P-Modular homochiral bis(phosphanes) with 1,2-disubstituted cyclopentane backbones in asymmetric hydrogenation

The review surveys synthetic aspects of a class of bidentate phosphanes based on the trans-1,2-disubstituted cyclopentane framework and the application of such ligands in transition-metal-catalyzed enantioselective hydrogenation. In particular, we address the preparative potential of the isomerically pure multi-purpose P-H and P-Cl reagents (R,R)and (S,S)-C5H8(PX2)(2) (X = H, Cl), which can serve to construct a family of optically active bis(phosphanes) with structural components ("modules") that are easily and systematically interchanged. The so-designed chelate ligands allow access to rhodium catalysts with stereo discriminating properties, depending on parameters such as (i) presence of P-substituents that are equal or pairwise different in steric demand, (ii) spatial orientation of such substituents as defined by the endo- and exo-chelate P-C-C-P and P-Rh-P-C torsion angles, and (iii) existence of C- and P-chirogenic stereoelements in matched (or mismatched) combination. (C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.