example 47-1) (195 mg, 0.492 mmol) was added to toluene (20 mL), after which p-toluenesulfonic acid hydrate (280 mg, 1.47 mmol) was added and this was refluxed with stirring for 4 hours. After the solvent was concentrated under reduced pressure, a sodium bicarbonate water (10 mL) was added and this was stirred at room temperature for 1 hour. The precipitated crystals were filtered off, and after being washed with water were dried with heating at reduced pressure to yield the title compound (144 mg, 77.4% yield) as a pale yellow solid.

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