Diastereo- and Enantioselective Metathesis Dimerization/Kinetic Resolution of Racemic Planar-Chiral Vinylferrocenes

Area of Science:

• Organometallic Chemistry
• Asymmetric Catalysis
• Synthetic Organic Chemistry

Background:

• Planar-chiral ferrocenes are valuable building blocks in asymmetric synthesis.
• Kinetic resolution of racemic compounds is crucial for obtaining enantiopure materials.
• Asymmetric metathesis dimerization (AMD) offers a powerful route for creating complex chiral structures.

Purpose of the Study:

• To develop a diastereoselective and enantioselective kinetic resolution of racemic planar-chiral 1-R-2-vinylferrocenes.
• To synthesize a novel planar-chiral bisphosphine ligand for asymmetric catalysis.
• To evaluate the performance of the synthesized ligand in palladium-catalyzed asymmetric allylic alkylation.

Main Methods:

• Molybdenum-catalyzed asymmetric metathesis dimerization (AMD) of racemic 1-R-2-vinylferrocenes.
• Sequential AMD reactions to achieve high enantiomeric excess (>99% ee).
• Conversion of the resolved product to a planar-chiral bisphosphine ligand ((S,S)-5).
• Coordination of the bisphosphine ligand to a dichloropalladium(II) fragment.
• Application of the resulting chiral palladium complex in asymmetric allylic alkylation.

Main Results:

• Successful kinetic resolution of racemic planar-chiral 1-R-2-vinylferrocenes via AMD.
• Obtained (E)-(S,S)-1,2-di(2-bromoferrocenyl)ethylene with >99% ee.
• Synthesized the planar-chiral bisphosphine ligand (S,S)-1,2-bis[(2-diphenylphosphino)ferrocenyl]ethane.
• Demonstrated the efficacy of the ligand in palladium-catalyzed asymmetric allylic alkylation, achieving up to 90% ee.

Conclusions:

• AMD is an effective strategy for the kinetic resolution of planar-chiral vinylferrocenes.
• The novel bisphosphine ligand derived from this process is suitable for asymmetric catalysis.
• This methodology provides access to enantiomerically enriched ferrocene derivatives and chiral ligands.