Highly Enantioselective Ring-Opening of meso-Epoxides with O- and N-Nucleophiles Catalyzed by a Chiral Sc(III)/bipyridine Complex
Abstract
The ring-opening of epoxides is a synthetically significant process widely applied in all kinds of chemistry. Herein, we report the catalytic and highly enantioselective variant of this reaction exploiting our recent endeavors to design and synthesize chiral bipyridine type ligands.
A Sc-complex with a newly developed bipyridine ligand exhibited high reactivity and stereocontrol in the desymmetrization of meso-epoxides with various alcohols. The respective enantiomerically enriched 1,2-alkoxyalcohols were obtained with e.r. values of up to 99.5:0.5 for various alcohols regardless of their nature (benzyl, alkyl, cycloalkyl, allyl, propargyl, etc.).
We attempted ring-opening of meso-epoxides with anilines as well; however, it proceeded with lower enantioselectivity and was strongly depended on the electronic effect of substituents attached to the aromatic ring.