Nanocrystalline MgO catalysts for the Henry reaction of benzaldehyde and nitromethane

Abstract

Nanocrystalline MgO particles of about 3 nm were examined as catalysts for the Henry reaction between benzaldehyde and nitromethane at 273 K. The surface area of nanocrystalline MgO was greater than 600 m 2 g −1 except after thermal treatment in N 2 at 823 K, which reduced the surface area to 359 m 2 g −1. The areal rate of the Henry reaction over nanocrystalline MgO at 273 K was 0.015 ± 0.002 μmol m −2 s −1 and was independent of pretreatment temperature over the range of 523–823 K. Addition of (S)-BINOL to nanocrystalline MgO has been reported previously to favor the production of one enantiomer of the Henry reaction. In the current work, negligible enantiomeric excess was observed on (S)-BINOL-modified nanocrystalline MgO catalysts, regardless of the source of nanocrystalline MgO, the MgO activation temperature, the reaction temperature, the sequence of reactant addition or the loading of (S)-BINOL. Adsorption of l-proline onto nanocrystalline MgO catalyst induced a small enantiomeric excess in the Henry reaction products, but the catalytic activity of the catalyst was low.