Copper‐Catalyzed Enantioselective β‐Boration of Acyclic Enones

AbstractJosi or Mandy? Asymmetric conjugate addition of diboron to acyclic enones catalyzed by copper affords chiral organoboronates that possess a boronate group at the β stereocenter with excellent chemical yields and enantioselectivities (see scheme). This method accommodates the structural variation of acyclic enones and provides access to highly functionalized chiral organoboronates in one step.magnified imageThe enantioselective β‐boration of various acyclic enones has been studied by using chiral diphosphine–copper complexes. Good to excellent yields and enantioselectivities (up to 97 % ee (enantiomeric excess)) were observed for a range of substrates under optimized conditions. In this transformation, the addition of a controlled amount of alcohol, especially methyl alcohol, is critical to obtain products in high ee and yield. This methodology accommodates structural variation of acyclic enones and provides access to a range of functionalized chiral organoboronates in high enantiomeric purity.