The commercially available and cheap Pd/C was found to promote Sonogashira couplings in the environmentally friendly choline chloride/glycerol eutectic mixture in the absence of external ligands. Under heterogeneous conditions, (hetero)aryl iodides were successfully coupled with both aromatic and aliphatic alkynes in yields ranging from 50 to 99 % within 3 h at 60 °C. The aforementioned catalytic system proved to be effective also towards electron-rich iodides, which are notoriously known to be poorly reactive in Pd-catalyzed Sonogashira coupling reactions. The eutectic mixture and the catalyst could easily and successfully be recycled up to four times with an E-factor as low as 24.4.
|Titolo:||Sustainable Ligand-Free Heterogeneous Palladium-Catalyzed Sonogashira Cross-Coupling Reaction in Deep Eutectic Solvents|
|Data di pubblicazione:||2020|
|Appare nelle tipologie:||1.1 Articolo in rivista|