Copper-catalyzed enantioselective beta-boration of acyclic enones.

The enantioselective beta-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.