Oximes to lactams

The transformation of oximes to lactams (the Beckmann rearrangement) was one of the earliest such acid-catalyzed reactions to be reported with TS-1 (138) and TS-2 (247) catalysts. The rearrangement of cyclohexanone oxime to e-caprolactam proceeds with high selectivity in the presence of TS-1, with high catalyst stability (138,247). 

A soln. of tripbenylpbospbine in benzene added slowly at room temp, to a spin, of tbe equivalent amount of 1-cbloro-l-nitrosocyclobexane in tbe same solvent, and 1 N HGl added after 0.5 br. f-caprolactam. Y 96%. F. e., also direct Beckmann rearrangement of oximes to lactams with halogen in tbe presence of tripbenylpbospbine, s. M. Obno and I. Sakai, Tetrab. Let. 1965, 4541. 

Not only do oximes undergo the Beckmann rearrangement, but so also do esters of oximes with many acids, organic and inorganic. A side reaction with many substrates is the formation of nitriles (the abnormal Beckmann rearrangement, 17-31). Cyclic ketones can be converted directly to lactams in one laboratory step by... 

In contrast, the isomeric Erythromycin A 9(Z)-oxime 460 produced an isomeric nitril-ium ion intermediate 465 as the result of different oxime geomehy (equation 199). In comparison with the products obtained from the ii-oxime, isomeric lactam 468 and imino ethers (466 and 467) were isolated. Reaction conditions (including solvent polarity and the concentration of the reaction mixture) proved to have a strong influence on the yields of the various products of the rearrangement. 

In conclusion, decrease in cyclohexanone oxime yield and caprolactam selectivity with time on stream is a major factor in the use of boria on alumina catalyst in the rearrangement reaction. Coke deposition and basic by-product adsorption have been suggested as a means of deactivation. In addition the conversion of water soluble boron, which is selective to lactam formation, to an amorphous water insoluble boron species is another factor that can account for the catalyst deactivation. 

Scheme 114 Five-bond-cleavage rearrangement of O-propargyl oximes to P-lactams...

These bicyclo[4.2.0]octanones also undergo aza-ring expansion to lactams. Beckmann rearrangement of the oxime of a typical bicyclic butanone (1) results in an octahydroisoindolone (2), whereas rearrangement of the methylnitrone (3) with tosyl chloride (4, 510 511 6, 598) proceeds in the opposite direction to give an octahydroindolone (4) as the only product.2... 

The rearrangement of cyclohexanone oxime to caprolactam is still an important step in nylon production, and the heterogeneously catalyzed Beckmann rearrangement has been extremely well investigated (4, 16-19). In order to obtain catalysts that couple a high lactam selectivity to long lifespan, careful tuning of the zeolite properties is required. Some important factors are ... 

Dehydration. This reagent is useful for synthesis of acyl azides from carboxylic acids, NaCN, and pyridine, with tetrabutylammomum bromide as catalyst (75-95% yield). In combination with pyridine, it effects dehydration of oximes to nitriles in 80-90% yield, P-Lactams can be prepared directly in 40-75 )t yield from carboxylic acids and imines with the reagent (1 equiv,) and triethylamine (excess). In general, a mixture of cis- and rra/j5-azetidinones is formed. 

Photorearrangement of a spiro-oxaziridine such as (95) to the lactam (96) has been employed in alkaloid synthesis. Oxaziridines have also been proposed as intermediates in the photorearrangement of oximes. The lactams (97) and (98), for example, have been prepared in this way by irradiation of either (Z)- or (E)-dihydromayurone oxime (99). ... 

The Beckmann rearrangement converts oximes to amides or lactams and was reviewed recently (equation 33) ... 

Cyclohexanone oximes undergo ring expansion to form caprolactams, such as 357 and 358 (Scheme 6.165).1109 The mechanism involves E Z photoisomerization, followed by transformation of the singlet excited oximes to an oxaziridine intermediate and subsequent concerted isomerization of singlet excited oxaziridine to the corresponding lactams.1061... 

Cycloadditions. With Et2A10Et present, a-chloroalkenyl acetates react with carhonyl compounds and imines to furnish 3-lactones and 3-lactams, respectively. The ketene equivalent also combines with oximes to give 5-isoxazolidones. ... 

Oxaziridines are accepted as intermediates in the photorearrangements of oximes to amides and lactams. The formation of host-guest complexes in acetophenone oxime derivatives that incorporate a crown ether moiety has been shown to stimulate triplet-derived Z-J -isomerization and to depress singlet-derived oxaziridine formation. Low yields of lactams (115>—(117) have been obtained on irradiation of D-nor-5a-androstan-16-one oxime (118) in methanol. The unusual formation of lactam (117), in which the chirality of the... 

A new route to lactams (e.g. e-caprolactam, 96%) by the reaction of 1-nitroso-and 1-nitro-l-halogeno-cycloalkanes, e.g. (12), with triphenylphosphine, or via the one-step reaction of the cycloalkanone oxime with halogen and triphenylphosphine, goes via successive Perkov and Beckmann reactions, " as shown in Scheme 1. 

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. 

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