Oximes rearrangements with

Beckmann rearrangement of 6-endo-chlorocamphor oxime (Vol. 7, p. 43) yields (220) and the cis- and frans-ring-fused (221), and camphor oxime rearranges with hydrazoic acid in polyphosphoric acid to yield (222). ... 

A photochemical partial synthesis of aldosterone (19) made the hormone available on an industrial scale for the first time (114). Corticosterone acetate (51 acetate) is treated with nitrosyl chloride in pyridine at 20°C to yield the 11-nitrite (115). Irradiation of (115) leads to rearrangement with formation of the C g-oxime (116). Removal of the oxime residue with nitrous acid furnishes aldosterone (19) in excellent yield. 

The contradictory observations that 16-dehydropregnenolone oxime fails to rearrange with phosphorus oxychloride while pregnenolone oxime undergoes the normal reaction " remain unexplained. The respective 3-acetates in both series rearrange in the expected fashion. 

Neither the oxide nor the amidine function are in fact required for activity. Treatment of the oxime, 7, with chloro-acetyl chloride in the presence of sodium hydroxide proceeds directly to the benzodiazepine ring system (14)(the hydroxyl ion presumably fulfills a role analogous to methylamine in the above rearrangement). Reduction of the N-oxide function of 14 leads to diazepam (15). ... 

The reaction of ketoximes 235 with dimethyl carbonate in the presence of K2CO3, carried out in an autoclave at 180-190 °C, afforded 3-methyl-4,5-disubstituted 4-oxazolin-2-ones 236 (equation 102). The formation of compounds 236 occurred via [3,3]sigma-tropic rearrangement of intermediates of the oxime methylated with dimethyl carbonate. 

The reaction of oxime 323 with concentrated aqueous HCl proceeded with a ring contraction and afforded pyridazine 324 as a single product (equation 140) . On the contrary, the rearrangement of pyrrol-3-one oxime in the presence of hydrazine proceeded with ring enlargement and led to l//-pyridazin-4-one oxime . ... 

The reaction of aliphatic and aromatic ketone oximes 97 with a dialkyl carbonate 98 in the presence of K2CO3 at 180-190 °C yields 3-alkyl-4,5-disubstituted-2(3//)-oxazolones 104 in 22-48% yields. Mechanistically, it is proposed that N-alkylation of the initially formed oxime O-carbonate 99 yields 100, which affords the enamine 101 in the presence of base. A [3,3] sigmatropic rearrangement ensues to produce 102, which then cyclizes to 104. In cases where 97 contains two methylene groups in proximity to the C=N bond, one of which is benzylic, the above reaction sequence is regioselective for the benzylic methylene group (Fig. 5.25 Table 5.6, Fig. 5.26). ... 

The benzenesulfonate of cycloheptanone oxime rearranges readily at room temperature to give the very electrophilic O- benzenesulfonate (7), which reacts with pyridine to give the salt (8) (67CB3024). Treatment of (8) with water gives (2), and with H2S the thione (9) is produced (58CB972). The reaction of aluminum alkyls with cycloheptanone oxime mesylate provides a direct route to 2-alkyl-substituted octahydroazocines (81JA7368). 

A -(2-Fluoro-2,2-dinitroethyl)hydroxylamine (1) is oxidized by 3-chloroperoxybenzoic acid or bromine to afford oxime 2.218 This compound is unstable and over the course of several weeks at ambient temperature it rearranges quantitatively to amide 3.218 Further oxidation of the oxime 2 with nitric acid or aqueous chromic acid gives a product mixture, from which bis(fluorodinitromethyl)furoxane 4 is isolated.218... 

When acetophenone oxime (1) is thermically treated with acidic solids in "dry media" under soft experimental conditions, two main products are obtained the rearrangement one acetanilide (N-phenyl acetamide) (2) obtained by Beckmann rearrangement with migration of the phenyl group, and the hydrolysis one acetophenone (3), obtained by the hydrolysis of the imino group (C=N) (eqn.2). 

Oximes rearrange when heated with a strong acid, and this reaction provides a useful synthesis of amides ... 

Treatment of oximes 14 with PCls or PzOs in CHC13 and aqueous HC1 solution (1 1) afforded 4-nitro-57/-furan-2-one 96 (Scheme 20) <1998CCA557> the Beckmann rearrangement was not observed. 

Beckmann rearrangement, The p-toluenesulfonates of an oxime rearrange to amides in 45-90% yield when stirred at room temperature with Si02. 

Beckmann rearrangement.3 Reaction of oxime sulfonates with simple Grignard reagents in dry toluene at —78° results in imines, which can be reduced to a-alkylamincs or alkylated with allylic or propargylic Grignard reagents to furnish a,a-diulkylnmincs. 

Treatment of the oxime (17) with lithium aluminum hydride-aluminum chloride led to a rearrangement of the ferrocene residue to give 20.11 The oxime (21) was unchanged under these conditions. Treatment of the quaternary methiodide of 20 with base led to the ring-opened product (22). 

The participation of nitrilium salts has also been postulated42 in the Schmidt reaction and in some Beckmann rearrangements when concentrated sulfuric acid is employed. Hill43 has demonstrated recently that some Beckmann rearrangements carried out in a concentrated sulfuric acid medium are Ritter-type reactions in which the nitrile formed in situ from the oxime combines with a carbonium ion to yield a nitrilium salt, which, when diluted with water, leads to the N-alkylamide. 

An improved synthesis7 of aldosterone acetate lb was based on the readily available dienone 30. Conversion to the nitrite and photolysis affords the oxime 31 with no attack on C19. On warming in iso-propyl alcohol this oxime 31, cyclized smoothly to the nitrone 32 with the loss of water. This nitrone is at the right oxidation level to rearrange to the 21-acetoxyimine. The overall yield of nitrone from 30 was 55%. 

The reaction of 2-acetyl-3-hydroxypyridine (441) with hydroxylamine 0-sulfonic acid afforded a 1 1 mixture of compound (442) and 2-methylisoxazolo[4,5-6]pyridine (443) (Equation (35)) <87H(26)292i). The formation of the oxazolo[4,5-6]pyridine (442) results from a Beckmann rearrangement. The reaction of the oxime (444) with hydroxylamine O-sulfonic acid also gave Beckmann rearrangement products, such as (445) and (446) as a 1 1 mixture (Equation (36)). 

In classical processes cyclohexanone is converted to the corresponding oxime by reaction with hydroxylamine (see Fig. 2.27). The oxime subsequently affords caprolactam via the Beckmann rearrangement with sulphuric or phosphoric acid. Alternatively, in a more recent development, not yet commercialized, a mixture of cyclohexanone, ammonia and hydrogen peroxide is directly converted to cyclohexanone oxime over a titanium(IV)-silicalite (TS-1) catalyst. This route is more direct than the classical route and reduces the amount of salt formation but it involves the use of a more expensive oxidant (H2O2 rather than O2). 

The reaction of oxime 385 with polyphosphoric acid results in ring expansion via Beckmann rearrangement leading to the fused 1,4-benzothiazepine derivative 386 (Scheme 207) <1997JHC921, CHEC-III(13.09.10.2)286>. 

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