Synthesis of 4-Organoselanyl-1H-pyrazoles: Oxone -Mediated Electrophilic Cyclization of α,β-Alkynyl Hydrazones by Using Diorganyl Diselenides
A simple and efficient method for the synthesis of 4organoselanyl-1 H -pyrazoles has been developed, taking place under metal- and halogen-free conditions. Electrophilic species of selenium were easily generated in situ by the reaction of diorganyl diselenides with Oxone in ethanol as solvent in an open-flask at 70 °C. These electrophilic selenium species were employed in the selenylation/cyclization of α,β-alkynyl hydrazones, giving the title compounds in moderate to excellent yields. The final species of selenium obtained from the reaction of diphenyl diselenide with Oxone were characterized by 77 Se NMR spectroscopy and high-resolution mass spectrometry (HRMS).
Perin, Gelson,Nobre, Patrick C.,Mailahn, Daniela H.,Silva, Márcio S.,Barcellos, Thiago,Jacob, Raquel G.,Lenard?o, Eder J.,Santi, Claudio,Roehrs, Juliano A.
p. 2293 - 2304
(2019/05/24)
A Regioselective Approach to Trisubstituted Pyrazoles via Palladium-Catalyzed Oxidative Sonogashira-Carbonylation of Arylhydrazines
A palladium-catalyzed oxidative carbonylation of arylhydrazines and alkynes with balloon pressure CO/O2 to afford trisubstituted pyrazoles in a one-pot manner has been developed. The formation of trisubstituted pyrazoles involves a sequential C-N bond cleavage, carbonylation, Sonogashira coupling, Michael addition, and intramolecular condensation cyclization tandem process. An unprecedented oxidative Sonogashira-carbonylation reaction of arylhydrazine plays a key role for such a facile approach to pyrazoles.
Regioselective synthesis of 1-aryl-3,4-substituted/annulated-5-(methylthio) pyrazoles and 1-aryl-3-(methylthio)-4,5-substituted/annulated pyrazoles
Highly efficient and regioselective synthesis of 1-aryl-3,4-substituted/ annulated-5-(methylthio)-pyrazoles and 1-aryl-3-(methylthio)-4,5-substituted/ annulated pyrazoles has been reported via cyclocondensation of arylhydrazines with either α-oxoketene dithioacetals or β-oxodithioesters.
Peruncheralathan,Khan,Ila,Junjappa
p. 10030 - 10035
(2007/10/03)
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