- Primary Vinyl Ethers as Acetylene Surrogate: A Flexible Tool for Deuterium-Labeled Pyrazole Synthesis
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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.
- Ananikov, Valentine P.,Lebedev, Andrey N.,Ledovskaya, Maria S.,Polynski, Mikhail V.,Voronin, Vladimir V.
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- Copper-Promoted Coupling of Propiophenones and Arylhydrazines for the Synthesis of 1,3-Diarylpyrazoles
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Synthesis of 1,3-diarylpyrazoles from commercial substrates and/or simple transformations is still underrated. In this report, we have developed a method for copper-promoted coupling of propiophenones and arylhydrazines. The reactions afforded substituted pyrazoles in the presence of TEMPO oxidant, acetic acid additive, and DMF solvent. A number of functionalities were compatible with reaction conditions, including halogens, methoxy, trifluoromethyl, and nitro groups. An indazole could be obtained if an electron-poor propiophenone was used.
- Dang, Ha V.,Le, Ha V.,Nguyen, Tien M.,Nguyen, Tung T.,Pham, Thuyet L. D.,Phan, Nam T. S.,Tran, Khuong A.
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supporting information
p. 801 - 804
(2020/05/19)
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- Molybdenum-Mediated One-Pot Synthesis of Pyrazoles from Isoxazoles
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A one-pot approach for the direct synthesis of substituted pyrazoles from isoxazoles is reported. The process involves isoxazole N-O bond cleavage mediated by a molybdenum complex, in situ hydrolysis of the resulting β-amino enone to the corresponding 1,3-diketone, followed by pyrazole formation in the presence of hydrazine or substituted hydrazine. Good to excellent yields and regioselectivities are obtained with nonsymmetric isoxazoles. By using readily available starting materials, a wide range of substituted pyrazoles may be synthesized by this method.
- Beaumont, Stéphane,Rey, Marine
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p. 3796 - 3804
(2019/10/11)
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- [3+2]-cycloaddition of in situ generated nitrile imines and acetylene for assembling of 1,3-disubstituted pyrazoles with quantitative deuterium labeling
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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.
- Voronin, Vladimir V.,Ledovskaya, Maria S.,Gordeev, Evgeniy G.,Rodygin, Konstantin S.,Ananikov, Valentine P.
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p. 3819 - 3828
(2018/04/14)
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- Facile synthesis of pyrazoles by iron-catalyzed regioselective cyclization of hydrazone and 1,2-diol under ligand-free conditions
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A facile synthesis of pyrazoles by the cyclization of hydrazones and 1,2-diols was described. In the presence of ferric nitrate, the reaction occurs under neat conditions and makes the use of potassium persulfate to oxidize the diol to α-hydroxy carbaldehyde for the reaction with hydrazones to produce 1,3- and 1,3,5-substituted pyrazoles selectively. The overall regioselective transformation occurs in one-pot under ligand-free, mild conditions even in the presence of air.
- Panda, Niranjan,Ojha, Subhadra
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p. 244 - 251
(2018/03/13)
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- Solvent-dependent copper-catalyzed synthesis of pyrazoles under aerobic conditions
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We present a copper-catalyzed oxidative cyclization of β,γ-unsaturated hydrazones, utilizing molecular oxygen as a stoichiometric oxidant. The methodology provides distinct classes of pyrazoles simply by changing the reaction solvent. Tris-substituted pyr
- Pünner, Florian,Sohtome, Yoshihiro,Sodeoka, Mikiko
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p. 14093 - 14096
(2016/12/09)
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- An efficient regioselective copper catalyzed multi-component synthesis of 1,3-disubstituted pyrazoles
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An efficient synthesis of unsymmetrically substituted 1,3-pyrazole derivatives has been developed via three-component coupling reaction involving 3-(dimethylamino)-1-phenylprop-2-en-1-one, hydrazine, and aryl halides in one pot process exhibiting high regioselectivity. The pyrazole synthesis proceeds via a sequential series of reactions such as Michael addition, heterocyclization, dehydration, and Ullmann cross-coupling.
- Raghunadh, Akula,Meruva, Suresh Babu,Mekala, Ramamohan,Raghavendra Rao,Krishna, Thalishetti,Gangadhara Chary,Vaikunta Rao,Syam Kumar
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p. 2986 - 2990
(2014/05/06)
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- Practical synthesis of pyrazoles via a copper-catalyzed relay oxidation strategy
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Various 1,3- and 1,3,4-substituted pyrazoles are smoothly formed via copper-catalyzed cascade reactions of oxime acetates, amines and aldehydes. This relay oxidative process involves copper-promoted N-O bond cleavage and C-C/C-N/N-N bond formations to furnish pyrazolines, and sequential Cu-O2 system-involved oxidative dehydrogenation of pyrazolines to afford pyrazoles. This transformation provides a novel and versatile approach for the synthesis of pyrazoles, with an inexpensive copper catalyst and green oxidants. It is atom- and step-economical, and possesses a good functional group tolerance, as well as operational simplicity. This journal is
- Tang, Xiaodong,Huang, Liangbin,Yang, Jidan,Xu, Yanli,Wu, Wanqing,Jiang, Huanfeng
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supporting information
p. 14793 - 14796
(2014/12/11)
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- Fe-catalyzed one-pot synthesis of 1,3-Di- and 1,3,5-trisubstituted pyrazoles from hydrazones and vicinal diols
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An iron-catalyzed route for the regioselective synthesis of 1,3- and 1,3,5-substituted pyrazoles from the reaction of diarylhydrazones and vicinal diols has been developed. This method was found to be practical with wide substrate scope.
- Panda, Niranjan,Jena, Ashis Kumar
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p. 9401 - 9406,6
(2012/12/11)
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- Fe-catalyzed one-pot synthesis of 1,3-Di- and 1,3,5-trisubstituted pyrazoles from hydrazones and vicinal diols
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An iron-catalyzed route for the regioselective synthesis of 1,3- and 1,3,5-substituted pyrazoles from the reaction of diarylhydrazones and vicinal diols has been developed. This method was found to be practical with wide substrate scope.
- Panda, Niranjan,Jena, Ashis Kumar
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p. 9401 - 9406
(2013/01/15)
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- Single-step synthesis of pyrazoles using titanium catalysis
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A simple titanium complex catalyzes the coupling of alkynes, isonitriles, and monosubstituted hydrazines to generate substituted pyrazoles in a single step.
- Dissanayake, Amila A.,Odom, Aaron L.
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supporting information; experimental part
p. 440 - 442
(2012/01/05)
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- Cu(OAc)2·H2O-catalyzed N-arylation of nitrogen-containing heterocycles
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In the absence of any additional ligands, the efficient N-arylation of nitrogen-containing heterocycles with aryl iodides catalyzed by relative low catalyst amount of Cu(OAc)2·H2O was developed. This simple catalytic system is involved in the C-N cross-coupling reaction and works for a variety of pyrazole, pyrrole, imidazole, triazole, indole, benzoimidazole, benzotriazole, carbazole, and anilines as well as aryl iodides with different electronic properties. Highly efficient copper(II)-catalyzed N-arylation protocol was established.
- Xu, Zhong-Lin,Li, Hong-Xi,Ren, Zhi-Gang,Du, Wei-Yuan,Xu, Wei-Chang,Lang, Jian-Ping
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supporting information; experimental part
p. 5282 - 5288
(2011/08/04)
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- Regioselective microwave-assisted synthesis of substituted pyrazoles from ethynyl ketones
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Reaction of α,β-ethynyl ketones and hydrazine derivatives gives 1,3- and 1,5-disubstituted pyrazoles in good yield. Microwave irradiation in concentrated hydrochloric acid-methanol (1.5% v/v), with concurrent cooling at sub-ambient temperatures or at 120°
- Bagley, Mark C.,Lubinu, M. Caterina,Mason, Christopher
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p. 704 - 708
(2007/12/27)
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