Acetophenone oximes, formation

Figure 3 presents kinetic curves for the formation of 2-phenylpyrrole (Scheme 2) at 96°C and atmospheric C2H2 pressure in various solvents such as DMSO, HMPA, l-methyl-2-pyrrolidone, sulfolane, polyethyleneglycol (PEG) with Mm = 1000, and tetramethylurea [89KGS770]. DMSO is confirmed to possess a specific catalytic effect in this reaction, which is much superior to that of HMPA, l-methyl-2-pyrrolidone, and tetramethylurea. According to their capability to catalyze the formation of 2-phenylpyrrole from acetophenone oxime and acetylene, the solvents under consideration are arranged in the following order DMSO > HMPA l-methyl-2-pyrrolidone > sulfolane > PEG > tetra-... 

A Bac2 mechanism is proposed for die saponification of ethyl benzoate in ethanol-water.37 The reactions of aryl benzoates in absolute ethanol with ethoxide, aryloxides and acetophenone oximates occur via a stepwise mechanism in which the formation of the tetrahedral intermediate is rate determining.38 A stepwise mechanism is also supported for the reactions of /7-nitrophenyl-substituted benzoates with hydroxide and / -chlorophcnoxidc. The evidence comes from breaks in Hammett plots as the acyl... 

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... 

The formation of imidoyl bromides (XIII) in the reaction of 2-bromo-acetophenone oxime (XIV) with triphenylphosphorus has been reported by Masaki et al. ( ). 

Similarly, Friedel-Crafis acylation (Chapter 6 cf. Scheme 6.88) of aromatic systems produces carbonyl compounds, which can be converted to the corresponding oximes with hydroxylamine hydrochloride (H2NOH-HC1) (see, e.g.. Scheme 9.65, Table 9.4, item 4). So, acylation of benzene to form phenylethanone (acetophenone, methylphenylketone, C6H5COCH3) can be followed by oxime formation. 

Scheme 10.1. A representation of oxime formation from phenylethanone (acetophenone, methylphenylketone, C6H5COCH3) on reaction with hydroxylamine hydrochloride. (H2NOH HCl), followed by Beckmann rearrangement of the (Z)-isomer to produce aminobenzene (aniline, C6H5NH2) after hydrolysis.

SCHEME 1.155 Side formation of 2,4,6-triphenylpyridine in the synthesis of 2,5-diphenyl-pyrrole from acetophenone oxime and phenylacetylene in the system LiOH/DMSO. 

SCHEME 1.161 Trace formation of -terphenyl in the reaction of acetophenone oxime with phenylacetylene in the system NaOH/DMSO. 

SCHEME 1.172 Trace formation of 5-ethyl-2-phenylpyrrole from acetophenone oxime and acetylene. 

Aldehydes and ketones may be converted into the corresponding primary amines by reduction of their oximes or hydrazones (p. 93). A method of more limited application, known as the Leuckart Reaction, consists of heating the carbonyl compound with ammonium formate, whereby the formyLamino derivative is formed, and can be readily hydrolysed by acids to the amine. Thus acetophenone gives the i-phenylethylformamide, which without isolation can be hydrolysed to i-phenylethylamine. 

Aldehydes and ketones may frequently be identified by their semicarbazones, obtained by direct condensation with semicarbazide (or amino-urea), NH,NHCONH a compound which is a monacidic base and usually available as its monohydrochloride, NHjCONHNH, HCl. Semicarbazones are particularly useful for identification of con jounds (such as acetophenone) of which the oxime is too soluble to be readily isolated and the phenylhydrazone is unstable moreover, the high nitrogen content of semicarbazones enables very small quantities to be accurately analysed and so identified. The general conditions for the formation of semicarbazones are very similar to those for oximes and phenylhydrazones (pp. 93, 229) the free base must of course be liberated from its salts by the addition of sodium acetate. 

CAN-mediated nitration provides a convenient route for the introduction of a nitro group into a variety of substrates. Alkenes on treatment with an excess of sodium nitrite and CAN in chloroform under sonication afford nitroalkenes. When acetonitrile is used as the solvent, nitroacetamidation occurs in a Ritter-type fashion. However, the attempted nitroacetamidation of cyclo-pentene-1 -carboxaldehyde under similar conditions resulted in the formation of an unexpected dinitro-oxime compound. A one-pot synthesis of 3-acetyl- or 3-benzoylisoxazole derivatives by reaction of alkenes (or alkynes) with CAN in acetone or acetophenone has been reported. The proposed mechanism involves a-nitration of the solvent acetone, oxidation to generate the nitrile oxide, and subsequent 1,3-dipolar cycloaddition with alkenes or alkynes. The nitration of aromatic compounds such as carbozole, naphthalene, and coumarins by CAN has also been investigated. As an example, coumarin on treatment with 1 equiv of CAN in acetic acid gives 6-nitrocoumarin in 92% yield. ... 

Mesityl oxide Methyl benzoate Nitroethane Propyl alcohol Propylene dichloride Tetrahydrofurfuryl alcohol Trichloroethylene solvent, cellulose ethers Acetone oxime Acetophenone Butyl benzoate Butyl formate Cyclohexane Cyclohexyl acetate Dibutyl tartrate Diethyl oxalate Epichlorohydrin Ethyl butyrate Ethylene glycol diacetate Ethyl-(S)-lactate Ethyl propionate Isopropyl butyrate Mesityl oxide... 

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