The present invention provides a method of removing undesired isomers, including substituted cyclopentadiene regioisomers, from the desired fulvene in a crude fulvene composition by selectively reacting the undesired isomers with pyrrolidine and 4-(N,N-dimethylamino)benzaldehyde. This reaction converts the undesired substituted cyclopentadienes into fulvene-type compounds that is readily separated from the desired fulvene.