Lewis-acid catalyzed dehydrative [3+2] cycloaddition reaction: A facile synthetic approach to spiro-benzoindoline oxindoles

[Display omitted] •Lewis acid-catalyzed synthesis of new spiro-benzoindoline oxindole scaffold from spiro-aziridine oxindole.•Strategy involves regioselective spiro-aziridine ring opening followed by dehydrative formal [3+2] cycloaddition.•The regioselectivity was confirmed unambiguously by X-ray analysis. An efficient one-pot method for the construction of C–C and C–N bond has been established from activated spiro-aziridine oxindoles using different substituted 2-naphthols by employing BF3‧OEt2 as a catalyst. This method features spiro-aziridine ring-opening (Friedel-Crafts type C–C bond formation) with concomitant dehydrative formal [3+2] cycloaddition leading to the formation of a complex and diverse benzoindoline fused spiro-oxindoles in moderate to good yields with wide substrate scope. Moreover, this protocol provides an avenue for the generation of a library of bioactive spiro-cyclic fused heterocyclic motifs which may prove to be of therapeutic interest.