Acetic Acid → 4-Bromo-3,5-difluorobenzonitrile

Participants

Reaction Conditions

Reaction Steps

While stirring 420 cm3 of concentrated H2SO4 on an ice water bath, 54 g (0.78 mol) of pulverized NaNO2 was added at a rate that maintained a temperature under 40° C., and after the addition it was stirred in a hot water bath at 50° C. until the crystals dissolved completely. While stirring this solution on an ice water bath, 700 cm3 of glacial acetic acid was added dropwise, then 108 g (0.7 mol) of 4-amino-3,5-difluorobenzonitrile was added at a rate maintaining the temperature at 20°-25° C., and after the addition was completed it was stirred at this temperature until the crystals were completely dissolved to prepare a diazonium salt solution. A solution with 143 g (1.0 mol) of CuBr dissolved in 420 cm3 of 47% HBr was stirred in an ice water bath while the previously prepared diazonium salt solution was added dropwise for 2 hours, and after the dropping was completed, it was stirred on an ice water bath for 1 hour and at room temperature overnight. The crystals formed were filtered, and after washing the crystals in glacial acetic acid, they were recrystallized from a mixture of acetone and methanol to obtain 98 g (0.44 mol) of 4-bromo-3,5-difluorobenzonitrile.

Provenance & Evidence