Iron acyl complexes enantioselective

The final example of asymmetric enolates concerns the iron acyl complexes developed by the Davies group. t O] These complexes give excellent enantioselectivity in a wide variety of asymmetric reactions but unfortunately the auxiliary can only be obtained by a tedious resolution procedure, is very expensive and cannot readily be recycled. 

Liebeskind and Davies " ° have independently developed the use of this chiral iron complex for enantioselective organic syntheses, particularly of a variety of optically active molecules. The reasons for this behaviour are that the complex is chiral-at-iron and one face is hindered by the PPha ligand reaction of these acyl-iron enolates occur with very high stereoselectivity (Scheme 3.7). 

Another original synthesis of tetrahydrolipstatin comes from Stephen Davies. [278] The two central building blocks are on the one hand an enantio-mericaUypure )S-hydroxyaldehyde, which is accessible by acylation of Meldrum s acid with dodecanoyl chloride, followed by an enantioselective hydrogenation of the -keto-ester along Noyori s method, and on the other hand an enantio-mericallypure acyl-iron complex [279], which is obtained by alkylation ofthe acetyl complex. [280] It is noteworthy that from the beginning the aldehyde component possesses the correct absolute configuration. The side-specific course ofthe anh-aldol addition is exclusively determined by the iron complex. First, the iron complex is deprotonated with butyl-lithium, then transmetallated with diethylaluminium chloride, and finally reacted with the aldehyde. The re-... 

---