Liquid-phase Beckmann rearrangement

Phosphorous pentoxide effectively catalyzed the homogeneous liquid phase Beckmann rearrangement of cyclohexanone oxime 5 to lactam 6 in DMF. The catalytic activity was significantly increased by addition of trifluoromethanesulfonic acid as a co-catalyst. This protocol was fiuther extended to the rearrangement of acetone, acetophenone and cyclopentanone oxime to the corresponding amides. 

Chung et al reported the liquid phase Beckmann rearrangement of 4-hydroxyacetophenone oxime using zeolite H p catalyst. The reaction was found to be an example of active solvent participation. A solvent having higher dielectric constant or more polar nature is preferred in the rearrangement step. 

The liquid phase Beckmann rearrangement of cyclohexanone oxime 5 in the presence of a series of mesoporous molecular sieves with various Si02/Al203 ratios has been reported. The surface silanol groups ineffectively catalyzed the rearrangement, whereas the acid sites generated by incorporation of aluminium improved the activity and selectivity to lactam 6. 

The effect of various organic additives on the catalj ic performance of zeolites and Al-containing MCM-41 in the liquid phase Beckmann rearrangement of cyclohexanone oxime 5 was investigated at 130 °C. Over USY zeolite with a large amount of EFAL, the lactam yield was improved by adding ethanol, dimethyl sulfoxide, ammonia, diethylamine or pyridine to the... 

Paracetamol (a widely used over-the-counter analgesic and antipyretic) was synthesized by the environmentally benign liquid-phase Beckmann rearrangement of 4-hydroxyacetophenone oxime over Al-MCM-41 modified with HjPO [158]. The conversion of 4-hydroxyacetophenone oxime to paracetamol increased with the HjPO loading in the catalysts with the maximum at 30wt.%. 

Microwave radiation promoted liquid-phase Beckmann rearrangement of cyclohexanone oxime was also carried out by Cheng et al. (2011) for preparing 8-caprolactam over P2O5 catalyst. 

The control of selectivity in the vapor phase Beckmann rearrangement seems to be difficult this can be ascribed to the drastic experimental conditions required. Liquid-phase reactions over heterogeneous catalysts have been investigated. The Beckmann rearrangement of cyclohexanone oxime in the liquid phase was performed under reflux conditions in a variety of solvents [44]. When chlorobenzene was used solvent conversion and selectivity increased with temperature up to 405 K. From plots of conversion against time it was concluded that catalyst deactivation under liquid-phase conditions is small, in contrast with the rapid deactivation observed when the reaction was conducted in the vapor phase. 

Catalytic Properties. Mc30+BF4 has been used as a catalyst for the polymerization of cyclic sulfides and in the polymerization of THF to macrocyclic ethers. A valuable modem application is the catalytic Beckmann rearrangement of oximes in homogeneous liquid phase,the active species being a formamidinium salt. 

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