p-Toluenesulfonic acid → 4,6-dichloro-3-(4-(trifluoromethyl)benzyl)-3H-imidazo[4,5-c]pyridine

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4,6-dichloro-3H-imidazo[4,5-c]pyridine (500 mg, 2.6 mmol), PPh3 (762 mg, 2.91 mmol) and THF (20 mL) were combined and stirred under a nitrogen atmosphere. A solution of 4-trifluoromethyl benzyl alcohol (513 mg, 2.91 mmol) in THF (5 mL) was added at rt. The reaction mixture was cooled to 0° C., and diisopropyl azodicarboxylate (587 mg, 2.91 mmol) was added dropwise. The reaction was warmed to rt and stirred overnight under N2. The reaction was then diluted with EtOAc, washed with brine, dried over Na2SO4, filtered, and concentrated. The crude residue was dissolved in EtOAc (20 ml), p-toluenesulfonic acid (500 mg, 2.91 mmol) was added at rt, and the mixture was stirred for 3 h. The precipitate which formed was collected by filtration and rinsed with EtOAc. The collected precipitate was slurried in EtOAc (50 mL) and was stirred vigorously with aqueous sat'd NaHCO3 (5 mL) for 30 min. The organic layer was separated, and the aqueous layer was extracted several times with EtOAc. The combined organic layers were dried over Na2SO4, filtered, and concentrated. The crude product was purified by silica gel chromatography with 20% to 100% EtOAc/hexanes to obtain the desired isomer, 4,6-dichloro-3-(4-(trifluoromethyl)benzyl)-3H-imidazo[4,5-c]pyridine. 1H NMR (400 MHz, CDCl3): δ8.85 (s, 1H); 7.96 (s, 1H); 7.71 (d, J=8.0 Hz, 2H), 7.33 (d, J=8.0 Hz, 2H), 5.89 (s, 2H). MS APCl calc'd. for C14H8Cl2F3N3 [M+H]+ 346, found 346.

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