Untersuchungen zu Kobalt-katalysierten Diels-Alder-Reaktionen und [2+2+2]-Cycloadditionen

Within this work the cobalt-catalysed Diels-Alder-reaction of 1-boron functionalised dienes with alkynes was succesfully established. The dihydroaromatic products were subsequently reacted in a one-pot procedure with various aldehydes. The reaction was demonstrated by a modell system and the scope of the reaction was shown by reacting various aldehydes and alkynes. Further investigations, concerning an enantioselective reaction were carried out with commercially available chiral ligands. The desired products were obtained in very good yields and good enantioselectivities. In addition, for the first time, selenium substituted alkynes and phenylpropargylselenide were used in the cobalt-catalysed Diels-Alder-reaction. The reaction was studied by a simple modell system and, to this time, reasonable yields were obtained. In the third part of this work, a modification of the known Hilt-catalyst was used to accomplish the [2+2+2]-cycloaddition of two alkynes and one diene. The reaction was studied by a modell system consisting of phenylacetylene and isoprene or butadiene. In the last part of this work a simple, efficient and economical catalyst system for the cobalt-catalysed trimerisation of alkynes was developed. Furthermore investigations concerning the influence of the solvent and ligand were carried out. The cataylst was also used to trimerise some representative terminal and internal alkynes in very good yields.