Metal-free visible light-induced cross-dehydrogenative coupling of benzocyclic imines with water/P(O)H compounds: efficient access to functionalized benzazepines/ones

Visible light-induced cross-dehydrogenative coupling is a general and highly efficient protocol for the synthesis of functionalized benzazepines/ones in a one-pot fashion, and is reported with good to excellent yields and high chemoselectivity. Control and electron paramagnetic resonance experiments...

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Bibliographic Details
Published in:Organic chemistry frontiers an international journal of organic chemistry 2024-01, Vol.11 (2), p.270-276
Main Authors: Fu, Zhicheng, Feng, Luping, Yu, Qin, Mu, Xinhui, Zhong, Xuqing, Wang, Zhouyu, Wang, Ting, Deng, Jinni, Li, Jingfang, Chen, Mingjun
Format: Article
Language:English
Subjects:
Catalysts
Chemical reactions
Continuous flow
Cross coupling
Dehydrogenation
Electron paramagnetic resonance
Electron spin resonance
Epoxy resins
Flame retardants
Imines
Light effects
Nucleophiles
Organic chemistry
Oxidants
Oxidizing agents
Polymers
Single electrons
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Summary:Visible light-induced cross-dehydrogenative coupling is a general and highly efficient protocol for the synthesis of functionalized benzazepines/ones in a one-pot fashion, and is reported with good to excellent yields and high chemoselectivity. Control and electron paramagnetic resonance experiments reveal radical–radical cross-coupling and oxidative dehydrogenation processes via single-electron chemistry in this reaction. The reaction is free of metal catalysts and external oxidants, and has mild and redox-neutral reaction conditions. A coupling reaction rather than the addition of active benzocyclic imines and nucleophiles is first established. More importantly, the functionalized benzazepines/ones can be synthesized on the gram scale using a continuous-flow technique. The product benzo[d]thiazol-2-yldiphenylphosphine oxide presents superior flame retardancy in epoxy resin, in which only a 0.46 wt% ultra-low phosphorus loading is needed to reach the highest flame-retardant rating of the polymer material.
ISSN:2052-4110
2052-4110
DOI:10.1039/d3qo01609a