Palladium and a simple chiral amine are used as co‐catalysts for the enantioselective conjugate addition of aryl boronic acids to α,β‐unsaturated aldehydes (see scheme). The synthetic utility of this co‐catalyzed reaction was demonstrated in the short total syntheses of (R)‐(−)‐curcumene and 4‐aryl‐2‐ones.
Palladium(II)-catalyzed 1,4-addition of arylboronic acids to β-arylenals for enantioselective syntheses of 3,3-diarylalkanals: a short synthesis of (+)-(R)-CDP 840
1,4-Addition of arylboronic acid to trans-beta-arylenals proceeded smoothly in acetone-water (10/1) at 10-25 degrees C in the presence of [Pd(S,S-chirapbos)(PhCN)(2)](SbF6)(2) (0.5 mol %), AgX (X = BF4, SbF6, 10 mol %) and aqueous 42% HBF4 to afford optically active 3,3-diarylalkanals with high enantioselectivities in a range of 86-97% ee. The protocol provided a method for short-step synthesis of optically active (+)-(R)-CDP 840. (c) 2007 Published by Elsevier Ltd.
Heterogeneous Rh and Rh/Ag bimetallic nanoparticle catalysts immobilized on chiral polymers
chiral Rh and Rh/Ag bimetallic nanoparticle catalysts consisting of polystyrene-based polymers with chiral diene moieties. The catalysts enable high-to-excellent yields and enantioselectivities to be obtained in asymmetric 1,4-addition reactions of arylboronic acids with α,β-unsaturated carbonyl compounds such as ketones, esters, and amides, and in other asymmetric reactions. The catalysts could be readily