The synthesis of bidentate cyclopentadienyl-alkoxide ligands and their complexation
to titanium are described. The focus has been on methodology for stereoselective synthesis
of ansa half-sandwich titanocenes with rigid C2- and C3-bridges which are embedded in a spirane scaffold. Intermediate reactions involve
tandem acylation-alkylation in the conversion of a carbonyl carbon into a quaternary
carbon and rhodium(I)-effected spiroannulations. Titanocene formation involved reaction
between the dilithiated ligand and titanium(III) chloride, and subsequent oxidation
of the trivalent titanium with lead(II) chloride whereby the semi-metallocene was
formed.
spirane scaffold -
ansa semi-titanocenes - C2- and C3-spirane bridges - geminal acylation-allylation - rhodium(I)-catalyzed spiroannulation
