Rh phosphoramidite

Hoen, R., Boogers, J.A.E., Bemsmann, H., Minnaard, A.J., Meetsma, A., Tiemersma-Wegman, T.D., de Vries, A.H.M., de Vries, J.G. and Eeringa, B.L. Achiral Ligands Dramatically Enhance Rate and Enantioselectivity in the Rh/Phosphoramidite-catalyzed Hydrogenation of ot, -Disubstituted Unsaturated Acids. Angew. Chem. Int. Ed. 2005, 44, 4209-4212. 

Scheme 6.15 The Rh/phosphoramidite-catalyzed addition of arylboronic acids to A/,A/-dimethylsulfamoyl-protected aldimines developed by Feringa s group [20] and their putative mechanism.

Generally, alkoxides are problematic nucleophiles because of their basic character. In metal-catalyzed allylic substitutions, superior results were obtained with Zn-alkoxides (achiral Ir-catalysts) [66] and Cu-alkoxides (achiral Rh-catalyst with chiral substrates) [67]. Shu and Hartwig developed aUyUc substitutions with alkoxides using Ir/phosphoramidite catalysts [68] these authors used catalysts obtained from [Ir(COD)Cl]2 and LI or L3 without explicit base activation [procedure (a) in Section 9.2.4.2) (Scheme 9.34). 

Chiral monodentate phosphites and phosphoramidites are also effective ligands for Rh-catalyzed asymmetric hydrogenation of enamide substrates. As seen in the structure of MonoPhos illustrated in Figure 1.2, combination of the mod-ihed BINOF backbone and the amine part gives a structural variety to this type of ligand. Combinatorial methods are effective for optimization of the chiral structures.Elucidation of the hydrogenation mechanism catalyzed by the MonoPhos-Rh complex is in progress." ... 

Scheme 9.11 Rh catalyzed asymmetric hydrogenation of ortho substituted arylenamides with a triphosphorus bidentate phosphine phosphoramidite ligand 49.

Hoffman and Carreira [31] reported a Rh-catalyzed asymmetric intramolecular hydroacylation of pent-4-enal substrates, providing P-substituted cyclopentanones in good yield and excellent selectivity by using chiral spiro phosphoramidite-alkene ligand (R)-29 (Scheme 29). 

Reek et al.73 developed a new bicarbazolediol-74 (BICOL)-based, chiral monodentate phosphoramidite ligand, in which the Ai-sites in the bicarbazole skeleton permitted the easy introduction of metal centers. As a model reaction, the Rh-catalyzed asymmetric hydrogenation of methyl 2-acetamidocinnamate was evaluated. Using a ligand to rhodium ratio of 2.2, the enantioselectivity induced by the rhodium complex (Figure 10.7) was 93% at full conversion,... 

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