Achiral and planar chiral ferrocene diols: preparation and complexation with titanium(IV)

Abstract

Achiral ferrocene diol, 1,1′-bis(diphenylhydroxymethyl)ferrocene 5, was prepared by the direct dilithiation of ferrocene with n-butyllithium in the presence of TMEDA followed by treatment with benzophenone, while the first chiral C 2-symmetric ferrocene diol possessing only the planar chirality, (+)-( R, R)-1,1′-bis(diphenylhydroxymethyl)-2,2′-dimethylferrocene 6, was prepared from (+)-( R, R)-1,1′-bis(oxazolinyl)-2,2′-dimethylferrocene 1b by the transformation of the oxazoline moieties. It was shown that diols 5 and 6 can form 1:1 complexes with tetraisopropyl titanate with ease. The X-ray crystal structure analysis of 5 with an intramolecular hydrogen-bonding showed that the phenyl groups in the molecule occupy quasi-axial and quasi-equatorial positions and these structures can be taken as the models of the titanium complexes of ferrocene diols. As a preliminary experiment, the titanium-catalyzed hydrosilylation of a ketone with 6 has also been carried out.