Visible-Light-Mediated Aerobic Tandem Dehydrogenative Povarov/Aromatization Reaction: Synthesis of Isocryptolepines |
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| Authors: | Eva Schendera Lisa-Natascha Unkel Phung Phan Huyen Quyen Gwen Salkewitz Frank Hoffmann Alexander Villinger Prof Dr Malte Brasholz |
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| Institution: | 1. Institute of Chemistry, Organic Chemistry, University of Rostock, Albert-Einstein-Strasse 3A, 18059 Rostock, Germany;2. Department of Chemistry, Institute of Inorganic Chemistry, University of Hamburg, Martin-Luther-King-Platz 6, 20146 Hamburg, Germany;3. Institute of Chemistry, Inorganic Chemistry, University of Rostock, Albert-Einstein-Strasse 3A, 18059 Rostock, Germany |
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| Abstract: | A metal-free, photoinduced aerobic tandem amine dehydrogenation/Povarov cyclization/aromatization reaction between N-aryl glycine esters and indoles leads to tetracyclic 11H-indolo3,2-c]quinolines under mild conditions and with high yields. The reaction can be performed by using molecular iodine along with visible light, or by combining an organic photoredox catalyst with a halide anion. Mechanistic studies reveal that product formation occurs through a combination of radical-mediated oxidation steps with an iminium ion or N-haloiminium ion 4+2]-cycloaddition, and the N-heterocyclic products constitute new analogues of the antiplasmodial natural alkaloid isocryptolepine. |
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| Keywords: | aerobic oxidation cycloaddition dehydrogenation heterocycles photochemistry |
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