Synthesis of [1,2-A]-fused tricyclic dihydroquinolines by palladiumcatalyzed intramolecular C-N cross-coupling of polarized heterocyclic enamines

Abstract

A simple methodology for [1,2-A]-fused tricyclic dihydroquinolines is established. The key ste of the methodology is an intramolecular Buchwald-Hartwig amination reaction of suitabl halogenated (both bromo and chloro) cyclic enaminoketones, enaminoesters and enaminonitrile with various ring size (from five-to seven-membered). Optimal reaction conditions (palladiu source, base, ligand) depend on the ring size of the starting enamine, giving 65-98% yield of th tricyclic product. A treatment of the products with perchloric acid gives respective quinoliniu perchlorates.