1,5-DIARYLPENT-4-ENE-1,3-DIONES IN THE SYNTHESIS OF SPIRO[(THIA)PYRROLIZIDINE-3,3'-OXINDOLES] AND 1,3-DIARYL-5-SPIRO[OXINDOLE-3,3'-PYRROLIZIDIN-2'-YL]-1H-PYRAZOLES

Abstract

The three-component reaction of (E)-1,5-diarylpent-4-ene-1,3-diones, isatins, and (thia)proline in i-PrOH at room temperature proceeds regio- and stereoselectively leading to the formation of spiro[(thia)pyrrolizidine-3,3'-oxindoles] with the 1,3-dicarbonyl moiety in the (thia)pyrrolizidine ring. Subsequent treatment of these tetracyclic products with arylhydrazine hydrochlorides under reflux in the EtOH–AcOH system gave 5-substituted 1,3-diaryl-1H-pyrazoles in high yields.