C-Boron Enolates Enable Palladium Catalyzed Carboboration of Internal 1,3-Enynes.

A new family of carbon-bound boron enolates, generated by a kinetically controlled halogen exchange between chlorocatecholborane and silylketene acetals, is described. These C-boron enolates are demonstrated to activate 1,3-enyne substrates in the presence of a Pd0 /Senphos ligand complex, resulting in the first examples of a carboboration reaction of an alkyne with enolate-equivalent nucleophiles. Highly substituted dienyl boron building blocks are produced in excellent site-, regio-, and diastereoselectivity by the described catalytic cis-carboboration reaction.