The synthesis and characterization of 1-formyl-2-acylcyclopentadienylthallium compounds

The reaction of sodium cyclopentadienide with RCOOEt (R=Me, Ph, 2-thienyl, or OEt) or ButCOCl followed by Vilsmeier reagent in the presence of excess sodium methoxide produces the 2-substituted-6-dimethylaminofulvenes 1a–e in modest yields. Basic hydrolysis results in the formation of 2-substituted-6-hydroxyfulvenes 2a–e in very good yields. Subsequent deprotonation with TlOEt yields the 1-formyl-2-acyl or carboethoxy cyclopentadienylthallium compounds 3a–e.