Rearrangement, Beckman

The Beckman rearrangement of the oxime of 4-methyl-5-acetylthiazole (12) gives low yields (30% ) of 4-methyl-5-acetamidothiazole (Scheme 12) (58). 

A large batch exploded violently (without flame) during vacuum distillation at 90-100°C/20-25 mbar. Since the distilled product contained up to 12% butyroni-trile, it was assumed that the the oxime had undergone the Beckman rearrangement to butyramide and then dehydrated to the nitrile. The release of water into a system at 120°C would generate excessive steam pressure which the process vessel could not withstand. The rearrangement may have been catalysed by metallic impurities [1]. This hypothesis was confirmed in a detailed study, which identified lead oxide and rust as active catalysts for the rearrangement and dehydration reactions [2],... 

An unusual approach toward the preparation of a-bisphospho-nates began by treatment of an oxime with a phosphorus nucleophile (trialkyl or dialkyl phosphite) and phosphorus oxychloride (as promoter).354 The oxime undergoes a Beckman rearrangement the phosphorus nucleophile attacks the intermediate cation leading to an imine, which is then further attacked by the phosphorus nucleophile to give the a-bisphosphonate (Equation 3.21). 

Beckman rearrangement of nitrone (262) into amide (263) occurs in the reaction with lithium cyanide. However, this reaction gives lactam (264) instead of the expected 2-cyanopyrrolidine 1-oxide (265) (Scheme 2.96) (473). 

Photochemical Beckman rearrangement of oximes results in the formation of carboxamides as the major product151 (equation 92). 

Beckman rearrangement TS-1 and TS-2 catalysts, 41 295 Beer s law, 34 209 Beidellite, idealized formula, 33 337 Bentonite, 27 173 Benzaldehyde... 

Thieno[4,3,2-/g]benz[l]azocine 187 is produced in high yield (79MI397) from oxime 186 by Beckman rearrangement in PPA. Transformations of amide and thioamide groups of azocines 187 and 188, lead to derivatives 189-192, as shown in Scheme 52. 

Pyrrolidone is a lactone used for the production of nylon-4. This reactant may be produced by the reduction ammoniation of maleic anhydride. s-Caprolactam, used in the production of nylon-6, may be produced by the Beckman rearrangement of cyclohexanone oxime (structure 17.11). The oxime may be produced by the catalytic hydrogenation of nitrobenzene, the photolytic nitrosylation of cyclohexane (structure 17.9), or the reaction of cyclohexanone and hydroxylamine (structure 17.10). Nearly one-half of the production of caprolactam is derived from phenol. 

The structures of the acetylation products of 1 and 2 were also proved by the following conversions. The oximes derived from the acetyl thienothiophenes gave the corresponding acylamino compounds on Beckman rearrangement. The latter were identical with the derivatives obtained by reduction (Hj/Ni) in acetic anhydride of the 2-nitro-substituted thienothiophenes 1 and 2 [Eq. (61)]. 

BECKMAN REARRANGEMENT Poly-phosphoric acid. Trimethylsilyl polyphosphate. 

Treatment of a number of isatin-3-oximes with sodium methoxide at 140°293 or simply thermally274,294 leads to o-aminobenzonitriles. Thermal treatment of isatin-2-oxime gave isatin and 79.294 Beckman rearrangement of isatin-3-oximes resulted in the formation of o-cyano-phenylisocyanates.26,295 With the Vilsmeier reagent, phosphorus... 

The Beckman rearrangement could occur by either a stepwise or a concerted mechanism. 

Reaction of hydroxylamine with tri- and tetrasubstituted pyrylium salts yields pyridine iV-oxides and/or 2-isoxazo-lines via the intermediacy of keto-ketoximes <1998T9747>. The regiochemistry of 2-isoxazoline formation from unsymmetrical pyryliums, and the Beckman rearrangement of the intermediate keto ketoximes have also been explored C1998T9747, 1999T15011>. 

So effective was the collinear three-center transition state in clarifying the Walden inversion problem, that concerted backside attacks were proposed or considered for the Beckman rearrangement, isomerization of alkenes, etc. (Olson, 1933 Marvel, 1943), as well as substitution in alkenes (Gold, 1951 Ross et al., 1952). Since an appropriate arrangement of hybrid orbitals is available, some of the transition states did not... 

Beckman rearrangement of cyclohexanone oxime in the presence of zinc oxide and without any additional solvent afforded the azocane-2-one 120 (Scheme 70 <2002S1057>). This is an environmentally friendly alternative to the usual Beckmann rearrangement performed with highly corrosive, strong Bronsted and Lewis acids, such as cone, sulfuric acid, phosphorus pentachloride in EtzO, or HG1 in acetic anhydride. 

Ammoximation on its own represented a great simplification in the production of -caprolactam, and the catalyzed Beckman rearrangement introduced by... 

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