Base catalyzed abnormal [3+2]-cycloaddition reaction of isatin N,N′‑cyclic azomethine imine with malononitrile via C-3 umpolung of oxindole

In this paper, we described a base promoted annulation reaction of isatin N,N'-cyclic azomethine imine and malononitrile for the synthesis of 1′,2′-dihydrospiro[indoline-3,6′-pyrrolo[1,2-b]pyrazole] derivatives using a new abnormal [3 + 2]-cycloaddition reaction. A variety of pyrrolo-pyrazole bearing oxindole scaffolds with medicinal capability were synthesized in moderate to high yields via C3 umpolung of oxindole.