Enantioselective [2 + 2] Photocycloaddition via Iminium Ions: Catalysis by a Sensitizing Chiral Brønsted Acid
Franziska Pecho, Yeshua Sempere, Johannes Gramüller, Fabian M. Hörmann, Ruth M. Gschwind, Thorsten Bach
Abstract
-substituted phenyl linker. NMR studies confirmed the formation of an iminium ion which is attached to the acid counterion in a hydrogen-bond assisted ion pair. The catalytic activity of the acid rests on the presence of the thioxanthone moieties which enable a facile triplet energy transfer and an efficient enantioface differentiation.
Topics & Concepts
ChemistryIminiumEnantioselective synthesisThioxanthoneCatalysisCounterionPhosphoric acidMedicinal chemistryOrganocatalysisArylIonOrganic chemistryPolymerizationAlkylPolymerPhotopolymerAsymmetric Synthesis and CatalysisOxidative Organic Chemistry ReactionsAxial and Atropisomeric Chirality Synthesis