Synthesis of Pyrrolo(spiro-[2.3′]-oxindole)-spiro-[4.3″]-oxindole via 1,3-Dipolar Cycloaddition of Azomethine Ylides with 3‑Acetonylideneoxindole

A series of novel dispirooxindole
derivatives, 3-acetyl-5-phenyl-pyrrolo­(spiro-[2.3′]-1′-benzyl-oxindole)-spiro-[4.3″]-1″-benzyl-oxindoles,
were synthesized via 1,3-dipolar cycloaddition of the azomethine ylide
with 3-acetonylideneoxindole in high regioselectivities and yields.
An unusual regioselectivity was observed in this 1,3-dipolar cycloaddition,
leading to the construction of novel dispirooxindole skeleton. The
substituent effects on the regioselectivity were also investigated.