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An efficient approach to saccharin‐fused 1,4‐DHPs has been established by using a [3+3] annulation process. The chemical event was enabled by a Et3N‐catalyzed tandem Michael/aza‐Pinner reaction of alkyl cyclic N‐sulfonyl ketimines as nucleophiles with α,α‐dicyanoolefins. Under mild conditions, the desired products were readily prepared in good to excellent yields and with broad functional group tolerance (up to 95 % yield, 29 examples). Notably, this practical methodology features the synthesis of pentacyclic spirooxindoles bearing a quaternary spiro‐stereocenter. [ABSTRACT FROM AUTHOR]