Diastereo- and Enantioselective Metathesis Dimerization/Kinetic Resolution of Racemic Planar-Chiral Vinylferrocenes
Koji Nishimoto1, Haruka Taue1, Takehito Ohji1
1Department of Natural Science, Graduate School of Science and Technology, and Research Cluster on "Innovative Chemical Sensing", Tokushima University, Tokushima 770-8506, Japan.
Abstract:
Diastereo- and enantioselective kinetic resolution of racemic planar-chiral 1-R-2-vinylferrocenes (rac-1) was attained by the molybdenum-catalyzed asymmetric metathesis dimerization (AMD). Two sequential AMD reactions of rac-1a (R = Br) provided (E)-(S,S)-1,2-di(2-bromoferrocenyl)ethylene in >99% ee, which was converted to (S,S)-1,2-bis[(2-diphenylphosphino)ferrocenyl]ethane (S,S)-5. Planar-chiral bisphosphine (S,S)-5 coordinated to a dichloropalladium(II) fragment in a trans-chelating fashion, which was applied as a chiral ligand in the palladium-catalyzed asymmetric allylic alkylation showing enantioselectivity of up to 90% ee.
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