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Visible‐Light‐Mediated Aerobic Tandem Dehydrogenative Povarov/Aromatization Reaction: Synthesis of Isocryptolepines
Author(s) -
Schendera Eva,
Unkel LisaNatascha,
Huyen Quyen Phung Phan,
Salkewitz Gwen,
Hoffmann Frank,
Villinger Alexander,
Brasholz Malte
Publication year - 2020
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201903921
Subject(s) - chemistry , aromatization , iminium , dehydrogenation , cycloaddition , tandem , photochemistry , radical ion , decarboxylation , radical , carbocation , photocatalysis , catalysis , organic chemistry , medicinal chemistry , combinatorial chemistry , ion , materials science , composite material
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.