Organogermanium compounds anchored on Pt/SiO2 as chiral catalysts for the enantioselective hydrogenation of 3,4-hexanedione

Abstract

This work reports the synthesis of PtGe chiral catalysts using organogermanium compounds containing (−)-menthyl groups as substituents. Chiral inducers were carefully synthesized and characterized in order to obtain optically pure compounds.PtGe catalysts were prepared through a controlled surface reaction between the supported transition metal and the organometallic compound. This technique leads to reproducible and well defined phases. The catalysts were employed in liquid phase enantioselective hydrogenation of 3,4-hexanedione.The obtained systems were active (95% conversion) and enantioselective (enantiomeric excess of 25% for 4-hydroxy-3-hexanone and 10% for 3,4-hexanediol). These results are very encouraging as they are comparable to those obtained previously by our group with similar PtSn catalysts and those reported for classical Pt/cinchonidine systems.The organogermanium compounds presented here have advantages over their tin analogs, mainly due to their greater stability and nontoxicity.