Sulfuric Acid → 4-Bromo-1-fluoro-2-iodobenzene

Participants

Reaction Conditions

Reaction Steps

A solution of sodium nitrite (1.71 g) in water (4 cm3) was added dropwise to a stirred mixture of 5-bromo-2fluoroaniline (4.5 g), water (15 cm3), ice (15 g) and concentrated sulphuric acid (1.8 cm3) at a temperature maintained at 0°-5° C. The reaction mixture was stirred for 30 minutes, and further concentrated sulphuric acid (0.4 cm3) added. The resultant solution, containing 5-bromo-2-fluorobenzenediazonium sulphate, was then added dropwise to a solution of potassium iodide (4.23 g) in water (10 cm3) at a temperature of 5°-6° C.; vigorous effervescence was observed during the addition. When the addition was complete, the reaction mixture was allowed to warm to the ambient temperature (22° C.) and was then extracted twice with diethyl ether. The combined extracts were washed successively with brine and sodium thiosulphate solutions, dried over anhydrous magnesium sulphate, filtered and concentrated by evaporation of the solvent under reduced pressure. The residual oil was purified by flash column chromatography, using a silica gel support and eluting with petroleum ether (boiling range 40°-60° C.) containing 4% by volume diethyl ether, to give 4-bromo-1-fluoro-2-iodobenzene (4.63 g) as a colourless oil.

Provenance & Evidence