Functionalized cyclopentadienes: Synthesis of 1,2,3,4,5-pentaallylcyclopentadiene and 1,2,3,4-tetraallylcyclopentadiene

The synthesis of new penta- and tetraallylated cyclopentadienes is described. The title compounds 1a and 2a can be synthesized in a one-pot procedure from cyclopentadiene with a tenfold excess of both sodium hydride and allyl bromide under phase-transfer catalytical conditions. They are obtained in a mixture with their isomers from which they call be separated by metallation using potassium hydride giving the corresponding cyclopentadienides. Thus, these compounds are suitable candidates for the synthesis of multifunctionalizable organometallic systems.