Using Planar Chiral Iron(0) Tricarbonyl Diene Complexes: A Focus on Azaspirocycles and the Use of an Oxazolidinone Chiral Auxiliary
Murphy, Julia Saxton
For many years, the Paley laboratory has developed the use of planar chiral1l4 iron(O)
tricarbonyl complexes for use in directing the central chirality of adjacent centers. This work
examines the use of dienes functionalized at C2 with a chiral auxiliary.
The functionalization of a stereocontrolled [6,6]-azaspirocycle was taken on to great success.
This sequence involved a 2-sulfinyl diene complex. The keystone Grignard addition to the cyclic
imine was accomplished to afford a single diastereomer. Ring closing metathesis was used to
form the final ring of the azaspirocycle framework.
Two more sequences were attempted to form azaspirocycle centers. The first was an
attempt to employ an intramolecular Mannich. In this sequence, the cyclic imine and an enol
would form in situ in order to avoid isolating the imine species which has been known to
decompose. The final attempt at azaspirocycle formation was an attempt to directly replace a
tertiary alcohol with an amine, again in an attempt to avoid the imine species.
An alternative project working to use an alternative chiral auxiliary, an oxazolidinone,
was also developed. The 2-oxazolidinyl diene complex was successfully complexed and new
developments in this sequence included the development of a stannyicupration directed by a
propargylic acetal in order to have an aldehyde adjacent to the diene complex.
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