Cu‐Catalyzed Chemoselective Preparation of 2‐(Pinacolato)boron‐Substituted Allylcopper Complexes and their In Situ Site‐, Diastereo‐, and Enantioselective Additions to Aldehydes and Ketones

Abstract

Transformations that entail catalytic generation of reactive entities for in situ use in stereoselective synthesis are in high demand;[1] such processes are more efficient and operationally simpler than when a priori preparation and purification of stoichiometric quantities of sensitive intermediates are required.[2] Successful design of multi-component pathways hinges on high chemoselectivity: A starting material and a reagent must first be catalytically transformed into a new species, which then has to undergo reaction with another substrate. If the catalyst structure is incorporated within the intermediate molecule, reactivity and selectivity can be further controlled. When one or both partners carry several potentially reactive sites, other issues of selectivity must be addressed. Matters of efficiency and site- and/or stereoselectivity need to be resolved at every stage, and conditions must be found to ensure facile catalyst turnover.