Hydrochloric Acid → 5H-chromeno[2,3-b]pyridine

Participants

Reaction Steps

A mixture of 10 g of 5-hydroxy-5H-[1]benzopyrano[2,3-b]pyridine, 100 ml of isopropyl alcohol and 10 ml of 20% hydrochloric acid in isopropyl alcohol is refluxed for 3 hours. The reaction mixture is allowed to stand overnight, and then the isopropyl alcohol is removed by distillation under reduced pressure. An aqueous potassium carbonate solution is added to the residue, and the mixture is extracted with chloroform. The chloroform layer is dried, and the chloroform is distilled off. The residue is recrystallized from isopropyl ether or carbon tetrachloride to give 7.5 g of 5H-[1]benzopyrano[2,3-b]pyridine as white crystals melting at 87°-88°C.

Provenance & Evidence