Hydrogen Bromide → 5'-Bromo-2'-fluorobiphenyl-2-carbonitrile

Participants

Reaction Conditions

Reaction Steps

A solution of 5′-amino-2′-fluorobiphenyl-2-carbonitrile (7.85 g, 37 mmol) in 1,4-dioxane (25 ml) was treated with 48% hydrobromic acid (125 ml) and the resulting suspension stirred and cooled to 3° C. (internal temperature). A solution of sodium nitrite in water (5 ml) was then added dropwise over 20 min keeping the internal temperature <5° C. Stirring at <5° C. was continued for 2 h before pouring the reaction into a cooled (5° C.) solution of freshly purified copper(I) bromide (6.37 g, 44 mmol) in 48% hydrobromic acid (50 ml). The resulting purple reaction mixture was stirred at 5° C. for 10 min then warmed to 50° C. for 20 min. The reaction was diluted with ice-cold water (500 ml) and extracted with ethyl acetate (2×250 ml). The organics were combined, washed with 5% aqueous sodium sulfite, saturated aqueous ammonium chloride, dried over anhydrous magnesium sulfate, filtered and pre-adsorbed onto silica. Purification by chromatography on silica eluting with isohexane (containing 1% methanol) on a gradient of ethyl acetate (2-10%) afforded a colourless oil which crystallised on standing to give 5′-bromo-2′-fluorobiphenyl-2-carbonitrile as a white solid (6.5 g, 64%): δH (400 MHz, CDCl3) 7.09-7.14 (1H, m), 7.45-7.57 (4H, m), 7.66 (1H, td, J 8 and 2), 7.77 (1H, dd, J 8 and 2).

Provenance & Evidence