Diastereoselective Cyclizations of Enantiopure Planar Chiral N-Oxazolidinoyl Diene Iron(0) Tricarbonyl Complexes
Howell, Colin C.
Iron(0) tricarbonyl diene complexes have long been established as effective
stereodirecting groups due to their planar chirality and the steric bulk of the iron
fragment. If initial diastereoselective complexation can be achieved, these molecules are
therefore capable of acting as scaffolds for the stereoselective synthesis of architecturally
complex products. The Paley laboratory uses chiral auxiliaries, most recently
oxazolidinones, bound to acyclic dienes to assure diastereoselective complexation, before
exploring the potential of diverse diastereomeric chemistry on the diene periphery.
In this work we report progress on the development of an asymmetric,
intramolecular rhodium(II)-catalyzed C-H insertion adjacent to the diene to form five-
membered carbocycles with two determined stereocenters. In particular, we discuss the
synthesis of N-oxazolidinoyl diene iron(0) tricarbonyl complexes containing both
protected alcohol and indole functionalities, followed by diastereoselective cyclization to
form the corresponding cyclopentenes upon addition of the rhodium catalyst.
Additionally, initial steps towards the optimization of these synthetic pathways, including
the exploration of alternative methods to install the requisite diazo group, are detailed in
this report. It is predicted that these transformations will ultimately enable synthetic
access to new classes of natural products.
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