Organo‐Photoredox Catalyzed Oxidative Dehydrogenation of N‐Heterocycles

Abstract

We report here for the first time the catalytic oxidative dehydrogenation of N-heterocycles by a visible-light organo-photoredox catalyst with low catalyst loading (0.1-1 mol %). The reaction proceeds efficiently under base- and additive-free conditions with ambient air at room temperature. The utility of this benign approach is demonstrated by the synthesis of various pharmaceutically relevant N-heteroarenes such as quinoline, quinoxaline, quinazoline, acridine, and indole.

Visible‐Light‐Promoted Efficient Aerobic Dehydrogenation of N‐Heterocycles by a Tiny Organic Semiconductor Under Ambient Conditions

“…Based on the above experimental results and known literatures,, [5a], [5b], [5d], we proposed a possible reaction mechanism (Scheme ). Firstly, oxidative photo‐generated holes and reductive photo‐generated electrons are produced by excitation of the organic semiconductor PDI‐SN, respectively.…”

“…The site‐selective introduction of substituents onto N‐heteroarenes is a formidable challenge, while this is relatively straightforward to achieve for the corresponding N‐heterocycles. For example, tetrahydroquinoline can easily undergo 6‐site electrophilic substitution functionalization, and the corresponding substituted quinoline can be obtained by dehydrogenation . Therefore, the dehydrogenation of N‐heterocycles to N‐heteroarenes is considered a viable method.…”

“…When compared to thermally promoted organic reaction, the utilization of visible‐light energy as a driving force for organic transformation is appealing, as it is a mild, safe, and easy‐to‐handle energy resource . In general, there are two subclasses of visible‐light‐promoted dehydrogenation of N‐heterocycles: acceptorless[2e], and acceptor assisted,, depending on whether hydrogen acceptors are involved. Acceptor assisted dehydrogenation, especially aerobic oxidative dehydrogenation using oxygen as a cheap and readily available oxidant, has the advantages of scalability and operational simplicity.…”

Cobalt Nanoparticles Apically Encapsulated by Nitrogen‐doped Carbon Nanotubes for Oxidative Dehydrogenation and Transfer Hydrogenation of N‐Heterocycles

“…O 2 . The accompanying generation of H 2 O 2 during the reaction has been detected via an iodometric experiment and has been quickly consumed to form the H 2 O and quinoline . Moreover, the EPR in Figure S19 reveals the .…”

Inverse‐Electron‐Demand [4+2]‐Cycloaddition of 1,3,5‐triazinanes: Facile Approaches to Tetrahydroquinazolines

“…Tetrahydroquinazoline and 2,3-dihydroquinazolin-4(1H)-one skeletons constitute important structural motifs in natural products (e. g., Luotonin A [1] and Anisotine [2] ) and pharmaceutically active compounds ( Figure 1) such as butyrylcholinesterase inhibitor, [3] CCKA antagonist (Asperlicin D), [4] and clinical drug non-small cell lung cancer inhibitor (Erlotinib). [5] Therefore, the development of novel methods to construct tetrahydroquinazolines is a high value goal due to their promising bioactivities.…”