Abstract

This work reports the efficient synthesis of enantio-enriched alcohols by asymmetric hydrogenation of 1-phenyl-1,2-propanedione using chiral nanoparticles (NPs) supported on SiO2. The chiral catalysts were synthesized by reducing the [Rh(mu - OCH3)(C8H12)](2) precursor under H-2 in the presence of P-chiral ligands as stabilizers and SiO2 as support. Synthesis of catalysts in mild conditions was performed from labile organometallic precursor and chiral ligands provided small and well defined chiral nanoparticles (<= 3 nm). The catalysts were characterized by XPS, HR-TEM, EDS, XRD and N-2 physisorption isotherm. The physical chemical properties of the materials were correlated with the catalytic results obtained in the asymmetric hydrogenation of 1-phenyl-1,2-propanedione. In 1-phenyl-1,2-propanedione hydrogenation the best results using chiral catalysts allowed 98% conversion and enantiomeric excess of 67% to (R)-1-hydroxy-1-phenyl-propan-2-one and 59% for (R)-2-hydroxy-1-phenylpropan-1-one. Catalyst recycling studies revealed that chiral nanoparticles immobilized on SiO2 are stable. These catalysts do not need extra amount of chiral modifier or inducer added in situ and could be reused without loss of enantioselectivity.