Supported asymmetric catalysis

Gruttadauria, M., Riela, S., Lo Meo, P., D Anna, F., Noto, R. (2004) Supported Ionic Liquid Asymmetric Catalysis A New Method for Chiral Catalysts Recycling, the Case of ProUne-Catalysed Aldol Reaction. Tetrahedon Letters, 45(32), 6113-6116. 

Carbons and Carbon Supported Catalysts in Hydroprocessing 2 Chiral Sulfur Ligands Asymmetric Catalysis... 

Asymmetric catalysis provides access to several synthetically important compounds, and immobilized catalysts together with solid-supported chiral ligands have been equally instrumental. Chiral ligands immobilized on a solid support provide the advantage of being rapidly removable post-reaction while retaining their activity for further applications [139]. 

Bisphosphinamidites which are supported by an axially chiral framework are another important class of ligands. Although reported as early as 1980 [50], no reports on the use of binaphthyl-based bisphosphinamidite in asymmetric catalysis were published during the decade thereafter. As described above, the selectivity and substrate generality in these early attempts were very limited in scope. In 1998, we unveiled that by partially hydrogenating BINAM to H8-BINAM and... 

The Lectka group also reported an exciting development in this organocatalytic synthesis of /I-lactams - application of the concept of column asymmetric catalysis [50, 51]. This concept is based, e.g., on two jacketed columns linked together (Scheme 5.32) [50]. The top column is packed with the polymer-supported dehy-drohalogenation agent BEMP, which produces the desired ketenes, in high purity, from acid chlorides. In addition to this in-situ-formed pure ketene, an imine is... 

A new solid-support strategy - the sequential column asymmetric catalysis - has been developed for the synthesis of enantiopure p-lactams <02CEJ4115>. In this strategy, reagents and catalysts are attached to a solid-phase support and loaded onto sequentially-linked colums. The substrates are present in the liquid phase that flows through the column. As a substrate encounters each successive column, it grows in complexity. 

Canali, L., Sherrington, D. C. Utilization of homogeneous and supported chiral metal(salen) complexes in asymmetric catalysis. Chem. Soc. Rev. 1999, 28, 85-93. 

The observed activation of allyltrihalosilanes with fluoride ion and DMF and the proposition that these agents are bound to the silicon in the stereochemistry-determining transition structures clearly suggested the use of chiral Lewis bases for asymmetric catalysis. The use of chiral Lewis bases as promoters for the asymmetric allylation and 2-butenylation of aldehydes was first demonstrated by Denmark in 1994 (Scheme 10-31) [55]. In these reactions, the use of a chiral phos-phoramide promoter 74 provides the homoallylic alcohols in high yield, albeit modest enantioselectivity. For example, the ( )-71 and benzaldehyde affords the anti homoallylic alcohol 75 (98/2 antUsyn) in 66% ee. The sense of relative stereoinduction clearly supports the intermediacy of a hexacoordinate silicon species. The stereochemical outcome at the hydroxy center is also consistent with a cyclic transition structure. 

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