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Short Paper | Regular issue | Vol 100, No. 8, 2020, pp.1249-1259
Published online, 5th June, 2020
DOI: 10.3987/COM-20-14268
When Hydrazonoyl Chlorides Meet Terminal Alkynes: Regioselective Copper(I)-Catalysed "Click" Sequential Reactions to 5-Substituted Pyrazoles

Giorgio Molteni*

*Department of Chemistry, University of Milano, Via Golgi 19, 20133 Milano, Italy


In the presence of catalytic amounts of copper(I) salts, terminal alkynes underwent the formation of copper(I) acetylides that enabled their nucleophilic addition onto hydrazonoyl chlorides followed by spontaneous cyclisation of the resulting alkynylhydrazone intermediate. This sequential reaction sequence was exploited as a facile and regioselective synthesis of 1,3,5-substituted pyrazoles. A catalytic cycle has been proposed accounting for the observed results.