Facile One-Pot Preparation of 5-Substituted 4-Iodo-1-tosylpyrazoles from N-Propargyl-N'-tosylhydrazines through Iodocyclization

Aya Saito, Kazuhiro Yoshida, Hideo Togo*

*Graduate School of Science and Technology, Chiba University, Yayoi-cho 1-33, Inage-ku, Chiba 263-8522, Japan, Email: togofaculty.chiba-u.jp

A. Saito, K. Yoshida, H. Togo, Synthesis, 2022, 54, 153-160.

DOI: 10.1055/s-0041-1737395

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Abstract

Treatment of N-propargyl-N'-tosylhydrazines with molecular iodine in the presence of NaHCO₃ provided 5-substituted 4-iodo-1-tosylpyrazoles in good yields. In the presence of acetic acid, the corresponding 5-aryl-4-iodopyrazoles can be obtained in moderate yields. The reactions are simple and efficient transition-metal-free methods for the preparation of 5-substituted 4-iodo­pyrazoles.

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Key Words

pyrazoles, iodine

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ID: J66-Y2022