Methyl ketoxime

Ethyl methyl ketone, 10, 23 17, 74 Ethyl methyl ketoxime, 11, 59 Ethyl methylmalonate, 17, 56 Ethyl i-methylthiol-3-phthaIimidopro-pane-3,3-dicatboxylate, 14, 58 Ethyl nitrite, 10, 22, 25... 

Tables XXVIII and XXIX, respectively. Excellent correlations were obtained for all three sets. The stereochemistry of the sy -methyl ketoximes is discussed by Charton and Charton (73). The values of pj obtained for the trans-heterovinylene sets are not in good agreement with each other. Two sets gave values of 54 and 55, respectively, and the third set gave a value of 35. The difference in pj values cannot be accounted for. A value of 54 to 55 for pj suggests the possibility of some exaltation between substituent and reaction site such as that which occurs in para-substituted phenols and anilines. To demonstrate this with certainty requires that the value of pj be determined for a set of imines bearing a reaction site on the nitrogen which will not interact strongly with substituents. No such set of data is extant in the literature at the present time.

Unlike the reaction of alkyl aryl ketoximes with tetrasulfur tetranitride <1996CHEC-II(4)355>, the treatment of alkyl methyl ketoximes 189 with tetrasulfur tetranitride antimony pentachloride complex in either benzene or toluene at 50-80°C gave low yields (3-37%) of 3-alkyl-4-methyl-l,2,5-thiadiazoles 190 (Equation 39) <1999H(50)147>. Compounds 190 were volatile and the low yields are in part attributed to their loss as the solvent was removed in vacuo. Suprisingly, only single regioisomers were obtained. 3-Heptanone oxime 191 did, however, give a mixture of two isomers 192 and 193 (Equation 40). 

Table 2. Activation energies for the reaction of protonated benzyl methyl ketoximes and their sulfur analogous systems calculated by MP2/6-31G. ... 

The pKi, values of a series of para- and meffl-substituted benzaldoximes and phenyl methyl ketoximes, ArCR=NOH (R=H, Me), have been measured in DMSO. The aldoximes exhibit pK. = 20.05 + 3.21ap. The homolytic bond dissociation energy of the O-H bond has been estimated as 88.3 (aldoximes) and 89.2kcal mol" (ketoximes) by relating the pK to the oxidation potential of the conjugate base (i.e. ox for ArCR=NO- ArCR=NO ). 

Treatment of Af-monosnbstitnted acetamides as well as aryl or alkyl methyl ketoximes 441 with dimethyl(methylene)ammoninm chloride 442 in the presence of phosphorus oxychloride offers two promising, straightforward and generally applicable routes to 2-bis(dimethylaminomethyl)acetamides 443 as a result of the formation of unidoyl chlorides as intermediates (equation 188). 

The effect of ligands on the character and degree of the inner-sphere reorganization during electroreduction of aqua-, aquahydroxy-, hydroxy-, and ethylene-diamine tetraacetic acid (EDTA) complexes of Zn(II) [95] and electrochemical process of Zn(II) complexed by different ligands - glycinate [96], ethanol amine [97], azinyl methyl ketoximes [98], aspartame [99], glutathione [100, 101] and several cephalosporin antibiotics [102] -were studied at mercury electrodes in aqueous solutions. 

Similarly, (S4N4.SbCl5) reacted with alkyl methyl ketoximes 84 in aromatic solvents (e.g benzene and toluene) to give 3-alkyl-4-methyl-l,2,5-thiadiazoles 85, albeit in low yields (3-37%). A mechanism for the formation of 85 was proposed and the regioselective formation of 85 ascribed to the stability of an enamine intermediate. Suprisingly, this appears to be only the second example of a synthesis of a 3,4-dialkyl-l,2,5-thiadiazole that has been reported in the literature <99H147>. 

The one-stage transformation of 3-butenyl-l-methyl ketoxime (63) to 2-methyl-3-(2-propenyl-l)pyrrole (64) and 2-methyl-3-(l-propenyl-l)-l-vinylpyrrole (65) (Scheme 34) (82TL5063) is typical and demonstrates two essential features of this version of the reaction the reaction either can be stopped selectively at the stage of pyrrole ring formation without vi-nylation onto the N—H bond and prototropic isomerization of the alkenyl, or it can form an N-vinylpyrrole in which the double bond of the alkenyl is shifted into conjugation with the pyrrole ring. 

Further analysis of the regiodirection of the reaction was undertaken with benzyl methyl and benzyl ethyl ketoximes (88KGS193). The former was pure E-isomer and the latter consisted of E- and Z-isomers in a ratio of 45 55. As shown by Trofimov et al. (82KGS193), at room temperature the isomer ratio is not affected much by solvents. Upon heating for an hour in nitrobenzene, benzyl methyl ketoxime is partially converted to the Z-isomer, the content of which increases with temperature (according to H-NMR data) from 1% at 25°C to 36% at 150°C. 

In the KOH/DMSO system, benzyl methyl ketoxime is converted to a mixture of E- and Z-isomers (74 26) upon a short-term heating (80°C, 10 min) further temperature rise (150°C) has practically no effect on the isomer ratio. Consequently, the Z-form content of benzyl methyl ketoxime within the 26-36% range (depending on medium) seems to be close to the equilibrium value. Unlike benzyl methyl ketoxime, the isomer ratio of benzyl ethyl ketoxime evidently corresponds to the equilibrium value even in the initial sample, since upon heating in nitrobenzene (150°C) or in the KOH/DMSO mixture (170°C), it does not change much. 

Comparison of IR Spectra of Isomeric Pyrroles Obtained from Benzyl Methyl Ketoxime"... 

Reaction of aryl methyl ketoximes (118) with vinylchloride in the KOH (5-fold molar excess)/DMSO system at 120°C and atmospheric pressure gave 2-arylpyrroles (119) and their N-vinyl derivatives (120) (Scheme 58) (84KGS1359, 84MI3 87KGS1486). 

The best results were obtained at 130°C (3 hr) and with the oxime 121/KOH ratio 1 6 in DMSO. The total yield of pyrroles 122 and 123 attains 56%. Replacement of methyl by ethyl in the alkyl moiety of ketox-ime under comparable reaction conditions does not affect the total yield of pyrroles very much. However, on going from aryl methyl ketoximes (118) to aryl ethyl ketoximes (121), a downward trend in the yields for the corresponding N-vinylpyrroles (123) becomes evident. This is likely to be due to a decrease in polarizability and, consequently, to nucleophilicity of the 1-pyrrole anion as a result of distortion of the benzene and pyrrole ring coplanarity. 

As in the reaction with free acetylene (see Section II.A), acetoxime is least prone to pyrrole formation (the total yield of the pyrroles 126a and 127a is about 30%). The n-alkyl methyl ketoximes 125b,e,f react exclusively via the methylene group of the alkyl radical, whereas ketoxime 134 reacts by the methylene (preferably) and methyl groups to form pyrrole isomers. 

In the reaction with 1,2-dichloroethane in KOH/DMSO (100-125°C), aryl methyl ketoximes form 2-arylpyrroles (129) in 70% yield (Scheme 64). The maximum yield of simultaneously formed N-vinylpyrroles (130) and diethers (131) does not exceed 12 and 21%, respectively (86ZOR492). 

Cognate preparation. Hexyl methyl ketoxime. From hexyl methyl ketone (octan-2-one) (Expt 5.86) in 90 per cent yield b.p. 106-108 °C/12 mmHg. 

Anionic 1,4-silyl migrations of O-trialkylsilyl methyl ketoximes (268) were found to give o -trialkylsilyl ketoximes 269 after hydrolysis (equation 167). Intramolecularity of this migration was confirmed by crossover experiments. Upon heating 269 at 100 °C, a reverse migration to 268 took place. The reaction appeared to be limited to silyl ethers of methyl ketoximes having the (E)-configuration413. 

This third route is not as widely encountered as those described above. However, a number of characteristic impurities are found in amphetamine samples synthesized via this process, including nitrostyrene (16), benzyl methyl ketoxime (17) and l-methyl-2-phenylaziridine (18) (see structures in Figure 2.10). 

Beckmann Rearrangement.—When phenyl methyl ketoxime, aceto phenoxime, is treated with acid chlorides or phosphorus penta-chloride, it is converted into acet anilide. The steps in the reaction are as follows ... 

It has also been found that when the rearrangement involves the migration of an asymmetric carbon atom, the configuration is completely retained at that carbon atom. When (+) rc-pheny let hyl methyl ketoxime (Cl I) is treated with sulfuric acid, N-a-phenylcthyl acetamide (CHI) is formed in 99.6 per cent optical purity.65... 

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