Catalytic Beckmann Rearrangements

A similar mechanism to the previous ones was proposed by Deng, Shi and coworkers for the bis(2-oxo-3-oxazolidinyl)phosphinic chloride (BOP-Cl, 269) catalytic Beckmann rearrangement (equation 82). Addition of the Lewis acid zinc chloride improved the catalyst performance and amides were synthesized in excellent yields (92-99%). 

A -Butylpyridinium tetrafluoroborate, containing dissolved phosphorus pentachloride, allows catalytic Beckmann rearrangement of cyclohexanone oxime giving e-caprolactam with good conversion and selectivity <2001TL403>. The same ionic liquid containing dissolved ytterbium(m) trifluoromethanesulfonate was used to perform Friedel-Crafts acylation of furan and thiophene <2005JIG398>. 

Lee, J. K., Kim, D.-C., Song, C. E., Lee, S.-g. Thermal behaviors of ionic liquids under microwave irradiation and their application on microwave-assisted catalytic Beckmann rearrangement of ketoximes. Synth. Commun. 2003, 33, 2301-2307. 

The catalytic Beckmann rearrangement of ketoxirne trimethylsilyl ethers can be achieved with SbCls-AgSbFg, affording the corresponding amides or lactams (Scheme 14.28) [68]. 

As a novel approach, non-catalytic Beckmann rearrangement was recently reported to occur near the critical temperature (647 K) in subcritical or supercritical water [66]. 

Harada, T., Ohno, T., Kobayashi, S., and Mukaiyama, T. 1991. The catalytic Friedel-Crafts acylation reaction and the catalytic Beckmann rearrangement promoted by gallium(Itl) or an antimony(V) cationic species. Synthesis 1216-1220. 

Peng J, Deng Y (2001) Catalytic Beckmann rearrangement of ketoximes in ionic Liquids. Tetrahedron Lett 42 403 05... 

Ren, R.X., Zueva, D.L. Ou, W. (2001). Formation of e-Caprolactam via Catalytic Beckmann Rearrangement Using P2O5 in Ionic Liquids, Tetrahedron Lett., 42, pp. 8441- 8443 Ross, J. Xiao, J. (2002) Friedel-Crafts Acylation Reactions Using Metal Triflates in Ionic Liquids, Green Chem., 4, pp. 129-133... 

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. 

Catalytic activity of MAPO-36 and ion-exchanged MAPO-36 in Beckmann rearrangement... 

Beckmann rearrangement of oxime is an acid catalysed reaction. The environmental problems associated with the use of sulphuric acid instigated interest to use number of solid acid catalysts [1], There are only scanty references about Lewis acid ion-exchanged MeAlPOs. Beyer et al. [2], Mihalyi et al. [3] and Mavrodinova et al. [4] already suggested the presence of Lewis acid metal ions as MO+ species in zeolites. The present study focussed the synthesis and characterisation of Fe3+, La3+ and Ce3+ ion-exchanged MAPO-36. The catalytic results of Beckmann rearrangement of cyclohexanone oxime over ion-exchanged catalysts are delineated in this article. 

The Beckmann rearrangement of oximes to produce amides is promoted by perrhenate ions under phase-transfer catalytic conditions, in the presence of trifluoro-methanesulphonic acid in nitromethane [6]. Under these conditions, the rearrangement reaction is frequently accompanied by the solvolysis of the oxime to the ketone. This can be obviated by the addition of hydroxylamine hydrochloride. No reaction occurs in the absence of the ammonium catalyst or with the O-acetyl oximes. 

The previous referred inconveniences have prompted an increasing interest in the development of alternative, essentially neutral and more environmental-friendly catalysts to promote the rearrangement of O-unsubstituted oximes. The development of highly efficient and selective transformations and also of processes for catalyst recovery and its reuse are the aim of some of the more recent studies. Much of this work is being done in industry to improve current production processes and is the subject of new patent applications. During the last two decades environment concerns have led to the development of green, simple and cost-effective catalytic systems for the Beckmann rearrangement. 

Theoretical studies on the Beckmann rearrangement mechanism over zeolite catalyst supported by experimental data have increased. The catalytic activity of the zeohte is determined by Brpnsted and Lewis acid sites created by protonation or activation by metallic cations. The reactivity of the acid sites is strongly influenced by the geometry and flexibility of the zeolite framework ". ... 

In the presence of a catalytic amount of an antunony(V) salt (SbCU SbFe ), generated from antimony(V) chloride and silver hexafluoroantimonate, the Beckmann rearrangement of several ketoxime trimethylsilyl ethers proceeds smoothly to give the corresponding amides or lactams in good yields . ... 

The industrial e-caprolactam processes with cyclohexanone oxime as intermediate product were recently reviewed . The catalytic gas-phase Beckmann rearrangement has great industrial interest. Since the process proposed by DuPont in 1938 the investigation on catalytic gas-phase Beckmann rearrangement has been investigated, and a large variety of catalysts have been tested for the reaction. 

These derivatives may be obtained by reduction of the appropriate nitro derivative catalytically or with a metal-acid system, or by Beckmann or Hofmann rearrangements of suitable acyl or carboxamido derivatives. 4-Aminobenzo[6]thiophene has also been prepared by means of a Bucherer reaction with 4-hydroxybenzo[6 Jthiophene. Several 5-aminobenzo[6]thiophenes have been prepared by cyclization reactions of p-acetamino-phenylthio derivatives. 6-Acetaminobenzo[6 Jthiophenes may be obtained from the corresponding 6-acetyl derivative by Schmidt or Beckmann rearrangements. 7-Aminobenzo[6 ]thiophene can also be prepared from 7-hydroxybenzo[6 ]thiophene by a Bucherer reaction (70AHC(ll)l77). 

There is, as is well known, a close similarity between the crystalline and porous structures of silicalite-1 and silicalite-2. The same similarity therefore exists between TS-1 and TS-2, and it appears logical that they should have very similar catalytic properties. TS-2 has been evaluated as a catalyst for many different reactions, such as Beckmann rearrangement of cyclohexanone oxime with vapor-phase reactants H202 oxidation of phenol, anisole, benzene, toluene, n-hexane, and cyclohexane and ammoximation of cyclohexanone. As described in detail in Section V.C.3, differences that had been claimed between the catalytic properties of TS-1 and those of TS-2 have not been substantiated. Later investigations have shown that, when all the relevant parameters are identical, the catalytic activities of TS-1 and TS-2 are also identical. The small differences in the crystalline structure between the two materials have no influence on their catalytic properties (Tuel et al., 1993a). 

About 90% of the caprolactam is produced by the conventional cyclohexanone process. Cyclohexanone is obtained by catalytic oxidation of cyclohexane with air, or by hydrogenation of phenol and dehydrogenation of the cyclohexanol byproduct. The conversion of cyclohexanone to cyclohexanone oxime followed by Beckmann rearrangement gives caprolactam. About 10% of caprolactam is produced by photonitrosation of cyclohexane or by nitrosation of cyclohexanecarboxylic acid in the presence of sulfuric acid264. 

Gates and Malchick utilized the Beckmann rearrangement for their purposes (Scheme 24).217) When the Hofmann degradation of 142 and 143, followed by catalytic dehydrogenation over 5 % palladium on asbestos at 300—310 °C, afforded not 1-vinylpentalene but azulene, the workers concluded that the former was thermodynamically unstable relative to the latter. 

Bicyclo[3.2.1]octan-2-one underwent a highly selective Beckmann rearrangement in the presence of hydroxylamine 0-hydrogensulfate and formic acid (equation 16). A modification of this procedure using catalytic trifluoromethanesulfonic acid has been reported. ... 

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