Copper-Promoted Oxidative Intramolecular C-H Amination of Hydrazones to Synthesize 1<i>H</i>
-Indazoles and 1<i>H</i>
-Pyrazoles Using a Cleavable Directing Group
A facile and efficient copper‐promoted oxidative intramolecular C–H amination of hydrazones for the synthesis of 1H‐indazoles and 1H‐pyrazoles was developed using a tracelessly cleavable directing group. This reaction is characterized by its mild conditions, operational simplicity, readily available reagents, and excellent yields. A tentative mechanism for Cu‐mediated C–H‐oxidative amination was proposed
The diaza-Nazarov cyclization involving a 2,3-diaza-pentadienyl cation for the synthesis of polysubstituted pyrazoles
作者:Balakrishna Aegurla、Rama Krishna Peddinti
DOI:10.1039/c7ob01949a
日期:——
diaza-Nazarov (DAN) type cyclization for the construction of substituted pyrazoles from easily available starting materials via an enamine–iminium ion intermediate is described. The oxidative cyclization worked under green conditions with remarkable regioselectivity. This one-pot, efficient and operationally simple three-component intramolecular regioselective DAN cyclization displayed a wide range of
Iron(III) phthalocyanine chloride-catalyzed oxidation–aromatization of α,β-unsaturated ketones with hydrazine hydrate: Synthesis of 3,5-disubstituted 1H-pyrazoles
We have developed an iron(III) phthalocyanine chloride-catalyzed oxidation–aromatization of α,β-unsaturated ketones with hydrazine hydrate. Various 3,5-disubstituted 1H-pyrazoles were obtained in good to excellent yields. This method offers several advantages, including room-temperature conditions, short reaction time, high yields, simple work-up procedure, and use of air as an oxidant. The catalyst
A complementary method for the preparation of 3,5-substituted pyrazoles in moderate to high yields has been explored via TfOH-induced addition of tosylhydrazones to the terminal alkynes. This acid-induced addition procedure might be an operationally safe alternative compared to typical 1,3-dipolar cycloaddition as there is no involvement of diazo compounds.
One-Pot Synthesis of 3,5-Diphenyl-1H-pyrazoles from Chalcones and Hydrazine under Mechanochemical Ball Milling
作者:Ze Zhang、Ya-Jun Tan、Chun-Shan Wang、Hao-Hao Wu
DOI:10.3987/com-13-12867
日期:——
A highly efficient and environmentally friendly method has been developed for facile synthesis of 3,5-diphenyl-1H-pyrazoles under mechanochemical ball-milling conditions. The advantages of short reaction time, high efficiency, no separation of in situ generated intermediate, using cheap sodium persulfate as the oxidant, together with very simple work-up procedure, make this one-pot and solvent-free protocol a green and powerful alternative to traditional methods for the synthesis of these kinds of compounds.