Organozinc enolates, structure

Because zinc enolates are intrinsically reactive species, especially towards carbonyl compounds, the attempted synthesis of such species often results in the formation of selfcondensation products which are often polymeric materials. Only in a few cases could pure organozinc enolates be isolated and structurally characterized. 

A recent report on the first structurally characterized organozinc amide enolate has appeared, and the observations are consistent with ours. Hlavinka, M.L. Hagadom, J.R. Organometallics 2005,24,4116. Although drawn as monovalent in Equation 20.2 for clarity, it is assumed that lithium is tetracoordinate, and 12-crown-4 is displacing other hgands hound to lithium, such as THE. 

The organozinc reagent from ethyl a-bromoisobutyrate has been found to comprise two entities one of these, the bromozinc enolate (66), reacted as expected a dimeric structure (67) has been assigned to the other, inactive component. 

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