Ketones solvent-free Beckmann rearrangement

The direct conversion of ketones 1 to secondary amides 3 from a solvent-free Beckmann rearrangement was accomplished by heating the ketones with hydroxylamine hy(frochloride and anhydrous oxalic acid at 100 °C for 4-12... 

The quest for a solvent-free deprotection procedure has led to the use of relatively benign reagent, ammonium persulfate on silica, for regeneration of carbonyl compounds (Scheme 6.10) [48]. Neat oximes are simply mixed with solid supported reagent and the contents are irradiated in a MW oven to regenerate free aldehydes or ketones in a process that is applicable to both, aldoximes and ketoximes. The critical role of surface needs to be emphasized since the same reagent supported on clay surface delivers predominantly the Beckmann rearrangement products, the amides [49]. 

Under solvent-free conditions, one-step Beckmann rearrangement of a variety of ketones and aldehydes proceeded in the presence of alumina sulfuric acid 285 (equation 93). Good selectivities were also obtained in the rearrangement of aldoximes to primary amides using zinc oxide as catalyst " (equation 93). 

Sharghi, H., Hosseini, M. Solvent-free and one-step Beckmann rearrangement of ketones and aldehydes by zinc oxide. Synthesis 2002, 1057-1060. 

Chandrasekhar, S., Gopaiaiah, K. Ketones to amides via a formal Beckmann rearrangement in one pot a solvent-free reaction promoted by anhydrous oxalic acid. Possible analogy with the Schmidt reaction. Tetrahedron Lett. 2003,44, 7437-7439. 

The solvent-free one step Beckmann rearrangement of ketones 1 and aldehydes in the presence of zinc oxide afforded the corresponding amides 3 (R = alkyl, aryl, cycloalkyl = H, cycloalky 1). Symmetrical ketones furnished the amides in good to excellent yields. In the case of unsymmetrical ketones the reaction was selective and one of the two possible amides was formed. Aromatic and aliphatic aldehydes were converted to the corresponding primary amides. 

Alumina sulfuric acid (ASA) was found to be an effective catalyst for the solvent-free one pot Beckmann rearrangement of several alkyl and aryl aldehydes and ketones 1. It has been reported that the electron rich aldehydes and ketones require shorter reaction times than the electron poor aldehydes. Cyclic ketones require longer reaction time than the aryl ketones ascribable to the steric factors. ... 

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