Colloidal system based on Pd(Acac)₂–chiral stabilizer-H₂ in the enantioselective hydrogenation of <i>N</i>-acetyl-α-amidocinminamic acid

Abstract

It has been shown that the colloidal system Pd(Acac)2–mod–H2, where mod are chiral stabilizers of molecular (8S,9R)-cinhonidine, (-)-Сin, and ionic type (-)-Cin*HCl and (-)- Cin*2HCl, exhibits catalytic activity in the asymmetric hydrogenation of N-acetyl-α-amidocinnamic acid (AACA) at room temperature and a H2 pressure of 5 atm. In the presence of protonated forms of cinchonidine, the esterification reaction of the product N-acetylphenylalanine (N-APha) was observed. The excess of the R-(-)-enantiomer of N-acetylphenylalanine reaches 78% on the Pd(Acac)2–(-)-Сin–H2 system at the ratio (-)-Сin/Pd = 1.5, while the protonated forms of the quinine alkaloid as modifiers of catalytic systems show less efficiency with respect to chiral induction. Using XRD and HR-TEM, the formation of palladium nanoparticles with average size 5.3 ± 0.8 nm and 4.2 ± 0.5 nm, respectively, was established for the systems Pd(Acac)2–(-)-Cin–H2 and Pd(Acac)2–(-) -Сin *HCl–H2.