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Diazotrifluoroethyl Radical: A CF3-Containing Building Block in [3 + 2] Cycloaddition

Wen-Wen Zhao, Yong-Chao Shao, An-Ni Wang, Jia-Li Huang, Chun-Yang He, Bao-Dong Cui, Nan-Wei Wan, Yong-Zheng Chen* and Wen-Yong Han*

*Generic Drug Research Center of Guizhou Province, Zunyi Medical University, Zunyi 563006, P. R. China, Email: yzchenzmu.edu.cn, hanwyzmu.edu.cn

W.-W. Zhao, Y.-C. Shao, A.-N. Wang, J.-L. Huang, C.-Y. He, B.-D. Cui, N.-W. Wan, Y.-Z. Chen, W.-Y. Han, Org. Lett., 2021, 23, 9256-9261.

DOI: 10.1021/acs.orglett.1c03603



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Abstract

A visible-light-induced [3 + 2] cycloaddition of a hypervalent iodine(III) reagent with α-ketoacids enables the construction of 5-CF3-1,3,4-oxadiazoles. The reaction proceeds smoothly without a photocatalyst, metal, or additive under mild conditions.

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proposed mechanism



Representative procedure

A 10 mL Schlenk tube equipped with a magnetic stirring bar was charged with α-ketoacid (0.2 mmol, 1.0 equiv.), hypervalent iodine reagent (106.8 mg, 0.3 mmol, 1.5 equiv.), and degassed CH2Cl2 (2.0 mL). The mixture was then stirred at room temperature under argon atmosphere and irradiated with 12 W blue LEDs (Brand: Cunmeso; Model: CMS-125060IP33; S5 Wavelength range: 460-465nm; The distance is about 3 cm between the light source and the irradiation vessel) for 36 h. After completion of the reaction, the resulting mixture was quenched by H2O (20 mL), then extracted with CH2Cl2 (3 ×20 mL). The combined organic phase was dried over anhydrous Na2SO4, concentrated by vacuum and purified by flash column chromatography on silica gel (petroleum ether/ethyl acetate = 10:1) to afford the desired product.


Key Words

1,3,4-oxadiazoles, photochemistry


ID: J54-Y2021