Chiral Polymer Stabilized Bimetallic Nanocatalysts for Asymmetric Oxidations

Key words

asymmetric catalysis - oxidation - palladium catalysis - gold catalysis - copper catalysis - bimetallic catalyst

Significance

A 3:1 Pd/Au bimetallic nanocatalyst stabilized by the chiral substituted poly(N-vinylpyrrolidinone) 1, prepared according to eq. 1, catalyzed the selective oxidation of 1,2- and 1,3-cyclic diols (eq. 2; 15 examples), and the dihydroxylation of alkenes under oxygen in water (eq. 3; 7 examples, to afford the corresponding chiral products in high yields and high enantiomeric excesses. Cu/Au (3:1)–1, prepared by a similar method, catalyzed the C–H oxidation of cyclo­alkanes with H₂O₂ to give the corresponding ketones with high enantioselectivity (eq. 4).

Comment

In the oxidation of (±)-cyclohexane-1,3-diol, the catalyst was recovered and reused twice with a sharp decrease in its catalytic activity (first run: 49% yield; 99% ee; second run: 39% yield, 99% ee; third run: 18% yield, 98% ee).