Hexagonally packed Pd nanoarray catalyst was prepared via the "two solvents" strategy with mesoporous molecular sieve SBA-15 as a hard template. By using S-proline as the chiral modifier, the catalyst exhibited superior activity and selectivity in liquid-phase hydrogenation of acetophenone to R-(+)-1-phenylethanol with up to 100% chemoselectivity and 28.8% enantiomeric excess. The presence of S-proline and the regular hexagonal mesostructure of the Pd nanoarray catalyst are crucial for its superior catalytic performance. IntroductionLiquid-phase hydrogenation of acetophenone is a model reaction chosen by many researchers for heterogeneous enantioselective catalysis studies. First, it is of extensive industrial relevance because its product (chiral 1-phenylethanol) is used widely in the pharmaceutical and perfume industries. 1,2 Second, it is a good example of a multistep reaction. It involves a sequence of competitive parallel and consecutive reactions, and both the unsaturated aromatic ring as well as the carbonyl group in the acetophenone can be reduced. 3-5 Third, it is a good probe reaction among the heterogeneous enantioselective catalytic reactions, which have obvious advantages in green chemistry. 5 For nonactivated prochiral ketones such as acetophenone, it remains a great challenge to achieve high enantioselectivity to corresponding chiral alcohols by heterogeneous catalysis. 6-8 The best result reported so far for acetophenone was 22.5% enantiomeric excess (ee) at 77.9% conversion. 8 Thus, it is highly desirable to explore new categories of catalysts with improved low-temperature activity and enantioselectivity for this reaction.As is known, the morphology and structure of the nanoscaled materials have important effects on the performances of materials in practical applications. When the morphologies of the nanoscale materials are transformed from common spherical nanoparticles to one-dimensional nanorods, 9 two-dimensional ultrathin films, 10 or three-dimensional nanoarrays, 11,12 these nanostructured materials usually exhibit unique properties in mesoscopic physics, electronics, semiconductor fabrication, and catalysis. Although enantioselective hydrogenation over metal nanoparticles including supported metal catalysts has been practiced extensively, 6-8 the work is lacking over nanostructured metals.In this paper, we report on the enantioselective hydrogenation of acetophenone in the presence of S-proline over an ordered

An effective and facile strategy, ultrasound-assisted reductant-infiltration, was realized in the preparation of hexagonally packed Ni–B amorphous alloy nanoarray, which exhibits superior catalytic properties to their nanoparticle counterpart in selective hydrogenation of acetophenone to 1-phenylethanol.

No abstract

No abstract