First palladium-catalyzed Heck reactions with efficient colloidal catalyst systems

For the first time it has been shown that palladium colloids are effective and active catalysts for the olefination of aryl bromides (Heck reaction). Worthy of note are the high activities of the catalyst system for activated aryl bromides under optimized reaction conditions, which are better than or comparable with ''classical'' palladium phosphine complexes, Addition of phosphines strongly retards the reaction rate of the colloid catalyst, Nevertheless, this type of catalyst is not su:table for the activation of non-activated substrates, especially technically interesting aryl chlorides.