Methanesulfonic Acid → 5-(5-Nitrobenzoxazol-2-yl)-2-methyl-1-(tetrahydropyran-4-yl)benzimidazole

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To 2-methyl-1-(tetrahydropyran-4-yl)benzimidazole-5-carboxylic acid HCl salt (see Working Example 4-3) (264 mg, 0.888 mmol) was added thionyl chloride (2 mL), and this was stirred at reflux for 3 hours. After the reaction was complete, concentration at reduced pressure gave a residue that was added to 2-amino-4-nitrophenol (137 mg, 0.888 mmol), triethylamine (449 mg, 4.44 mmol) and tetrahydrofuran (10 mL), and this was stirred at room temperature for 14 hours. After the reaction was complete, this was concentrated, and to a dioxane (5 mL) solution of the residue obtained was added methanesulfonic acid (140 mg, 1.46 mmol), and this was heated to reflux for 18 hours. After the reaction solution was cooled, water and saturated aqueous sodium hydrogen carbonate solution were added, and this was extracted with chloroform. After the organic layer obtained was dried over anhydrous sodium sulfate, it was filtered and concentrated. The residue obtained was purified by silica gel column chromatography to yield the title compound (66 mg, 20% yield) as white crystals.

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