Hydrochloric Acid → 3-Bromo-5-chloropyridin-2-amine

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Reaction Steps

To produce 2-amino-3-bromo-5-chloropyridine, 30 parts of chlorine are introduced in the course of 50 minutes, with slight cooling, into a solution of 37.6 parts of 2-aminopyridine in 160 parts of concentrated hydrochloric acid (36%). A solution of 53 parts of potassium bromide in 50 parts of water is then added, and a further 30 parts of chlorine are introduced within one hour at a temperature of about 35° C., whereby finally a light-yellow precipitate occurs. The mixture obtained is stirred for a further 30 minutes. The solution is afterwards poured on to ice, and the free halogen still present is removed by the addition of sodium bisulphite solution. There is now added, with ice-cooling, a solution of 95 parts of sodium hydroxide in 190 parts of water. The resulting beige-coloured precipitate is filtered off with suction, washed with ice-water and dried at 30° to 40° C. in a water-jet vacuum. There are obtained 74 parts (90% of theory) of 2-amino-3-bromo-5-chloropyridine, m.p. 78°-79° C.

Provenance & Evidence