反应详情

A mixture of 3.4 g of isopropyl 5H-[1]benzopyrano[ 2,3-b]pyridine-7-carboxylate, 7 ml of concentrated hydrochloric acid and 17 ml of acetic acid is heated under reflux on an oil bath for 3 hours. The reaction mixture is concentrated, and a small amount of water is added to the residue. The mixture is adjusted to pH 2-3 by addition of 10% sodium hydroxide. The crystalline precipitate is filtered off and recrystallized from acetic acid to give 2.5 g of 5H-[1]benzopyrano[2,3-b]pyridine-7-carboxylic acid melting at 285°-286°C.

1. temperatureis heated
2. temperatureunder reflux on an oil bath for 3 hours
3. concentrationThe reaction mixture is concentrated
4. additiona small amount of water is added to the residue
5. additionThe mixture is adjusted to pH 2-3 by addition of 10% sodium hydroxide
6. filtrationThe crystalline precipitate is filtered off
7. customrecrystallized from acetic acid