Deprotonation hydrozirconation

The only other alkenyl carbenoid with a proton trans to the halide that can readily be generated by deprotonation is the parent 1-lithio-l-chloroethene 57 [43] (Scheme 3.13). Insertion into organozirconocenes arising from hydrozirconation of alkenes and alkynes, followed by protonation, affords terminal alkenes and ( )-dienes 59, respectively [38]. The latter provides a useful complement to the synthesis of 54 in Scheme 3.12 since the stereocontrol is >99%. 

Functional groups can be protected carboxylic acids as oxazolines or silyl esters and alcohols as THP derivatives or potassium alkoxides. In fact, it may not be necessary to protect alcohols at all just use two equivalents of reagent The first will deprotonate the alcohol to give an alkoxyzirconium complex, and the second can then hydrozirconate the C=C or C C bond (equation 23). Several examples are shown in Tables 3 and 5. The presence of such functional groups does frequently have regio-chemical consequences, as will be shown in the following section. 

Scheme 2 Hydrozirconation of an electrophilic and easily deprotonated substrate...

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