A clean and efficient cyclocondensation to pyrido[2,3-d]pyrimidine derivatives in aqueous media

A series of pyrido[2,3-d]pyrimidine derivatives were easily constructed by cyclocondensation reactions of 6-aminouracils or 6-aminothiouracil with α,β-unsaturated carbonyl compounds (aldehyde, ketone and ester) possessing a leaving group on the β position, in H2O under reflux conditions.