Palladium‐Catalyzed, Regio‐/Stereo‐ and Enantiospecific Anti‐Carboxylation of Unactivated Internal Allenes

We report herein a directing group‐controlled, palladium‐catalyzed, regio‐, stereo‐, and enantiospecific anti‐carboxylation of unactivated, internal allenes enabled via the synergistic interplay of a rationally designed bidentate directing group, palladium catalyst, and a multifunctional acetate ligand. The corresponding trans allyl ester was obtained in excellent yields with exclusive δ‐regioselectivity and anti‐carboxypalladation stereocontrol. The acetate ligand of the palladium catalyst controls the regio‐, stereo‐ and enantioselectivity in the desired transformation. The potential of this concept has been demonstrated by the development of the chiral version of this transformation by using axial‐to‐central chirality transfer with good yields and enantioselectivities. Detailed investigations, including kinetic studies, order studies, and DFT studies, were performed to validate the ligand‐assisted nucleopalladation process and the rationale behind the observed racemization of chiral allenes. The studies also indicated that the anti‐carboxypalladation step was the rate‐limiting as well as the stereo‐ and enantiodetermining step.