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

Two new syntheses of pyrazolo1,5-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-dimethylpyrazolo1, 5-a]-s-triazine ( 16 ). (b) Condensation of aminoguanidine with β-oxo-nitriles affords 1-amidino-5-aminopyrazoles 18 . These are cyclised to pyrazolo1,5-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 pyrazolo1,5-a]-s-triazines 30 with electrophiles leads to compounds substituted at position 8, e.g. 32a--e .