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Neue Synthesen von Pyrazolo[1,5‐ a ]‐ s ‐triazinen
Author(s) -
Vogel Arnold,
Troxler Franz
Publication year - 1975
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19750580312
Subject(s) - chemistry , electrophile , acetic anhydride , medicinal chemistry , formic acid , isocyanate , hydrolysis , urea , oxalate , organic chemistry , catalysis , polyurethane
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, SCH 3 , 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 .