Highly Efficient Asymmetric Conjugate Hydrocyanation of Aromatic Enones by an Anionic Chiral Phosphate Catalyst

Chiral keto nitriles (-cyano ketones) have been prepared by a facile and efficient asymmetric conjugate hydrocyanation of poorly active chalcone-type enones with benzophenone cyanohydrin. Using in situ generated 5-10 mol-% of sodium (S)-6,6-di(1-adamantyl)-1,1-binaphthyl-2,2-diyl phosphate as catalyst and 5-10 mol-% of 2-tert-butylphenol as an additive, high yields and excellent enantioselectivities were obtained within 2 h in toluene at 80 degrees C. The development of catalysts, optimization of the reaction parameters, and substrate scope are reported. On the basis of the experimental results, HCN is shown to be the real cyanide source and a mechanism is proposed to explain the origin of the enantioselectivity with the chiral-anion-modified nucleophile HCN.