Organosilanols as catalysts in asymmetric aryl transfer reactions.
[reaction: see text] Various ferrocene-based organosilanols have been synthesized in four steps starting from achiral ferrocene carboxylic acid. Applying these novel planar-chiral ferrocenes as catalysts in asymmetric phenyl transfer reactions to substituted benzaldehydes afforded products with high enantiomeric excesses. The best result (91% ee) was achieved in the addition to p-chlorobenzaldehyde with organosilanol 2b, which has a tert-butyl substituent on the oxazoline ring and an isopropyl group on the silanol fragment.
Ozçubukçu
Salih
S
Institut für Organische Chemie der RWTH Aachen, Landoltweg 1, D-52074 Aachen, Germany.
Schmidt
Frank
F
Bolm
Carsten
C