NanoSelect Precious Metal Catalysts and their Use in Asymmetric Heterogeneous Catalysis

We studied the surface modification of supported colloidal precious metal catalysts. Chiral compounds derived from cinchona alkaloids and prolinol were synthesized and used as stabilizers/reductants to yield Pd and Pt colloidal nanoparticles. The new Pd catalysts were found to be highly active and selective catalysts for the semihydrogenation of 3-hexyn-1-ol to cis-3-hexen-1-ol. The stabilizers affected the activity of the catalyst but not the selectivity. The catalysts were also evaluated in the asymmetric hydrogenation of methyl pyruvate and isophorone. No enantioselectivity was observed, which indicated that surface modification by the stabilizer did not induce chirality in the substrate. Achiral supported Pd and Pt colloidal catalysts were modified with cinchonidine. The modified Pt catalysts demonstrated a high activity for the hydrogenation of methyl pyruvate and a modest enantioselectivity of 47%, which indicated that the chiral induction of supported colloidal catalysts is possible by modifying the catalyst surface with a chiral reagent.