Recyclable and reusable PdCl2(PPh3)(2)/PEG-2000/H2O system for the carbonylative Sonogashira coupling reaction of aryl iodides with alkynes

PdCl2(PPh3)(2) in a mixture of water and poly(ethylene glycol) (PEG-2000) is shown to be an extremely active catalyst for the carbonylative Sonogashira coupling reaction of aryl iodides with terminal alkynes. The reaction can be conducted under an atmospheric pressure of carbon monoxide at 25 degrees C with Et3N as a base, yielding a variety of alkynyl ketones in good to excellent yields. Application of this synthetic method to prepare flavones from o-iodophenol and terminal alkynes was also achieved. The isolation of the products is readily achieved by extraction with diethyl ether, and the PdCl2(PPh3)(2)/PEG-2000/H2O system can be easily recycled and reused six times without any loss of catalytic activity.