Abstract
Treatment of tetramethylcyclopentadienyllithium (1 Li) with CuCl2 or bromotetramethylcyclopentadiene (4 ), respectively, as well as reaction of stannylated tetramethylcyclopentadiene with 4 in presence of PdBr2 gave two isomeric octamethyldihydropentafulvalenes (3 and 5 ), of which 5 was deprotonated to a highly substituted cyclopentadienyl anion. Conversion of 1 Li to iodotetramethylcyclopentadiene (7 ) and reaction of 7 with cyclopentadienyl anion yielded three tautomers of tetramethyldihydropentafulvalene (8a , 8b ,and 8c ) or exclusively 8a depending on the conditions. The crystal structures of 3 and 8a have been determined, and the isomers of 8 have been converted into the corresponding dianion.
Key words
dihydropentafulvalenes - bicyclopentadiendiyl dianion - coupling - cyclopentadienes - lithiation
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