Controlled mono- and double-Heck reaction catalyzed by a dicarbene dipalladium complex

The phosphine-free mono- and double-Heck reaction of terminal olefins with electron-deficient and electron-rich aryl halides (iodides and bromides) is described. These reactions are catalyzed by the dicarbene dipalladium complex 1 by controlling the stoichiometry of the aryl halide and the olefine, the loading of the palladium catalyst, as well as using different base, and with or without additive. The procedure of double-Heck reaction allows β,β-diarylation and β,β′-diarylation of terminal olefins and affords trisubstituted olefins in good to excellent yields.