Sulfuric Acid → 1,2,4-Triazolo(4,3-a)pyridin-3(2H)-one

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Reaction Steps

A mixture of 50 g. (0.44 mole) of 2-chloropyridine and 98.22 g. (0.88 mole) of semicarbazide hydrochloride in 150 ml. of 2-ethoxyethanol was heated to reflux and then treated with a solution of 1 ml. of concentrated sulfuric acid (36 N) in 5 ml. of 2-ethoxyethanol. The resulting solution was refluxed for 18 hr., cooled to about 60°, and treated with 150 ml. of water. The mixture was stirred, cooled to 0°, and kept 0.5 hr. and the solid was collected on a filter. The solid was washed well with water and dried under reduced pressure, to give 35.0 g (59%) of product, m.p. 230°-231°, which was sufficiently pure to be used for the next step.

Provenance & Evidence