Co(Salox)‐Catalyzed Enantioselective Reduction of α,β‐Unsaturated Esters

Abstract

AbstractCo‐Salox complexes are suitable catalysts for the reduction of prochiral α,β‐unsaturated esters. These ligands can be prepared in a single step from available and inexpensive materials, thus representing an easily accessible alternative to previously reported Co‐catalysts. NaBH4 is employed as reducing agent in the presence of EtOH as proton source, leading to the stereoselective formation of chiral esters, amides, and nitriles in up to 99 % yield and 96.5 : 3.5 er. The concentration of the reductant counter cation (Na+) and the solvent polarity have been shown to correlate with reactivity and enantioselectivity, suggesting that a relatively complex mechanistic manifold is in place.