Phosphine-Catalyzed Anti-Carboboration of Alkynoates with Alkyl-, Alkenyl-, and Arylboranes

We found that trialkylphosphine organocatalysts promoted unprecedented anti-carboboration of alkynoates with alkyl-, alkenyl-, or arylboranes to form β-boryl acrylates. The regioselectivity of the carboboration across the polar C-C triple bond exhibited inverse electronic demand, with the less electronegative B atom being delivered to the positively charged β carbon atom. The regioselectivity and the anti stereoselectivity were both complete and robust. In addition, the substrate scope was broad with excellent functional group compatibility.