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
13C chemical shifts and1H-13C coupling constants ofN-phenyl-,N-p-fluorophenyl- andN-o-nitrophenylpyrazoles
作者:Mikael Begtrup、Per Vedsø、Pilar Cabildo、Rosa Maria Claramunt、Jose Elguero、Wim Meutermans
DOI:10.1002/mrc.1260300518
日期:1992.5
The 13C chemical shifts and some 1H13Ccouplingconstants of twelve N‐arylpyrazoles are reported. The assignments were made by using the effects of a fluorine substituent and two‐dimensional techniques.
The visible light mediated oxidation of 1,3,5-trisubstitutedpyrazolines under metal-free conditions was developed. Various substituted pyrazolines were oxidized to pyrazoles by irradiation with visible light/sunlight. A plausible mechanism was proposed for the light mediated oxidation proceeding via formation of intermediates with electron rich C-3 positions and electron deficient C-5 positions. Correlation
Electrochemically enabled oxidative aromatization of pyrazolines
作者:Silja Hofmann、Martin Linden、Julian Neuner、Felix N. Weber、Siegfried R. Waldvogel
DOI:10.1039/d3ob00671a
日期:——
Pyrazoles are a very important structural motif widely found in pharmaceuticals and agrochemicals. An electrochemically enabled approach for the sustainable synthesis of pyrazoles via oxidativearomatization of pyrazolines is presented. Inexpensive sodium chloride is employed in a dual role as a redox mediator and supporting electrolyte in a biphasic system (aqueous/organic). The method is applicable
A copper-catalyzed efficient method for the synthesis of a diverse variety of substituted N-aryl pyrazoles from readily available α,β-alkynic N-tosyl hydrazones and diaryliodonium triflates is realized. This one-pot multi-step methodology features a broad scope with good yields, scalability, and appreciable functional group tolerance. Detailed control experiments reveal that the reaction proceeds through