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The dynamic kinetic asymmetric allylic alkylations of racemic allene acetates has been developed with the DACH-phenyl Trost ligand 2 to give general access to allenes with high enantiomeric excess (84-95%) for both malonate and amine nucleophiles. Further, a most unusual dependence of enantioselectivity on base has been uncovered. The magnitude of the enantioselectivity is heavily dependent on the base for the malonate nucleophiles, but the sense and magnitude of the asymmetric induction is dependent on the base for the amine nucleophiles. A Rh(I)-catalyzed intramolecular 4 + 2 cycloaddition of the DYKAT products was accomplished to afford formal Diels-Alder adducts, wherein the axial chirality is faithfully transferred into multiple stereogenic centers as well as olefin geometry.
Trost et al. (Tue,) studied this question.