Polycyclic Indoline Derivatives by Dearomatizing Anionic Cyclization of Indole and Tryptamine-Derived Ureas.

The base-promoted dearomatizing cyclization of anionic indole-containing urea derivatives provided tri- or tetracyclic indoline-containing scaffolds from lithiated urea intermediates. 3-Substituted indoles, including tryptamine derivatives, generally underwent the reaction in high yield and with excellent diastereoselectivity. In situ IR spectroscopy suggests a deprotonation-carbolithiation-reprotonation mechanism.