1,2‐Metallate Rearrangement of Boron Derivatives

Abstract

The 1,2‐metallate rearrangement of boronate complexes has proven to be a powerful method for the stereospecific formation of CC and Cheteroatom bonds to generate molecules with a rich array of functionality with full stereocontrol. The enantioselectivity of the process is dictated by either incorporating a chiral ligand into the boronic ester component (substrate control) or by forming a boronate complex through the addition of an enantioenriched carbenoid species to a boronic ester (reagent control). A limitation of a substrate‐controlled process is that a two‐step procedure to exchange the enantiomer of chiral ligand must be performed to obtain the opposite diastereoisomer of product. In contrast, a reagent‐controlled process can access either enantiomer/diastereoisomer of product by altering the enantiomer of chiral reagent employed. This chapter will describe key advances in the substrate‐ and reagent‐controlled homologation of boronic esters, with a specific focus on the 1,2‐metallate rearrangement.