Alumina Beckmann rearrangement

Keywords aldoxime, p-toluenesulfonyl chloride, pyridine, alumina, Beckmann rearrangement, microwave irradiation, nitrile... 

Rare-earth exchanged [Ce ", La ", Sm"" and RE (RE = La/Ce/Pr/Nd)] Na-Y zeolites, K-10 montmorillonite clay and amorphous silica-alumina have also been employed as solid acid catalysts for the vapour-phase Beckmann rearrangement of salicylaldoxime 245 to benzoxazole 248 (equation 74) and of cinnamaldoxime to isoquinoline . Under appropriate reaction conditions on zeolites, salicyl aldoxime 245 undergoes E-Z isomerization followed by Beckmann rearrangement and leads to the formation of benzoxazole 248 as the major product. Fragmentation product 247 and primary amide 246 are formed as minor compounds. When catalysts with both Br0nsted and Lewis acidity were used, a correlation between the amount of Br0nsted acid sites and benzoxazole 248 yields was observed. 

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). 

Allied Chemical recently proposed a simplified technique, producing caprolactam from cyclohexanone, ammonia and oxygen in a single step, in the vapor phase, on a sffica or alumina-based catalyst However, the drawback of this process resides in the fact that only half of the oxime is converted in situ to caprolactam. This makes it necessary to resort to the Beckmann rearrangement For a 50 per cent conversion of cyclohexanone, the molar selectivity of oxime and caprolactam is 68 per cent Although this method considerably reduces the production of ammonium sulfate, the yields are still too low for it to appear to be more economical than the foregoing routes. 

Aluminas modified by the addition of Cl , P04 , SO/ , Na, and B2O3 were used for the Beckmann rearrangement of cyclohexanone oxime [6]. Among the aluminas the B203-modified alumina was the best and that modified with Na the least suitable. B2O3 coupled with hydroxyapatite, Caio(P04)6(OH)2, was more selective than B2O3-AI2O3 and the enhanced selectivity was ascribed to the basicity of hydroxyapatite [7]. 

ITQ-2 zeolite prepared by delamination of MCM-22 precursor, is formed by disordered individual sheets of crystalline zeolitic layers in where the Bronsted acid sites are of zeolitic nature and the vast majority of them aecessible to large molecules. The delaminated zeolite combines the acid characteristic of microporous zeolites with accessibility of the sites of mesoporous Al/MCM-41 and amorphous silica-alumina. The superior catalytic performance of delaminated zeolites compared to conventional zeolites and Al/MCM- 1 is examplified for reactions involving large reactant molecules, namely the preparation of dimethyl acetals, the Beckmann rearrangement of bulky cycloalkanone oximes and hydroxylation of aromatics. 

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. ... 

Salicylaldoximes 38 and 40 underwent isomerization followed by Beckmann rearrangement at 200 °C in the presence of K-10 montmorillonite clay and silica-alumina to afford o-hydroxybenzamide 39 and benzoxazole 41, respectively. ... 

Cinnamaldoxime 65 in the presence of different H-zeolites, K-10 montmorillonite clay, amorphous SiOT-AhOa and y-alumina underwent the Beckmann rearrangement via the migration of the awft-styiyl moiety to electron-deficient nitrogen followed by an intramolecular cyclization to afford the isoquinoline 66 as the major product. Cinnamonitrile 67 and cinnamaldehyde were obtained as minor products. 

Fomi, L., Fomasari, G., Tosi, C., Trifirb, F., Vaccari, A., Dumeignil F., and Grimblot, J. Non-conventional sol-gel synthesis for the production of boron-alumina catalyst applied to the vapour phase Beckmann rearrangement. Appl. Catal. A Gen. 2003, 248, 47-57. 

Hosseini-Sarvari M, Sharghi H (2006) Alumina sulfuric acid mediated solvent-free and one-step Beckmann rearrangement of ketones and aldehydes and a useful reagent for synthesis of keto- and ald-oximes. J Chem Res 3 205-208... 

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