Pd-Catalyzed Cross-Coupling of Baylis−Hillman Acetate Adducts with Bis(pinacolato)diboron:  An Efficient Route to Functionalized Allyl Borates

The cross-coupling of Baylis−Hillman acetate adducts and bis(pinacolato)diboron proceeds readily in high yields in the presence of palladium catalyst to produce 3-substituted-2-alkoxycarbonyl allylboronates. These allylboronates can be transformed to stable allyl trifluoroborate salts by addition of excess aqueous KHF2. Both the allylboronate and allyltrifluoroborate derivatives react with aldehydes to afford functionalized homoallylic alcohols stereoselectively.