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 1,2alkoxyalcohols 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.

Recent Developments in Enantioselective Scandium-Catalyzed Transformations

“…The catalyst could be reused up to ten times without losing its performance. In 2021, Kotora et al developed novel types of chiral bipyridine ligands to be investigated in enantioselective scandium-catalyzed ring-opening reactions of meso-epoxides with alcohols (Scheme 40) [83]. When only 2 mol% of optimal ligand 159 was combined with the same quantity of Sc(OTf)3 in dichloromethane at 25 °C, a range of meso-epoxides 160 could be submitted to desymmetrization with various alcohols 161 to give the corresponding chiral 1,2-alkoxyalcohols 162 with low to high yields (27-88%) and uniformly high enantioselectivities (85-99% ee).…”

“…The process evolved through the mechanism detailed in Scheme 41 based on the formation of ortho-Scheme 40. Ring-opening reactions of meso-epoxides with alcohols/anilines [83].…”

Synthesis, Characterization, and Catalytic Reactivities of Novel Dinuclear Cu(II) Complexes : Efficient Ring Opening Reaction of Epoxide

“…[5,16,17,[57][58][59][60][61][62][63][64][65][66][67] They have some benefits such as simplicity to use and low cost and toxicity. [50,[67][68][69][70][71] On the other hand, the use of Cu complexes as ring-opening catalysts are less well explored, [72][73][74][75][76] because they showed long reaction time and needed sometimes high temperature. These facts inspired us to develop novel Cu complexes with efficient, mild, and simple catalytic activity for the ring-opening reactions of epoxide with alcohol.…”

“…Several transition metal complexes containing Fe and Cr were reported to catalyze ring opening of epoxide with alcohol [5,16,17,57–67] . They have some benefits such as simplicity to use and low cost and toxicity [50,67–71] . On the other hand, the use of Cu complexes as ring‐opening catalysts are less well explored, [72–76] because they showed long reaction time and needed sometimes high temperature.…”