Palladium- and Iridium-Catalyzed Deracemization of Allylic Oxygen Compounds with Oxygen Nucleophiles

Allylic oxygen compounds (AOCs) are an important class of versatile building blocks in natural and non-natural product synthesis. Catalytic in-situ deracemization is an attractive means for their enantioselective synthesis. Particularly attractive is the deracemization of AOCs through transition metal-catalyzed dynamic kinetic asymmetric transformation (DYKAT) with oxygen nucleophiles (ONus). This review describes pertinent aspects of the palladium-catalyzed DYKAT of racemic allylic carboxylates, vinyl oxiranes and vinyl dioxolanones with carboxylates, hydrogen carbonate, alcohols, phenols, oximes, diosphenols and water and the iridium-catalyzed DYKAT of racemic allylic alcohols, imidates and carboxylates with alcohols and carboxylic acids. Included in the discussion is the palladium-catalyzed desymmetrization of meso-cycloalkene bis(carboxylates) with hydrogen carbonate. While Trost's bisphosphinobenzamides, Zhou's spiro-phosphoramidite and Feringa's BINOL-phosphoramidite are highly efficient ligands in palladium-catalyzed DYKAT, Carreira-Dorta's BINOL-phosphoramidite-olefin is an excellent ligand in iridium-catalyzed DYKAT. This review also discusses mechanistic and structural aspects of eta(3)-allylpalladium-bisphosphinobenzamide and eta(3)-allyliridium-BINOL-phosphoramidite-olefin complexes and of the corresponding catalysts.