Sorgenfrei, Nils and Hioe, Johnny and Greindl, Julian and Rothermel, Kerstin and Morana, Fabio and Lokesh, N. and Gschwind, Ruth M. (2016) NMR Spectroscopic Characterization of Charge Assisted Strong Hydrogen Bonds in Bronsted Acid Catalysis. JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 138 (50). pp. 16345-16354. ISSN 0002-7863,
Full text not available from this repository. (Request a copy)Abstract
Hydrogen bonding plays a crucial role in Bronsted acid catalysis. However, the hydrogen bond properties responsible for the activation of the substrate are still under debate. Here, we report an in depth study of the properties and geometries of the hydrogen bonds in (R)-TRIP imine complexes (TRIP: 3,3'-Bis(2,4,6-triisopropylphenyl)-1,1'-binaphthyl-2,2'-diylhydrogen phosphate). From NMR spectroscopic investigations H-1 and N-15 chemical shifts, a Steiner-Limbach correlation, a deuterium isotope effect as well as quantitative values of (1)J(NH), (2h)J(PH) and (3h)J(PN) were used to determine atomic distances (r(OH), r(NH), r(NO)) and geometry information. Calculations at SCS-MP2/CBS//TPSS-D3/def2-SVP-level of theory provided potential surfaces, atomic distances and angles. In addition, scalar coupling constants were computed at TPSS-D3/IGLO-III. The combined experimental and theoretical data reveal mainly ion pair complexes providing strong hydrogen bonds with an asymmetric single well potential. The geometries of the hydrogen bonds are not affected by varying the steric or electronic properties of the aromatic imines. Hence, the strong hydrogen bond reduces the degree of freedom of the substrate and acts as a structural anchor in the (R)-TRIP imine complex.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | ORGANOCATALYTIC REDUCTIVE AMINATION; SCALAR COUPLINGS; LOW-BARRIER; ASYMMETRIC CATALYSIS; PHOSPHORIC-ACIDS; COMPLEXES; IMINES; ENANTIOSELECTIVITY; GEOMETRIES; MECHANISM; |
| Subjects: | 500 Science > 540 Chemistry & allied sciences |
| Divisions: | Chemistry and Pharmacy > Institut für Organische Chemie > Arbeitskreis Prof. Dr. Ruth Gschwind |
| Depositing User: | Dr. Gernot Deinzer |
| Date Deposited: | 08 Apr 2019 13:33 |
| Last Modified: | 08 Apr 2019 13:33 |
| URI: | https://pred.uni-regensburg.de/id/eprint/3773 |
Actions (login required)
 |
View Item |
