A General and Regioselective Synthesis of 5-Trifluoromethyl-pyrazoles
作者:Robert S. Foster、Harald Jakobi、Joseph P. A. Harrity
DOI:10.1021/ol3021918
日期:2012.9.21
Two synthetic approaches to 4-trifluoromethylsydnones, a novel class of these mesoionic reagents, are reported. These compounds undergo regioselective alkyne cycloaddition reactions, thereby providing a generalapproach to 5-trifluoromethylpyrazoles. This method has been employed in a short formal synthesis of the herbicide fluazolate.
Synthesis of 4-Fluoromethylsydnones and their Participation in Alkyne Cycloaddition Reactions
作者:Robert S. Foster、Harry Adams、Harald Jakobi、Joseph P. A. Harrity
DOI:10.1021/jo400381a
日期:2013.4.19
We report the synthesis and some structural studies of 4-trifluoromethyl, 4-difluoromethyl-, and 4-monofluoromethylsydnones. All but the latter compounds are stable and represent effective precursors to a range of pyrazoles after cycloadditionreactions with alkynes. The cycloadditions are generally highly regioselective and provide 5-fluoromethylpyrazole products, although we have observed that Bn-substituted
method for the synthesis of pyrazoles through a copper-catalyzed condensation reaction has been developed. The new catalytic system not only maintained a broad substrate scope but was also active under acid-free reaction conditions, overcoming the conventional requirement for an acid-catalyzed system. Furthermore, the copper catalyst enabled this reaction to be performed at roomtemperature and in a short
Application of Fe3O4@SiO2@sulfamic acid magnetic nanoparticles as recyclable heterogeneous catalyst for the synthesis of imine and pyrazole derivatives in aqueous medium
作者:B. Zakerinasab、M. A. Nasseri、H. Hassani、M. M. Samieadel
DOI:10.1007/s11164-015-2204-1
日期:2016.4
Sulfamic acid supported on Fe3O4@SiO2 superpara magnetic nanoparticles was successfully applied as a recyclable solid acid catalyst with a large density of sulfamic acid groups for the synthesis of pyrazole derivatives, an important class of potentially bioactive compounds. The products are obtained in high yield from the one-pot reaction procedure involving dicarbonyl compounds and hydrazines/hydrazides. This new method totally avoids the use of toxic or expensive solvents and organic acids in this reaction.
PEG–SO3H as a mild, efficient and green catalytic system for the synthesis of pyrazole derivatives in aqueous medium
作者:M. A. Nasseri、S. A. Alavi、B. Zakeri Nasab
DOI:10.1007/s13738-012-0143-y
日期:2013.4
A versatile, alternative and environmentally benign strategy for the synthesis of a series of pyrazoles has been successfully performed in water using PEG–SO3H as an acidic catalyst. The products are obtained in high yield from the one-pot reaction procedure involving dicarbonyl compounds and hydrazines/hydrazides. This new method totally avoids the use of organic acids and toxic or expensive solvents in this reaction. The catalyst is waste-free, easily prepared, and efficiently re-used.