p-Toluenesulfonic acid monohydrate → 2-Benzo[1,3]dioxol-5-yl-1-(4-methanesulfonyl-phenyl)-4-trifluoromethyl-1H-imidazole

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A mixture of 5-[1-[4-(methylsulfonyl)phenyl]-4-hydroxy-4-(trifluoromethyl)-4,5-dihydro-1H-imidazol-2-yl]-1,3-benzodioxole from Step 2 (1.26 g, 2.9 mmol) and p-toluenesulfonic acid monohydrate (200 mg) in toluene (50 mL) was heated to reflux for 72 hours. The reaction mixture was cooled and the solvent removed under reduced pressure. The crude residue was redissolved in methylene chloride and washed with water, aqueous sodium bicarbonate and brine. After drying (Na2SO4), filtration and concentration in vacuo, the crude mixture (1.34 g) was purified by chromatography on silica gel using toluene/ethyl acetate 1/1 to give pure 5-[1-[4-(methylsulfonyl)phenyl]-4-(trifluoromethyl)-1H-imidazol-2-yl]-1,3-benzodioxole (940 mg, 80%) as a white solid: mp (DSC) 165° C. Anal Calc'd. for C18H13N2SO4F3: C, 52.68, H, 3.19, N, 6.83. Found: C, 53.05, H, 3.19, N, 6.65.

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