73959-39-4Relevant articles and documents
Counterion Enhanced Organocatalysis: A Novel Approach for the Asymmetric Transfer Hydrogenation of Enones
Scharinger, Fabian,Márk Pálv?lgyi, ádám,Zeindlhofer, Veronika,Schnürch, Michael,Schr?der, Christian,Bica-Schr?der, Katharina
, p. 3776 - 3782 (2020/06/22)
We present a novel strategy for organocatalytic transfer hydrogenations relying on an ion-paired catalyst of natural l-amino acids as main source of chirality in combination with racemic, atropisomeric phosphoric acids as counteranion. The combination of a chiral cation with a structurally flexible anion resulted in a novel chiral framework for asymmetric transfer hydrogenations with enhanced selectivity through synergistic effects. The optimized catalytic system, in combination with a Hantzsch ester as hydrogen source for biomimetic transfer hydrogenation, enabled high enantioselectivity and excellent yields for a series of α,β-unsaturated cyclohexenones under mild conditions. Moreover, owing to the use of readily available and chiral pool-derived building blocks, it could be prepared in a straightforward and significantly cheaper way compared to the current state of the art.
ORGANIC SALTS AND METHOD FOR PRODUCING CHIRAL ORGANIC COMPOUNDS
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Page/Page column 7; 8, (2009/02/11)
The invention relates to a method for producing chiral organic compounds by asymmetric catalysis, using ionic catalysts comprising a chiral catalyst anion. The claimed method is suitable for reactions which are carried out over cationic intermediate stages, such as iminium ions or acyl pyridinium ions. The invention enables the production of chiral compounds with high ee values, that until now could only be obtained by means of costly purification methods.
Enantioselective hydrogenation of enones with a hydroformylation catalyst
Scheuermann Nee Taylor, Caroline J.,Jaekel, Christoph
supporting information; experimental part, p. 2708 - 2714 (2009/10/06)
Use of a typical rhodium precatalyst for hydroformylation results in the enantioselective hydrogenation of cyclic enones with up to 90% ee. Extensive screening of chiral ligands reveals the simple ligand Chiraphos as the best ligand, so far. The hydrogenation shows high chemoselectivity. Exclusive formation of saturated, chiral b-branched ketones is observed. It is proposed that the catalyst follows a frustrated hydroformylation pathway ("monohydride-based mechanism") and differs by that from the classical cationic Schrock-Osborn type rhodium precatalysts ("dihydride-based mechanism") for enantioselective hydrogenation. The catalyst operates under neat conditions and is easily recyclable by simply distilling off the reaction mixture and treatment with syn gas prior to hydrogenation.
