Hydrozirconation--Isomerisation. Reactions of Terminally Functionalised Olefins with Zirconocene Hydrides and General Aspects.

Unsaturated Fatty Alcohol Derivatives as a Source of Substituted Allylzirconocene

“…[8] Moreover, hydrozirconation of internal aliphatic olefins with terminal oxygen-, sulfur-, or nitrogen-containing functionalities has already been investigated and leads to an elimination reaction of the functional group after rearrangement of the zirconium moiety towards the carbon atom that bears the heteroatoms (Scheme 2, Path B). [9] On the other hand, if one equivalent of 1,2-dicarbanionic species [10] would be available and react in this process with the same unsaturated system, the final product should contain an organometallic derivative and therefore Path A would be a realistic route. [*] Dr. N. Chinkov We previously reported that simple nonconjugated unsaturated enol ethers react smoothly with (1-butene)ZrCp 2 (Negishi reagent; Cp = cyclopentadienyl) [10] to lead to polysubstituted dienyl zirconocene derivatives as single geometrical isomers (Scheme 2, Path C).…”

“…Communications 466 www.angewandte.org 3 d-f (with three-, four-, and eight-carbon-atom tethers, respectively) also underwent this tandem reaction (Table 1, entries [8][9][10][11][12][13][14] in 20 minutes at 34 8C. This migration-elimination reaction can be rationalized by the following mechanism on a three-carbon-atom tether (Scheme 3): (1-Butene)ZrCp 2 reacts first with the remote double bond of 6 to form a zirconacyclopropane derivative 6 a.…”

Hydrozirconation

“…As an example, at room temperature in benzene, 1-octene, cis-4-octene and trans-4-octene all yield the n-octylzirconocene derivative (Scheme 8-6) [80]. The major driving force for this hydrozirconation-isomerization process (which can occur even at low temperature) is steric hindrance, favoring the ultimate formation of the less-hindered terminal alkylzirconium species [81][82][83]. The rate and efficiency of isomerization is dependent on the substrate as well as the hydrozirconating reagent.…”

“…Formation of the least-hindered alkylzirconium complex during the course of the hydrozirconation-isomerization process of alkenes can be altered by the presence of aromatic rings, additional conjugative double bonds, chelating heteroatoms [81,94] or groups that can be lost by elimination [95,96].…”

“…However addition of chlorodiphenylphosphine to 14 leads to the isomerized 1,1-diphosphine 16, which demonstrated that subsequent transformation of alkylzirconocene may induce the formation of isomers different from those observed for the corresponding starting zirconium derivatives [109] (Scheme 8-14). Migration of the Cp 2 ZrCl metal fragment along an alkyl chain onto a heteroatom was first reported by Annby and Karlsson [81,95,96,[111][112][113]. Migration of the Cp 2 ZrCl metal fragment along an alkyl chain onto a heteroatom was first reported by Annby and Karlsson [81,95,96,[111][112][113].…”