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Synfacts 2025; 21(01): 43
DOI: 10.1055/a-2467-5418
Metals in Synthesis

Indazole Synthesis through the Copper-Catalyzed Cyclization of 2-Alkynylazobenzenes

Contributor(s):
Mark Lautens 
,
Andrew G. Durant
Mañas C, Herrero-Bourdieu J, Merino E *. Universidad de Alcalá, Madrid, Spain
Copper-Catalyzed Hydroamination of 2-Alkynylazobenzenes: Synthesis of 3-Alkenyl-2H-indazoles.

J. Org. Chem. 2024;
89: 16883-16888
DOI: 10.1021/acs.joc.4c02144
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Keywords

copper - indazoles - cyclization - alkynylazobenzenes

Significance

The authors report the synthesis of indazoles by a copper-catalyzed intramolecular cyclization of alkynylazobenzenes. The indazole core is found in a variety of biologically active compounds as well as some OLED compounds. The reaction proceeds through an intramolecular azacupration of an alkyne followed by a 1,2-hydride shift.


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Comment

The addition of radical-trapping reagents gave similar yields compared to the standard conditions indicating that the reaction is not radical in nature. DFT calculations indicate that the 1,2-hydride shift is the rate-determining step. The reported reaction is a simple and efficient route to a privileged scaffold.


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Publication History

Article published online:
20 December 2024

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