Pyrimidine Derivatives and Related Compounds, VII Synthesis of Some New Pyrazolo [1,5-a] -S-triazines, Pyrazolo [3,4-c] -as-triazines, Pyrazolo [1,5-a] pyrimidines and Pyrazolo [3,4-b] pyrones

Abstract

3-Amino-4-phenylhydrazono-2-pyrazolin-5-one (1) reacts with isothiocyanate to yield the corresponding pyrazolylthiourea derivatives (2 a-c). Whereas 2 a reacted with hydrazines to yield the pyrazolylamino-1,2,4-triazoles (3 a, b), it cyclised into the pyrazolo-[3,4-e]-as-triazine derivative (4) upon treatment with concentrated sulphuric acid. On the other hand, the pyrazolo[1,5-c]-S-triazine derivative (5) was formed from reaction of 2a with ethanolic sodium ethoxide. 3-Amino-2-pyrazolin-5-one (8) reacted with ethyl acrylate to yield a mixture of the 4-dialkylated derivative (9) and the pyrazolo[3,4-b]pyrone (11). Compound 11 could be converted into the corresponding pyrazolo[3,4-b]pyrones (12) and (13) by the action of acetic acid hydrochloric acid mixture and of concentrated sulphuric acid, respectively.