Synthesis 2008(6): 962-970  
DOI: 10.1055/s-2008-1032205
PAPER
© Georg Thieme Verlag Stuttgart · New York

Stereoselective Syntheses of Spirane Bridged Semi-titanocenes

Vidar Bjørnstad, Kjell Undheim*
Department of Chemistry, University of Oslo, 0315 Oslo, Norway
Fax: +47(22)855507; e-Mail: kjell.undheim@kjemi.uio.no;
Further Information

Publication History

Received 8 November 2007
Publication Date:
28 February 2008 (online)

Abstract

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.