- Zn[(l)proline]2 in water: A new easily accessible and recyclable catalytic system for the synthesis of pyrazoles
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Zn[(l)proline]2 has been found to be an efficient catalyst for the synthesis of pyrazole derivatives in pure water at room temperature. Reaction afforded moderate to excellent yield within a lesser time. Various pyrazoles which could not be prepared by other methods can be easily prepared by this method efficiently. Catalyst exhibits recyclability up to five runs. Hence our present protocol is economical and clean comprise of green reagent, solvent and catalyst.
- Kidwai, Mazaahir,Jain, Arti,Poddar, Roona
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experimental part
p. 1939 - 1944
(2011/06/19)
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- DMF-catalyzed direct and regioselective C-H functionalization: Electrophilic/nucleophilic 4-halogenation of 3-oxypyrazoles
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A novel, straightforward, and highly regioselective 4-chlorination of 3-oxypyrazole derivatives in boiling thionyl chloride (SOCl2) in the presence of catalytic N,N-dimethylformamide (DMF) has been developed. This reaction likely proceeds through a DMF-catalyzed electrophilic/nucleophilic chlorination mechanism and involves electrophilic attack by SOCl2 and nucleophilic substitution by Cl- as the key steps. Based on this mechanism, the corresponding 4-bromination and 4-iodination of 3-oxypyrazoles have also been achieved in good yield by adding Br- and I -, respectively, to the reaction system. This halogenation method enables quick access to many original 4-halo-3-oxypyrazole series. A novel DMF-catalyzed electrophilic/nucleophilic 4-halogenation of 3-oxypyrazole derivatives has been developed. This halogenation procedure provides quick access to many novel 4-halo-3-oxypyrazole series.
- Liu, Yuanyuan,He, Guangke,Chen, Kai,Jin, Yin,Li, Yufeng,Zhu, Hongjun
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supporting information; experimental part
p. 5323 - 5330
(2011/11/13)
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- Alkoxypyrazoles and the process for their preparation
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The present invention relates to a alkoxypyrazoles preparation process, and new alkoxypyrazole compounds.
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Page/Page column 8-9, 15
(2010/03/02)
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- An improved preparation of 3-alkoxypyrazoles
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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. Georg Thieme Verlag Stuttgart.
- Guillou, Sandrine,Bonhomme, Frederic J.,Janin, Yves L.
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experimental part
p. 3504 - 3508
(2009/05/09)
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- Synthesis of 3-ethoxyisoxazole derivatives and 3-ethoxy-1H-pyrazole derivatives from β-oxo thionoesters
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3-Ethoxyisoxazoles and 3-ethoxy-1H-pyrazoles were obtained in high yields from β-oxo thionoesters. The reaction of the ethyl β-oxo thionoesters with hydroxylamine hydrochloride in the presence of triethylamine at room temperature for 2 h gave the ethyl 3-oxopropiohydroximates and their hemiacetals, which were easily converted to the 3-ethoxyisoxazoles by refluxing for 3 h at pH 3-5. On the other hand, the reaction of the ethyl β-oxo thionoesters with hydrazine derivatives in the presence of triethylamine for 3-8 h at room temperature directly yielded the 3-ethoxy-1H-pyrazoles.
- Ohta,Fujisawa,Nakai,Furukawa
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p. 1861 - 1864
(2007/10/03)
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