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Metal-Free α-C(sp3)-H Aroylation of Amines via a Photoredox Catalytic Radical-Radical Cross-Coupling Process

Guo-Qiang Xu*, Teng-Fei Xiao, Guo-Xuan Feng, Chen Liu, Baoxin Zhang and Peng-Fei Xu*

*State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, P. R. China, Email: gqxulzu.edu.cn, xupflzu.edu.cn

G.-Q. Xu, T.-F. Xiao, G.-X. Feng, C.-Liu, B. Zhang, P.-F. Xu, Org. Lett., 2021, 23, 2846-2852.

DOI: 10.1021/acs.orglett.1c00226 (free Supporting Information)


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Abstract

A metal-free C(sp3)-H aroylation of amines via visible-light photoredox catalysis provides useful α-amino aryl ketones. A series of experiments indicate that this transformation undergoes a photoredox catalytic radical-radical cross-coupling pathway.

 

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proposed mechanism


4CzIPN



General Procedure

4CzIPN (0.40 mg, 0.0005 mmol, 0.5 mol%) and EtCO2K (33.6 mg, 0.3 mmol, 3.0 equiv.) were weighed into an oven-dried 8 mL quartz cuvette with a magnetic stirring bar, and then DCM (0.05 M, 2 mL) was added. The corresponding amine (0.1 mmol, 1.0 equiv.) was added into the mixture via micro-syringe. The reaction mixture was degassed by three cycles of freeze-pump-thaw. After the mixture was thoroughly degassed, the corresponding aroyl chloride (0.3 mmol, 3.0 equiv.) was added into the mixture via micro-syringe. The vial was placed beside a 3 W white LED, allowing the temperature to rise due to its proximity to the lights. The crude mixture was concentrated and purified by flash chromatography (silica gel, mixtures of petroleum ether/ethyl acetate) to afford the pure product.


Key Words

pyrrolidines, photochemistry, organocatalysis


ID: J54-Y2021