Isatins 3-C annulation vs ring-opening: Two different pathways for synthesis of spiro compounds via multicomponent reactions

An efficient synthesis of spiro compounds via two different pathways from the reactions of isatins, 3-phenylisoxazol-5(4H)-one (3-ethylisoxazol-5(4H)-one), and pyrazol-5-amine (6-aminopyrimidine-2,4(1H,3H)-dione) were reported. The catalyst Amberlyst-15 could be easy recycled and reused for many time without any appreciable loss in catalytic activity. The new type spiro compounds were gained through the ring-opening of isatins process. The structures of spiroindoline-3,4′-isoxazolo5,4-b]pyrazolo4,3-e]pyridin]-2-one, spiroisoxazolo5,4-b]quino line-4,5′-pyrrolo2,3-d]pyrimidine]-2′,4′,6′(1′H,3′H,7′H)-trione, and spiroindoline-3,4′-pyrazolo3,4-b]pyridine]-2,6′(5′H)-dione were successfully confirmed by ¹H NMR, ¹³C NMR, HRMS, and X-ray crystal diffraction analysis.