摘要：

The new ligand (R)-1-[(S)-2-(diphenylphosphino)ferrocenyl]ethyldicyclohexylphosphine ((R)-(S)-3a) was prepared in two steps from the commercially available N,N-dimethyl-(R)-1-ferrocenylethylamine via N,N-dimethyl(R)-1-[(S)-2-(diphenylphosphino)ferrocenyl]ethylamine ((R)-(S)-1) in good yields. The crucial second step, i.e., the substitution of the dimethylamino group by the dicyclohexylphosphino fragment, was achieved in 88% yield under complete retention of configuration in acetic acid solvent, using dicyclohexylphosphine as a reagent. This methodology constitutes an easy access to a class of chiral chelating diphosphines, where the two ligating moieties can be varied independently from one another, thus allowing the study of both the steric and electronic influence of the ligands on stereoselectivity. Compound 3a was used in Rh-catalyzed asymmetric hydrogenation and hydroboration as well as in Pd-catalyzed allylic alkylation reactions giving high enantioselectivities (up to 99%).

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