[摘要]：A new class of C2-sym. chiral bidentate phosphonite ligands was synthesized in moderate to good yields from readily available starting materials. Application of these air-stable chiral phosphonites in the Rh1-catalyzed asym. hydroformylation of styrene derivs., vinyl acetate, and allyl cyanide afforded the corresponding chiral aldehydes with high regio- and enantioselectivities under mild reaction conditions. The modular nature of the ligands allows fine-tuning of the selectivities through judicious modifications of the substituents on the ligand backbone. X-ray structural anal. of the catalyst precursor suggested that the steric hindrance caused by the protruding remote substituents of the ligands into the vicinity of the metal center might be an important factor for the enantio-control of the reaction, whereas the sense of asym. induction can be rationalized from a trigonal-bipyramidal transition state diagram.
