- Synthesis of pyrazoles by a one-pot tandem cyclization-dehydrogenation approach on Pd/C/K-10 catalyst
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A novel one-pot synthesis of substituted pyrazoles from chalcones and hydrazines via a tandem cyclization-dehydrogenation approach is described. This process is based on the use of a bifunctional noble-metal/solid-acid catalyst, Pd/C/K-10 montmorillonite
- Landge, Shainaz M.,Schmidt, Allison,Outerbridge, Verona,T?r?k, Béla
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- Facile One-Pot Transformation of Primary Alcohols into 3-Aryl- and 3-Alkyl-isoxazoles and -pyrazoles
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Various primary alcohols were smoothly transformed into 3-aryl- and 3-alkylisoxazoles in good yields in one pot by successive treatment with PhI(OAc) 2 in the presence of TEMPO, NH 2 OH, and then NCS, followed by reaction with alkynes in the presence of Et 3 N. Similarly, various primary alcohols were smoothly transformed into 3-aryl- and 3-alkylpyrazoles in good yields in one pot by successive treatment with PhI(OAc) 2 in the presence of TEMPO, PhNHNH 2, and then NCS and decyl methyl sulfide, followed by reaction with alkynes in the presence of Et 3 N. Thus, both 3-aryl- and 3-alkylisoxazoles, and 3-aryl- and 3-alkylpyrazoles could be prepared from readily available primary alcohols in one pot under transition-metal-free conditions.
- Kobayashi, Eiji,Togo, Hideo
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p. 3723 - 3735
(2019/09/30)
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- One-pot regioselective synthesis of substituted pyrazoles and isoxazoles in PEG-400/water medium by Cu-free nano-Pd catalyzed sequential acyl Sonogashira coupling-intramolecular cyclization
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Catalyst efficacy of in situ generated Pd-nanoparticles (PdNPs) in the regioselective one-pot synthesis of 3,5-di & 3,4,5-trisubstituted pyrazoles and 3,5-disubstituted isoxazoles in environmentally benign PEG-400/H2O medium, which involves the sequential (i) Cu-free acyl-Sonogashira coupling (ASC) and (ii) intramolecular ynone-amine cyclization under PTC conditions was described. The results of controlled experiments support the operation of two sequential catalytic cycles (ASC/cyclization) and achievement of complementary/opposite regioselectivity via ynone-bound palladium in a one-pot approach. Moreover, the in situ PdNPs recovered after the first catalytic cycle of the one-pot reaction sequence have been reused again five times successively. Besides, prior to the above studies, the efficacy of some common Pd-N-heterocyclic carbene (Pd-NHC) complexes in catalyzing the same one-pot two-step reaction sequence (Cu-free ASC/cyclization) both in water and organic solvents was also optimized. In situ generation of PdNPs from above Pd-NHCs in water was also identified, but they are not reusable due to their large size distribution.
- Thirukovela, Narasimha Swamy,Balaboina, Ramesh,Botla, Vinayak,Vadde, Ravinder,Jonnalagadda, Sreekantha Babu,Vasam, Chandra Sekhar
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p. 6471 - 6481
(2019/11/20)
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- Fast and Efficient Continuous Flow Method for the Synthesis of Ynones and Pyrazoles
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In this study, we developed a convenient and efficient two-step method for the synthesis of ynones in a flow reactor, through the generation of lithium acetylide and its subsequent reactions with acid chlorides. Using this approach, we obtained the ynones in moderate to good yields at room temperature. Moreover, we transformed the ynones into pyrazole derivatives through coupling with hydrazines. This transition metal-free process, mild reaction conditions, and broad functional group tolerance are all attractive features in comparison with conventional bench-top methods.
- Kandasamy, Mohanraj,Ganesan, Balaji,Hung, Min-Yuan,Lin, Wei-Yu
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p. 3183 - 3189
(2019/05/28)
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- A Regioselective Approach to Trisubstituted Pyrazoles via Palladium-Catalyzed Oxidative Sonogashira-Carbonylation of Arylhydrazines
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A palladium-catalyzed oxidative carbonylation of arylhydrazines and alkynes with balloon pressure CO/O2 to afford trisubstituted pyrazoles in a one-pot manner has been developed. The formation of trisubstituted pyrazoles involves a sequential C-N bond cleavage, carbonylation, Sonogashira coupling, Michael addition, and intramolecular condensation cyclization tandem process. An unprecedented oxidative Sonogashira-carbonylation reaction of arylhydrazine plays a key role for such a facile approach to pyrazoles.
- Tu, Yongliang,Zhang, Zhenming,Wang, Tao,Ke, Jiamei,Zhao, Junfeng
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supporting information
p. 3466 - 3469
(2017/07/15)
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- Radical Enamination of Vinyl Azides: Direct Synthesis of N-Unprotected Enamines
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An electron-withdrawing-group-generable radical-induced enamination of vinyl azides is reported, which results in a variety of β-functionalized N-unprotected enamines in a stereoselective manner. A plausible mechanism involving an unusual 1,3-H transfer of in situ generated iminyl radical intermediate was proposed on the basis of experimental results and DFT calculations.
- Ning, Yongquan,Zhao, Xue-Feng,Wu, Yan-Bo,Bi, Xihe
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p. 6240 - 6243
(2017/11/24)
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- Method for efficiently preparing 1,3,5-trisubstituted pyrazole compound
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The invention discloses a method for efficiently preparing a 1,3,5-trisubstituted pyrazole compound. According to the method for efficiently preparing the 1,3,5-trisubstituted pyrazole compound, with metal palladium as a catalyst and triethylamine as an additive, aryl hydrazide hydrochloride, terminal alkyne and carbon monoxide are used as raw materials and react with one another under a heated condition in the atmosphere of oxygen to obtain the 1,3,5-trisubstituted pyrazole compound; and the reaction formula is formula (1). The method for efficiently preparing the 1,3,5-trisubstituted pyrazole compound realizes a method for preparing the 1,3,5-trisubstituted pyrazole compound by using palladium-catalyzed one-pot multi-component cascade reaction; and the method for efficiently preparing the 1,3,5-trisubstituted pyrazole compound has the advantages of simplicity, feasibility, simply and easy obtaining of raw materials and wide application prospect.
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Page/Page column 8
(2017/08/29)
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- Nucleophilic ring-opening reactions of trans-2-aroyl-3-aryl-cyclopropane-1,1-dicarboxylates with hydrazines
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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.
- Sathishkannan, Gopal,Tamilarasan, V. John,Srinivasan, Kannupal
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p. 1400 - 1406
(2017/02/15)
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- Radical Addition of Hydrazones by α-Bromo Ketones to Prepare 1,3,5-Trisubstituted Pyrazoles via Visible Light Catalysis
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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.
- Fan, Xiu-Wei,Lei, Tao,Zhou, Chao,Meng, Qing-Yuan,Chen, Bin,Tung, Chen-Ho,Wu, Li-Zhu
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p. 7127 - 7133
(2016/08/30)
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- Four-component synthesis of β-enaminone and pyrazole through phosphine-free palladium-catalyzed cascade carbonylation
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The carbonylative domino synthesis of enaminones and pyrazoles has been performed with the N?N bidentate palladium catalyst to achieve excellent selectivity. These results have confirmed that the carbonylative Sonogashira coupling of iodobenzenes with ter
- Shi, Lijun,Xue, Liqin,Lang, Rui,Xia, Chungu,Li, Fuwei
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p. 2560 - 2566
(2015/04/14)
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- One-pot synthesis of Pd nanoparticle catalysts supported on N-doped carbon and application in the domino carbonylation
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In this work, we report a novel and facile procedure for a one-pot preparation of palladium nanoparticle catalysts supported on porous N-doped carbon (Pd@CNT) by direct carbonization of palladium-N-heterocyclic carbene coordination polymer (P-Pd-NHC). This method could be conveniently extended to the synthesis of the Ni and alloy (PdxNiy) nanoparticle catalysts (Ni@CN800, PdxNi y@CN800). The treatment temperature played an important role on the growth and properties of the resultant M@CNT, wherein M@CN800 carbonized at 800 C showed well-monodispersed metal nanoparticles (MNPs), graphene-like layers of the N-doped carbon supports, and strong interaction between MNPs and the support. Pd@CN800 displayed high efficiency and stable recyclability toward the domino carbonylative synthesis of pyrazole derivatives. Interestingly, its catalytic performance has been even higher than that of the representative PdCl2(PPh 3)2 within six runs.
- Li, Zelong,Liu, Jianhua,Huang, Zhiwei,Yang, Ying,Xia, Chungu,Li, Fuwei
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p. 839 - 845
(2013/07/25)
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- PTSA-catalyzed Mannich-type-cyclization-oxidation tandem reactions: One-pot synthesis of 1,3,5-substituted pyrazoles from aldehydes, hydrazines and alkynes
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A convenient one-pot Mannich-type-cyclization-oxidation tandem process has been developed for the synthesis of 1,3,5-trisubstituted pyrazoles derivatives from aldehydes, hydrazines and alkynes using p-toluenesulfonic acid monohydrate (PTSA) as a multifunctional catalyst. This method provides a flexible and rapid route to 1,3,5-trisubstituted pyrazoles.
- Liu, Pei,Pan, Ying-Ming,Xu, Yan-Li,Wang, Heng-Shan
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supporting information; experimental part
p. 4696 - 4698
(2012/08/08)
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- Regioselective Synthesis of 1,3,5-Substituted Pyrazoles from Acetylenic Ketones and Hydrazines
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The synthesis of diversely substituted 1,3,5-substituted pyrazoles from the reaction of acetylenic ketones with substituted hydrazines is reported. The reactions were shown to be highly regioselective regardless of the nature of the substituents in the su
- Bishop, Brian C.,Brands, Karel M. J.,Gibb, Andrew D.,Kennedy, Derek J.
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- REACTION OF SINGLET OXYGEN WITH 2-PYRAZOLINE: IMPLICATION FOR CATION RADICAL - SUPEROXIDE ION PAIR INTERMEDIATE
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Kinetic studies on photosensitized oxygenation of 1,3,5-triaryl-2-pyrazolines show that an electron-transfer from the pyrazoline to singlet oxygen may take place to give a cation radical and superoxide ion pair.The reaction of pyrazoline cation radicals with superoxide ion shows the same product distribution with singlet oxygenation.
- Akasaka, Takeshi,Nakagawa, Masaru,Nomura, Yuko,Sato, Rikiya,Someno, Kazuo,Ando, Wataru
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p. 3807 - 3812
(2007/10/02)
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