Synthesis of pyrazolo[1,5-a]pyrimidines in the reaction of 5-amino-3-arylpyrazoles with methoxymethylene meldrum's acid derivatives and thermolysis of their pyrazolylaminomethylene derivatives

A series of pyrazolo[1,5-a]pyrimidin-3-ones 3 was prepared from Meldrum's acid and 5-amino-3-arylpyrazoles 1 by cyclization in nitrobenzene of the corresponding 5-pyrazolylaminomethylene Meldrum's acid derivatives 2 . The structure of pyrazolo[1,5-a]pyrimidin-3-ones and their precursors were determined by nmr measurements.