Facile preparation of allyl amines and pyrazoles by hydrazinolysis of 2-ketoaziridines
摘要:
Allyl amines and pyrazoles can be obtained by hydrazinolysis of 2-ketoaziridines. A variety of aziridines, including N-unprotected, N-substituted, as well as bicyclic enamine and aminal type, can be transformed into diversely substituted linear or cyclic products. The hydrazinolysis of homochiral aziridines proceeds without racemization. (c) 2005 Published by Elsevier Ltd.
An iodine-catalyzed denitrative imino-diaza-Nazarov cyclization (DIDAN) methodology has been developed for the synthesis of pyrazoles with high to excellent yields by using α-nitroacetophenone derivatives and in situ generated hydrazones. The key transformation of this oxidative 4π-electrocyclization proceeds through an enamine–iminium ion intermediate. This rapid one-pot DIDAN protocol results in
DABCO-promoted synthesis of pyrazoles from tosylhydrazones and nitroalkenes
作者:Meng Tang、Wen Zhang、Yuanfang Kong
DOI:10.1039/c3ob41435c
日期:——
An efficient synthesis of pyrazoles fromtosylhydrazones and nitroalkenes was developed. In comparison with the previously reported 1,3-dipolar cycloaddition reaction of diazo compounds with electron-deficient alkenes or alkynes, this methodology proceeded with a sequential Baylis–Hillman/intramolecular cyclization mechanism and a variety of reversed regioselectivity products were prepared in good
been developed for the synthesis of pyrazole. Based on the analysis of UV‐Vis absorption of the substrate, the reaction was designed to avoid the use of external photocatalysis and proceeds via direct irradiation of N‐centred anion by sunlight. The key features of this reaction include operational simplicity, readily available reagents, and amenability to gram‐scale synthesis.
A new process for synthesis of 5-aryl-3-phenylpyrazole is achieved. The regioselective ring-opening reaction of 2-aryl-3-benzoyl-1,1-cyclopropanedicarbonitrile with hydrazine plays a crucial role in the described process.
An Efficient One-Pot Synthesis of 3,5-Disubstituted 1H-Pyrazoles
作者:Hua Chen、Lei-Lei Wu、Yi-Cen Ge、Ting He、Lei Zhang、Xing-Li Fu、Hai-Yan Fu、Rui-Xiang Li
DOI:10.1055/s-0031-1290772
日期:2012.5
An efficient, general, one-pot, three-component procedure for the preparation of 3,5-disubstituted 1H-pyrazoles via condensation of substituted aromatic aldehydes, tosylhydrazine and terminal alkynes in toluene is reported. The reaction tolerates a variety of functional groups and sterically hindered substrates to afford the desired pyrazoles in yields of 67-91%.