Strategies for the development of enantioselective catalysts

Novel C-2-symmetric diiminosphosphoranes and diketimines are useful ligands for Pd-and Cu-catalyzed C-C bond forming reactions, Angermund's molecular modeling based on accessible molecular surface serving as a guide in predicting catalyst activity. The first highly enantioselective diphosphites as ligands in Rh-catalyzed hydrogenation are also described, the selectivity principle being based on in situ selection of conformational enantiomers. Finally, a systematic study of chiral diphosphonites reveals that ferrocene-based derivatives are ideal in hydrogenation and certain conjugate addition reactions. These methods are compared to biocatalytic strategies based on the creation of enantioselective biocatalysts by in vitro evolution, a rational process which is independent of the catalyst structure or mechanism.