Phosphorus pentachloride → 5-Bromo-6-chloropyridine-3-sulfonyl chloride

Participants

Reaction Conditions

Reaction Steps

A cooled (0° C.) solution of 6-amino-5-bromopyridine-3-sulfonic acid (12.65 g; 50.00 mmol) in HCl (60 ml; 5 N solution in water) was treated carefully with a solution of sodium nitrite (3.80 g; 55.0 mmol) in water (15 ml) and stirred at 0° C. for 1 hour. The solvents were evaporated and the residue was dried under high vacuum for 2 days, then treated with phosphorus pentachloride (15.00 g; 72 mmol) and phosphorus oxide chloride (0.50 ml; 5.5 mmol). The solid mixture was heated at 125° C. to give a refluxing solution. After heating at 75° C. for 3 hours, the solution was cooled and carefully poured on crushed ice. EtOAc was added and the phases separated. The organic phase was washed with brine, dried on MgSO4, filtered and concentrated under reduced pressure to give the title compound as a brown oil (14.91 g, quantitative yield), which was used without purification.

Provenance & Evidence