Facile Synthesis of Spirocyclic Lactams via [3+2] and [3+3] Aza‐Annulation Reactions

Spirocyclic pyrrolidones and piperidones were synthesized starting from readily available α‐ketolactones and α‐ketolactams employing [3+2]‐ and [3+3]‐aza‐annulation reactions. Annulation reactions proceeded with good yields and further reduction of the exocyclic C=C double bond of the enamide moiety proceeded with excellent diastereoselectivity. Overall, one C−C and two C−N bonds, as well as three new stereocenters were created in a diastereoselective manner resulting in a fast upbuild of molecular complexity.