l-Proline Catalyzed Synthesis of Highly Functionalized 4-Hydroxy-4H-chromene-pyrazoles and 4-Hydroxy-4Hchromene-barbiturates in Aqueous Medium

摘要

A simple and efficient method for the synthesis of novel 4-hydroxy-4H-chromene-pyrazoles and 4-hydroxy-4H-chromenebarbiturates was developed from the reaction of 2-ethoxy-2Hchromene chalcones with pyrazolin-5-one and barbituric acid catalyzed by l-proline in water.The developed protocol is applicable for the construction of biologically important 4Hchromenes from easily accessible chalcones having various substituents.This reaction proceeds through Aldol condensation,Michael addition and hydrolysis reactions followed by the elimination of ethoxy group.This methodology offers cleaner conversion,a shorter reaction time and high yields.For the first time,we report the synthesis of novel 4-hydroxy-4H-chromenes from 2-ethoxy-2H-chromene chalcones and pyrazolin-5-one/barbituric acid using l-proline(72–86% yield in 6h).Water was used as the solvent for all the compounds it represents a green synthetic protocol.