New strategy for the regioselective synthesis of 1-phenyl-3-trifluoromethyl-1H-pyrazoles
摘要:
A regioselective synthesis of 3-trifluoromethyl-1-phenyl-1H-pyrazoles (1,3-isomers) as well as their 1,5-isomers (5-trifluoromethyl-1-phenyl-1H-pyrazoles), is described. The 1,3-isomers were obtained from the reaction of 4-alkoxy-1,1,1-trifluoroalk-3-en-2-ones with arylhydrazones followed by deprotective hydrolysis while the 1,5-isomer was obtained by direct cyclocondensation of 4-alkoxy-1,1,1-trifluoroalk-3-en-2-ones with phenylhydrazine. An unequivocal assignment of the 1,3- and 1,5-isomers of the pyrazole products is given. (C) 2013 Elsevier Ltd. All rights reserved.
The arylation of pyrazole and derivatives can be achieved by coupling arenediazonium species (formed in situ fromanilines) by using a catalytic system that employs low‐toxicity and inexpensive copper metal under very mild and ligand‐free conditions (T=20 °C). From other nitrogenheterocycles, the presence of an additive (NBu4I) significantly improves the efficiency of the catalytic system. These results
Mild Conditions for Copper-CatalysedN-Arylation of Pyrazoles
作者:Henri-Jean Cristau、Pascal P. Cellier、Jean-Francis Spindler、Marc Taillefer
DOI:10.1002/ejoc.200300709
日期:2004.2
Copper-catalysed N-arylation of pyrazoles with aryl or heteroaryl bromides or iodides, which can include functional substituents, was performed under the mildest conditions yet described, with excellent yields and selectivity, by the use as catalyst of a combination of cuprous oxide with a set of inexpensive, chelating oxime-type ligands not previously known to promote such reactions. Other original
their cycloadditions with norbornadienes. The nitrile oxide was subjected to the cycloaddition with 2,3-disubstituted norbornadienes to evaluate the effect of the substituents on the exo/endo stereoselectivity. The electron-withdrawing substituents tend to favor the formation of the exo-adducts.
Trifluoromethyl-substituted pyridyl- and pyrazolylboronic acids and esters: synthesis and Suzuki–Miyaura cross-coupling reactions
作者:Kate M. Clapham、Andrei S. Batsanov、Martin R. Bryce、Brian Tarbit
DOI:10.1039/b901024f
日期:——
allows for further cross-couplings to yield tetra-substituted pyrazolyl derivatives (Scheme 5). X-Ray crystal structures are reported for selected pyridylboronic acids, pyrazolylboronic esters and derived trifluoromethyl-substituted heterobiaryl systems. These multi-ring CF3-substituted systems are of interest as buildingblocks for drug discovery and materials chemistry.
Copper-catalyzed C–N cross-coupling of arylboronic acids with N-acylpyrazoles
作者:Jin Zhang、Run-Ping Jia、Dong-Hui Wang
DOI:10.1016/j.tetlet.2016.06.044
日期:2016.8
A copper-catalyzed C–N bond forming reaction of arylboronicacids and N-acylpyrazoles was developed. This procedure used N-acetyl protected pyrazoles as starting material instead of free pyrazoles (NH). The reaction worked under neutral conditions and did not require any base or ligand. The reaction showed good functional group tolerance.