1028092-59-2Relevant academic research and scientific papers
A robust protocol for Pd(ii)-catalyzed C-3 arylation of (1H) indazoles and pyrazoles: Total synthesis of nigellidine hydrobromide
Ye, Mengchun,Edmunds, Andrew J.F.,Morris, James A.,Sale, David,Zhang, Yejia,Yu, Jin-Quan
, p. 2374 - 2379 (2013/07/25)
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.
A simple, modular method for the synthesis of 3,4,5-trisubstituted pyrazoles
McLaughlin, Mark,Marcantonio, Karen,Chen, G-Yi,Davies, Ian W.
, p. 4309 - 4312 (2008/09/21)
(Chemical Equation Presented) A modular approach for the regiocontrolled preparation of pyrazoles bearing substituents on all three carbon atoms is described. Central to this method is the use of a switchable metal-directing group (MDG) to enable sequential direct lithiation of the 3- and 5-positions of the pyrazole ring. Pyrazole boronic esters obtained from these lithiated intermediates can undergo efficient Suzuki cross-coupling under the developed nonaqueous conditions, which minimize undesirable protolytic deboronation. Halogenation of the 4-position provides the means for substitution at the remaining carbon atom.
