Neue Synthesen von Pyrazolo[1,5‐a]‐s‐triazinen

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Abstract
Two new syntheses of pyrazolo[1,5‐a]‐s‐triazines are reported: (a) Addition of acetyl isocyanate to 5‐amino‐3‐methyl‐pyrazole followed by hydrolysis yields N‐(3‐methyl‐5‐pyrazolyl)‐urea (15), which on cyclisation with triethyl orthoacetate gives 2‐hydroxy‐4,7‐dimethylpyrazolo[1, 5‐a]‐s‐triazine (16). (b) Condensation of aminoguanidine with β‐oxo‐nitriles affords 1‐amidino‐5‐aminopyrazoles 18. These are cyclised to pyrazolo[1,5‐a]‐s‐triazines 19‐‐21 by reaction with orthoesters, acetic‐formic anhydride, phenylisocyanide dichloride, dimethyl oxalate, N, N′‐carbonyldiimidazole, and N, N′‐thiocarbonyldiimidazole. The 4‐amino group in 19 is converted by standard procedures to OH, SH, SCH3, Cl and NRR′. Reaction of pyrazolo[1,5‐a]‐s‐triazines 30 with electrophiles leads to compounds substituted at position 8, e.g. 32a‐‐e.