Atom-Economic Synthesis of Pentaleno[2,1‑<i>b</i>]indoles via Tandem Cyclization of Alkynones Initiated by Aminopalladation

An atom-economic Pd­(OAc)2-catalyzed tandem cyclization of alkynones to synthesize pentaleno­[2,1-b]­indoles was developed efficiently. In the formed tetracyclic indole framework, two neighboring stereocenters, one being all-carbon quaternary, are being constructed in a single process with excellent diastereoselectivity. This reaction was initiated by aminopalladation of alkynes and quenched by addition to the intramolecular carbonyl groups.