Synthesis of 1H-Indazoles and 1H-Pyrazoles via FeBr3/O2 Mediated Intramolecular C–H Amination
摘要:
A new synthesis of substituted 1H-indazoles and 1H-pyrazoles from arylhydrazones via FeBr3/O-2 mediated C-H activation/C-N bond formation reactions is reported. The corresponding 1,3-diaryl-substituted indazoles and trisubstituted pyrazoles were obtained in moderate to excellent yields under mild conditions.
A mild and efficient protocol for the synthesis of fluorinated pyrazoles has been developed via gold(I)-catalyzed tandem aminofluorination of alkynes in the presence of Selectfluor. This method offers a broad substrate scope.
Vanadium-catalyzed C-N dehydrogenative cross-coupling of alkenyl hydrazones leading to functionalized pyrazoles is described in a 1:1 mixture of toluene/H2O using air as the terminal oxidant. Significant practical features include use of the commercial nontoxic VOSO4 as a recyclable catalyst, mild reaction conditions, scalability, and the broad substrate scope. Some of the product pyrazoles exhibit interesting photophysical properties. Fluorescence light-up sensing of BSA protein by one of the pyrazoles is also highlighted.
Synthesis of 1<i>H</i>-Indazoles and 1<i>H</i>-Pyrazoles via FeBr<sub>3</sub>/O<sub>2</sub> Mediated Intramolecular C–H Amination
作者:Tianshui Zhang、Weiliang Bao
DOI:10.1021/jo3026862
日期:2013.2.1
A new synthesis of substituted 1H-indazoles and 1H-pyrazoles from arylhydrazones via FeBr3/O-2 mediated C-H activation/C-N bond formation reactions is reported. The corresponding 1,3-diaryl-substituted indazoles and trisubstituted pyrazoles were obtained in moderate to excellent yields under mild conditions.