Enantioselective α-Hydroxylation by Modified Salen-Zirconium(IV)-Catalyzed Oxidation of β-Keto Esters

The highly enantioselective alpha-hydroxylation of beta-keto esters using cumene hydroperoxide (CHP) as the oxidant was realized by a chiral (1S,2S)-cyclohexanediamine backbone salen-zirconium(IV) complex as the catalyst. A variety of corresponding chiral alpha-hydroxy beta-keto esters were obtained in excellent yields (up to 99%) and enantio-selectivities (up to 98% ee). The zirconium-catalyzed enantioselective alpha-hydroxylation of beta-keto esters was scalable, and the zirconium catalyst was recyclable. The reaction can be performed in gram scale, and corresponding chiral products were acquired in 95% yield and 99% ee.