Summary

Oximes can be catalytically transformed to amides by different inorganic solid materials following molecular rearrangement processes (Beckmann reactions). These reactions take place in “dry media” conditions, i.e. without any solvent, at relative low temperature (100°-160°C). The yield and the selectivity depend on the nature of the solids (structure, composition, texture, etc) differing, in some cases substantially, with respect to that obtained in the classical homogeneous conditions. Thus acidic solids, as aluminosilicates with layer structure (A1³⁺-montmorillonite), proton-exchanged zeolite (HNaY) or amorphous silica-alumina materials, as well as sulphoarylcompounds (sulphopolystyrene and sulphoarylderivates of silica), have been employed as catalysts, showing good conversion rates and selectivities to the amide formation, in particular after elimination of adsorbed water molecules. The competitive reaction is the hydrolysis of the oxime to carbonyl compounds, which is enhanced by the presence of water at the surface of the solids, in particular when these materials are of less acidic character (silica, alumina, Na-exchanged zeolites and montmorillonites).