Hydrochloric Acid → 2-Chloropyridine-3-sulfonyl chloride

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Reaction Steps

A solution of sodium nitrite (6.5 g) in water (15 ml) was added gradually to a solution of 3-amino-2-chloropyridine (10 g) in acetic acid (100 ml) and concentrated hydrochloric acid (37 ml) at 0-5° C. This cold solution was then added portion-wise to a stirred and cooled (5° C.) mixture of copper(I) chloride (2.33 g) in acetic acid (160 ml) saturated with sulphur dioxide keeping the temperature below 10° C. After the addition was complete the cooling bath was removed and the mixture was stirred a further 90 minutes at ambient temperature. Volatile material was removed by evaporation and water (300 ml) was added to the residue to give a solid. The water was decanted off and the solid was dissolved in ether (500 ml) and washed with saturated aqueous sodium hydrogen carbonate solution (200 ml), water (200 ml) and saturated sodium chloride solution and was then dried (MgSO4). Volatile material was removed by evaporation to give 2-chloropyridine-3-sulphonyl chloride (12.1 g) as an oil which solidified upon refrigeration and was used without further purification; 1H NMR (CDCl3): 7.5 (dd, 1H), 8.5 (dd, 1H), 8.7 (dd, 1H).

Provenance & Evidence