FIRST PALLADIUM-CATALYZED HECK REACTIONS WITH EFFICIENT COLLOIDAL CATALYST SYSTEMS

For the first time it has been shown that palladium colloids are effec tive and active catalysts for the olefination of aryl bromides (Heck r eaction). Worthy of note are the high activities of the catalyst syste m for activated aryl bromides under optimized reaction conditions, whi ch are better than or comparable with ''classical'' palladium phosphin e complexes, Addition of phosphines strongly retards the reaction rate of the colloid catalyst, Nevertheless, this type of catalyst is not s u:table for the activation of non-activated substrates, especially tec hnically interesting aryl chlorides.