Regioselective Synthesis of 5-Trifluoromethylpyrazoles by [3 + 2] Cycloaddition of Nitrile Imines and 2-Bromo-3,3,3-trifluoropropene
Hao Zeng, Xiaojie Fang, Zhiyi Yang, Chuanle Zhu* and Huanfeng Jiang
*School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510640, China, Email: cechlzhuscut.edu.cn
H. Zeng, X. Fang, Z. Yang, C. Zhu, H. Jiang, J. Org. Chem., 2021, 86, 2810-2819.
A regioselective [3 + 2] cycloaddition of hydrazonyl chlorides with the environmentally friendly and large-tonnage industrial feedstock 2-bromo-3,3,3-trifluoropropene (BTP) provides 5-trifluoromethylpyrazoles. This catalyst-free reaction is operationally simple and features mild conditions, high yields, gram scalability, a broad substrate scope, and high functional group tolerance.
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proposed reaction pathway
in situ generation of hydrazonyl chlorides
pyrazoles, 1,3-dipolar cycloaddition