Enantio- and Regioselective Dihydroboration of Enals

Asymmetric hydroboration is among the most powerful and straightforward methods to construct chiral organoboron compounds, which are extensively used in natural products, bioactive molecules, and materials science. Among them, enantioselective hydroboration of a single functional group has been well-established and experienced significant advances, but the asymmetric hydroboration of multiple functional groups is rarely developed due to the extremely challenging chemo-, regio-, and enantioselectivity control. Herein, we present a Co-catalyzed enantio- and regioselective dihydroboration of enals and achieved the chemo-, regio-, and enantioselective hydroboration of both the C═O bond and the C═C bond. This protocol features mild reaction conditions, wide substrate scope, and good functional group tolerance and provides a highly efficient method for the preparation of highly valuable chiral 1,4-borylethers and their downstream products such as 1,4-diols and amino alcohols. Preliminary mechanistic studies suggested that this Co-catalyzed dihydroboration involved a tandem 1,2-hydroboration/dissociative isomerization/asymmetric hydroboration process.