Palladium‐Catalyzed Cycloisomerization of 1,6‐Allene‐Ene via [1,8]‐Sigmatropic Hydrogen Shift of Allylic C−H

Abstract

A ligand‐free palladium‐promoted [1,8]‐sigmatropic hydrogen shift reaction of 1,6‐allene‐ene was reported, which went through an intramolecular Ene cyclization using base as a hydrogen shuttle. Notably, the transformation could realize the HAT process via the hydrogen shift from an old allylic C‐H bond to a new one in the presence of oxidant, between which have low BDE distinction. The mild reaction conditions, high atom economy and good chemo/regioselectivity proved the valuable of this strategy. The control experiments using acetone‐D6/D2O proved that neither solvent nor water were involved in the cycloisomerization process and HAT process was more convincible. The target products could achieve more valuable molecules via convenient synthetic transformation.