trans‐Chelating Chiral Diphosphane Ligands Bearing Flexible P‐Alkyl Substituents (AlkylTRAPs) and their Application to the Rhodium‐Catalyzed Asymmetric Hydrosilylation of Simple Ketones

Not bulky substituents but flexible alkyl groups led to the hitherto highest enantioselectivities for the asymmetric hydrosilylation of simple ketones catalyzed by diphosphanerhodium complexes. The reduction of acetophenone in the presence of the diphosphane ligand 1, R = nPr,nBu, gave 92% ee, whereas with 1, R = Ph and R = iPr, ee values of only 15% and 1%, respectively, were achieved.