反应详情

4.75 g of 2-(5-oxo-5H-[1]benzopyrano[2,3-b]pyridin-7-yl)propionic acid is dissolved in a solution of 0.88 g of sodium hydroxide in 25 ml of water. To the solution are added 5 g of sodium borohydride and a small amount of toluene, and the mixture is heated under reflux for 3 hours. The reaction mixture is adjusted to pH 3 by adding concentrated hydrochloric acid under ice cooling. The resulting crystalline precipitate is filtered off, washed with water, and recrystallized from aqueous dioxane to give 2.5 g of 2-(5H-[1]benzopyrano[2,3-b]pyridin-7-yl)propionic acid as white needles melting at 182.5°-183.5°C.

1. temperatureunder reflux for 3 hours
2. filtrationThe resulting crystalline precipitate is filtered off
3. washwashed with water
4. customrecrystallized from aqueous dioxane