Pyrimidine Derivatives and Related Compounds, I Synthesis of Some 2,3-Disubstituted-4,5,6,7-Tetrahydropyrazolo[1,5-a]-Pyrimidine Derivatives

Abstract

The 5-aminopyrazole derivatives (1 a-c) react with acrylonitrile to yield the corresponding 1-β-cyanoethyl-5-aminopyrazole derivatives (2 a-c) which could be readily cyclised into the corresponding pyrazolo[1,5-a]pyrimidines (3 a-c). Under similar conditions 1 a-c has failed to react with methylacrylonitrile or methyl methactylate. However, when the reaction of 1 a-d with these reagents was conducted in ethanolic sodium ethoxide, the pyrazolo[1,5-a]pyrimidine derivatives (3d-f) were formed. Structures of resulting products was established by their synthesis via interaction of β-cyanoethylhydrazine (4) and β-cyanopropylhydrazine (10) with the appropriate β-bifunctionalnitrile. Compounds 1 a, b also reacted with methyl phenylpropiolate to yield the pyrazolo[1,5-a]pyrimidine derivatives (18).