title: Brønsted Acid Catalyzed Addition of Enamides to ortho-Quinone Methide Imines-An Efficient and Highly Enantioselective Synthesis of Chiral Tetrahydroacridines.
abstract: The direct and highly enantioselective synthesis of tetrahydroacridines was achieved through the phosphoric acid catalyzed addition of enamides to in situ generated ortho-quinone methide imines and subsequent elimination. This novel one-step process constitutes a very efficient, elegant, and selective synthetic approach to valuable N-heterocycles with a 1,4-dihydroquinoline motif. By subsequent highly diastereoselective hydrogenation and N-deprotection the reaction products were easily converted into free hexahydroacridines with a total of three new stereogenic centers.
authors.affiliation: Institut für Organische Chemie, Universität Leipzig, Johannisallee 29, 04103, Leipzig, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Kretzschmar
authors.affiliation: Institut für Organische Chemie, Universität Leipzig, Johannisallee 29, 04103, Leipzig, Germany.
authors.forename: Tomáš
authors.initials: T
authors.lastname: Hodík
authors.affiliation: Institut für Organische Chemie, Universität Leipzig, Johannisallee 29, 04103, Leipzig, Germany. schneider@chemie.uni-leipzig.de.
authors.forename: Christoph
authors.initials: C
authors.lastname: Schneider
keywords: asymmetric synthesis; chiral phosphoric acids; nitrogen heterocycles; organocatalysis; ortho-quinone methide imines