Dehydration of aldoximes over H-zeolites: A convenient and highly atom economic method for the preparation of nitriles

In this paper, an application of solid-acid catalysts in the dehydration/Beckmann rearrangement of aldoximes producing nitriles and amides is described. Vapor-phase dehydration/Beckmann rearrangement of benzaldoxime and 4-methoxybenzaldoxime were carried out over different protonated zeolites, K-10 montmorillonite clay and γ-alumina at 473 K. Benzonitrile was obtained in (near) quantitative yields by the dehydration of benzaldoxime over H-Beta, H-MOR, H-ZSM-5 and H-Y zeolites. 4-Methoxybenzaldoxime produced both Beckmann rearrangement (4-methoxyphenylformamide) and dehydration products (4-methoxybenzonitrile) in high overall yields. The difference in behavior of the aldoximes is explained in terms of electronic effects. The optimal protocol allows nitriles to be synthesized in excellent yields through the dehydration of aldoximes.