19311-79-6Relevant articles and documents
Preparation method of pyrazole derivative (by machine translation)
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Paragraph 0151-0155, (2019/12/02)
The preparation method comprises the following steps: mixing an alkyne propyl alcohol derivative, a halogen source, an acid and a solvent, heating and reacting, and reacting to Meyer - Schuster generate the pyrazole derivative. Compared with the prior art, the preparation method disclosed by the invention has 91% the advantages of maximum yield, simple operation, mild conditions, high conversion rate, few byproducts and the like, and provides a brand-new synthetic method for construction of pyrazole compounds. (by machine translation)
Mechanistic Studies on the Michael Addition of Amines and Hydrazines to Nitrostyrenes: Nitroalkane Elimination via a Retro-aza-Henry-Type Process
Kallitsakis, Michael G.,Tancini, Peter D.,Dixit, Mudit,Mpourmpakis, Giannis,Lykakis, Ioannis N.
, p. 1176 - 1184 (2018/02/09)
In this article we report on the mechanistic studies of the Michael addition of amines and hydrazines to nitrostyrenes. Under the present conditions, the corresponding N-alkyl/aryl substituted benzyl imines and N-methyl/phenyl substituted benzyl hydrazones were observed via a retro-aza-Henry-type process. By combining organic synthesis and characterization experiments with computational chemistry calculations, we reveal that this reaction proceeds via a protic solvent-mediated mechanism. Experiments in deuterated methanol CD3OD reveal the synthesis and isolation of the corresponding deuterated intermediated Michael adduct, results that support the proposed slovent-mediated pathway. From the synthetic point of view, the reaction occurs under mild, noncatalytic conditions and can be used as a useful platform to yield the biologically important N-methyl pyrazoles in a one-pot manner, simple starting with the corresponding nitrostyrenes and the methylhydrazine.
Nucleophilic ring-opening reactions of trans-2-aroyl-3-aryl-cyclopropane-1,1-dicarboxylates with hydrazines
Sathishkannan, Gopal,Tamilarasan, V. John,Srinivasan, Kannupal
, p. 1400 - 1406 (2017/02/15)
trans-2-Aroyl-3-aryl-cyclopropane-1,1-dicarboxylates when treated with arylhydrazines in refluxing EtOH gave dihydropyrazoles, whereas with hydrazines in refluxing AcOH, they formed cyclopropane-fused pyridazinones. Although in both cases the corresponding hydrazones are formed initially, the former case involves a subsequent 5-exo-tet nucleophilic ring-opening, and the later, a 6-exo-trig nucleophilic attack by the other hydrazone nitrogen. The products are obtained in moderate to excellent yields with complete regio-and diastereoselectivity.
Visible-light photocatalytic aerobic annulation for the green synthesis of pyrazoles
Ding, Ya,Zhang, Te,Chen, Qiu-Yun,Zhu, Chunyin
supporting information, p. 4206 - 4209 (2016/09/09)
A selective and high yielding synthesis of polysubstituted pyrazoles through a VLPC (visible light photoredox catalysis)-promoted reaction of hydrazine with Michael acceptors is reported. The method employs very mild reaction conditions and uses air as the terminal oxidant, which makes the process environmentally benign. Different types of Michael acceptors with various substituents can undergo the reaction to afford corresponding pyrazoles in good to excellent yields. The reaction is proposed to go through VLPC-promoted oxidation of hydrazine to diazene followed by its addition to Michael acceptors, other than the conventional condensation of hydrazine with a carbonyl.
Radical Addition of Hydrazones by α-Bromo Ketones to Prepare 1,3,5-Trisubstituted Pyrazoles via Visible Light Catalysis
Fan, Xiu-Wei,Lei, Tao,Zhou, Chao,Meng, Qing-Yuan,Chen, Bin,Tung, Chen-Ho,Wu, Li-Zhu
, p. 7127 - 7133 (2016/08/30)
A novel efficient tandem reaction of hydrazones and α-bromo ketones is reported for the preparation of 1,3,5-trisubstituted pyrazoles by visible light catalysis. In this system, the monosubstituted hydrazones show wonderful reaction activity with alkyl radicals, generated from α-bromo ketones. A radical addition followed by intramolecular cyclization affords the important pyrazole skeleton in good to excellent yields. This efficient strategy under mild conditions with wide group tolerance provides a potential approach to the 1,3,5-trisubstituted pyrazoles.
Phosphine- and copper-free palladium catalyzed one-pot four-component carbonylation reaction for the synthesis of isoxazoles and pyrazoles
Iranpoor, Nasser,Firouzabadi, Habib,Etemadi-Davan, Elham
supporting information, p. 837 - 840 (2016/02/05)
The palladium catalyzed one-pot synthesis of isoxazoles and pyrazoles from aryl iodides, terminal alkynes, chromium hexacarbonyl and hydroxylamine hydrochloride or aqueous hydrazine solution is described. The Sonogashira carbonylative coupling intermediate was trapped in situ by hydroxylamine hydrochloride or aqueous hydrazine to deliver isoxazoles or pyrazoles, respectively, in high yields. This efficient method proceeds at atmospheric pressure and moderate temperature and does not require the use of copper, phosphine ligands or gaseous carbon monoxide.
Regioselective synthesis of 1,3,5-Trisubstituted Pyrazoles from N-Alkylated Tosylhydrazones and terminal Alkynes
Kong, Yuanfang,Tang, Meng,Wang, Yun
, p. 576 - 579 (2014/04/03)
An efficient synthesis of 1,3,5-trisubstituted pyrazoles from Nalkylated tosylhydrazones and terminal alkynes was developed. The protocol was applied to a wide range of substrates and demonstrated excellent tolerance to a variety of substituents, includin
HCV NS5A replication complex inhibitors. Part 3
Lopez, Omar D.,Nguyen, Van N.,St. Laurent, Denis R.,Belema, Makonen,Serrano-Wu, Michael H.,Goodrich, Jason T.,Yang, Fukang,Qiu, Yuping,Ripka, Amy S.,Nower, Peter T.,Valera, Lourdes,Liu, Mengping,O'Boyle II, Donald R.,Sun, Jin-Hua,Fridell, Robert A.,Lemm, Julie A.,Gao, Min,Good, Andrew C.,Meanwell, Nicholas A.,Snyder, Lawrence B.
, p. 779 - 784 (2013/02/25)
In a recent disclosure,1 we described the discovery of dimeric, prolinamide-based NS5A replication complex inhibitors exhibiting excellent potency towards an HCV genotype 1b replicon. That disclosure dealt with the SAR exploration of the peripheral region of our lead chemotype, and herein is described the SAR uncovered from a complementary effort that focused on the central core region. From this effort, the contribution of the core region to the overall topology of the pharmacophore, primarily vector orientation and planarity, was determined, with a set of analogs exhibiting 50 in a genotype 1b replicon assay.
Copper on iron promoted one-pot synthesis of β-aminoenones and 3,5-disubstituted pyrazoles
Kovács, Szabolcs,Novák, Zoltán
, p. 8987 - 8993 (2013/09/24)
The reaction of hydroximoyl chlorides with acetylenes in the presence of a copper on iron bimetallic system leads to β-aminoenones via reductive ring opening of isoxazole intermediates. The valuable β-aminoenone building blocks can be isolated or transformed into pyrazoles with the addition of hydrazine in a straightforward one-pot procedure.
One-pot synthesis of pyrazoles through a four-step cascade sequence
Hao, Lu,Hong, Jun-Jie,Zhu, Jun,Zhan, Zhuang-Ping
supporting information, p. 5715 - 5720 (2013/06/04)
A one-pot synthesis of 3,4,5- and 1,3,5-pyrazoles from tertiary propargylic alcohols and para-tolylsulfonohydrazide has been accomplished. The pyrazoles are formed through a four-step cascade sequence, including FeCl 3-catalyzed propargylic substitution, aza-Meyer-Schuster rearrangement, base-mediated 6πelectrocyclization, and thermal [1,5] sigmatropic shift. In this reaction, the 3,4,5- and 1,3,5-pyrazoles are produced selectively according to different substituents in the starting alcohols. A one-pot recipe: The synthesis of 3,4,5- and 1,3,5-pyrazoles from tertiary propargylic alcohols and para-tolylsulfonohydrazide has been accomplished. The pyrazoles are formed through a four-step cascade sequence (see figure), and are produced selectively according to different substituents in the starting alcohols.