Abstract:
Iron(D) tricarbonyl-diene complexes have emerged from the field of
organometallics as motifs of particular importance due to their robust synthetic
applications. As a result of their planar chiral configurations, these removable iron units
have been effectively used as diene protecting groups, stereodirecting groups and dienyl
cation stabilizers to facilitate the total synthesis of architecturally complex structures,
such as pharmaceutically-relevant natural products. However, to further optimize ironeD)
tricarbonyl utilization in diastereoselective synthesis, methods must be developed to
direct iron-diene complexation reactions in a facially selective manner and to characterize
these optical outcomes. Additionally, the established number of reactions tolerant to
ironeD) tricarbonyl mediation must be expanded to facilitate the use of such
methodologies on a widespread or industrial level.
Herein we report the synthesis and characterization ofN-oxazolidinoyl diene
ironeD) tricarbonyl complexes as model platforms to address both of these existing
challenges. The use of enantiopure N-oxazolidinoyl chiral auxiliaries as directing groups
has now been shown to efficiently and predictably direct facially-selective complexation
reactions. Furthermore, the planar chirality of these species was ascertained via
crystallographic and circular dichroism spectroscopy, the latter being a novel technique
for such complexes. Efforts to utilize an N-oxazolidinoyl complex in the first
intramolecular Pictet-Spengler cyclization directed by planar chirality were also
undertaken, ultimately producing the most structurally demanding N-oxazolidinoyl
complex synthesized to date. Lastly, projects involving novel auxiliaries, such as cyclic
ureas and sulfonamides, to better direct complexation reactions are also detailed.
