Dynamic Multiligand Catalysis: A Closed/Open Shell Crossover Strategy Expands Alkyne Carboboration to Unactivated Secondary Alkyl Halides

We describe a dual strategy in Cu catalysis based on an unprecedented dynamic multiligand coordination pool that enables cooperative closed/open shell pathways. This strategy has been applied to address a restricting limitation inherent to Cu-catalyzed B2(pin)2-carboboration of alkynes: conventional methods usually fail with alkyl electrophiles other than simple primary halides due to the very low reactivity of the intermediate vinyl-Cu(I) species. The crossover strategy enabled by ligand exchange in an organometallic intermediate overcomes this reactivity issue, thus expanding the scope of carboboration to unactivated secondary alkyl halides and opening new avenues to access of stereodefined tetrasubstituted vinylboronates. The method is regio- and stereoselective, shows excellent functional group tolerance, and allows the incorporation of complex carbo- and heterocyclic fragments at either reaction partner.