Selective oxidation of benzylic alcohols to aldehydes with metal nitrate reagents catalyzed by BEA zeolites or clays

The oxidation of benzylic alcohols to benzaldehydes by bismuth( III) nitrate was investigated in the presence of various acidic aluminosilicates. The solid acid was used either as support for the nitrate or simply added in the reaction medium as a catalyst of the decomposition of Bi nitrate. The reactivity of the clay-supported reagent is controlled by the dispersion of the nitrate. A high dispersion requires both high surface area and high acidity of the support. There is a good correlation in the oxidation of benzyl alcohol as the model reaction between the structure and the chemical activity of the two main groups of supports (K10 and KSF vs. KSF/0 and KP10). In supported reagents made with zeolitic materials such as ZSM-5 or BEA the pores are blocked by the salt, therefore the solvent used for their preparation could not be eliminated completely from the solid. Zeolites cannot, therefore, be used to prepare conventional supported reagents, but work remarkably well, especially BEA, as a catalyst for the oxidation of benzyl alcohol or m-phenoxybenzyl alcohol by bismuth nitrate. Similar oxidation results were obtained with iron( III) nitrate.