Oxime acetates Beckmann rearrangement

Zeolites have also been described as efficient catalysts for acylation,11 for the preparation of acetals,12 and proved to be useful for acetal hydrolysis13 or intramolecular lactonization of hydroxyalkanoic acids,14 to name a few examples of their application. A number of isomerizations and skeletal rearrangements promoted by these porous materials have also been reported. From these, we can underline two important industrial processes such as the isomerization of xylenes,2 and the Beckmann rearrangement of cyclohexanone oxime to e-caprolactam,15 which is an intermediate for polyamide manufacture. Other applications include the conversion of n-butane to isobutane,16 Fries rearrangement of phenyl esters,17 or the rearrangement of epoxides to carbonyl compounds.18... 

Acylation of thiochromanones with boron trifluoride and acetic anhydride readily affords (92), which may be elaborated into (93) (equation 36) (79CJC3292), while conversion of the keto function to an oxime (94) permits the formation of the palladium complex (95) as a first step towards functionalization of the aromatic ring (equation 37) (78BCJ3407), or ring expansion by Beckmann rearrangement (equation 38) (76JCS(P1)2343). 

Oximes of ketones undergo rearrangement (the Beckmann rearrangement) to amides under the influence of a variety of acidic reagents (e.g. sulphuric acid, hydrogen fluoride, acetic anhydride, phosphorus pentachloride, thionyl chloride, etc.). The process is illustrated by the conversion of benzophenone oxime to benzanilide in the presence of phosphorus pentachloride. 

The abnormal Beckmann rearrangement displayed by the oxime of 17-oxo-5a-androstan-3/3-yl acetate (248) to yield the 13,17-seco-nitrile (249) has provided the key step in a synthetic route to 17-oxo-18-nor-5a,13/8-androstan-3/S-yl acetate and its 13a-epimer.114 The reaction sequence is shown in Scheme 12. The 17-ketone (248) was converted via its oxime into the seco-nitrile in a yield of 52%. Treatment of the oxime by the more conventional toluene-p-sulphonyl chloride reagent... 

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. 

Again, the configuration of the oxime is of significance. The acetate (20, R = Ph) provides the indoxazene smoothly on pyrolysis, while its isomer (21) gives only a small yield of the same product.42 A Beckmann rearrangement diverts the pyrolysis of some of the oxime benzoate (22) to the formation of the benzoxazole (23).43... 

This oxime, however, undergoes the Beckmann rearrangement and yields benzanilide just as aceto phen-oxime yields acet anilide. 

Dimethylaniline has been prepared by reduction of the corresponding nitro compound, either chemically or catalyti-cally. It has been prepared from 3,4-dimethylphenol by heating with ammonia, ammonium bromide, and zinc bromide from w-toluidine hydrochloride by alkylation with methanol at high temperatures from anhydro-4-amino-2-methylbenzyl alcohol by dry distillation from calcium hydroxide from 2-methyl-S-aminobenzyl alcohol by reduction with sodium from 2-methyl-5-nitrobenzyl chloride and 2-methyl-S-nitrobenzyl acetate by catalytic reduction from o-xylene by direct amination with hy-droxylamine hydrochloride in the presence of aluminum chloride and from 3,4-dimethylacetophenone by the Beckmann rearrangement of the oxime.i" The present method has been published. ... 

In the laboratory of J.D. White, the asymmetric total synthesis of the non-natural (+)-codelne was accomplished via intramolecular carbenoid insertion In the late stages of the total synthesis It was necessary to Install a 6-membered piperidine moiety. This transformation was accomplished utilizing a Beckmann rearrangement of the cyclopentanone oxime portion of one of the intermediates. Later the 6-membered lactam was reduced to the corresponding amine with LAH. To this end, an oxime brosylate (Bs) was prepared, which underwent a smooth Beckmann rearrangement in acetic acid to provide a 69% yield of two isomeric lactams in an 11 1 ratio in favor of the desired isomer. 

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