Acetophenone oxime Beckmann rearrangements

O-Acylated or mesylated oximes such as the ethyl carbonate of acetophenone-oxime 1772 react with TIS 17, with Beckmann rearrangement to the imidoyl iodide 1773, which adds phenylmagnesium bromide in situ to give 61% of the sec-... 

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). 

Figure 6.20 Plot of log k vs. cr + for the Beckmann rearrangement of acetophenone oximes in 98.2 percent sulfuric acid at 80°C. From B. J. Gregory, R. B. Moodie, and K. Schofield, J. Chem. Soc., 13, 338 (1970). Reprinted by permission of K. Schofield and The Chemical Society.

The fact that under the same conditions acetophenone oxime does not form amides, but remains intact, also provides evidence against the classical Beckmann rearrangement. The conditions found can be employed for preparing amides from nitriles and aldoximes, especially when the latter contain fragments unstable to acids. In the absence of DMSO, benzaldoxime is dehydrated with alkali only at the boiling point (200°C). 

Pearson et al. (1952) employed this approach to derive a series of substituent parameters for electron-deficient reactions of substituted benzenes. These constants, designated as sigmae, were based on a study of the Beckmann rearrangement of -substituted acetophenone oximes. These authors considered the rates of the rearrangement reaction of the oximes to deviate from the Hammett eq. (1). It is pertinent that, with the sole exception of the yi-OMe group, the deviations were not major. The entropy of activation, AS, for the -anisyl derivative was, however, 20 e.u. different from the essentially constant values for the other substituents. To remedy the deviations, Pearson and his associates suggested the sigmae constants. It was indicated that these constants were more suitable for the correlations of electron-deficient reactions than the conventional cr-values. 

A Acetophenone derivatives can be prepared from benzene by a Friedel-Crafls acylation. The derived oxime, formed using hydrox-yiamine, undergoes a Beckmann rearrangement to produce the... 

Butler, R. N., O Donoghue, D. A. Direct detection of intermediates and synthetic applications of the reaction of thionyl chloride with oximes of substituted acetophenones and benzaldehydes Beckmann rearrangements. J. Chem. Res., Synop. 1983,18-19. 

In a kinetic study of the Beckmann rearrangement of acetophenone oximes, Pearson and Stone found that rearrangement is 12-35 times as fast in PPA as it is in sulfuric acid and that the rates of rearrangement of substituted acetophenone oximes in PPA are nearly all the same. They conclude that the PPA reaction follows a mechanism different from that of the H2SO4 reaction. 

Beckmann rearrangement. Aryl alkyl ketone oximes (acetophenone oxime) or diaryl ketone oximes (benzophenone oxime) undergo Beckmann rearrangement when refluxed with anhydrous or hydrated pyridine hydrochloride. If the ketone has a methoxyl group in the para position concomitant demethylation occurs.15... 

Benzoxazoles. - Both o- and m-halogenobenzanilides (413) are converted into the amidines (415) by potassium amide in liquid ammonia these are formed by aryne cyclization to 2-phenylbenzoxazole (414) and subsequent aminoly-sis." The conversion of acetophenone oxime into 2-methylbenzoxazole by the action of phosphorus oxychloride involves a Beckmann rearrangement. Pyrolysis of aryl azidoformates, ArOaCNa, gives benzoxazol-2-ones. The azide (416) is converted into the benzoxazole (417) on heating. The... 

Phosphorous pentoxide effectively catalyzed the homogeneous liquid phase Beckmann rearrangement of cyclohexanone oxime 5 to lactam 6 in DMF. The catalytic activity was significantly increased by addition of trifluoromethanesulfonic acid as a co-catalyst. This protocol was fiuther extended to the rearrangement of acetone, acetophenone and cyclopentanone oxime to the corresponding amides. 

Problem lO.L Predict the products resulting from the Beckmann rearrangement of the (Z)-isomer of the oxime derived from reaction of hydroxylamine (H2NOH HCl) with phenylethanone (acetophenone, methylphenylketone, C6H5COCH3). 

The Beckmann rearrangement of acetophenone oxime using zeolites as catalysts has been investigated by means of N and C solid-state NMR spectroscopy in combination with theoretical calculations. ... 

Against the Beckmann rearrangement is also the fact that acetophenone oxime in the same conditions does not form amide and is recovered from the reaction intact. 

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