Formation of a Palladalactone Complex by C-O Bond Cleavage of Diketene Promoted by a Zerovalent Palladium Complex

Intramolecular 1,5-hydrogen atom transfer of an aryl radical generated by reduction of an o-iodophenyl group on the allylic position of allyl ethers by SmI2 regioselectively generates (alpha)allyloxy carbanions, which undergo [2,3]-Wittig rearrangement to afford a substituted 4-phenyl-S-buten-l-ol. The effect of HMPA concentration on distribution of the 1,5-hydrogen transfer giving Wittig rearranged products and hydrogen abstraction giving reductive deiodination products is described.