- Arylchlorocarbenes in the synthesis of heterocycles containing two nitrogen atoms
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Substituted pyrazoles and pyrrolo[1,2-c]pyrimidines were prepared from the reaction of arylchlorocarbenes with 1,2-diazabuta-1,3-dienes and 4- vinylpyrimidines, respectively.
- Romashin, Yuri N.,Liu, Michael T. H.,Nijjar, Satnam S.,Attanasi, Orazio A.
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- Cycloaddition of hydrazones and 1, 2-diarylalkynes promoted by t-BuOK/DMF: A convenient synthesis of tetraarylpyrazoles
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A facile synthesis of tetraarylpyrazoles has been developed via t-BuOK/DMF promoted intermolecular cycloaddition of hydrazones and 1,2-diarylalkynes. A possible reaction pathway via a hydrazone radical is proposed.
- Tong, Lang,Mao, Zhifeng,Tang, Xiangzheng,Zhang, Xuejing,Yan, Ming
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- Multicomponent Pyrazole Synthesis from Alkynes, Nitriles, and Titanium Imido Complexes via Oxidatively Induced N-N Bond Coupling
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Pyrazoles are an important class of heterocycles found in a wide range of bioactive compounds and pharmaceuticals. Pyrazole synthesis often requires hydrazine or related reagents where an intact N-N bond is conservatively installed into a pyrazole precursor fragment. Herein, we report the multicomponent oxidative coupling of alkynes, nitriles, and Ti imido complexes for the synthesis of multisubstituted pyrazoles. This modular method avoids potentially hazardous reagents like hydrazine, instead forming the N-N bond in the final step via oxidation-induced coupling on Ti. The mechanism of this transformation has been studied in-depth through stoichiometric reactions of the key diazatitanacyclohexadiene intermediate, which can be accessed via multicomponent coupling of Ti imidos with nitriles and alkynes, ring opening of 2-imino-2H-azirines, or direct metalation of 4-azadiene-1-amine derivatives. The critical transformation in this reaction is the 2-electron oxidation-induced N-N coupling on Ti. This is a rare example of formal N-N coupling on a metal center, which likely occurs through an electrocyclic mechanism analogous to a Nazarov cyclization. Conveniently, these 2-electron-oxidized diazatitanacyclohexadiene intermediates can be accessed via disproportionation of the 1-electron-oxidized species, which allows utilization of weak oxidants such as TEMPO
- Pearce, Adam J.,Harkins, Robin P.,Reiner, Benjamin R.,Wotal, Alexander C.,Dunscomb, Rachel J.,Tonks, Ian A.
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supporting information
p. 4390 - 4399
(2020/03/04)
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- Novel synthesis method of tetraarylpyrazole compound
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The invention provides a novel synthesis method of a tetraarylpyrazole compound. The method comprises the following steps that hydrazone and diaryl acetylene are used as raw materials; one kind of alkali is added at a certain temperature; reaction is perf
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Paragraph 0019-0027; 0031-0033
(2021/02/16)
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- Synthesis and biological evaluation of 1,3,4,5-tetrasubstituted pyrazole derivatives
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We report a solvent-free synthesis of novel 1,3,4,5-tetrasubstituted pyrazoles and investigate their inhibitory activity against soybean 15-lipoxygenase. It was revealed that all synthesized compounds exhibited good activity, and among them, 3-(furan-2-yl
- Yahyavi, Hoda,Hosseinzadeh, Fatemeh,Karimi, Nastaran,Moghimi, Setareh,Mahdavi, Mohammad,Nadri, Hamid,Moradi, Alireza,Shafiee, Abbas,Foroumadi, Alireza
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p. 973 - 977
(2016/10/13)
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- AIEE phenomenon: Tetraaryl vs. triaryl pyrazoles
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Tetraarylpyrazoles are synthesized from commercially available materials in three steps and found to exhibit Aggregation Induced Emission Enhancement (AIEE) characteristics. Removing one aryl unit from tetraarylpyrazole leads to Aggregation Caused Quenching (ACQ), thus the number of aryl groups plays an important role in exploring such a phenomenon.
- Mukherjee, Sayani,Salini,Srinivasan,Peruncheralathan
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supporting information
p. 17148 - 17151
(2015/12/05)
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- Facile one-pot synthesis of 1,3,5-trisubstituted pyrazoles from α,β-enones
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A practical and efficient one-pot synthesis of 1,3,5-trisubstituted pyrazoles from α,β-enones and arylhydrazine hydrochlorides has been developed. The pyrazoles were formed via a tandem formation of the corresponding pyrazolines and an acid-catalyzed aerobic oxidation process.
- Yu, Jin,Kim, Ko Hoon,Moon, Hye Ran,Kim, Jae Nyoung
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p. 1692 - 1696
(2014/07/07)
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- TEMPO-mediated aliphatic C-H Oxidation with Oximes and hydrazones
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A method for aliphatic C-H bond oxidation of oximes and hydrazones mediated by 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO) has been developed, which enables the concise assembly of substituted isoxazole and pyrazole skeletons.
- Zhu, Xu,Wang, Yi-Feng,Ren, Wei,Zhang, Feng-Lian,Chiba, Shunsuke
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supporting information
p. 3214 - 3217
(2013/07/26)
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- A robust protocol for Pd(ii)-catalyzed C-3 arylation of (1H) indazoles and pyrazoles: Total synthesis of nigellidine hydrobromide
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C3-arylated indazole and pyrazoles are privileged structural motifs in agrochemicals and pharmaceuticals. C-3 C-H arylation of (1H) indazole and pyrazole has been a significant challenge due to the poor reactivity of the C-3 position. Herein, we report a practical Pd(ii)/Phen catalyst and conditions for the direct C-3 arylation of indazole and pyrazole with ArI or ArBr without using Ag additives as halide scavengers. The use of toluene, chlorobenzene, trifluoromethylbenzene and mesitylene as the solvent was found to be crucial for the selectivity and reactivity. We further demonstrate the robustness of this protocol through the first total synthesis of nigellidine hydrobromide as well as the expedient preparation of heterocycles structurally related to pesticides and drug molecules.
- Ye, Mengchun,Edmunds, Andrew J.F.,Morris, James A.,Sale, David,Zhang, Yejia,Yu, Jin-Quan
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p. 2374 - 2379
(2013/07/25)
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- Pyrazoles by Cyclisation of Benzoin Phenylhydrazone with Aldehydes
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By fusing (E)- or (Z)-benzoin phenylhydrazone and aldehydes, 3-substituted 1H-pyrazoles (2) are obtained.The structure of 2d was confirmed by X-ray analysis.
- Gnichtel, Horst,Brockmanns, Manfred,Salem, Widah I.,Luger, Peter
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p. 589 - 592
(2007/10/02)
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