Chiral Helical Oligotriazoles: New Class of Anion-Binding Catalysts for the Asymmetric Dearomatization of Electron-Deficient N‑Heteroarenes
journal contributionposted on 08.10.2014, 00:00 by Mercedes Zurro, Sören Asmus, Stephan Beckendorf, Christian Mück-Lichtenfeld, Olga García Mancheño
Helical chirality and selective anion-binding processes are key strategies used in nature to promote highly enantioselective chemical reactions. Although enormous efforts have been made to develop simple helical chiral systems and thus open new possibilities in asymmetric catalysis and synthesis, the efficient use of synthetic oligo- and polymeric helical chiral catalysts is still very challenging and rather unusual. In this work, structural unique chiral oligotriazoles have been developed as C–H bond-based anion-binding catalysts for the asymmetric dearomatization of N-heteroarenes. These rotational flexible catalysts adopt a reinforced chiral helical conformation upon binding to a chloride anion, allowing high levels of chirality transfer via a close chiral anion-pair complex with a preformed ionic substrate. This methodology offers a straightforward and potent entry to the synthesis of chiral (bioactive)heterocycles with added synthetic value from simple and abundant heteroarenes.