Studies of pyrimidine-2,4-diones: synthesis of novel condensed pyrido[2,3-d]pyrimidines via intramolecular cycloadditions

Abstract

Suitably functionalised pyrimidine-2,4-diones (1) cyclised intramolecularly to yield the novel furo[2″,3″:4′,5′]isoxazolo[3′,4′:4,5]pyrido[2,3-d]pyrimidines (5) and (9) in excellent yields. Remarkably, the pyrimidone nucleus was unaffected nor were there any side-reactions in this synthesis.