Asymmetric Conjugate Reduction of Enoates with Co(II)-Salox Complexes

Enantioselective conjugate reductions of α,β-unsaturated carbonyl compounds is a straightforward method for generating chiral building blocks useful in drug and agrochemical synthesis. Several catalytic systems exist that provide good to excellent performances, but these often require employing precious metals or complex ligands. In this work, we report the reactivity of simple Salox-Co(II) complexes in this context. These bear a phenol and an oxazoline ligating moieties which can be conveniently synthetized using inexpensive and available compounds. Up to 98% yield an 93% ee were obtained in the reduction of enoates using convenient NaBH4 as the reducing agent. Preliminary mechanicistic insight is also given, furnishing a basis for further future optimization.