Unusual mechanistic pathway for the synthesis of novel spiro-oxindoles via 3-phenyl-5-isoxazolone ring cleavage by secondary amino acids

A new approach to synthesize a series of spiro-oxindole derivatives via a multicomponent reaction of isatin, 3-phenyl-5-isoxazolone, and sarcosine or l-proline which play a dual role of base and nucleophile in methanol under reflux condition is reported. Also spiroindan-1,3-diones were synthesized from ninhydrin and 3-phenyl-5-isoxazolone. The methodology affords high yields of products in a short reaction time.