Thiamine hydrochloride as an acid catalyst for the facile green synthesis of pyrazolopyranopyrimidines under aqueous conditions

摘要

A clean, highly efficient, and environmentally safe methodology is introduced for the synthesis of pyrazolopyranopyrimidines via multicomponent reaction of ethyl acetoacetate, hydrazine hydrate, barbituric acid, and aldehyde, using thiamine hydrochloride as a catalyst. The prominent features of this reaction are tolerance of a wide range of functional groups at room temperature; moderate to excellent yields of final products; short reaction time with a straightforward work-up procedure. Water as a solvent for the reaction medium and the use of cheap acidic catalyst are added advantages of this environmentally benign protocol.