Bicyclic pyrimidine derivatives with a bridgehead nitrogen atom. Part I. Synthesis of s-triazolo[4,3-a]pyrimidines

Abstract

The reaction of 2-hydrazinopyrimidines with ethyl imidate hydrochlorides has been explored as a new route to 3-substituted s-triazolo[4,3-a]pyrimidines. The synthesis of certain s-triazolo[4,3-a]pyrimid-7-ones by lead tetra-acetate oxidation of 1-alkyl-2-benzylidenehydrazinopyrimid-6-ones is described. 6-Ethoxycarbonyl-s-triazolo[4,3-a]pyrimid-7-ones readily isomerise to s-triazolo[1,5-a]pyrimid-5-ones.