4492-01-7Relevant articles and documents
Thermal cyclization of 3-(1-naphthyl)-1-phenylpyrazole- 4-carboxylic acid in polyphosphoric acid [12]
Bratenko,Chornous,Vovk
, p. 1156 - 1157 (2002)
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Primary Vinyl Ethers as Acetylene Surrogate: A Flexible Tool for Deuterium-Labeled Pyrazole Synthesis
Ananikov, Valentine P.,Lebedev, Andrey N.,Ledovskaya, Maria S.,Polynski, Mikhail V.,Voronin, Vladimir V.
, (2020/07/24)
A novel synthetic path to 1,3-disubstituted pyrazoles and their deuterated derivatives was developed. It is based on the reaction of vinyl ethers with hydrazonoyl chlorides in the presence of triethylamine. The reaction mechanism, clarified by the joint experimental and computational study, involves 1,3-dipolar cycloaddition of the in situ generated nitrile imines to vinyl ethers and subsequent cleavage of alcohol from the formed alkoxypyrazoline. The results highlight the possibility of using vinyl ethers as acetylene surrogate and provide a novel access to pyrazoles, 4,5-dideuteropyrazoles and their regioselectively labeled derivatives, 5-deuteropyrazoles.
Ruthenium-catalyzed formation of pyrazoles or 3-hydroxynitriles from propargyl alcohols and hydrazines
Kaufmann, Julia,J?ckel, Elisabeth,Haak, Edgar
supporting information, p. 91 - 101 (2019/07/09)
Functionalized pyrazoles are generated from secondary propragyl alcohols and hydrazines in a ruthenium-catalyzed cascade process, consisting of redox isomerization, Michael addition, cyclocondensation and dehydrogenation steps. The same bifunctional catalyst mediates the conversion of tertiary propargyl alcohols with hydrazine to 3-hydroxynitriles via anti-Markovnikov hydroamination followed by elimination of ammonia.
[3+2]-cycloaddition of in situ generated nitrile imines and acetylene for assembling of 1,3-disubstituted pyrazoles with quantitative deuterium labeling
Voronin, Vladimir V.,Ledovskaya, Maria S.,Gordeev, Evgeniy G.,Rodygin, Konstantin S.,Ananikov, Valentine P.
, p. 3819 - 3828 (2018/04/14)
A novel synthetic methodology for the preparation of 1,3-disubstituted pyrazoles from in situ generated nitrile imines and acetylene is reported. The reactions are performed in a simple two-chamber reactor. One part of the reactor is loaded with hydrazonoyl chloride precursors of active nitrile imine species and a base. The other part is used to generate acetylene from CaC2 and water. Partitioning of the reactants improves the yields of desired pyrazoles up to 99% and simplifies their isolation to a simple procedure of solvent evaporation. The approach requires no complex equipment and utilizes inexpensive, safe, and easy to handle calcium carbide as a starting material. A model deuterium incorporation is carried out according to the developed methodology, producing a series of novel 4,5-dideuteropyrazoles with excellent deuterium enrichment. Theoretical calculations on reaction mechanism and characterization of possible intermediate structures were performed.
