4-(4-Methoxybenzoyl)-5-(4-methoxyphenyl)-2,3-furandione 1 reacted with N-aryl substituted phenyl-hydrazones 3a-h via the p,p'-dimethoxydibenzoylketene intermediate 2 giving the proponohydrazide derivatives 5a-h. In addition, compounds 5a-h were converted into corresponding pyrazolone derivatives 7i,j by the reactions of hydrolysis in acidic solution. The structures of these new synthesized compounds were determined by C-13 NMR, H-1 NMR and IR spectroscopic data and elemental analysis.