Tetrafluoroboric acid → 2-n-Butyl-1-{(2-chlorophenyl)methyl}-4-fluoro-5-carboethoxyimidazole

Participants

Reaction Conditions

Reaction Steps

The 4-amino product was fluorinated using the procedure of K. L. Kirk and L. J. Cohen, JACS, 95 (14), 4619 (1973). Fluoroboric acid (48%, 150 mL) was added to 2-n-butyl-1-{(2-chlorophenyl)methyl}-4-amino-5-carboethoxyimidazole (10.75 g, 0.032 mol) in a quartz flask. The resulting solid mass was sonicated and stirred vigorously to form a suspension. This suspension was cooled to 0° C. and then sodium nitrite (2.80 g, 0.0406 mol) in 5 mL of water was added slowly. The ice bath was removed and then the reaction mixture was irradiated for 20 hours with a 450-watt mercury vapor lamp placed in a quartz immersion well, cooled by circulating water. The reaction mixture was cooled to -20° C. and the pH was adjusted to 6.4 with 50% aqueous sodium hydroxide. The product was extracted into ethyl acetate (3×) and the combined extracts were washed with water and saturated sodium chloride solution. The organic extract was dried with anhydrous sodium sulfate and concentrated to give 8.43 g of a crude product, which was chromatographed on silica gel eluting with chloroform to give 4.31 g of 2-n-butyl-1-{(2-chlorophenyl)methyl}-4-fluoro-5-carboethoxyimidazole.

Provenance & Evidence