Octene hydrozirconation

Scheme 6.1 shows typical reactions of 2 [11]. Hydrozirconation of 1-octene produces predominantly a primary alkyl complex 4. When 4-octene is used, isomerization... 

Most alkenes can be employed in hydrozirconation reactions as shown in the equations below and in Table 1. When internal alkenes such as 4-octene are used as substrates, only the primary alkylzirconium is obtained () -Cp)2Zr(Cl)C8Hi, ... 

The relative reactivity is measured qualitatively. At RT the rate of hydrozirconation of various alkenes is 1-octene > cis-4-octene > trans-4-octene > methylenecyclo-hexane > cyclopentene > cyclohexene > 3-methyl-2-butene. In competitive studies, a terminal alkene reacts 70 times faster that a disubstituted alkene. These relative rates are attributed to steric effects. Double bonds y to zirconium are less reactive than dienes since ( -Cp)2Zr(CH2CH2CH=CH2)Cl can be isolated from the reaction of ((j -Cp)2ZrHCl and butadiene . 

Hydrozirconation of alkenes. This organic metallic reagent reacts with olefins at 25-40° to form alkylzirconium complexes of the type (C5115)2 Zn(R)Cl, in which the transition metal moiety is attached to the least hindered position of the olefin. For example, when a suspension of (1) in benzene is shaken with 1-octene or either cis- or tran -4-octene, (2) is formed in quantitative yield. Thus internally metalated zirconium compounds undergo rearrangement much more rapidly than organoboron or aluminum analogs. Other examples of hydrozircon-ation are formulated. Very hindered olefins e.g., tetramethylethylene) fail to react at 40°. 

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