title: The stereodynamics of 5,5'-disubstituted BIPHEPs.
abstract: We investigated the stereodynamics of 5,5'-substituted tropos BIPHEP ligands (2,2'-bis(diphenylphosphino)-biphenyls) by enantioselective dynamic high-performance liquid chromatography (DHPLC) to elucidate the influence of the substitution pattern and electronics of the substituents (methyl, methoxy, and hydroxyl groups). By temperature-dependent dynamic HPLC measurements the activation parameters ΔG(╪), ΔH(╪), and ΔS(╪) could be determined with high precision, revealing that the activation barrier of these 5,5'-substituted BIPHEP ligands ranges in a narrow band between 87.8 and 93.0 kJ mol(-1), making them highly attractive as deracemizable dynamic chiral ligands in asymmetric catalysis. Interestingly, the activation parameters are highly influenced by a hydroxyl or methoxy group in the 5,5'-position of the BIPHEP ligands.
authors.affiliation: Ruprecht-Karls-Universität Heidelberg, Organisch-Chemisches Institut, Heidelberg, Germany.
authors.forename: Frank
authors.initials: F
authors.lastname: Maier
authors.forename: Oliver
authors.initials: O
authors.lastname: Trapp