Palladium-Catalyzed, Stereoselective, Cyclizative Alkenylboration of Carbon-Carbon Double Bonds through Activation of a Boron-Chlorine Bond

Palladium-catalyzed alkenylboration of carbon carbon double bonds has been achieved using the reaction of chloro(diisopropylamino)boryl ethers of homoallylic alcohols with alkenylzirconium reagents. The reaction may proceed through an initial oxidative addition of the B Cl bond, intramolecular insertion of the C=C bond into the B-Pd bond, transmetalation from the alkenylzirconium reagent, and reductive elimination of the products. The cyclization proceeds with high diastereoselectivity for the formation of cis-3,5- or trans-3,4-disubstituted-1,2-oxaborolane products. Cross-coupling of the resultant products with aryl iodides proceeds with retention of configuration at the boron-bound secondary carbon atom.