Palladium-Catalyzed Sonogashira and Hiyama Reactions Using Phosphine-Free Hydrazone Ligands

Palladium/copper-catalyzed Sonogashira cross-coupling reaction of aryl halides with a variety of terminal alkynes under
amine-free conditions in dimethylformamide (DMF) at 80
°C gave internal arylated alkynes using PdCl2(MeCN)2 with
phosphine-free hydrazone 2a as a ligand and CuI as the
cocatalyst in good yields. We also found PdCl2/hydrazone
ligand 1d in PhMe at 80 °C was a phosphine-free efficient
catalyst system for a Hiyama cross-coupling reaction of aryl
bromides with aryl(trialkoxy)silanes in good yields.