Synthesis of 2,5-Diarylpyrroles by Ligand-Free Palladium-Catalyzed CH Activation of Pyrroles in Ionic Liquids
作者:Peter Ehlers、Andranik Petrosyan、Jens Baumgard、Stefan Jopp、Norbert Steinfeld、Tariel V. Ghochikyan、Ashot S. Saghyan、Christine Fischer、Peter Langer
DOI:10.1002/cctc.201300099
日期:2013.8
The palladium‐catalyzed CHactivation and arylation of N‐methylpyrrole and N‐phenylpyrrole allowed a convenient synthesis of diarylpyrroles. The reactions were performed by using tetrabutylammonium acetate as an ionic solvent, which allowed for the application of a ligand‐free catalytic system by using simple palladium salts or polyvinylpyrrolidone‐stabilized palladium nanoparticles as the catalyst
Palladium-Catalysed Direct Polyarylation of Pyrrole Derivatives
作者:Liqin Zhao、Christian Bruneau、Henri Doucet
DOI:10.1002/cctc.201200521
日期:2013.1
palladium‐catalysed direct polyarylation of 1‐methylpyrrole and 1‐phenylpyrrole was studied. As the C2 and C5 positions of pyrroles are more reactive for CH bond functionalisation than the C3 and C4 positions, the formation of 2,5‐diarylpyrroles was found to proceed selectively in the presence of 3 equiv. of a variety of arylbromides. The sequential C2 arylation followed by C5arylation to prepare non‐symmetrically
作者:Daniel T. Gryko、Olena Vakuliuk、Dorota Gryko、Beata Koszarna
DOI:10.1021/jo902124c
日期:2009.12.18
A methodology that affords N-alkyl-2-arylpyrroles and N-aryl-2-arylpyrroles via direct coupling from aryl iodides has been developed. After examining various reaction parameters: solvent, ratio of reagents, catalyst, base and additives the optimal conditions for the condensation were identified. Two crucial factors, (a) anhydrous DMSO as solvent and (b) 5 M excess of pyrrole counterpart, were found to strongly influence the reaction outcome. The conditions identified (PdCl2(PPh3)(2), AgOAc, anhyd DMSO, KF, 100 degrees C, 5 h) resulted in the formation of 2-arylpyrroles in 14-80% yield. Furthermore, the synthesis is compatible with electron-withdrawing and electron-donating groups on the aryl moiety.