Enantioselektive Cobalt-katalysierte Hydrovinylierung von Vinylarenen und Anwendung in der Totalsynthese der Naturstoffe (-)-α-Cedren und (+)-Erogorgiaen

This work describes the development and application of a highly reliable and efficient protocol for the enantioselective Cobalt-catalyzed 1,2-hydrovinylation of vinylarenes applying chiral taddol-based phosphine-phosphite ligands. Evaluation of the substrate scope resulted in a broad functional group tolerance including halogenes, ester, acids, unprotected amines and alcohols. Furthermore, sterically-hindered arylalkenes, heterocyclic structures and vinyl metallocenes could be successfully transformed. With (-)-α-Cedrene, a natural product could be established in a stereoselective, modified and optimized sequence based on a literature-known racemic synthesis. Instead of the hydrovinylation reaction, which was not able to induce satisfying enantiomeric excesses in this case, an already well-established protocol for the asymmetric allylic substitution could be successfully applied. Furthermore, the asymmetric hydrovinylation could be efficiently implemented as a chirogenic key step in the total synthesis of the marine natural product (+) Erogorgiaene. In an additional project, a ferrocenophane was synthesized stereoselectively via hydrovinylation to examine its thermochromic behavior in comparison to ferrocene.!