- Silver-Mediated [3 + 2] Cycloaddition of Alkynes and N-Isocyanoiminotriphenylphosphorane: Access to Monosubstituted Pyrazoles
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A silver-mediated [3 + 2] cycloaddition of "CNN" and "C≡C" for constructing pyrazoles has been described. The "CNN" building block used is N-isocyanoiminotriphenylphosphorane, which is a stable, safe, easy-to-handle, and odorless solid isocyanide. The reaction is characterized by its mild conditions, broad substrate scope, and excellent functional group tolerance.
- Yi, Fanhua,Zhao, Wanjun,Wang, Zikun,Bi, Xihe
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supporting information
p. 3158 - 3161
(2019/05/10)
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- Molybdenum-silver co-catalyzed cycloaddition of alkynes with: N -isocyanoiminotriphenylphosphorane (NIITP): An efficient strategy for the synthesis of monosubstituted pyrazoles
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A new molybdenum-silver co-catalyzed [3+2] cycloaddition of alkynes with N-isocyanoiminotriphenylphosphorane (NIITP) has been described. The NIITP serves as a non-toxic, facile "CNN" source. Over 30 substrates were successfully converted to the desired compounds in good to excellent yields.
- Mi, Pengbing,Lang, Jiajia,Lin, Shaojian
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supporting information
p. 7986 - 7989
(2019/07/10)
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- Preparation method of pyrazole derivative (by machine translation)
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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)
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Paragraph 0061-0065
(2019/12/02)
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- Preparing method for monosubstituted pyrazole compound
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The invention belongs to the field of chemical synthesis, and particularly relates to a preparing method for a monosubstituted pyrazole compound. The preparing method includes the following steps thatunder catalysis of a molybdenum compound, an alkyne compound and N-isocyano triphenyl phosphinimine react in an organic solvent, and the monosubstituted pyrazole compound is obtained. The alkyne compound is of a structure in a formula (I), and the monosubstituted pyrazole compound is of a structure in a formula (II), wherein R is alkyl or substitution alkyl or aryl or substitution aryl or heteroaryl or substitution heteroaryl. According to the method, the alkyne compound and the N-isocyano triphenyl phosphinimine serve as reaction substrates, the molybdenum compound serves as a catalyst, anda series of monosubstituted pyrazole compounds can be synthesized by adjusting the specific type of the alkyne compound. The method is easy to operate, the raw materials and reagents are easy to obtain, and the method is mild in condition, environmentally friendly and particularly suitable for large-scale industrial production.
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Paragraph 0060; 0065-0073
(2019/10/01)
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- Transition Metal, Azide, and Oxidant-Free Homo- and Heterocoupling of Ambiphilic Tosylhydrazones to the Regioselective Triazoles and Pyrazoles
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With N-tosylhydrazone as an ambiphilic reagent, an unprecedented cyclization reaction of two identical or different tosylhydrazones has been developed to access various 4,5-disubstituted-2H-triazoles under transition metal, azide, and oxidant-free conditi
- Panda, Subhankar,Maity, Pradip,Manna, Debasis
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supporting information
p. 1534 - 1537
(2017/04/13)
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- Calcium carbide as the acetylide source: Transition-metal-free synthesis of substituted pyrazoles via [1,5]-sigmatropic rearrangements
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Under transition-metal-free conditions, calcium carbide was used as the acetylide source to react with a wide range of N-tosylhydrazones derived from aldehydes or ketones, affording various substituted pyrazoles in good yields with high regioselectivities. The transformations go through [3 + 2] cycloadditions followed by [1,5]-sigmatropic rearrangements, which are supported by deuterium-labeling experiments.
- Yu, Yue,Huang, Wei,Chen, Yang,Gao, Bingjie,Wu, Wanqing,Jiang, Huanfeng
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supporting information
p. 6445 - 6449
(2018/06/08)
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- Chemoselective Reduction of α-Cyano Carbonyl Compounds: Application to the Preparation of Heterocycles
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β-Aminoacrylates are reactive intermediates that are useful building blocks in synthesis. General methods for their preparation typically afford α and β disubstitution patterns or β only. Molecules with only α-substituents (β-hydrogen) are much less well-known. A chemoselective reductive tautomerization of α-cyanoacetates, using DIBAL-H, has been developed to access these valuable synthons. α,β-Unsaturated cyanoacetates and α-cyanoketones can, also, be selectively reduced via this methodology. A series of heterocycles were prepared using these β-enamino carbonyl compounds.
- Pollack, Scott R.,Kuethe, Jeffrey T.
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supporting information
p. 6388 - 6391
(2016/12/23)
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- Clean and efficient synthesis of pyrazole derivatives in aqueous media
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A series of 5-aryl-1H-pyrazole derivatives were synthesized via the reaction of 3-(dimethylamino)-1-arylprop-2-en-1-one with hydrazine in aqueous media without using any catalyst. This method has the advantages of easier work-up, mild reaction condition, high yields, and an environmentally benign procedure.
- Xu, Pan,Xi, Yu-Kun,Chen, Hui,Shi, Da-Qing
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p. 611 - 613
(2015/03/30)
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- Novel crown ether functionalized imidazolium-based acidic ionic liquid catalyzed synthesis of pyrazole derivatives under solvent-free conditions
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Abstract An innovatively designed novel crown ether functionalized imidazolium-based reusable acidic ionic liquid [crown ether MIm] [HSO4] has been efficiently implemented for the synthesis of pyrazole derivatives using various substituted enaminones, hydrazine hydrate and phenyl hydrazine under solvent-free conditions. Structural novelty and task efficiency of the catalyst, high yields of desired products, greener approach attributing high atom economy and solvent-free conditions render this protocol suitable to cope with the current demand in contemporary organic chemistry. The inventive idea of utilizing crown ether functionalized ionic liquid as a catalyst was for the first time demonstrated in this protocol.
- Patil, Dayanand,Chandam, Dattatraya,Mulik, Abhijeet,Jagdale, Suryabala,Patil, Prasad,Deshmukh, Madhukar
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p. 6843 - 6858
(2015/08/18)
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- An efficient synthesis of isoxazoles and pyrazoles under ultrasound irradiation
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A series of 5-arylisoxazole and 5-aryl-1H-pyrazole derivatives was synthesized by the reaction of 3-(dimethylamino)-1-arylprop-2-en-1-one with hydroxylamine hydrochloride or hydrazine hydrate under ultrasound irradiation without using any catalyst. This m
- Huang, Zhi-Bin,Li, Li-Li,Zhao, Yan-Wei,Wang, Hui-Yuan,Shi, Da-Qing
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p. E309-E313
(2014/11/07)
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- Consecutive three-component synthesis of 3-(hetero)aryl-1H-pyrazoles with propynal diethylacetal as a three-carbon building block
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A novel consecutive three-component synthesis of 3-(hetero)aryl-1H- pyrazoles via room temperature Sonogashira arylation of propynal diethylacetal used as a propargyl aldehyde synthetic equivalent has been disclosed. The final acetal cleavage-cyclocondensation with hydrazine hydrochloride at 80 °C rapidly furnishes the title compounds in a one-pot fashion.
- Levi, Lucilla,Boersch, Christina,Gers, Charlotte F.,Merkul, Eugen,Mueller, Thomas J. J.
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p. 9340 - 9356
(2012/01/04)
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- An efficient solvent-free synthesis of NH-pyrazoles from β-dimethylaminovinylketones and hydrazine on grinding
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A series of NH-pyrazoles was efficiently synthesized from the reaction of β-dimethylaminovinylketones ([R1C(O)C(R2){double bond, long}CHN(Me2)], where R1 = Me, Ph, 3-MeO-Ph, 4-Me-Ph, 4-MeO-Ph, 4-F-Ph, 4-Cl-Ph, 4
- Longhi, Kelvis,Moreira, Dayse N.,Marzari, Mara R.B.,Floss, Vagner M.,Bonacorso, Helio G.,Zanatta, Nilo,Martins, Marcos A.P.
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supporting information; experimental part
p. 3193 - 3196
(2010/08/05)
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- Half-sandwich η6-benzene Ru(II) complexes of pyridylpyrazole and pyridylimidazole ligands: Synthesis, spectra, and structure
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New series of half-sandwich ruthenium(II) complexes supported by a group of bidentate pyridylpyrazole and pyridylimidazole ligands [(η6-C6H6)Ru(L2)Cl][PF6] (1), [(η6-C6H6/s
- Mishra, Haritosh,Mukherjee, Rabindranath
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p. 3545 - 3555
(2007/10/03)
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- Synthesis of 3-substituted arylpyrazole-4-carboxylic acids
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A method was suggested for preparing previously unknown 3-aryl-substituted pyrazole-4-carboxylic acids, involving Vilsmeier formylation of semicarbazones of 26 available mono- and disubstituted acetophenones and 2-acetylthiophene followed by oxidation of
- Lebedev,Lebedeva,Sheludyakov,Kovaleva,Ustinova,Kozhevnikov
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p. 782 - 789
(2007/10/03)
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- The α-effect in reactions of sp-hybridized carbon atom: Michael-type reactions of 1-aryl-2-propyn-1-ones with primary amines
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Second-order rate constants (kN) have been measured for the Michael-type reaction of 1-(X-substituted phenyl)-2-propyn-1-ones (2a-f) with a series of primary amines in H2O at 25.0 ± 0.1 °C. A linear Bronsted-type plot with a small βnuc value (βnuc = 0.30) has been obtained for the reactions of 1-phenyl-2-propyn-1-one (2c) with non-α-nucleophile amines. Hydrazine is more reactive than other primary amines of similar basicity (e.g., glycylglycine and glycine ethyl ester) and results in a positive deviation from the linear Bronsted-type plot. The reactions of 2a-f with hydrazine exhibit a linear Hammett plot, while those with non-α-nucleophile amines give linear Yukawa-Tsuno plots, indicating that the electronic nature of the substituent X does not affect the reaction mechanism. The α-effect increases as the substituent X in the phenyl ring of 2a-f becomes a stronger electron-donating group. However, the magnitude of the α-effect for the reactions of 2a-f is small (e.g., kNhydrazine/kN glycylglycine = 4.6-13) regardless of the electronic nature of the substituent X. The small βnuc has been suggested to be responsible for the small α-effect. A solvent kinetic isotope effect (e.g., kNH2O/kND2O = 1.86) was observed for the reaction with hydrazine but absent for the reactions with non-α-nucleophile amines. The reactions with hydrazine and other primary amines have been suggested to proceed through a five-membered intramolecular H-bonding structure VI and a six-membered intermolecular H-bonding structure VII, respectively. The transition state modeled on VI can account for the substituent dependent α-effect and the difference in the solvent kinetic isotope effect exhibited by the reactions with hydrazine and other primary amines. It has been proposed that the βnuc value is more important than the hybridization type of the reaction site to determine the magnitude of the α-effect.
- Um, Ik-Hwan,Lee, Eun-Ju,Seok, Jin-Ah,Kim, Kyung-Hee
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p. 7530 - 7536
(2007/10/03)
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- A novel one-pot method for the preparation of pyrazoles by 1,3-dipolar cycloadditions of diazo compounds generated in situ
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A convenient one-pot procedure for the preparation of pyrazoles by 1,3-dipolar cycloaddition of diazo compounds generated in situ has been developed. Diazo compounds derived from aldehydes were reacted with terminal alkynes to furnish regioselectively 3,5-disubstituted pyrazoles. Furthermore, the reaction of N-vinylimidazole and diazo compounds derived from aldehydes gave exclusively 3-substituted pyrazoles in a one-pot process.
- Aggarwal, Varinder K.,De Vicente, Javier,Bonnert, Roger V.
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p. 5381 - 5383
(2007/10/03)
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- 5-Hydroxy-2-pyrazolines and some of their 1-substituted analogs
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The use of 1,3-dicarbonyl compounds containing strong electron-withdrawing substituents (perfluoroalkyl, 4-nitrophenyl) at one of the carbonyl groups in reaction with hydrazine or its monosubstituted derivatives (4-nitro- and 2,4-dinitrophenylhydrazines) leads to the formation of stable intermediates for the synthesis of pyrazoles (5-hydroxy-2-pyrazolines) or their linear tautomers (hydrazones).
- Zelenin,Tugusheva,Yakimovich,Alekseev,Zerova
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p. 668 - 676
(2007/10/03)
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- Effect of Electron-withdrawing Groups on the Thermal Ring Opening of 3H-Pyrazoles to Diazoalkenes
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3-Cyano-3H-pyrazoles, bearing a cyano, a p-chlorophenyl, or a p-chlorobenzyl group at C-3, generated from elimination reaction of the corresponding dihydropyrazoles with a leaving group such as a chlorine or p-chlorobenzoyloxy group, gave diazolkene derivatives, resulting from the ring-opening of the 3H-pyrazoles.However, 3-methoxycarbonyl-3H-pyrazoles bearing a methoxycarbonyl, a p-chlorophenyl, or p-chlorobenzyl group at C-3, prepared in a similar manner, gave mainly 1-methoxycarbonyl-1H-pyrazole derivatives, resulting from migration of the 3-methoxycarbonyl group to the adjacent nitrogen within the generated 3H-pyrazoles.Treatment of 3H-pyrazoles (8a and 29b) and 5-substituted 1-methoxycarbonyl-1H-pyrazoles (10a and 31b) with triethylamine gave 3-substituted 1-methoxycarbonyl-1H-pyrazoles, resulting from migration of the methoxycarbonyl group to the remote nitrogen.
- Nakano, Yoshihiko,Ilamaguchi, Masashi,Nagai, Toshikazu
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p. 1701 - 1757
(2007/10/02)
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- Chain Elongation of Carbohydrates: Synthesis of Pyrazoles from Optically Active Carboxylic Acids
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By chain elongation via the C-phenylglycine method optically active carboxylic acids may be converted into 3-substituted pyrazoles in few steps with good chemical yields.Starting with peracetylated glyconic acids this technique permits an easy access to u
- Klein, Ulrich,Mohrs, Klaus,Wild, Hanno,Steglich, Wolfgang
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p. 485 - 490
(2007/10/02)
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- POLARISED KETENE DITHIOACETALS. PART 50. REACTIONS OF α-AROYL-α-BROMOKETENE DITHIOACETALS WITH HYDRAZINE HYDRATE: FORMATION OF REARRANGED PYRAZOLES
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The reactions of α-aroyl-α-bromoketene dithioacetals (2a-c) with hydrazine hydrate yields unexpected pyrazoles, i.e. 3(5)-aryl-5(3)-4-bis(alkylthio)pyrazoles (9) in varying yields.The corresponding S-ethyl-α-bromoketene dithioacetals (2d) gave only the bis(ethylthio)pyrazole (7d) and 4-amino-4(3)-ethylthiopyrazole (9d) under similar conditions.The reactions of cyclic α-bromoketene dithioacetals (2e-g) with hydrazine hydrate on the other hand afforded only the dithiinopyrazole derivatives (7e-g) in high yields.The probable mechanisms for the formation of the pyrazoles (7)-(9) have been suggested.
- Singh, Gurdeep,IIa, Hiriyakkanavar,Junjappa, Hiriyakkanavar
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p. 1945 - 1950
(2007/10/02)
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