title: Stereodynamic tetrahydrobiisoindole "NU-BIPHEP(O)"s: functionalization, rotational barriers and non-covalent interactions.
abstract: Stereodynamic ligands offer intriguing possibilities in enantioselective catalysis. "NU-BIPHEPs" are a class of stereodynamic diphosphine ligands which are easily accessible via rhodium-catalyzed double [2 + 2 + 2] cycloadditions. This study explores the preparation of differently functionalized "NU-BIPHEP(O)" compounds, the characterization of non-covalent adduct formation and the quantification of enantiomerization barriers. In order to explore the possibilities of functionalization, we studied modifications of the ligand backbone, e.g., with 3,5-dichlorobenzoyl chloride. Diastereomeric adducts with Okamoto-type cellulose derivatives and on-column deracemization were realized on the basis of non-covalent interactions. Enantioselective dynamic HPLC (DHPLC) allowed for the determination of rotational barriers of ΔG (‡) 298K = 92.2 ± 0.3 kJ mol(-1) and 99.5 ± 0.1 kJ mol(-1) underlining the stereodynamic properties of "NU-BIPHEPs" and "NU-BIPHEP(O)s", respectively. These results make the preparation of tailor-made functionalized stereodynamic ligands possible and give an outline for possible applications in enantioselective catalysis.
authors: Organisch-Chemisches Institut, Ruprecht-Karls Universität Heidelberg, Im Neuenheimer Feld 270, 69120 Heidelberg, Germany.
authors: Golo
authors: G
authors: Storch
authors: Organisch-Chemisches Institut, Ruprecht-Karls Universität Heidelberg, Im Neuenheimer Feld 270, 69120 Heidelberg, Germany.
authors: Sebastian
authors: S
authors: Pallmann
authors: Organisch-Chemisches Institut, Ruprecht-Karls Universität Heidelberg, Im Neuenheimer Feld 270, 69120 Heidelberg, Germany.
authors: Frank
authors: F
authors: Rominger
authors: Organisch-Chemisches Institut, Ruprecht-Karls Universität Heidelberg, Im Neuenheimer Feld 270, 69120 Heidelberg, Germany.
authors: Oliver
authors: O
authors: Trapp
keywords: Okamoto phases; atropisomer; enantioselective DHPLC; ligand design; non-covalent interactions; phosphine ligand; stereodynamic ligands