One-pot synthesis of isomeric cycloalkatriazolopyrimidines

Three-component condensation of 4H-1,2,4-triazol-3-amine with furfural (benzaldehyde) and cycloalkanone gave [1,2,4]triazolo[1,5-a]pyrimidine derivatives with a C6–C8 cycloalkene ring fused at the C5–C6 bond as mixtures of two isomers differing by the position of the double bond in the cycloalkene ring. The double bond in the major isomers is common to the cycloalkene and tetrahydropyrimidine rings, while the minor isomers have the C4a=C5 double bond. The isomers were isolated in the pure state, and their structure was determined on the basis of spectral data.