Phosphinooxazolines are used as ligands in allylic substitution reactions as both enantio- and regioselectivity is required to give an enantiomerically pure product due to the transition state being highly symmetric. In the example below all additions are enantioselective however the symmetric complex has no regiocontrol, resulting in a racemic product. The asymmetric complex is both regioselective and enantioselective, resulting in a single enantiomer.
The primary application of PHOX ligands is in palladium catalysts used for enantioselective allylic substitutions. They are able to effect a wide range of substitutions including allylic alkylations (Tsuji-Trost reaction), aminations and sulfonylations.