Cheng D, Shen Y, Wu Z, Xu X, Yan J. Metal-Free Tandem Oxidative Cyclization for the Synthesis of 1,2-Dihydropyridazines and Pyrazoles.
J Org Chem 2021;
86:8563-8575. [PMID:
34133155 DOI:
10.1021/acs.joc.1c00020]
[Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Mediated by 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), a novel oxidative coupling of hydrazones and 1,3-diarylpropenes has been disclosed to generate appealing β,γ-unsaturated hydrazones, which further undergo 5-exo-trig or 6-endo-trig cascade cyclization to give the respective 1,2-dihydropyridazines or pyrazoles selectively under metal-free conditions. The mechanisms of the coupling and subsequent cyclization are proposed.
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