Pyrazole-4-carboxaldehyde from chromone-3-carboxaldehyde

It has been perviously reported that the action of hydrazine hydrate on chromones affordes the respective disubstituted pyrazoles [1]. Szabo et al.[2] reported in 1979 that hydrazine hydrate attacks 3-phenylchromone [isoflavone] at C-2 to give 3-[Q-hydroxyphenyl]- 4-phenylpyrazole. Also, the cyclization of acetophenone semicarbazone to 3-phenyl-pyrazole-4-carboxaldehyde was reported by Kira et al. [3]