Page 34 - Book of Invited & Keynotes Talks

th
8 Biannual Conference on Chemistry - CHEM 08

Oxy Anion Accelerated Reactions at π Complexes of

Chromium and Iron
Holger Butenschön
Institut fur Organische Chemie, Leibniz Universitat Hannover, Germany

ABSTRACT
The connection of the two parts of the lecture are oxy-anion driven reactions:
If it were possible to run a reaction under anionic reaction conditions
resulting in a resonance stabilized species – mostly an enolate or a phenolate
– the reaction is usually highly accelerated allowing for reaction
temperatures of –78 °C.
In the context of our interest in π complexes and reactions at the coordinated
ligands the synthesis and reactions of tricarbonylchromium complexes of
benzocyclobutenone and benzocyclobutenediones will be discussed. This
includes oxy-anion driven ring opening reactions as well as dianionic oxy-
Cope rearrangements. These reactions are often followed by an
intramolecular aldol addition providing polycyclic products in high yield
and stereoselectivity.
In the second part, attempts directed to aryne π complexes will be presented.
Here the first anionic thia-Fries rearrangements of coordinated aryl triflates
and ferrocenyl triflates will be discussed as another example of oxy-anion
accelerated rearrangements. Among other reactions the unprecedented
interannular stereoinduction between the cyclopentadienyl ligands of a
ferrocene will be presented.
Finally, some actual results on catalytic C,H activation at ferrocene using
cobalt and iron complexes as catalysts will be reported.

BOOK OF INVITED SPEAKERS & KEYNOTES CHEM 08 (2020) Page 34