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.