Enthalpy- and/or entropy-controlled asymmetric oxidation: stereocontrolling factors in Mn–salen-catalyzed oxidation

The degree of enantioselection by second-generation Mn–salen complexes was found to depend upon the conformation of their ligand and substrate nucleophilicity. Oxidation of usual olefins was better effected by using (R,S)-Mn–salen complexes as catalysts, while that of more nucleophilic ones was achieved by using (R,R)-Mn–salen complexes. This phenomenon was explained by analyzing the enthalpy and entropy factors of the reactions.