Nitric Acid → 2,6-Dibromo-4-nitropyridine

Participants

Reaction Conditions

Reaction Steps

A solution of 20 g (78 mmol) of 2,6-dibromopyridine 1-oxide in 70 ml of H2SO4 is warmed to 40° C. Nitrating acid (70 ml of H2SO4 and 34 ml of fuming HNO3) is added to the solution at this temperature. The reaction mixture is heated at 90° C. for 3 h. After cooling, the mixture is poured into 800 ml of ice-water. The precipitated solid is filtered off and washed with water. After drying, the 2,6-dibromo-4-nitropyridine 1-oxide (17.9 g) is suspended in 200 ml of chloroform, 6 ml of phosphorus tribromide (64 mmol) are added at room temperature, the mixture is stirred for 1 h and then heated under reflux for 2 days. After cooling, the solution is poured into 500 ml of ice-water and neutralised using solid NaHCO3. The aqueous phase is separated off and extracted a number of times with CHCl3, the combined organic phases are washed with a sodium thiosulfate solution and then with water, dried and evaporated. The residue is recrystallised from EtOH. Yield: 41.7 g (148 mmol), 70% of theory.

Provenance & Evidence