Abstract A green, rapid, and efficient methodology is developed for the synthesis of 1-phenyl-3,5-pyrazolidinedione (3) by the reaction of malonic acid with phenyl hydrazine in the presence of phosphorous oxychloride under solvent-free conditions. The later compound 3 was used as a versatile precursor for green synthesis of chalcone derivatives (4a-h) and spiroheterocyclic compounds (5a-h) with good to excellent isolated yields. The chemical structures of the synthesized compounds were elucidated on the basis of elemental and spectral analyses.