3-Fluoro-4-nitrobenzaldehyde → 2-(4-tert-Butyl-phenyl)-4-[4-(3-fluoro-4-nitro-benzyl)-piperazin-1-yl]-1H-benzoimidazole

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To a stirring solution of 2-(4-tert-Butyl-phenyl)-4-piperazin-1-yl-1H-benzoimidazole (0.857 g, 2.56 mMol) and 3-Fluoro-4-nitro-benzaldehyde (0.52 g, 3.07 mMol) in N-methylpyrrolidinone (20 mL) was added sodium triacetoxyborohydride (1.36 g, 6.40 mMol) and the solution stirred overnight. Upon arrival the solution was diluted with ethyl acetate (200 mL). The mixture was washed with saturated sodium bicarbonate solution (75 mL), water (75 mL), and brine (75 mL). The organic layer was then dried with magnesium sulfate, filtered, concentrated, and purified by flash column chromatography on silica gel using 40% ethyl acetate in hexane as the eluant to yield 850 mg (68% yield) of 2-(4-tert-Butyl-phenyl)-4-[4-(3-fluoro-4-nitro-benzyl)-piperazin-1-yl]-1H-benzoimidazole as a light yellow solid. 1H NMR (DMSO-d6): δ=12.69 (s, 1H), 8.16 (t, 1H, J=8.2 Hz), 8.04 (d, 2H, J=8.5 Hz), 7.59 (m, 1H), 7.55 (d, 2H, J=8.5 Hz), 7.47 (d, 1H, J=8.6 Hz), 7.03 (m, 2H), 6.50 (dd, 1H, J=7.0, 1.8 Hz), 3.71 (s, 2H), 3.60 (br s, 4H), 2.66 (br s, 4H), 1.33 (s, 9H). LC/MS (Method A), rt=1.24 mins., purity=100%, calculated mass=487, [M+H]+=488, [M−H]−=486.

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