- Molecular iodine: A green and inclusive catalyst for the synthesis of highly functionalized 1,3,5-trisubstituted pyrazoles in aqueous medium
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A library of 1,3,5-trisubstituted pyrazoles was synthesized in excellent yields from the reaction of aldehyde, phenylhydrazine and alkynes in the presence of iodine via an eco-friendly, simple process performed in aqueous medium. This single pot transformation generates new CN, C-C, C-N bonds and proceeds by a domino reaction involving the formation of Schiff base, Mannich addition and finally intramolecular cyclisation. The Royal Society of Chemistry 2014.
- Rai, Pratibha,Srivastava, Madhulika,Singh, Jagdamba,Singh, Jaya
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Read Online
- Cycloaddition of Nitrile Imines with Enamides: An Approach to Functionalized Pyrazolines and Pyrazoles
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An efficient [3 + 2] cycloaddition of in situ generated nitrile imines with enamides has been established. A wide range of functionalized pyrazoline derivatives (53 examples) were obtained in moderate to good yields (up to 96%) under very mild conditions. This protocol features broad substrate scope, good functional group tolerance, and operational simplicity. Practical transformation of the products into useful pyrazoles via a one-pot process and the scalability of this protocol highlight the utility of this synthetic methodology.
- Tu, Liang,Gao, Limei,Wang, Xiaomeng,Shi, Ruijie,Ma, Rupei,Li, Junfei,Lan, Xiaoshuang,Zheng, Yongsheng,Liu, Jikai
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supporting information
p. 559 - 573
(2021/01/09)
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- Visible light mediated metal-free oxidative aromatization of 1,3,5-trisubstituted pyrazolines
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The visible light mediated oxidation of 1,3,5-trisubstituted pyrazolines under metal-free conditions was developed. Various substituted pyrazolines were oxidized to pyrazoles by irradiation with visible light/sunlight. A plausible mechanism was proposed f
- Annes, Sesuraj Babiola,Rajmohan, Rajamani,Ramesh, Subburethinam,Vairaprakash, Pothiappan
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supporting information
(2019/07/22)
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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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- 13C NMR spectroscopy of heterocycles: 1-phenyl-3-aryl/t-butyl-5-arylpyrazoles
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A series of chalcones 1-12 were converted to pyrazolines (1Pi-12Pi) by reaction with phenylhydrazine followed by DDQ oxidation to produce the corresponding pyrazoles (1Pz-12Pz). Three 1-phenyl-3-t-butyl-5-arylpyrazoles (13Pz-15Pz) were synthesized using an analogous approach. Molecular modeling studies predicted the 5-aryl group of the pyrazoles for both series to have a torsion angle of 52°-54° whereas the 1-phenyl group was predicted to have 35°-37° torsion angles. The 3-aryl group was predicted to be essentially coplanar (-3°) with the pyrazole system in the first series. 13C NMR data for both series, 1Pz-12Pz and 13Pz-15Pz, were collected in DMSO-d6 at 50°C. A plot of the C4 chemical shifts for 1Pz-12Pz versus Hammet constants for 5-aryl substituents yielded a very good linear correlation (R2=0.96) with a slope of 1.5. The chemical shift data for C4 showed little or no dependence on 3-aryl substituents. The result for 13Pz-15Pz, despite only three points, was consistent with the first series results and yielded a ρ value of 2.0. Distal transmission of substituent effects (5-aryl groups) to C4 of the pyrazole system was reduced by roughly 50-60% of that of the analogous planar isoxazole system, but are not consistent with results for the similarly twisted 4-bromoisoxazoles.
- Hockstedler, Amy N.,Edjah, Beatrice A.,Azhar, Saajid Z.,Mendoza, Hadrian,Brown, Nicole A.,Arrowood, Hayley B.,Clay, Andrew C.,Shah, Anand B.,Duffek, Glenda M.,Cui, Jianmei,Baumstark, Alfons L.
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p. 125 - 131
(2017/04/14)
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- Visible light catalyzed aromatization of 1,3,5-triaryl-2-pyrazolines by platinum(II) polypyridyl complex under oxidant-free condition
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With visible light (λ=450 nm) irradiation of a catalytic amount of platinum(II) terpyridyl complex, 1,3,5-triaryl-2-pyrazolines can be smoothly converted to their corresponding pyrazoles and hydrogen in quantitative yields with no use of any oxidant at ro
- Ye, Pan,Wang, Deng-Hui,Chen, Bin,Meng, Qing-Yuan,Tung, Chen-Ho,Wu, Li-Zhu
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p. 175 - 179
(2016/02/16)
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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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- Br?nsted acid-mediated annulations of 1-cyanocyclopropane-1-carboxylates with arylhydrazines: Efficient strategy for the synthesis of 1,3,5-trisubstituted pyrazoles
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1-Cyanocyclopropane-1-carboxylates are reacted with arylhydrazines to afford 1,3,5-trisubstituted pyrazoles under the influence of a Br?nsted acid. Formally, this transformation can be regarded as an annulation of three-membered rings with α-carbonyl and
- Xue, Shuwen,Liu, Jiaming,Qing, Xushun,Wang, Cunde
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p. 67724 - 67728
(2016/08/02)
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- Synthesis and anticancer activity of 1,3,5-triaryl-1H-pyrazole
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Previous studies demonstrated that some pyrazole derivatives could be considered as potential anticancer agents. A series of 1,3,5-triaryl-1H-pyrazole derivatives were prepared by the reaction of phenylhydrazin and different chalcones. The previous classi
- Ghadbeigi, Sajad,Ostad, Seyed Nasser,Shafiee, Abbas,Amini, Mohsen
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p. 754 - 759
(2015/10/05)
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- SAR studies of differently functionalized chalcones based hydrazones and their cyclized derivatives as inhibitors of mammalian cathepsin B and cathepsin H
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Cathepsins have emerged as potential drug targets for melanoma therapy and engrossed attention of researchers for development and evaluation of cysteine cathepsin inhibitors as cancer therapeutics. In this direction, we have designed, synthesized, and ass
- Raghav, Neera,Singh, Mamta
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p. 4233 - 4245
(2014/08/18)
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- Preparation of 3,5-disubstituted pyrazoles and isoxazoles from terminal alkynes, aldehydes, hydrazines, and hydroxylamine
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The reaction of terminal alkynes with n-BuLi, and then with aldehydes, followed by the treatment with molecular iodine, and subsequently hydrazines or hydroxylamine provided the corresponding 3,5-disubstituted pyrazoles or isoxazoles in good yields with high regioselectivity, through the formations of propargyl secondary alkoxides and α-alkynyl ketones. The present reactions are one-pot preparation of 3,5-disubstituted pyrazoles from terminal alkynes, aldehydes, molecular iodine, and hydrazines, and 3,5-disubstituted isoxazoles from terminal alkynes, aldehydes, molecular iodine, and hydroxylamine.
- Harigae, Ryo,Moriyama, Katsuhiko,Togo, Hideo
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p. 2049 - 2058
(2014/04/03)
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- 3,4-Dihydro-2H-pyran promoted aerobic oxidative aromatization of 1,3,5-trisubstituted pyrazolines and Hantzsch 1,4-dihydropyridines
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An unprecedented facile oxidation of 1,3,5-trisubstituted pyrazolines and Hantzsch 1,4-dihydropyridines (DHPs) to the corresponding pyrazoles and pyridines was observed, mediated by 3,4-dihydro-2H-pyran in air. The reaction showed excellent reactivity, functional group tolerance, and high yield without using any metal and/or halogen based oxidizing agents.
- Banerjee, Dipanwita,Kayal, Utpal,Karmakar, Rajiv,Maiti, Gourhari
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supporting information
p. 5333 - 5337
(2015/01/08)
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- I2-mediated oxidative C-N bond formation for metal-free one-pot synthesis of di-, tri-, and tetrasubstituted pyrazoles from α,β-unsaturated aldehydes/ketones and hydrazines
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An I2-mediated metal-free oxidative C-N bond formation methodology has been established for the regioselective pyrazole synthesis. This practical and eco-friendly one-pot protocol requires no isolation of the less stable intermediates hydrazone
- Zhang, Xinting,Kang, Jinfeng,Niu, Pengfei,Wu, Jie,Yu, Wenquan,Chang, Junbiao
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p. 10170 - 10178
(2015/02/19)
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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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- Synthesis of 1 H-indazoles and 1 H-pyrazoles via FeBr3/O 2 mediated intramolecular C-H amination
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A new synthesis of substituted 1H-indazoles and 1H-pyrazoles from arylhydrazones via FeBr3/O2 mediated C-H activation/C-N bond formation reactions is reported. The corresponding 1,3-diaryl-substituted indazoles and trisubstituted pyr
- Zhang, Tianshui,Bao, Weiliang
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p. 1317 - 1322
(2013/04/10)
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- Dess-Martin periodinane-mediated oxidative aromatization of 1,3,5-trisubstituted pyrazolines
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(Chemical Equation Presented) A general method for the oxidative aromatization of 1,3,5-trisubstituted pyrazolines under mild conditions has been developed using Dess-Martin periodinane as oxidant. Copyright Taylor & Francis Group, LLC.
- Gamapwar, Sumit V.,Tale, Nilesh P.,Karade, Nandkishor N.
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experimental part
p. 2617 - 2623
(2012/08/07)
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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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- Aromatization of 1,3,5-trisubstituted of 4,5-dihydro-1H-pyrazoles by in-situ generation of I+ from hydrogen Peroxide/Acids/iodide potassium or sodium systems
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A simple, green and cost-effective protocol was used for the aromatization of 1,3,5-trisubstituted-2-pyrazolines to the corresponding pyrazoles by in situ generation of iodine (I+) from H2O2/AcOH or SSA or oxalic acid /KI
- Maleki, Behrooz,Veisi, Hojat
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experimental part
p. 4366 - 4370
(2012/02/16)
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- A convenient and efficient protocol for the synthesis of 5-aryl-1,3-diphenylpyrazole catalyzed by hydrochloric acid under ultrasound irradiation
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The synthesis of 5-aryl-1,3-diphenylpyrazole via the reactions of 3-aryl-2,3-epoxy-1-phenyl-1-propanone with phenylhydrazine was carried out in 69-99% yields at room temperature under ultrasound irradiation. This method provides several advantages such as
- Li, Ji-Tai,Yin, Ying,Li, Ling,Sun, Ming-Xuan
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experimental part
p. 11 - 13
(2010/11/16)
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- Aromatization of Hantzsch 1,4-dihydropyridines and 1,3,5-trisubstituted pyrazolines with HIO3 and I2O5 in water
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Hantzsch 1,4-dihydropyridines and 1,3,5-trisubstituted pyrazolines were converted to the corresponding pyridines and pyrazoles efficiently by the treatment of a catalytic amount of HIO3 or I2O5 in water.
- Chai, Lingzhi,Zhao, Yankai,Sheng, Qiuju,Liu, Zhong-Quan
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p. 9283 - 9285
(2007/10/03)
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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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- Regioselective synthesis of polysubstituted pyrazoles and isoxazoles
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A regioselective synthesis has been developed for the preparation of unsymmetrical 1,3,5-triaryl-4-alkylpyrazolines and -pyrazoles by treatment of α-benzotriazolyl-α,β-unsaturated ketones with monosubstituted hydrazines followed by alkylation at the 4-position of the pyrazoline ring. Reaction of α-benzotriazolyl-α,β-unsaturated ketones with hydroxylamine gives 3,5-disubstituted isoxazoles regioselectively.
- Katritzky,Wang,Zhang,Voronkov,Steel
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p. 6787 - 6791
(2007/10/03)
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- CYCLOADDITION DIPOLAIRE 1,3 DES 4-ARYLIDENE OXAZOL-5-ONES AVEC LA DIPHENYLNITRILIMINE
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The 1,3-dipolar cycloaddition of 4-arylidene oxazol-5-ones with diphenylnitrilimine is regiospecific and gives one adduct (2).The nature of solvent and the temperature promote the formation of adduct (2) and/or pyrazoline (3).
- Baba, N.,Soufiaoui, M.
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p. 1709 - 1712
(2007/10/02)
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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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