Crystal iron enolate

By far the most frequently occurring acetylacetonate derivatives are those in which the enolate anion is coordinated to a central metal atom through both oxygen atoms. A classic example of this is the well-known tris(acetylacetonato)iron(III) complex (Fig. IB) whose structure has been determined by single crystal X-ray structure analysis (7). Crystallographic data show that the two chelate ring C—C bond distances are... 

Another early solution to the acetate aldol problem came from the so-called Davies-Liebeskind enolates already mentioned in the context of enolate alkylation. As elaborated independently by the groups of Davies [138] and Liebeskind [139], the deprotonation of the chiral acetyl iron complex 124b, transmetallation of the lithium enolate, and addition to aldehydes lead to the predominant formation of diastereomers 279, as proved by a crystal structure analysis. The diastereoselectivity strongly depends on the transmetallation, the best results being obtained with diethylaluminum chloride. With other additives, the topicity is reversed, and the diastereomer 280 is obtained as the major product. The decomplexation of the adducts leads to P-hydroxycarboxylic acids (Scheme 4.64). 

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