ELECTRONIC EFFECTS IN ASYMMETRIC CATALYSIS - ENANTIOSELECTIVE CARBON-CARBON BOND-FORMING PROCESSES

Transition metal complexes of 1,2-diol phosphinites and phosphites derived from readily available sugars catalyze a variety of asymmetric reactions of prochiral olefins including the asymmetric Makovnikov addition of HCN to vinyl arenes. The enantioselectivity of this reaction can be optimized by steric and electronic tuning of a readily available carbohydrate-derived ligand system. Both R and S enantiomers of a prototypical 2-arylpropionitrile, a precursor to widely used 2-arylpropionic acids, can thus be synthesized over 90 % enantiomeric excess at or below room temperature. An unusual electronic effect on the selectivity of this reaction may have wider implications for other related reactions.