of aryl iodides were coupled with aromatic and aliphatic terminal alkynes to give the corresponding 1,2-disubstituted aromatic alkynes in good yields by using only 0.4 mol % of the heterogeneous 10 % Pd/C as the catalyst without a ligand, copper salt, or amine in an aqueous medium.
Easy Copper-, Ligand- and Amine-Free Sonogashira Coupling Reaction Catalyzed by Palladium on Carbon at Low Catalyst Loading and by Exposure to Air
作者:Guolin Zhang
DOI:10.1055/s-2005-863720
日期:——
An easy copper-, ligand and amine-free Sonogashira coupling reaction catalyzed by commercially available palladium on carbon with air at low catalyst loading (0.2 mol% Pd) has been developed. Aryl iodides coupled with aromatic alkynes gave good to excellent yields and with aliphatic alkyne gave moderate to good yields. The reaction system is easy to handle.
γ-Valerolactone (GVL) can be used as an efficient and practical alternative to the banned and commonly used dipolar aprotic solvents. In this contribution GVL has been used as a non-toxic, biodegradable, biomass-derived medium, for the definition of a simple and general protocol for the Sonogashira cross-coupling reaction. The chemical efficiency of GVL as a medium is excellent and the best results
for the Sonogashira cross-coupling exploiting the safe use of a CPME/water azeotropic mixture and the utilization of a heterogeneous hybrid palladium catalyst supported onto a silica/β-cyclodextrin matrix in continuousflow. The use of the aq CPME azeotrope has proven to be crucial to enhance the catalyst performance including very low metal leaching. In addition, we have also completed the flow protocol