Hydrogenation hydrozirconation

Hydrides. Zirconium hydrides react easily with unsaturated molecules. This process, termed hydrozirconation, replaces the hydrogen with the unsaturated group ... 

Some hydrometalation reactions have been shown to be catalyzed by zirconocene. For instance, CpiZrCf-catalyzed hydroaluminations of alkenes [238] and alkynes [239] with BU3AI have been observed (Scheme 8-34). With alkyl-substituted internal alkynes the process is complicated by double bond migration, and with terminal alkynes double hydrometalation is observed. The reaction with "PrjAl and Cp2ZrCl2 gives simultaneously hydrometalation and C-H activation. Cp2ZrCl2/ BuIi-cat-alyzed hydrosilation of acyclic alkenes [64, 240] was also reported to involve hydrogen transfer via hydrozirconation. 

Enantioselective, multiple centers 153, 166,189 Hydroamination Intermolecular Alkene 30 Alkyne 1 Intramolecular Alkene 30 Alkyne 13,170 Hydrogen peroxide Oxidation of alcohols 26, 86 Hydrogenolysis of epoxide 1 Hydrozirconation 32... 

Hydrozirconation of alkyne 14, followed by cuprate addition, was then used to install the Cl3 20 side chain of 15. Reduction of the ketone (L-selectride) followed by hydrogen fluoride cleavage provides the F-series derivatives 16, while direct cleavage of 15 gave the E-series compounds 17. 

The hydrozirconation of alkenes will generally result in positional isomerization of the Zr to the least-hindered position. The Zr-intermediate can be replaced with Br (Br2, NBS), I (I2), Cl (NCS). OH (MCPBA, or basic aq. hydrogen peroxide). 

Hydrozirconation of imines.1 Reaction of Schiff bases containing an a-hydrogen with 1 followed by acylation provides a route to enamides and/or imides and amides. Examples ... 

Ballenwey S, Gleiter R, Kratshmer W (1993) Hydrogenation of buckminsterfullerene c-60 via hydrozirconation - a new way to organofullerenes. Tetrahedron Lett 34 3737-3740... 

Perhaps the most useful application of the hydrozirconation/protodezirconation sequence is for specific introduction of deuterium label some examples were presented in the previous section. Although most such work indicates that deuterium incorporation is essentially complete, Svenson and coworkers have found that around 20% of the alkane thus obtained from simple alkenes is undeuterated. The amount of alkane-reaction times, so transfer of hydrogen to give alkane prior to hydrolysis is probably responsible. This in situ hydrogenation was found to be even more pronounced for a,p-unsaturated carboxylic acid oxazolines, giving 70% of the undeuterated saturated product. ... 

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