Storch Golo, Pallmann Sebastian, Rominger Frank, Trapp Oliver
Organisch-Chemisches Institut, Ruprecht-Karls Universität Heidelberg, Im Neuenheimer Feld 270, 69120 Heidelberg, Germany.
Beilstein J Org Chem. 2016 Jul 14;12:1453-8. doi: 10.3762/bjoc.12.141. eCollection 2016.
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.
立体动态配体在对映选择性催化中提供了有趣的可能性。“NU-BIPHEPs”是一类立体动态二膦配体，可通过铑催化的双[2 + 2 + 2]环加成反应轻松获得。本研究探索了不同功能化的“NU-BIPHEP(O)”化合物的制备、非共价加合物形成的表征以及对映异构化能垒的量化。为了探索功能化的可能性，我们研究了配体骨架的修饰，例如用3,5-二氯苯甲酰氯进行修饰。基于非共价相互作用，实现了与冈本型纤维素衍生物的非对映异构加合物和柱上消旋。对映选择性动态高效液相色谱（DHPLC）能够测定旋转能垒，ΔG (‡) 298K分别为92.2 ± 0.3 kJ mol(-1)和99.5 ± 0.1 kJ mol(-1)，这分别突出了“NU-BIPHEPs”和“NU-BIPHEP(O)s”的立体动态性质。这些结果使得制备定制的功能化立体动态配体成为可能，并为对映选择性催化中的可能应用提供了概述。
