A highlyregioselectivesynthesis of 1-aryl-3,4,5-substituted pyrazoles based on the condensation of 1,3-diketones with arylhydrazines is described. The reaction proceeds at room temperature in N,N-dimethylacetamide and furnishes pyrazoles in 59-98% yields.
Synthesis of 1,3,5-Trisubstituted [4-<i>tert</i>-Butyl 2-(5,5-difluoro-2,2-dimethyl-6-vinyl-1,3-dioxan-4-yl)acetate]pyrazoles via a Pd-Catalyzed CH Activation
The gem‐difluoromethylenated acetonide 2 was efficiently synthesized as new precursor of HMG‐CoA reductase inhibitor. Straightforward olefination via Pd‐catalyzed C4‐Hactivation of 1,3,5‐trisubstituted pyrazoles 1 was proceeded smoothly in the presence of Pd(OAc)2 and AgCO3. This protocol has merits in terms of the improved atomic economy and prevention from the generation of by‐products.
The reaction of aryl and heteroarylhydrazines with aryl-trifluoromethyl β-diketones
作者:Shiv P. Singh、Vinod Kumar、Ranjana Aggarwal、Jose Elguero
DOI:10.1002/jhet.5570430428
日期:2006.7
We report the results obtained when five aromatic or heteroaromatic hydrazines react with six β-diketones bearing trifluoromethyl and aryl substituents. Forty-two compounds have been isolated corresponding to two isomeric trifluoromethyl pyrazoles and the intermediate 5-CF3, 5-OH pyrazolines. The results have provided useful information for establishing the mechanism of the synthesis of pyrazoles.
Synthesis of 3-trifluoromethylpyrazoles via trifluoromethylation/cyclization of α,β-alkynic hydrazones using a hypervalent iodine reagent
作者:Guojing Ji、Xi Wang、Songnan Zhang、Yan Xu、Yuxuan Ye、Ming Li、Yan Zhang、Jianbo Wang
DOI:10.1039/c4cc01280a
日期:——
A mild and efficient method for the synthesis of 3-trifluoromethylpyrazoles has been established via trifluoromethylation/cyclization of α,β-alkynic hydrazones using a hypervalent iodine reagent.
Selective, Metal-Free Approach to 3- or 5-CF<sub>3</sub>-Pyrazoles: Solvent Switchable Reaction of CF<sub>3</sub>-Ynones with Hydrazines
作者:Vasiliy M. Muzalevskiy、Alexander Yu. Rulev、Alexey R. Romanov、Evgeniy V. Kondrashov、Igor A. Ushakov、Vyacheslav A. Chertkov、Valentine G. Nenajdenko
DOI:10.1021/acs.joc.7b00774
日期:2017.7.21
A detailed study of the reaction of trifluoroacetylated acetylenes and aryl (alkyl) hydrazines was performed, aimed to the regioselective synthesis of 3- or 5-trifluoromethylated pyrazoles. It was found that the regioselectivity of reaction depends dramatically on the solvent nature. Highly polar protic solvents (hexafluoroisopropanol) favor the formation of 3-trifluoromethylpyrazoles. In contrast