Y. Akcamur et al., FUNCTIONALIZATION AND CYCLIZATION REACTIONS OF 4-BENZOYL-1,5-DIPHENYL-1H-PYRAZOLE-3-CARBOXYLIC ACID, Journal of heterocyclic chemistry, 34(1), 1997, pp. 221-224
The 1H-pyrazole-3-carboxylic acid 2 or its remarkably stable acid chlo
ride 3 can easily be converted into the corresponding ester or amide d
erivatives 4 or 5, respectively, from reaction with alcohols or N-nucl
eophiles. Pyrazolo[3,4-d]pyridazines 6a,b are obtained from cycloconde
nsation reactions of the pyrazoles 3 and 3, respectively, with phenylh
ydrazine or hydrazine hydrate, while 6c is formed in an one-pot proced
ure from the furan-a,3-dione 1 and hydrazine hydrate.