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Published on: May 21, 2019
Brønsted Acid Catalysis in Visible-Light-Induced [2+2] Photocycloaddition Reactions of Enone Dithianes
Christoph Brenninger1, Alexander Pöthig1, Thorsten Bach1
1Department Chemie and Catalysis Research Center (CRC), Technische Universität München, Lichtenbergstrasse 4, 85747, Garching, Germany.
Abstract:
1,3-Dithiane-protected enones (enone dithianes) were found to undergo an intramolecular [2+2] photocycloaddition under visible-light irradiation (λ=405 nm) in the presence of a Brønsted acid (7.5-10 mol %). Key to the success of the reaction is presumably the formation of colored thionium ions, which are intermediates of the catalytic cycle. Cyclobutanes were thus obtained in very good yields (78-90 %). It is also shown that the dithiane moiety can be reductively or oxidatively removed without affecting the photochemically constructed ring skeleton.
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