A new 1H-pyrazole-5-carboxylic acid 2 was synthesized from the reactions of 4-(4-methylbenzoyl)-5-(4-methylphenyl)furan-2,3-dione (1) and 4-nitrophenylhydrazine. Then compound 2 was transformed into the corresponding hydroxamate 5 or amino acid ester 6 derivatives, via reactions of its acid chloride 4 with several nucleophiles. Compound 4 was also converted easily into the new derivative consisting of 5-[4-(4-methylbenzoyl)-3-(4-methylphenyl)-1-(4-nitrophenyl)-1H-pyrazol-5-yl]-4H-1,2,4-triazol-3-thione (7) by simple treatment with thiosemicarbazide.