Donor‐Acceptor Aminocyclobutane Monoesters: Synthesis and Silylium‐Catalyzed (4+2) Annulation with Indoles

A convenient one-step synthesis of β-aminocyclobutane monoesters starting from commercially available reagents is reported. The obtained strained rings undergo (4+2) dearomative annulation with indole partners using silylium catalysis. This organocatalyzed provided tricyclic indolines four new stereocenters in up to quantitative yield and >95 : 5 diastereoselectivity can proceed both intra- intermolecularly. When performed intramolecularly, the tetracyclic structure either akuamma or malagasy alkaloids was selectively depending on temperature reaction. divergent outcome could be rationalized based DFT calculations.