Asymmetric pentafulvene carbometalation-access to enantiopure titanocene dichlorides of biological relevance
Cini, Melchior and Bradshaw, Tracey D. and Woodward, Simon and Lewis, William (2015) Asymmetric pentafulvene carbometalation-access to enantiopure titanocene dichlorides of biological relevance. Angewandte Chemie International Edition, 54 (47). pp. 14179-14182. ISSN 1521-3773
Unprecedented asymmetric copper-catalyzed addition of ZnEt2 (ZnBu2) to the exocyclic C[DOUBLE BOND]C bond of pentafulvenes C5H4([DOUBLE BOND]CHAr) (Ar=2-MeOPh and related species) results in enantiomerically enriched (up to 93:7 e.r.) cyclopentadienyl ligands (C5H4CHEtAr; abbreviated CpR). Copper catalyst promotion with both chiral phosphoramidite ligands and a phosphate additive is vital in realizing both acceptable enantioselectivities and reaction rates. Enantiomeric CpR2TiCl2 complexes have been prepared; the (S,S) isomer is twice as active towards pancreatic, breast, and colon cancer cell lines as its (R,R) enantiomer at 24 h.
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