α‐Hydroxyboronate Esters: Formation and Synthetic Applications

Abstract The synthesis of α‐oxyboronate esters by the copper‐catalyzed diboration of carbonyls provides a facile method to access these versatile intermediates. The evolution of diboration conditions and approaches to allow the isolation of products derived from α‐hydroxyboronate esters is discussed. Both experimental and computational evidence for the mechanism of the copper‐catalyzed diboration reaction distinguishes the potential pathways of the key migratory insertion of the carbonyl into the copper–boron bond. α‐Hydroxyboronate esters and their derivatives have been used in a number of synthetic transformations, including homologation, coupling, and elimination reactions.