Catalysts increase the rate of chemical reactions without being consumed. Thus, small amounts of catalytically active species allow the preparation of large amounts of products. As far as carbon-carbon bond forming reactions are concerned, most of the established catalytic processes rely upon the use of nobel metals such as palladium, rhodium, ruthenium etc. Other transition metals which do not spontaneously regenerate a low-valent oxidation state after the desired C-C-bond formation cannot be used in a catalytic manner so far. This project tries to explore ways which allow to overcome this severe limitation.
Chlorosilanes as cheap, readily available and non-toxic
additives may pave the way. Specifically, studies on the titanium-mediated reductive coupling of carbonyl compounds to alkenes (McMurry synthesis) are proposed. A recently deviced procedure will be refined which has proved for the first time that this notoriously stoichiometric but highly useful transformation can in fact be rendered catalytic in titanium. Part of this project deals with the synthesis and evaluation of tailor-made ligands and with a detailed study of the actual nature of the intermediates involved in this catalytic process by spectro- scopic means. The insight gained during the course of this investigation will be applied to other transition metal induced reactions, which may also become catalytic when performed in the presence of an appropriate chlorosilane. The efforts will focus on those processes which hitherto require expensive and/or toxic metals in (over)stoichiometric amounts and which would become much more attractive for applications in natural product chemistry or for the synthesis of pharmacologically relevant targets if a catalytic alternative would exist.