METHOD OF PREPARING 1-PHENYL-3-METHYL-5-PYRAZOLONE Russian patent published in 1998 - IPC

FIELD: pharmaceutical industry, more particularly, manufacture of antipyretics and chemistry of paints. SUBSTANCE: stage of condensation of phenyl hydrazine and acetoacetic acid ester and stage of cyclization of the resulting phenyl-hydrazone are combined. Reaction is carried out in aqueous medium at 50-1000 C for at least 0.5 h (40-50 min), to give product containing 98.2% main compound. Synthesis time is reduced to 0.5 h and yield is increased to 95%. EFFECT: reduced time to 0.5 h, yield is increased to 95%.