Issue 6, 2013

A robust protocol for Pd(ii)-catalyzed C-3 arylation of (1H) indazoles and pyrazoles: total synthesis of nigellidine hydrobromide

Abstract

C3-arylated indazole and pyrazoles are privileged structural motifs in agrochemicals and pharmaceuticals. C-3 C–H arylation of (1H) indazole and pyrazole has been a significant challenge due to the poor reactivity of the C-3 position. Herein, we report a practical Pd(II)/Phen catalyst and conditions for the direct C-3 arylation of indazole and pyrazole with ArI or ArBr without using Ag additives as halide scavengers. The use of toluene, chlorobenzene, trifluoromethylbenzene and mesitylene as the solvent was found to be crucial for the selectivity and reactivity. We further demonstrate the robustness of this protocol through the first total synthesis of nigellidine hydrobromide as well as the expedient preparation of heterocycles structurally related to pesticides and drug molecules.

Graphical abstract: A robust protocol for Pd(ii)-catalyzed C-3 arylation of (1H) indazoles and pyrazoles: total synthesis of nigellidine hydrobromide

Supplementary files

Article information

Article type
Edge Article
Submitted
21 Jan 2013
Accepted
18 Mar 2013
First published
18 Mar 2013

Chem. Sci., 2013,4, 2374-2379

A robust protocol for Pd(II)-catalyzed C-3 arylation of (1H) indazoles and pyrazoles: total synthesis of nigellidine hydrobromide

M. Ye, A. J. F. Edmunds, J. A. Morris, D. Sale, Y. Zhang and J. Yu, Chem. Sci., 2013, 4, 2374 DOI: 10.1039/C3SC50184A

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