Ammonia → 5-(Benzothiazol-2-yl)-2-methyl-1-(tetrahydropyran-4-yl)benzimidazole

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A 4-neck flask (50 mL) equipped with reflux condenser was charged with 2-methyl-1-(tetrahydropyran-4-yl)benzimidazole-5-carboxylic acid HCl salt (see Working Example 4-3) (0.28 g, 1.08 mmol), 2-aminobenzenethiol (0.14 g, 1.08 mmol) and polyphosphoric acid (approx. 11 g), and this was heated to 150° C. and stirred for 17 hours. After being allowed to cool to room temperature, this was cooled in ice (0 to 5° C.), and concentrated aqueous ammonia (28%) was added to the liquid to give approx. pH 9. After distilling off the solvent under reduced pressure, the brown viscous residue was extracted with ethyl acetate, this was dried over anhydrous magnesium sulfate. The residue obtained after again distilling off the solvent under reduced pressure was purified by PTLC to yield the title compound (0.007 g, 1.8% yield) as greenish-pale yellow crystals.

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