Reactions with heterocyclic diazonium salts: New routes for the synthesis of pyrazolo[1,5‐<i>c</i>]‐1,2,4‐triazoles and pyrazolo[1,5‐<i>c</i>]‐as‐triazines

Abstract

Abstract 3‐Phenylpyrazole‐5‐(liazonium chloride ( 1 ) couples with α‐chloro derivatives of acetylacetone, ethyl acetoacetate and aceto‐ o ‐anisidine to yield the corresponding pyrazole‐5‐yl hydrazonyl chloride derivatives 2a‐c . Compounds 2a,b were cyclised to yield either the pyrazolo[1,5‐ c ]‐1,2,4‐triazole derivatives 3a,b or the pyrazolo[1,5‐ c ]‐as‐triazines 4a,b depending on the applied reaction conditions. Compound 2c cyclised only into 3c under different cyclization conditions. The pyrazolo[1,5‐ c ]‐ as ‐triazine derivatives 4c‐e could be prepared via condensation of 2a with potassium cyanide. Compound 2d reacted with aromatic thioles and with sodium benzene‐sulphonate to yield the pyrazolo[1,5‐ c ]‐ as ‐triazine derivatives 6a‐d . Compound 1 reacted with activated double bond systems to yield pyrazolo[1,5‐ c ]‐as‐triazines 8a,b and 9 .