Hydrogen Bromide → 6-Bromo-3-chloropicolinic acid

Participants

Reaction Conditions

Reaction Steps

20.0 g (104.2 mmol) of 3,6-dichloropyridine-2-carboxylic acid are admixed with 50 ml of acetic acid. Then 5 ml (33% by weight; 28.96 mmol) of a solution of hydrogen bromide in acetic acid are added. The mixture is heated to 110° C., and a further 22 ml (33% by weight; 127.4 mmol) of a solution of hydrogen bromide in acetic acid are added dropwise at this temperature. The reaction mixture is stirred at 110° C. until monitoring of the reaction by HPLC indicates virtually complete conversion. To accelerate the conversion, a further 40 ml in total (33% by weight; 231.7 mmol) of a solution of hydrogen bromide in acetic acid are added dropwise on three occasions during the reaction. For workup, the reaction mixture is poured onto ice-water. The contents are filtered and the residue is washed with water. The residue obtained is 20.5 g of the product with a purity of approx. 95% by weight. The filtrate is freed of the solvents on a rotary evaporator and the residue is stirred with water. The mixture is filtered; the residue obtained is 2.78 g of the product with a purity of approx. 89% by weight.

Provenance & Evidence