Development Of Novel Organic Reactions Using Zirconocene Complexes

The discovery of ferrocene opened the door to the metallocene complexes in 1951.The special sandwich structure of ferrocene encouraged people to study the reaction of organic synthesis which transition metals participated.Since then many metallocene complexes with different structures and properties have be en synthesized for the important applications in the field of synthesis,catalysis,bio-pharmaceuticals,and optical materials.Zirconocene complexes(such as zirconocene dichloride Cp2 ZrC l2,bis(indenyl)zirconium dichloride Ind2 ZrC l2)are typical of the metallocene complexes which are well known as olefin polymerization catalysts.Recently zirconocene complexes have been intensively used on organic synthesis as intermediates.Here we developed several new organic reactions on zirconocene complexes and synthesized a series of new compounds.This paper mainly contains three parts.The first part,we synthesized zirconacyclopentadiene from the reaction of bis(indenyl)zirconium dichloride with n-butyllithium and alkyne.C hlorodienylzirconocene derivatives were formed by the reaction of zirconacyclopentadienes with NCS(N-Chlorosuccinimide)or NBS(N-Bromosuccinimide).Coupling products of indenyl ligand were obtained through the reaction of chlorodienylzirconocene with TiC l4.Different products were formed in different solvents.Coupling product of indenyl ligand with dienyl moiety was obtained in toluene.However when the reaction was carried out in THF,coupling product of two indeny ligands was obtained alternatively.Experimental procedure was simplified by experimental exploration.Coupling product of two indeny ligands was obtained through the reaction of Ind2 Zr Bu2 or Ind2 Zr Et2 with TiC l4.When using Ind2 ZrC l2 or Ind2ZrMe2 as the raw material coupling products can not be generated.The second part,propadiene(allene)derivatives were synthesized by the elimination reaction of alkoxy on zirconocene complexes.Zirconacyclopentenes were formed from the reaction of alkoxy alkynes and Cp2ZrEt2 which was prepared from the reaction of Cp2 ZrC l2 and ethylmagnesium bromide.Then terminal allenes were obtained via the elimination reaction of alkoxy on zirconium.Zirconacyclopentenes can also be formed from the reaction of α-alkenes,alkoxy alkynes and Cp2ZrBu2 which was prepared from the reaction of Cp2 ZrC l2 and n-butyllithium.The elimination of alkoxy group also gave terminal al ene derivatives.The third part,cyclization reaction of allenes was studied.When allenes on zirconium were treated with C uC l,transmetalation from zirconium to copper proceeded to form Cu-allene species,then endo-cyclization occurred to afford five-membered ring compounds.It is in sharp contrast to the known reaction on allenyl zirconocene where exo-cyclization occurred to form four-membered ring compound..In this paper,zirconocene complexes were used to explore new organic reactions.A series of important results were obtained which provides a new theoretical data for the methodology in organic synthesis,and also provides new ideas for the applications of zirconocene complexes in organic synthesis.