novel efficient tandem reaction of hydrazones and α-bromo ketones is reported for the preparation of 1,3,5-trisubstituted pyrazoles by visible light catalysis. In this system, the monosubstituted hydrazones show wonderful reaction activity with alkyl radicals, generated from α-bromo ketones. A radical addition followed by intramolecular cyclization affords the important pyrazole skeleton in good to
Transition-Metal-Free<i>N</i>-Arylation of Pyrazoles with Diaryliodonium Salts
作者:Zsombor Gonda、Zoltán Novák
DOI:10.1002/chem.201502995
日期:2015.11.16
developed for the N‐arylation of pyrazoles using diaryliodoniumsalts. The transformation does not require any transition‐metal catalyst and provides the desired N‐arylpyrazoles rapidly under mild reaction condition in the presence of aqueous ammonia solution as a mild base without the use of inert atmosphere. The chemoselectivity of unsymmetric diaryliodoniumsalts was also explored with large number
The 1,3-dipolar cycloaddition of diversely N-substituted 4-iodosydnones with 3-halopropiolates produces easily separable mixtures of dihalogenated pyrazolylcarboxylic esters at a preparative scale level, with the 3,5-dihalogenopyrazole regioisomers always predominating. Further decarboxylation of the major isomers provided the corresponding 3,5-dihalogenopyrazoles with a free C-4 position. These were
A Ceric Ammonium Nitrate N-Dearylation of <i>N</i>-<i>p</i>-Anisylazoles Applied to Pyrazole, Triazole, Tetrazole, and Pentazole Rings: Release of Parent Azoles. Generation of Unstable Pentazole, HN<sub>5</sub>/N<sub>5</sub><sup>-</sup>, in Solution
作者:Richard N. Butler、John M. Hanniffy、John C. Stephens、Luke A. Burke
DOI:10.1021/jo702423z
日期:2008.2.1
pentazole ring. The unstable HN5/N5- produced at −40 °C did not build up in the solution but degraded to azide ion and nitrogen gas with a short lifetime. The 15N-labeling of the N3- ion obtained from all samples proved unequivocally that it came from the degradation of HN5 (tautomeric forms) and/or its anion N5- in the solution.
Biomimetic Cleavage of Aryl–Nitrogen Bonds in N-Arylazoles Catalyzed by Metalloporphyrins
作者:Zongjiang Yu、Guoqing Zhai、Mo Xian、Ming Lu、Pengcheng Wang、Tao Jiang、Chao Xu、Weizhi Sun
DOI:10.1007/s10562-018-2446-9
日期:2018.9
The cleavage of C–N single bonds of N-containing compounds provides either an excellent nitrogen source or an excellent carbon source. In this study, an efficient metalloporphyrins/H2O2 cleavage of C–N bonds of arylpyrazoles was investigated. The effects of different factors, including different catalysts, catalyst dosages, H2O2 dosages, reaction temperature and reaction time were studied. The experimental