Abstract
Cerium(III) chloride activated (+)-camphor ( 1) and (−)-fenchone ( 2) react with lithiated ferrocene (reagent 3, (Li-Cp) 2Fe/LiCp-FeCp = 50:1) to give the corresponding optically active ferrocenyl diols 4 and 6 and monosubstituted ferrocenyl alcohols 5 and 7. The preparation of the diols 4 and 6, as well as of the alcohols 5 and 7 respectively, in high yields is optimized depending on the composition of the lithiated ferrocenes (reagent 3 contains mainly 1,1′-dilithium ferrocene; reagent 8 contains mainly monolithium ferrocene) and on the amounts (stoichiometric, diminished or catalytic) of the CeCl 3 used for activation of the ketones 1 and 2. The catalytic CeCl 3 promotion (5 mol%) of the addition reactions of reagents 3 and 8 to 1 and 2 respectively is observed only in the case of fenchone ( 2). The new optically active ferrocenyl alcohols 4, 5, 6 and 7 have been studied in detail by NMR, MS and IR spectroscopy. The crystal structure of diol 4 has been determined, and shows an unusual eclipsed conformation of the ferrocenyl moiety, possibly a result of the observed strong intramolecular hydrogen bond formation.
Published Version
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