Oximes, acid catalyzed hydrolysis

NaN02, 1 N HCl, CH3OH, H2O, 0°, 3 h, 76% yield. In the last step of a synthesis of erythronolide A, acid-catalyzed hydrolysis of an acetonide failed because the carbonyl-containing precursor was unstable to acidic hydrolysis (3% MeOH, HCl, 0°, 30 min, conditions developed for the synthesis of erythronolide B). Consequently, the carbonyl group was protected as an oxime, the acetonide was cleaved, and the carbonyl group was regenerated. 

One of the best known reactions of 1-azirines is the acid/catalyzed hydrolysis to aminoketones. Since the Neber reaction also accomplishes this same synthetic end, this reaction may appear to have little practical value. This is not the situation because with the Neber reaction there is no control over the aminoketone that will be obtained from a given ketone. For example, when oxime (127) derived from benzyl methyl ketone (126) is subjected to the Neber reaction aminoketone 128 is obtained.59 The amino function is substituted for the most acidic a-hydrogen. The isomeric aminoketone (132) that could not be prepared by the Neber reaction can be formed by the hydrolysis of 1-azirine (131). The synthesis of this 1-azirine has been accomplished from allyl benzene (129) through vinyl azide (130) using iodine azide.22... 

Lazarevski, T., Radobolja, G., and Djoklc, S. (1978). Erythromycin VI Kinetics of acid-catalyzed hydrolysis of erythromycin oxime and erythromycylamine. J. Pham. Sci. 67, 1031-1033. 

Write the steps involved in the acid-catalyzed hydrolysis of an oxime. Predict the relative rates of the primary steps in this mechanism. 

The formation of imines, oximes, hydrazones, and related derivatives from carbonyl compounds is reversible. Write a detailed mechanism for the acid-catalyzed hydrolysis of eyclohexanone semicarbazone to cyclohexanone and semicarbazide. 

Hydrolysis methods for mono[ C]nitriles and the spectrum of chemical transformations of the resulting [l- C]carboxylic acids differ little from those for their unlabeled counterparts, so that the synthesis of [l- C]tetralones 42 and [l- " C]indanones 46 from w-arylalkyl [ C]nitriles will suffice as examples (Figure 7.11). Acid-catalyzed hydrolysis of 4-phenylbutyro[ C]nitrile followed by polyphosphoric acid-mediated cyclization of the resulting phenyl[l- C]butanoic acid converted it into 42 in 89% radiochemical yield. Sequential bromination and oxime formation provided the a-bromooxime 43, which upon treatment with polyphosphoric acid underwent a Beckman rearrangement to provide the ring-expanded tetrahydro-2H-l-[2- C]benzazepine-2-one derivative 44- This was a key intermediate for the preparation of a series of labeled ACE inhibitors" . The acid-catalyzed cyclization of a mixture of 3-(2-hydroxyphenyl[l- " C]propionic acid and its ethyl ester, prepared by treatment of the propio[ " C]nitrile with ethanolic HCI proved to be a two-step sequence. In the first step, 2- [2- " C ]chromanone I4SI was formed and had to be submitted to... 

The acid catalyzed conversion of oximes over different acidic solids in "dry media under soft conditions gives as major products the amide (Beckmann rearrangement) and the ketone (hydrolysis). The... 

Biacetyl is produced by the dehydrogenation of 2,3-butanediol with a copper catalyst (290,291). Prior to the availability of 2,3-butanediol, biacetyl was prepared by the nitrosation of methyl ethyl ketone and the hydrolysis of the resultant oxime. Other commercial routes include passing vinylacetylene into a solution of mercuric sulfate in sulfuric acid and decomposing the insoluble product with dilute hydrochloric acid (292), by the reaction of acetal with formaldehyde (293), by the acid-catalyzed condensation of 1-hydroxyacetone with formaldehyde (294), and by fermentation of lactic acid bacterium (295—297). Acetoin [513-86-0] (3-hydroxy-2-butanone) is also coproduced in lactic acid fermentation. 

Base-catalyzed fragmentation also occurs on treatment of 5,6j9-epoxy-19-aldehyde (hemiacetal, hemiacetal-acetate or 3)5,6/ -acetal) accessible from nitrous acid-acetic acid treatment of 5a-bromo-6jS-hydroxy-19-oximes followed by mild base hydrolysis (yield not reported)... 

Reduction of oximes to ketones. Ketoximes can be converted to ketones by hydrogenation catalyzed by Raney nickel (deactivated with acetone) in THF/CH,OH/H,0 or in CHiOH/H,0 containing boric acid to facilitate hydrolysis of the intermediate imine... 

Several 1,3,5-triazine mono- and dialdoximes 5 can be prepared by the base-catalyzed condensation of the corresponding methyl-1,3,5-triazines 4 with alkyl nitrites. The formation of either the mono- or the dialdoxime is dependent on the reaction conditons used. Hydrolysis of the oximes to 1,3,5-triazinecarbaldehydes 6 can only be achieved for 4,6-diaryl-l, 3,5-triazine 2-al-doximes. These aldehydes can also be obtained by reaction of 4,6-diaryl-2-methyl-l,3,5-triazi-nes with sodium nitrite in concentrated sulfuric acid.162... 

A number of carbamates have been used as insecticides and a few as herbicides. Kinetic parameters for several of these compounds are summarized in Table 8.6. Note that the base-catalyzed reaction is the more important, however, some reports indicate that for some compounds, the direct reaction with water can be significant with values of 6-7. Unfortunately, there is only limited information in this area. Note that these data also illustrate how the substituents on the N influence hydrolysis. The feb values for the dimethyl compounds are orders of magnitude lower than the methyl counterparts. Aldicarb represents a variation in that the ester component of the molecule is derived from an oxime (RCH=NOH) rather than an alcohol. It also illustrates the significance of hydrolysis in understanding its environmental behavior. Aldicarb has been very effective in controUing insect pests in potatoes, but because of its high water solubility (6000 ppm) has been detected as a contaminant in groundwater. This effect has been observed only in acid (pH 5.5) but not in basic (pH 8.0) soils. 

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