Synthesis of New Fused and Spiro Heterocyclic Systems from 3,5‐Pyrazolidinediones

4-Bromo-1-phenyl-3,5-pyrazolidinedione 2 reacted with different nucleophilic reagents to give the corresponding 4-substituted derivatives 3-8. The cyclized compounds 9-11 were achieved on refluxing compounds 3, 4 4 or 6, in glacial acetic acid or diphenyl ether. 4,4-Dibromo-1-phenyl-3,5-pyrazolidinedione 12 reacted with the proper bidentates to give the corresponding spiro 3,5-pyrazolidinediones 13-15, respectively. The 4-aralkylidine derivatives 16 a - c , were subjected to Mannich reaction to give Mannich bases 17 a - c -22 a - c , respectively. 4-(p-Methylphenylaminomethylidine)-1-phenyl-3,5-pyrazolidinedione 23 or 4-(p-methylphenylazo)-1-phenyl-3,5-pyrazolidinedione 29 were prepared and reacted with active nitriles, cyclic ketones and N,S-acetals to give pyrano[2,3-c]pyrazole, pyrazolo[4',3':5,6]pyrano[2,3-c]pyrazole, spiropyrazole-4,3'-pyrazole and spiropyrazole-4,3'-[1,2,4]triazolane derivatives 24-34, respectively.