Grignard reagents/zirconocene dichloride

Alternately, CpjZr can also be prepared by the reaction of Cp2ZrCl2with two equivalents of n-BuLi at —78°C E.-I Negishi, F. K. Cederbaum and T. Takahashi, Reaction of zirconocene dichloride with alkyl lithiums or alkyl Grignard reagents as a convenient method for generating a zirconocene equivalent and its use in zirconium promoted cyclization of alkenes, alkynes dienes, eneynes and diynes, Tetrahedron Lett. 27 2829 (1986). 

Zirconocene dichloride was used as a catalyst for allylic displacement of allyl ethers with Grignard reagents [449]. An asymmetric version of this reaction by the use of a catalytic amount of a chiral zirconocene dichloride was independently reported, and it achieved a nearly complete chirality induction [Eq. (205) 450]. 

Treatment of zirconocene dichloride, 50, with 2 equiv. of an appropriate alkyllithium or Grignard reagent generates transient zirconocene olefin complexes that upon loss of alkene provide access to zirconocene, 109, and the powerful reduction chemistry of divalent zirconium.48 Owing to the utility of this reagent in organic synthesis and organometallic reactions, the low-temperature alkylation of zirconocene dichloride, 50, with BunLi has been... 

Addition of oxalyl chloride to zirconacycles (498), prepared from 1-all nylphosphonates (496), zirconocene dichloride (497) and two equivalents of Grignard reagent, smoothly produced 2-oxo-cyclopente-nylphosphonates (499) in 58-81% yields (Scheme 148). ... 

---