- Copper-catalyzed acylation of pyrazolones with aldehydes to afford 4-acylpyrazolones
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Copper-catalyzed direct acylation of the alkenyl C-H bond in 1,2-dihydro-3H-pyrazol-3-ones has been developed, affording a series of 4-acylpyrazolones in moderate to good yields. Notably, this protocol involves readily accessible substrates and reagents, which have good functional group tolerance leading to pyrazolone derivatives under mild reaction conditions.
- Xiao, Yan,Wu, Xiaopeng,Teng, Jiangang,Sun, Song,Yu, Jin-Tao,Cheng, Jiang
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p. 7552 - 7557
(2019/08/20)
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- Copper/Persulfate-Promoted Oxidative Decarboxylative C?H Acylation of Pyrazolones with α-Oxocarboxylic Acids: Direct Access to 4-Acylpyrazolones under Mild Conditions
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A facile and efficient oxidative C?H acylation of N-substituted pyrazolones using α-oxocarboxylic acids as an acyl group source was developed. A combination of Cu(OAc)2 and K2S2O8 enables the reaction to proceed smoothly under air and provides a wide array of 4-acylpyrazolone products in moderate to excellent yields. The mechanism of this transformation is believed to proceed via a copper-induced decarboxylation to form the acyl-copper species. This method provides a convenient and useful route for a direct installation of an acyl moiety into bioactive pyrazolone derivatives, which can be further utilized in many applications. (Figure presented.).
- Kittikool, Tanakorn,Thupyai, Akkharaphong,Phomphrai, Khamphee,Yotphan, Sirilata
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p. 3345 - 3355
(2018/09/10)
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- The structure of 4-benzoyl-5-methyl-2-phenylpyrazol-3-one oxime and its methyl derivatives
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1H and 13C NMR spectroscopic investigations of 4-benzoyl-5-methyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one oxime (4) and different methylation products thereof (5-11) indicate that 4 exists predominantly as 4-enaminopyrazolone in [D6]DMSO solution. Single-crystal X-ray analysis revealed that in the solid state the same tautomeric structure of 4 was present, and closely resembles that of the corresponding N-methylamino product (6). Both compounds are stabilised by an intramolecular hydrogen bond between the pyrazolone C=O group and the N-OH proton. A 1,2-dihydro-3H-pyrazol-3-one structure was found in a clathrate of O-methyloxime 5 and dichloromethane. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.
- Holzer, Wolfgang,Hahn, Katharina,Brehmer, Thomas,Claramunt, Rosa M.,Perez-Torralba, Marta
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p. 1209 - 1219
(2007/10/03)
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- Preparation of new polyfunctional magnesiated heterocycles using a chlorine-, bromine-, or iodine-magnesium exchange
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The reaction of heteroaryl iodides with i-PrMgBr (ca. 1.0 equiv) in THF provides the corresponding magnesiated heterocycles. Functional groups such as an ester, cyano, or chloride functions are tolerated in these new Grignard reagents if the exchange can be performed below -20 °C. This is the case for all heterocycles bearing electron-withdrawing groups or chelating functions facilitating the iodine-magnesium exchange. In many cases, the exchange can be extended to heteroaryl bromides, and a case of a chlorine-magnesium exchange is described with tetrachlorothiophene. This new preparation of functionalized heteroarylmagnesium compounds provides after reaction with various electrophiles a new entry to a broad range of polyfunctional pyridines, imidazoles, furanes, thiophenes, pyrroles, antipyrines, and uracil derivatives. The application of the halogenmagnesium exchange in the solid phase allows the performance of solid-phase synthesis, with potential applications for combinatorial chemistry.
- Abarbri, Mohamed,Thibonnet, Jerome,Berillon, Laurent,Dehmel, Florian,Rottlaender, Mario,Knochel, Paul
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p. 4618 - 4634
(2007/10/03)
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- Preparation of new magnesiated functionalized imidazoles and antipyrines via an iodine-magnesium exchange
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The iodine-magnesium exchange using i-PrMgBr allows the preparation of magnesiated 3-pyrazolin-5-ones (antipyrines) and functionalized imidazoles which after reaction with various electrophiles afford polyfunctional 5- membered heterocycles.
- Dehmel, Florian,Abarbri, Mohamed,Knochel, Paul
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p. 345 - 346
(2007/10/03)
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- Alkylation of pyrazolones via the mitsunobu reaction
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The reaction of 3-methyl-1-phenyl-2-pyrazolin-5-one and 4-acyl derivatives thereof (R4 = COPh, 2-thienoyl, COCH2CH2Ph, COCH=CHPh) with various alcohols under 'Mitsunobu'-conditions was studied. In many cases selective O-alkylation could be achieved.
- Holzer, Wolfgang,Plagens, Brigitte,Lorenz, Karin
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p. 309 - 314
(2007/10/03)
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- On the methylation of pyrazolones
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Reaction of a series of 1,2-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-ones having a COR substituent (R = Me, Ph, 2-thienyl, CH2CH2Ph, CN = CHPh) in 4-position of the pyrazole ring (tautomer with 4-substituted 5-hydroxy-3-methyl-1-phenyl
- Holzer, Wolfgang,Plagens, Brigitte
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p. 455 - 462
(2007/10/03)
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