An asymmetric synthesis of the vitamin E core by Pd catalyzed discrimination of enantiotopic alkene faces

An asymmetric synthesis of the vitamin E core derives from the employment of the palladium catalyzed asymmetric allylic alkylation (AAA) reaction. The requisite substrate, available in 7 steps from trimethylhydroquinone, involves asymmetric creation of a quaternary center. In contrast to literature reports using a wide variety of asymmetric ligands which gave a maximum ee of 54%, the ligand derived from trans-1,2-diaminocyclohexane and 2-diphenylphosphinobenzoic acid gave an 84-87% ee in 89-96% yield. Asymmetric induction derives from chiral recognition of the enantiotopic faces of the substrate during the ionization event.