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Triplet Energy Transfer from Ruthenium Complexes to Chiral Eniminium Ions: Enantioselective Synthesis of Cyclobutanecarbaldehydes by [2+2] Photocycloaddition

Hörmann, Fabian M. and Kerzig, Christoph and Chung, Tim S. and Bauer, Andreas and Wenger, Oliver S. and Bach, Thorsten. (2020) Triplet Energy Transfer from Ruthenium Complexes to Chiral Eniminium Ions: Enantioselective Synthesis of Cyclobutanecarbaldehydes by [2+2] Photocycloaddition. Angewandte Chemie International Edition, 59 (24). pp. 9659-9668.

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Abstract

Chiral eniminium salts, prepared from alpha,beta-unsaturated aldehydes and a chiral proline derived secondary amine, underwent, upon irradiation with visible light, a ruthenium-catalyzed (2.5 mol %) intermolecular [2+2] photocycloaddition to olefins, which after hydrolysis led to chiral cyclobutanecarbaldehydes (17 examples, 49-74 % yield), with high diastereo- and enantioselectivities. Ru(bpz)(3)(PF6)(2) was utilized as the ruthenium catalyst and laser flash photolysis studies show that the catalyst operates exclusively by triplet-energy transfer (sensitization). A catalytic system was devised with a chiral secondary amine co-catalyst. In the catalytic reactions, Ru(bpy)(3)(PF6)(2) was employed, and laser flash photolysis experiments suggest it undergoes both electron and energy transfer. However, experimental evidence supports the hypothesis that energy transfer is the only productive quenching mechanism. Control experiments using Ir(ppy)(3) showed no catalysis for the intermolecular [2+2] photocycloaddition of an eniminium ion.
Faculties and Departments:05 Faculty of Science > Departement Chemie > Chemie > Anorganische Chemie (Wenger)
UniBasel Contributors:Wenger, Oliver and Kerzig, Christoph
Item Type:Article, refereed
Article Subtype:Research Article
Publisher:Wiley
ISSN:1433-7851
e-ISSN:1521-3773
Note:Publication type according to Uni Basel Research Database: Journal article
Language:English
Identification Number:
Last Modified:18 Aug 2020 07:23
Deposited On:11 Aug 2020 13:37

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