CO insertion reaction of zirconacyclopentadienes

Alkyl-substituted zirconacyclopentadienes reacted with CO directly at room temperature to give cyclopentenone derivatives as a mixture of cis and trans isomers after hydrolysis. Cyclopentadienones were not obtained. In the case of zirconaindene, both of indanones and indenones were obtained after hydrolysis. Treatment of unsymmetrical zirconacyclopentadienes prepared from diphenylacetylene and 4-octyne with CO at room temperature afforded cyclopentenones as a mixture of positional isomers of the double bond.