Alexander Zapf

In the mid 1990s, we started a program on the development of more efficient palladium catalysts for the C–C and C–N coupling reactions of aryl halides, especially aryl chlorides. In this contribution, our investigations on new catalyst systems and their application in organic synthesis are summarized.

Arenes and heteroarenes are ubiquitous substructures in biologically active agents and new materials. Thus, functionalization (“refinement”) of simple arene precursors is still of major importance for preparative organic chemistry. During the last 20 years, especially transition‐metal‐catalyzed cross‐coupling reactions of aryl halides and triflates have given arene chemistry new impetus. The first industrial applications were realized a few years ago. Quite recently, carbonic acid derivatives such as anhydrides and esters have added to the scope of substrates for these coupling reactions. Some recent developments in this area are presented in this Minireview.

Aromaten und Heteroaromaten sind allgegenwärtige Strukturelemente in Wirkstoffen und neuen Materialien. Die Funktionalisierung (“Veredelung”) von einfachen aromatischen Vorstufen ist deshalb nach wie vor von zentraler Bedeutung für die präparative Organische Chemie. In den letzten 20 Jahren haben vor allem Übergangsmetall‐katalysierte Kreuzkupplungen von Arylhalogeniden und ‐triflaten der Aromatenchemie neue Impulse gegeben, vor wenigen Jahren wurden auch erste technische Anwendungen realisiert. Seit kurzem ergänzen nun Carbonsäurederivate wie Anhydride und Ester das Substratspektrum derartiger Kupplungsreaktionen. Einige aktuelle Entwicklungen auf diesem Gebiet werden in diesem Aufsatz vorgestellt.

A detailed investigation into the influence of phosphines, additives, bases, and solvents on the Heck coupling reaction of 4-trifluoromethyl-1-chlorobenzene (2) is presented. It is shown that a number of catalyst systems exist for efficient cross coupling of electron deficient aryl chlorides with various olefins. Basicity and steric demand of the ligand are two factors which determine the success of the reaction. In addition the phosphine / palladium ratio, the correct type and amount of additive, and finally the use of an appropriate base and solvent are also important. The optimised reaction conditions are applied for the arylation of styrene, butyl vinyl ether, and N,N-dimethyl acrylic amide with various aryl chlorides.