Solid catalysts for the production of fine chemicals: the use of ALPON and hydrotalcite base catalysts for the synthesis of arylsulfones

Abstract

α#x2010;phenylsulfonylcinnamononitrile and derivatives as well as α-phenylsulfonylchalcone have been obtained by condensation of phenylsulfonylacetonitrile and phenylsulfonylacetophenone with benzaldehyde and 4-substituted benzaldehydes, using solid base catalysts with different basic strengths. Cs-exchanged X zeolite showed low activity for the above reactions, while high-surface-area MgO and MgO–Al2O3 mixed oxides derived from hydrotalcite were active and selective catalysts. An optimum basicity was observed with MgO–Al2O3 with the atomic ratio Al/(Al+Mg) between 0 and 0.20, showing the increase in basicity when introducing Al in the MgO structure. Nitridation of a high-surface-area aluminophosphate gives active and selective catalysts for the above reactions. The activity per unit surface area for the less demanding reaction between sulfonylacetonitrile and benzaldehyde is directly proportional to the level of nitridation. However, formation of α-phenylsulfonylchalcone, which is a more demanding reaction, does not increase linearly but goes through a maximum with the nitrogen content of the solid, showing the heterogeneity of active sites on ALPONs and the decrease in the activity coefficient of the basic sites when the density of N atoms increases.