Stereoselective synthesis of an ansa-zirconocene in a spirane scaffold

A rigid C2-bridged zirconocene catalyst system with the C2-bridge embedded in a spirane scaffold has been prepared from 3,4-dihydro-2H-fluoren-1(9H)-one. The oxo group was converted into a spirocyclobutanone and a fulvene before regio- and stereoselective saturation yielded cis-2-(cyclopentadienyl)-1′,2′,3′,4′-tetrahydro-9H-spiro[cyclobutane-1,1′-fluorene]. Lithiation and zirconation furnished the precatalyst (η5-cyclopentadienyl)-spiro[cyclobutane-1,1′-(η5-fluorenyl)]zirconium dichloride complex. The structure was confirmed by an X-ray structure analysis.