Enantioselective hydrogenation of ethyl pyruvate over ionic exchange resins supported catalyts

NICOLÁS CARRARA; G. MENDOW; JUAN M. BADANO; DORIS POLETT RUIZ; CECILIA R. LEDERHOS; CAROLINA BETTI; M. JULIANA MACCARRONE; CARLOS VERA; MÓNICA E. QUIROGA

Congreso; 16th International Congress on Catalysis (ICC 16); 2016

The synthesis of optically active compounds is of scientific and industrial interest, asymmetric synthesis being themost efficient route for the production of pure enantiomers. In this kind of reactions, traces of a chiral modiffier caninduce the preferential formation of a enantiomer [1]. Enantioselective hydrogenations are of special interest,particularly in the pharmaceutical industry, because many products and intermediates are synthesized by this route.Traditional catalysts used in these reactions are based on noble metals and have high metal loading and demand a complex preparation. It is of interest to prepare improved new catalysts for these reactions. Catalysts based on ion exchange resins have many advantages, such as simple preparation procedures, easy metal complex anchoring, low solubility in common solvents and easy access due its high porous structure . In this work catalysts of Pd, Pt, Rh and Au supported on a styrene-divinylbenzene ion exchange resin were prepared. A screening of catalysts suitable for the enantioselective hydrogenation of ethyl pyruvate was made.  The effect of the metal loading, metal particle size and nature of the chiral modiffier on the enantioselectivity were also studied.The use of noble metal catalysts supported on ionic exchange resins for the enantioselective hydrogenation of ethylpyruvate was studied. High activity and selectivity values were obtained. Pt was the best active metal, followed by Pd,Au and Rh. The use of a Pt-Cinchonidine system produced (R)-ethyl lactate enantiomeric excess. Pt-Cinchonineyielded the unwanted (S) enantiomer. The reaction was found to be structure sensitive and the importance of the metalparticle size for the adsorption of the chiral modiffier was proved. Sintering of the metal particles during the nitritereduction reaction seemingly occurs with migration of the particles to the surface layers and a decrease of thedispersion. There exists an optimal particle size that maximizes the enantiomeric excess, corresponding to 24 hsintering treatment time in the current experiments