Use of Organoaluminum Species Supported by Chelating Ligands Selected Examples

8 Use of Organoaluminum Species Supported by Chelating Ligands Selected Examples 

1 Organoaluminum Species Bearing N- andlor 0-Type Ligands 

More recent work on the 1,2-rearrangement of variously substituted a-siloxy aldehydes has represented an avenue for extending the catalytic chemistry of close relatives of 86 [290]. 

There has been unremitting interest in the development of various reaction systems initiated by Al(III) complexes based on sterically encumbered dianionic ligands bearing various Lewis base moieties at properly designed positions. In this area, a series of optically active Al(III) triamine complexes, such as complex 88 (Fig. 29), have been reported as Lewis acid catalysts for the mediation of various asymmetric transformations, including ketene-aldehyde cycloaddition reactions (Eq. 16 for more detail on these transformations, see Chapter 6 Reactions triggered by Lewis acidic organoaluminum species ) [225, 226]. 

The authors examined various A,W, W -amine ligands to evaluate catalyst efficiency as a function of the triamine ligand s backbone and terminal amine functionality. For instance, these studies demonstrated that compound 88 was catalytically active in contrast to the related compound 89 (differing only in the chelate size), which was found to be completely inactive as a cycloaddition 

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