Beckmann rearrangements cyclopentanone oximes

But for hormones such as oestrone and testerone two carbon atoms need removing to make a cyclopentanone. This is accomplished using a Beckmann rearrangement. The oxime forms with the OH group trans to the more bulky... 

Derivatives of cyclopentanone oximes undergo Beckmann rearrangement to corresponding tetra- or hexahydropyridines or quinolines in the presence of Lewis acid (AICI3391.392 BF3.0Et2 or PPA ) or DIBAH (/-BujAlHl/CHiCb . ... 

A series of analogues of 2-iminopiperidine have been prepared and have been shown to be potent inhibitors of the human nitric oxide synthase isoforms °. The cyclopentanone oxime 346 was esterified with sodium hydroxide and benzenesulfonyl chloride and the subsequent Beckmann rearrangement afforded the 6-propylvalerolactam 348 as the major product and 3-propylvalerolactam 347 as a minor product (equation 133). The major product was converted into the intended 2-iminopiperidine 349. 

Another synthetic route via the Beckmann rearrangement, which is promoted by organoaluminum reagent along with alkylation, involves a new stereoselective reduction of the imino group. The starting oxime sulfonate (228) was synthesized from cyclopentanone (226) in three steps Reaction of 226 with 1-undecene in the presence of silver oxide produced the a-undecylcyclopentanone (227) which on successive treatment with hydroxylamine and methanesulfonyl chlo-ride-triethylamine gave the mesylate (228). Treatment of the oxime mesylate... 

Cyclopentanone Oxime. Violent reaction occurred on heating the oxime with 85% sulfuric acid to effect a Beckmann rearrangement.12... 

By treating o-chloromethylaniline hydrochloride with cu-benzyloxy-butyro- and -valeronitriles in refluxing o-dichlorobenzene in the presence of stannic chloride, Mufloz and Madroilero obtained the tricyclic compounds 124 and 202, respectively. The pyrido[2,l- )]quinazolines 289 were prepared by refluxing o-chloromethylaniline hydrochloride in dichlorobenzene with 2-chloropyridine and its tetrahydro derivative. The latter was obtained in situhy Beckmann rearrangement of cyclopentanone oxime with phosphorus pentachloride. 

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. 

Cyclobutane.—Further reports of grandisol (90) synthesis include Magnus s full paper (Vol. 6, p. 22) and an almost identical Japanese report of an earlier synthesis (Vol. 3, p. 25) based upon a dihydropyranone-ethylene cycloaddition.A third synthesis utilizes cyclopropanation of 4-methoxy-3,6,6-trimethylcyclohexa-2,4-dienone to yield (91) followed by rearrangement of the a-oxycyclopropylcarbinyl cation of (91) to (92). After reduction of the cyclobutanone, second-order Beckmann cleavage of the cyclopentanone oxime gave (93) from which grandisol (90) was readily obtained. 

The parent compound of this series, 2-chloro-3,4,5,6-tetrahydro-pyridine (XXXIX), was obtained as an intermediate in the Beckmann rearrangement of cyclopentanone oxime ( ). Thus, heating of cyclo-pentanone oxime with thionyl chloride affords about equal amounts of the lactam hydrochloride XL and the imidoyl chloride XXXIX ( ). 

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. 

Beckmann rearrangement of benzophenone oxime to PhC(Cl)=NPh (82%) is promoted by Ph3PCl2/Et3N in CH2CI2 at rt. Cyclopentanone and cyclohexanone oxime are converted to 8-valero- and e-caprolactam (76 and 86%) with PhsPCh in PhH at 50-60 The action of heat... 

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