Functionalization and cyclization reactions of 4‐benzoyl‐1,5‐diphenyl‐ 1<i>H</i>‐pyrazole‐3‐carboxylic acid

Abstract

Abstract The 1 H ‐pyrazole‐3‐carboxylic acid 2 or its remarkably stable acid chloride 3 can easily be converted into the corresponding ester or amide derivatives 4 or 5, respectively, from reaction with alcohols or N ‐nucleophiles. Pyrazolo[3,4‐ d ]pyridazines 6a,b are obtained from cyclocondensation reactions of the pyrazoles 2 and 3, respectively, with phenylhydrazine or hydrazine hydrate, while 6c is formed in an one‐pot procedure from the furan‐2,3‐dione 1 and hydrazine hydrate.