Study on the Application of Beckmann Rearrangement in the Synthesis of Amides from Oximes

In order to prepare amides under moderate and environment-friendly conditions using Beckmann rearrangement, we replaced traditional liquid-acid catalysts with Nafion perfluorinated sulphonic acid resins. We used diphenylketone oxime as the template substrate and carried out experimental studies to explore the optimal reaction conditions for Beckmann rearrangement. We studied the effects of reaction temperature, reaction time, catalyst dosage, and solvent type and volume on Beckmann rearrangement and established the following optimal reaction conditions: diphenylketone oxime (2 g), acetonitrile (solvent; 20 mL), Nafion (catalyst; 0.4 g), reaction temperature (70°C), and reaction time (4 h). Under these conditions, the degree of conversion of diphenylketone oxime was 36.32%, while benzanilide selectivity and yield were 44.06% and 16%, respectively. We also studied the adaptability of other substrates for Beckmann rearrangement at the optimal conditions and found that Nafion can catalyse both aromatic and aliphatic ketone oximes. Melting point, infrared, and 1H and 13C nuclear magnetic resonance analyses were conducted to characterise the obtained products. Reuse experiments of the catalyst showed that Nafion exhibited good recovery performance and hence is a green and promising catalyst.