Rothermel, Kerstin and Zabka, Matej and Hioe, Johnny and Gschwind, Ruth M. (2019) Disulfonimides versus Phosphoric Acids in Bronsted Acid Catalysis: The Effect of Weak Hydrogen Bonds and Multiple Acceptors on Complex Structures and Reactivity. JOURNAL OF ORGANIC CHEMISTRY, 84 (21). pp. 13221-13231. ISSN 0022-3263, 1520-6904
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In Bronsted acid catalysis, hydrogen bonds play a crucial role for reactivity and selectivity. However, the contribution of weak hydrogen bonds or multiple acceptors has been unclear so far since it is extremely difficult to collect experimental evidence for weak hydrogen bonds. Here, our hydrogen bond and structural access to Bronsted acid/imine complexes was used to analyze BINOL-derived chiral disulfonimide (DSI)/imine complexes. H-1 and N-15 chemical shifts as well as (1)J(NH) coupling constants revealed for DSI/imine complexes ion pairs with very weak hydrogen bonds. The high acidity of the DSIs leads to a significant weakening of the hydrogen bond as structural anchor. In addition, the five hydrogen bond acceptors of DSI allow an enormous mobility of the imine in the binary DSI complexes. Theoretical calculations predict the hydrogen bonds to oxygen to be energetically less favored; however, their considerable population is corroborated experimentally by NOE and exchange data. Furthermore, an N-alkylimine, which shows excellent reactivity and selectivity in reactions with DSI, reveals an enlarged structural space in complexes with the chiral phosphoric acid TRIP as potential explanation of its reduced reactivity and selectivity. Thus, considering factors such as flexibility and possible hydrogen bond sites is essential for catalyst development in Bronsted acid catalysis.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | NONCOVALENT INTERACTIONS; ASYMMETRIC CATALYSIS; ACTIVATION; REDUCTION; ENANTIOSELECTIVITY; SELECTIVITY; MODEL; |
| Subjects: | 500 Science > 540 Chemistry & allied sciences |
| Divisions: | Chemistry and Pharmacy > Institut für Organische Chemie Chemistry and Pharmacy > Institut für Organische Chemie > Arbeitskreis Prof. Dr. Ruth Gschwind |
| Depositing User: | Dr. Gernot Deinzer |
| Date Deposited: | 25 Mar 2020 05:33 |
| Last Modified: | 25 Mar 2020 05:33 |
| URI: | https://pred.uni-regensburg.de/id/eprint/25927 |
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