Palladium-Catalyzed Cascade Wacker/Allylation Sequence with Allylic Alcohols Leading to Allylated Dihydropyrones

We describe a cascade Wacker/allylation sequence of β-hydroxy ynones by directly using simple allylic alcohols. This palladium(II)-catalyzed reaction occurs under mild conditions (0 °C to room temperature) and provides a new and efficient synthetic method for the preparation of allylated dihydropyrones. The regiochemical outcomes are consistent with a reaction pathway that includes an insertion/β-OH elimination sequence to form the allylic moiety. A remarkable changeover from allyl to formylethyl products occurs under the simple action of LiBr.