A novel P(NMe2)3-mediated reductive [1+4] annulation reaction between isatins and enones has been developed, providing the facile synthesis of spirooxindole-dihydrofurans. This reaction unveils the first practical approach to construct five-membered cyclic motifs via a Kukhtin-Ramirez adduct involved [1+4] annulation mode.

An unusual formal [1+4] annulation of α-dicarbonyl compounds with 1,1-dicyano-1,3-dienes has been realized, leading to facile syntheses of cyclopentenimines and cyclopentenones in a unique manner. Mechanistic investigation implies that this reaction takes place through a P(NMe2 )3 -mediated cyclopropanation followed by a base-catalyzed cyclopropane rearrangement. It therefore represents an unprecedented [1+4] annulation mode involving Kukhtin-Ramirez adducts.

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A formal [1+4] annulation of α‐dicarbonyl compounds with 1,1‐dicyano‐1,3‐dienes is realized, leading to facile syntheses of cyclopentenimines and cyclopentenones in a unique manner.