YCLO[8.2.1.0(2,9).0(3,7)]TRIDECA-3,6-DIENYLLITHIUM - TENTATIVE EVIDENCE FOR A QUINTERNARY EQUILIBRIUM INVOLVING A CYCLOPENTADIENIDE ION

The title anion 9 was prepared starting from (+)-tricyclo[5.2.1.0(2,6) ]deca-4,8-dien-3-ol, the less reactive enantiomer from lipase-mediated transesterification with vinyl acetate, by sequential Jones oxidation , hydrogenation, condensation with cyclopropyldiphenylsulfonium ylide, Baeyer-Villiger oxidation, acid-catalyzed rearrangement, hydride redu ction, and dehydration. The derived lithium cyclopentadienide 9 reacte d with TiCl3 and CpTiCl(3) to give only exo titanocenes. Comparison of cross peak intensities in Li-6,H-1 HOESY spectra of 9 indicates the e xistence of the exo-monomer at +24 degrees C. At -110 degrees C, the L i-6 spectrum indicates the presence of five distinct species which are in mutual exchange of the lithium cation as is shown by Li-6,Li-6-EXS Y. The two major species are assigned as an exo-monomer and an exo,exo -dimer. MNDO calculations on various monomeric and dimeric solvatomers of 9 confirm the NMR findings.