Vinylogous Reactivity of Enol Diazoacetates with Donor–Acceptor Substituted Hydrazones. Synthesis of Substituted Pyrazole Derivatives
摘要:
A regiospecific synthesis of multifunctional pyrazoles has been developed from a cascade process triggered by Rh(II)-catalyzed dinitrogen extrusion from enol diazoacetates with vinylogous nucleophilic addition followed by Lewis acid catalyzed cyclization and aromatization.
Base-Mediated Reaction of Hydrazones and Nitroolefins with a Reversed Regioselectivity: A Novel Synthesis of 1,3,4-Trisubstituted Pyrazoles
作者:Xiaohu Deng、Neelakandha S. Mani
DOI:10.1021/ol800200j
日期:2008.3.1
A regioselectivesynthesis of 1,3,4-tri- or 1,3,4,5-tetrasubstituted pyrazoles by the reaction of hydrazones with nitroolefins is described. Mediated with strong bases such as t-BuOK, the reaction exhibits a reversed, exclusive 1,3,4-regioselectivity. Subsequent quenching with strong acids such as TFA is essential to achieve good yields. A plausible stepwise cycloaddition reaction mechanism is proposed
Electrochemical Synthesis of Pyrazolines and Pyrazoles via [3+2] Dipolar Cycloaddition
作者:Martin Linden、Silja Hofmann、Antonia Herman、Nicole Ehler、Robin M. Bär、Siegfried R. Waldvogel
DOI:10.1002/anie.202214820
日期:2023.2.20
Electrochemically initiated [32] cycloaddition reactions of readily available and less toxic starting materials enable a facile synthesis of pyrazolines and pyrazoles. Application of a biphasic system and sodium iodide in a dual role as mediator and electrolyte allows for selective reactions with outstanding robustness towards scalability.