Enantioselective Hydrogenation of Enones with a Hydroformylation Catalyst

Abstract

AbstractUse 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 β‐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.