Transformation of Zirconocene−Olefin Complexes into Zirconocene Allyl Hydride and Their Use as Dual Nucleophilic Reagents:  Reactions with Acid Chloride and 1,4-Diketone

Abstract

Zirconocene-olefin complexes Cp(2)Zr(H(2)C=CHR), prepared in benzene-THF at 0 degrees C, react with acid chlorides to provide homoallylic alcohols. The key is an equilibrium between the zirconocene-olefin complexes and the corresponding zirconocene allyl hydride complexes via allylic C-H bond cleavage of the coordinating alkenes. Furthermore, the zirconocene-olefin complexes are also available for the reaction with 1,4-diketone to afford anti-1,4-diols with excellent diastereoselectivity. Thus, Cp(2)Zr(H(2)C=CHR) serves as a donor of both hydride and an allylic group. These reactions also proceed efficiently by using zirconocene-olefin complexes, derived from Cp(2)ZrCl(2), Mg metal, and 1-alkenes.

Zirconium Sandwich Complexes with η9 Indenyl Ligands: Well-Defined Precursors for Zirconocene-Mediated Coupling Reactions

“…Characterization of 5-( η 3 -CH 2 C(Me)CH 2 )H by solution 1 H and 13 C NMR spectroscopy revealed a dynamic molecule at ambient temperature. Variable-temperature NMR studies are consistent with η 1 ,η 3 allyl interconversion as well as hydride transfer between the zirconium and the allyl fragments . The full details of these experiments will be published elsewhere.…”

Unsaturated Fatty Alcohol Derivatives as a Source of Substituted Allylzirconocene

“…However, cross‐contamination of the product with the Wurtz coupling adduct always occurs (the longer the alkyl chain R in 1 , the more abundant the Wurtz coupling product). Alternatively, the source of the metal can be an organometallic derivative or a metallic salt (Scheme , Path B) 5d. However, all of these methods required a presynthesized allyl substrate 1 that has to be prepared independently in as few steps as possible.…”

Controllable, Sequential, and Stereoselective C–H Allylic Alkylation of Alkenes

“…Third, to generate C−C bonds with three distinct carbon groups, the mode of activation must be controllable to avoid undesired overfunctionalization of C−H bonds in any step of the process. Elegant methods have been reported for the generation of fully substituted carbon centers via C−H functionalization 5 and for branch-selective C−H allylic alkylation. 6 However, these strategies are not amenable to the conversion of simple alkenes such as propylene into products with substituted allylic carbon centers via sequential C−H allylic alkylation.…”