The First Preparation of 4-Substituted 1,2-Oxaborol-2(5H)-ols and their Palladium­-Catalyzed Cross-Coupling with Aryl Halides to Prepare Stereodefined­ 2,3-Disubstituted Allyl Alcohols

4-Substituted 1,2-oxaborol-2(5H)-ols were prepared through copper-catalyzed carbomagnesation of propargyl alcohol, followed by the transmetallation of magnesium to boron in a one-pot procedure. The Suzuki-Miyaura cross-coupling of these new 2,2-disubstituted alkenylboronic acids with aryl halides afforded stereodefined 2,3-disubstituted allyl alcohols in good to excellent yields.