Efficient Regiocontrolled Synthesis and Antimicrobial Activity of Pyrazoles

Braibante, Mara Elisa Fortes; Braibante, Hugo T. S.; Tavares, Luciana de Carvalho; Rohte, Simone F.; Costa, Caria C.; Morel, Ademir F.; Stüker, Caroline Z.; Burrow, Robert A.

doi:10.1055/s-2007-983771

Cited by 14 publications

(3 citation statements)

References 13 publications

(19 reference statements)

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“…Related approaches, based on a transitory N-carboxylation, have also been reported. 23,24 An even more recent report 25 describing results related to ours prompted us to describe our finding in the following. Scheme 2 provides an illustration of the selectivity problem encountered with the alkylation of pyrazol-3-ones.…”

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confidence: 61%

An Improved Preparation of 3-Alkoxypyrazoles

Guillou¹,

Bonhomme²,

Janin³

2008

Synthesis

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The condensation between alkyl acetoacetates and hydrazines constitutes the very well-known Knorr synthetic method leading to pyrazol-3/5-ones. However, contemporary reports describe an alternate reaction pathway leading to low yields of 3/5-alkoxypyrazoles using hydrazine salts. No general method for the selective synthesis of 3-alkoxypyrazoles has been reported to date, hence we focused on this side reaction in an attempt to turn it into the main transformation. Depending on the starting material, various 3-alkoxypyrazoles (methoxy, ethoxy, benzyloxy, isopropoxy, allyloxy) were obtained in up to 56% yield.

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confidence: 61%

An Improved Preparation of 3-Alkoxypyrazoles

Guillou¹,

Bonhomme²,

Janin³

2008

Synthesis

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“…1 Our research group has been studying methodologies for the synthesis of heterocyclic systems using the reactions of 1,3-dielectrophiles, such as -oxothioxo--oxoketene-O,N-acetals, ethyl-2-chloro-acetoacetate and -enamino carbonylic and functionalized with a series of dinucleophiles. [2][3][4][5][6] The synthesis of these compounds has been successfully exploited through the methodology of reaction in solid support using montmorillonita, K-10, as a solid support associated to microwave energy or ultrasound sonication. These studies have provided different heterocyclic classes as pyrazoles, isoxazoles, 1,2-diazetine and triazin-3-one.…”

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confidence: 99%

The use of benzil to obtain functionalized N-heterocycles

Braibante¹,

Braibante²,

Uliana³

et al. 2008

J. Braz. Chem. Soc.

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Neste trabalho foi estudada a reatividade da benzila, empregando-se C,N-e N,N-nucleófilos tais como 2-butenoatos de etila 3-amino substituidos 4a-c, (S,Z)-3-(1-etóxi-3-hidróxi-1-oxo-2-propanilamina)-2-butenoato de etila 6, semicarbazida 8 e tiossemicarbazida 10, para avaliar os centros eletrofílicos na formação de compostos heterocíclicos polifuncionalizados, obtendo-se pirrolinonas 5a-c, pirrol 7, triazinona 9 e triazintiona 11. A dibenzoila 3 empregada foi obtida pela oxidação da benzoina na ausência de solvente em um estudo comparativo entre diferentes protocolos de oxidação, utilizando suportes sólidos associados ou não a energia de microondas com bons rendimentos sem empregar reagentes agressivos.In this work, the reactivity of benzil was studied, employing C,N-and N,N-nucleophiles, such as ethyl(3-amino substituted) 2-butenoates 4a-c , (S,Z)-ethyl 3-(1-ethoxy-3-hydroxy-1-oxopropan-2-ylamino)but-2-enoate 6, semicarbazide 8 or thiosemicarbazide 10, to evaluate their electrophilic centers as building blocks for the synthesis of the polyfunctionalized heterocyclic compounds, resulting in pyrrolinone 5a-c, pyrrole 7, triazinone 9 and triazinethione 11. The employed benzil 3 was obtained by the oxidation of the benzoin under solvent free conditions in a comparative study between different protocols of oxidation, using the methodology under mild reaction conditions and supported reagent associated to the microwave irradiation, with good results and without aggressive reagents.

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“…Functionally substituted 1H-, 3H-, and 4H-pyrazoles possess practically important properties, in particular high biological activity, which stimulates studies on their synthesis and applications [1][2][3][4]. One of the most efficient methods for the preparation of pyrazole derivatives is based on 1,3-dipolar cycloaddition of diazoalkanes to acetylenic compounds [5,6].…”

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confidence: 99%

Synthesis of 3H-pyrazoles by reaction of methyl and p-tolyl phenylethynyl sulfones with diphenyldiazomethane and their thermal and acid-catalyzed transformations

et al. 2015

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Methyl and p-tolyl phenylethynyl sulfones reacted with diphenyldiazomethane in diethyl ether at 20°C to give 1,3-dipolar cycloaddition products both according and contrary to the von Auwers rule, sulfonylsubstituted 3H-pyrazoles at a ratio of 1 : 1.5 and 1.3 : 1, respectively. On heating in toluene for 2 h, the Auwers adducts underwent van Alphen-Hüttel rearrangement with 1,5-sigmatropic shift of one phenyl substituent to afford sulfonyl-substituted 4H-pyrazoles. Under analogous conditions, the anti-Auwers adducts rearranged into sulfonyl-substituted N-phenyl-1H-pyrazoles containing a small amount of the denitrogenation product, sulfonyl-substituted cyclopropene. The Auwers adducts, as well as 4H-pyrazoles resulting from their thermal rearrangement, were converted in 5-7 days at 20°C into 3,4,4-triphenyl-1H-pyrazol-5(4H)-one by the action of a catalytic amount of sulfuric acid in acetic acid. Under analogous conditions, the regioisomeric anti-Auwers adducts gave rise to 3,4,5-triphenyl-1H-pyrazole with an impurity of 4-(R-sulfonyl)-1,3,5-triphenyl-1Hpyrazoles.* In the reaction of diphenyldiazomethane with propynal only Auwers 3H-pyrazole was obtained [7], whereas in the reaction with 3-phenylpropynenitrile, only the anti-Auwers adduct was formed [13].

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Efficient Regiocontrolled Synthesis and Antimicrobial Activity of Pyrazoles

Cited by 14 publications

References 13 publications

An Improved Preparation of 3-Alkoxypyrazoles

An Improved Preparation of 3-Alkoxypyrazoles

The use of benzil to obtain functionalized N-heterocycles

Synthesis of 3H-pyrazoles by reaction of methyl and p-tolyl phenylethynyl sulfones with diphenyldiazomethane and their thermal and acid-catalyzed transformations

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