Phosphine-Catalyzed Formal [3 + 2] Annulation of γ-Vinyl Alkynoates with para -Quinamines

We report an unconventional phosphine-catalyzed formal [3 + 2] annulation of a new class of activated 1,4-enynes with para-quinamines, enabling efficient access to cis-hydroindoles bearing stereodefined conjugated dienoate motifs. The transformation proceeds under mild conditions, exhibiting excellent diastereoselectivity and a broad substrate scope. Preliminary asymmetric studies employing chiral phosphine catalysts delivered enantioenriched products with up to 92:8 er. Notably, the protocol is also compatible with para-quinols. Initial mechanistic investigations suggest that the reaction proceeds via a zwitterionic pathway involving remote δ,ε-activation followed by cascade annulation.