Visible‐Light‐Mediated Aerobic Tandem Dehydrogenative Povarov/Aromatization Reaction: Synthesis of Isocryptolepines. Issue 1 (27th November 2019)

• Record Type: Journal Article
• Authors: Schendera, Eva; Unkel, Lisa‐Natascha; Huyen Quyen, Phung Phan; Salkewitz, Gwen; Hoffmann, Frank; Villinger, Alexander; Brasholz, Malte
• Is Part Of: Chemistry. Volume 26:Issue 1(2019)
• Page Start: 269
• Page End: 274
• Publication Date: 2019-11-27
• Subjects: aerobic oxidation -- cycloaddition -- dehydrogenation -- heterocycles -- photochemistry; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201903921
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: A metal‐free, photoinduced aerobic tandem amine dehydrogenation/Povarov cyclization/aromatization reaction between N ‐aryl glycine esters and indoles leads to tetracyclic 11 H ‐indolo[3, 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. Abstract : All metal‐free : A photoinduced tandem amine dehydrogenation/Povarov cyclization/aromatization reaction leads to isocryptolepine analogues with high yields, by using molecular iodine under visible light, or by combining an organic photoredox catalyst with a halide anion (see scheme; PC=photocatalyst).