Phosphinite Thioethers Derived from Chiral Epoxides. Modular P,S-Ligands for Pd-Catalyzed Asymmetric Allylic Substitutions

A new family of modular P,S-ligands has been prepared from enantiopure arylglycidols. These ligands have been iteratively optimized with respect to four different structural parameters for use in Pd-catalyzed allylic substitutions. As a final output, highly active and enantioselective ligands for these synthetically important transformations have been developed, and the factors controlling their catalytic behavior have been rationalized. From a methodological point of view, a convenient procedure for the regioselective ring-opening of cis-glycidic esters with bulky thiols to yield the corresponding β-alkylthio-α-hydroxy carboxylic acids has been developed.