Cyclopentadienone cyclopentadienediyl dithioketals

Reaction of di-tert-butylcyclopentadiene with excess potassium tert-butoxide in the presence of elemental sulfur leads to hitherto unknown cyclopentadienes bridged by sulfur atoms via one or two dithioketal functionalities. The X-ray crystal structures of compounds 1, 3, and 4 showing short inter- and intramolecular sulfur–sulfur interactions are reported. Analogous structures are assigned to compounds 2, 5, 6, and 7 by 1H, 13C NMR, and mass spectroscopy.