Pecho, Franziska and Sempere, Yeshua and Gramuller, Johannes and Hoermann, Fabian M. and Gschwind, Ruth M. and Bach, Thorsten (2021) Enantioselective [2+2] Photocycloaddition via Iminium Ions: Catalysis by a Sensitizing Chiral Bronsted Acid. JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 143 (25). pp. 9350-9354. ISSN 0002-7863, 1520-5126
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N,O-Acetals derived from alpha,beta-unsaturated beta-aryl substituted aldehydes and (1-aminocyclohexyl)methanol were found to undergo a catalytic enantioselective [2 + 2] photocycloaddition to a variety of olefins (19 examples, 54-96% yield, 84-98% ee). The reaction was performed by visible light irradiation (lambda = 459 nm). A chiral phosphoric acid (10 mol %) with an (R)-1,1'-bi-2-naphthol (binol) backbone served as the catalyst. The acid displays two thioxanthone groups attached to position 3 and 3' of the binol core via a meta-substituted phenyl linker. NMR studies confirmed the formation of an iminium ion which is attached to the acid counterion in a hydrogen-bond assisted ion pair. The catalytic activity of the acid rests on the presence of the thioxanthone moieties which enable a facile triplet energy transfer and an efficient enantioface differentiation.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | CYCLOBUTANE DERIVATIVES; PHOSPHORIC-ACID; PHOTOCHEMISTRY; |
| 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: | 13 Sep 2022 13:49 |
| Last Modified: | 13 Sep 2022 13:49 |
| URI: | https://pred.uni-regensburg.de/id/eprint/47338 |
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