Hierarchically structured monolithic silicalite-1 consisting of crystallized nanoparticles and its performance in the Beckmann rearrangement of cyclohexanone oxime

In this study, we present a synthetic pathway for the fabrication of self-supporting zeolite monoliths consisting of crystallized nanoparticles. A resorcinol-formaldehyde-based organic aerogel is used as a template, and silicalite-1 is used as the zeolite example. The silicalite-1 monoliths obtained consist of individual well-defined zeolite nanocrystals with sizes of 30-40 nm. The monoliths exhibit a high mechanical stability and have hierarchical porosity, with micropores within the zeolite particles, a mesopore system formed by the packing of the nanoparticles, and a macropore system on the monolith level. Such monolithic zeolites show high selectivity typically above 80% to epsilon-caprolactam combined with a high rate of reaction of 0.46 g(caprolactame)/(g(catalyst).h) in the Beckmann rearrangement of cyclohexanone oxime.     

Beckmann rearrangement of 5-arylfurfural oximes

The acylation of 5-arylfurfural oximes with acetic anhydride in the presence of pyridine is accompanied by Beckmann rearrangement and gives 5-arylpyromucic acid acetamides. Under the same conditions, 5-arylpyromucic acid nitriles are obtained from aldoxime anti-acetates.     

Abnormal Beckmann rearrangement in 23-hydroxyiminodiosgenin acetate

A new transformation of the spiroketal side chain of diosgenin is reported: treatment of 23-hydroxyiminodiosgenin acetate with phosphorous oxychloride in pyridine produced an abnormal Beckmann rearrangement directing to the cleavage of the spiroketal side chain and generating 23,24-bisnorchol-5-enic skeletons: (2′R)-3′-cyano-2′-methylpropyl 3β-acetoxy-16α-chloro-23,24-bisnorchol-5-en-22-oate as the main product, and small amounts of (2′R)-3′-cyano-2′-methylpropyl 3β-acetoxy-16β-hydroxy-23,24-bisnorchol-5-en-22-oate and vespertilin acetate.     

Highly efficient Beckmann rearrangement and dehydration of oximes

Under mild conditions, Beckmann rearrangement of a variety of ketoximes could proceed in the presence of chlorosulfonic acid using toluene as a solvent with excellent conversion and selectivity. This procedure could also be applied in the dehydration of aldoximes for obtaining the corresponding nitriles.     

Dehydrative Beckmann rearrangement and the following cascade reactions

The Beckmann rearrangement has been predominantly studied for the synthesis of amide and lactam.By strategically using the in situ generated Appel’s salt or Mitsunobu’s zwitterionic adduct as the dehydrating agent, a series of Beckmann rearrangement and following cascade reactions have been developed herein. The protocol allows the conversion of various ketoximes into amide, thioamide, tetrazole and imide products in modular procedures. The generality and tolerance of functionalities of this met...     

Silicalite-1空心球材料制备及其在Beckmann重排反应中催化应用研究

以碳微球作为硬模板、纳米Silicalite-1分子筛作为壳层,采用水热法合成了Silicalite-1空心球材料。采用XRD、SEM、FT-IR、N_2吸附、29Si M AS NM R、TG、XPS等技术对催化剂的物相、形貌和性能等进行表征,发现该空心材料具有较高的结晶度、发达的多级孔道结构和丰富的表面羟基。与传统方法制备的Silicalite-1分子筛催化剂相比,Silicalite-1空心材料在环己酮肟Beckmann重排反应中表现出优异的催化性能,使环己酮肟的转化率达99%、己内酰胺的选择性达94%,同时催化剂保持极佳的稳定性。研究表明,Silicalite-1空心材料中具有的大量巢式硅羟基和末端硅羟基是Beckmann重排反应的主要活性位,且可通过简单焙烧再生实现羟基活性位的完全恢复。     

Quantum-chemical modelling of proton transfer in the Beckmann rearrangement

A model of proton transfer in the Beckmann rearrangement was developed by density functional theory (DFT) for the example of acetaldoxime. It was concluded that the Beckmann rearrangement of acetaldoxime may consist of three stages: Transfer of a proton from the imine carbon atom to the nitrogen atom with the formation of an acetaldoxime cation; formation of an enolic imine by an intermolecular mechanism; formation of acetamide (the final product of the Beckmann rearrangement) also by an intermolecular mechanism. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 44, No. 3, pp. 144–147, May–June, 2008.     

Beckmann rearrangement of oximes under very mild conditions

A variety of ketoximes, easily prepared from the corresponding ketones, undergo the Beckmann rearrangement upon treatment with 2,4,6-trichloro[1,3,5]triazine in N,N-dimethylformamide at room temperature in excellent yields. This procedure can be applied to aldoximes for obtaining the corresponding nitriles.     

Beckmann rearrangement of 11-deoxo-glycyrrhetic acid 3-ketoxime

A-Homo-4-aza-3-oxo- and 3-cyano-3,4-seco-olean-4,12-diene derivatives of 11-deoxo-glycyrrhetic acid were synthesized by first- and second-order Beckmann rearrangement of 3-hydroxyiminoolean-12-en-30-oic acid methyl ester.     

Solvent effect on the kinetics of Beckmann rearrangement

The rate constants for the Beckmann rearrangement of cyclohexanone oxime p-toluenesulfonate in 11 solvents are satisfactorily described by a three-parameter linear correlation including polarizability, electrophilicity, and molar volume of the solvent. The first two factors favor the reaction, whereas increase of the solvent molar volume makes the reaction slower, presumably due to steric hindrances to solvation.     

Efficient Beckmann rearrangement and dehydration of oximes via phosphonate intermediates

Under mild conditions, conversion of a variety of ketoximes and aldoximes to their corresponding amides and nitriles proceeded in the presence of diethyl chlorophosphate with excellent yields.     

Concerning the Beckmann rearrangement of aryl heteryl ketoxime ions

The possible Beckmann rearrangement of aryl heteryl ketoxime ions has been investigated by studies on the 70 eV mass spectra, metastable ion spectra and collision induced dissociation spectra of pairs of isomeric ketoximes and corresponding amides. Aryl cycloalkyl ketoximes were also studied, and the molecular ions of these and the corresponding amides showed no evidence of interconversion. The introduction of the heterocyclic moieties made little change to this situation although some novel rearrangements were observed.     

Beckmann rearrangement of ketoximes to lactams by triphosphazene catalyst

Triphosphazene, 1,3,5-triazo-2,4,6-triphosphorine-2,2,4,4,6,6-chloride (TAPC), was found to be an efficient catalyst for the Beckmann rearrangement of cyclohexanone oxime and cyclododecanone oxime to epsilon-caprolactam and laurolactam, which are raw materials of nylon-6 and nylon-12, respectively.     

An improved procedure for the Beckmann rearrangement of cyclobutanones

γ-Lactams are important building blocks for the synthesis of biologically active molecules and can easily be accessed via Beckmann rearrangement of cyclobutanones. However, Beckmann fragmentation is often a competing reaction for these strained ketones. We found that performing the Beckmann rearrangement with Tamura’s reagent in the presence of aqueous HCl suppresses the undesired fragmentation reaction. This improved procedure was applied to a broad scope of substrates affording monocyclic, bicyclic, tricyclic or spirocyclic lactams.Our experimental results and DFT calculations suggest that the mechanism of the rearrangement probably involves a tetrahedral intermediate and doesn’t proceed via oxime fragmentation as in a classical Beckmann rearrangement.     

Syntheses of 2-arylated 1-benzazocines via Beckmann rearrangement

One-step and highly efficient syntheses of 2-aryl-1-benzazocines via Beckmann rearrangement of 5H-benzocyclohepten-5-one oxime mesylates in dry toluene was described, in which aryl Grignard reagents were used for the first time to induce Beckmann rearrangement directly without any additional protic agents. Iodotrimethylsilane was also employed to promote Beckmann rearrangement of the mesylates, followed by the treatment of the intermediate imidoyl iodide with phenylmagnesium bromide to complete the synthesis of benzazocines.     

Beckmann rearrangement of cyclohexanone oxime p-toluenesulfonate on acidic catalysts

The Beckmann rearrangement of cyclohexanone oxime p-toluenesulfonate has been studied using several catalysts. The reaction is catalyzed by weakly acidic sites and seems to occur by way of O-(p-toluenesulfonyl)--caprolactim.

---

- -, . - -(-)--.

     

An apparent syn Beckmann rearrangement of a stannyl ketoxime

Chloro(4-oximinopentyl)diphenyltin was shown to have the cyclic structure A: when this compound was treated with phosphorus pentachloride the product arising from exchange of groups which are syn to each other was obtained.     

Beckmann rearrangement in benzophenone oxime,a mass spectrometric study

The isomerization of benzophenone oxime to benzanilide, previously observed to take place in the ion source of a mass spectrometer and attributed to a Beckmann type rearrangement of the benzophenone oxime molecule ion, has been shown to occur by a thermal mechanism prior to ionization. Mass spectrometric evidence is supplemented by infrared spectrophotometric examination of solid samples and shows that in the solid state, at room temperature, benzophenone oxime has a lifetime of about 600 h.     

Cyanuric chloride as a mild and active Beckmann rearrangement catalyst

The first general organocatalytic Beckmann rearrangement of ketoximes into amides has been realized by the catalytic use of cyanuric chloride. Furthermore, acids such as HCl and ZnCl2 are effective as cocatalysts with cyanuric chloride. For example, azacyclotridecan-2-one, which is synthetically useful as a starting material for nylon-12, was prepared in quantitative yield by the Beckmann rearrangement of cyclododecanone oxime (100 mmol scale) catalyzed by cyanuric chloride (0.5 mol %) and ZnCl2 (1 mol %).