Nanoconfinement in a Supramolecular Capsule Promotes the Formation of 5- to 8‑Membered Rings in Cycloalkane-[b]-indoles

Challenging cyclization of common- to medium-sized rings is promoted by nanoconfinement inside the cavity of a self-assembled hexameric resorcinarene capsule. While no cyclization occurs outside the capsule, high to excellent yields of cycloalkane-[b]-indoles are obtained inside the capsule irrespective of ring size (5−8 members). Kinetic analysis coupled to NMR investigation of substrate binding shows that the cyclization step under nanoconfinement is not rate-determining, not even for the formation of an 8-membered ring.