Complementary Photocatalytic Toolbox: Control of Intramolecular endo- versus exo-trig Cyclizations of α-Phenyl Olefins to Oxaheterocyclic Products
Fabian Weick, Desirée Steuernagel, Arina Belov, Hans-Achim Wagenknecht*
*Institute of Organic Chemistry, Karlsruhe Institute of
Technology (KIT), Fritz-Haber-Weg 6, 76131 Karlsruhe, Germany,
Email: Wagenknechtkit.edu
F. Weick, D. Steuernagel, A. Belov, H.-A. Wagenknecht, Synlett, 2022, 33, 1199-1203.
DOI: 10.1055/s-0040-1719871
see article for more reactions
Abstract
The regioselectivity of the intramolecular cyclization of bifunctional α-phenyl alkenes can be controlled simply by the choice of the organic chromophore as the photocatalyst. Whereas N,N-(4-diisobutylaminophenyl)phenothiazine catalyzes exo-trig cyclizations, 1,7-dicyanoperylene-3,4,9,10-tetracarboxylic acid bisimides catalyze endo-trig additions.
see article for more examples
Details
The study explores the control of regioselectivity in the intramolecular cyclization of α-phenyl alkenes to oxa-heterocyclic products using photoredox catalysis. The choice of organic chromophore as the photocatalyst determines the regioselectivity. N,N-(4-Diisobutylaminophenyl)phenothiazine catalyzes exo-trig cyclizations, yielding products with Markovnikov orientation, while 1,7-dicyanoperylene-3,4,9,10-tetracarboxylic acid bisimides catalyze endo-trig cyclizations, resulting in anti-Markovnikov products. The study demonstrates the conversion of 11 substrates into 20 oxaheterocycles, highlighting the complementarity of these two catalytic approaches. The research emphasizes the importance of oxaheterocycles in medicinal chemistry and presents a sustainable alternative to metal-catalyzed reactions. The solubility of perylene bisimides was improved for better catalytic performance. The study concludes that the regioselectivity of cyclizations can be effectively controlled by the choice of organic photocatalyst and irradiation wavelength, offering a versatile and sustainable photoredox catalytic toolbox for organic synthesis. The research was supported by the Deutsche Forschungsgemeinschaft and KIT, with no conflicts of interest declared.
Key Words
photochemistry, organocatalysis, tetrahydrofurans, perylene bisimide, phenothiazine, nucleophilic addition, cyclization
ID: J72-Y2022