Acetophenone oxime, reaction with

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

A possible synthesis of the extensively studied 4,5-dichloro-l,2,3-dithiazolium chloride (Appel salt) analogs (see next section) was found in the reaction of acetophenone oxime and its 4-nitro derivative with S2CI2 (1994H1827, 1997BSB605 Scheme 73). 

FIGURE 8. Hammett plots for reactions of 4-nitrophenyl benzoate (PNPB) with Z-substituted acetophenone oximates ( ) and phenoxides (O) in 20 mol% DMSO (A) and 90 mol% DMSO (B) at 25.0 0.1 °C. Reprinted from Tetrahedron Lett., 36, Um, Oh and Kwon, 6903, Copyright (1995), with permission from Elsevier... 

Sheradsky has found that the hydroxyl function of a ketoxime such as acetophenone oxime can be made to react with DMAD when the reaction is carried out in methanol with a basic catalyst, to give mixture of the fumarate and maleate isomers (164) in the ratio 2 1. This mixture on heating undergoes a hetero-Cope rearrangement followed by cyclization and dehydration to give dimethyl 5-phenylpyrrole-2,3-dicarboxylate (168) (Scheme 25). Similarly, Heindel and Chun have reported that vinyl ether adducts (171), obtained by the condensation of arylamide oximes with DMAD, get thermally converted into oxa-diazolines (172) or imidazolinones (174), depending on the reaction conditions. A similar reaction occurs with aromatic amidoxime-methyl propiolate adducts to give imidazoles (170) (Scheme 26). 1,2,4-Dioxazoles have been reported to be formed in the reaction of hydrox-amic acids with DMAD. - ... 

An imine moiety can, interestingly, be interposed in the ether linkage used to connect the two halogenated aromatic rings. The requisite oxime (55-1) is obtained in a straightforward fashion by reaction of imidazo acetophenone (54-2) with hydroxyl-amine alkylation with a,2,3-trichlorotoluene leads to oxiconazole (55-2) [60]. 

Oximes of aliphatic and aromatic ketones are catalytically reduced in the presence of hydrogen to ketimines. Acetophenone oxime gives the imine in 30% yield [28]. This reaction is not of practical value and gives much poorer yields than the direct reaction of ammonia or amines with the carbonyl compounds. 

The starting oximes (acetophenone oxime and cyclohexanone oxime) were prepared by reaction of the corresponding carbonyl compound with hydroxylamine hydrochloride. The purity of the resulting oximes was checked by GC and IR spectroscopy after recrystallisation of the samples. 

The yield of the reaction (Table 1) clearly depends or the nature of the solid and on the experimental conditions (temperature, time). Thus, with silica and alumina, amorphous solids with a relatively low acidity, the acetophenone oxime molecule reacts with a very low yield, being the only reaction product the hydrolysis one, acetophenone. With the synthetic mixed oxide silica-alumina, that possesses simultaneously BrOnsted and Lewis acidic centres, the conversion is quantitative, being also the major product the hydrolysis one (3), when the reaction is carried out at 160°C. 

Conversion (%) and selectivity (%) in the reaction of acetophenone oxime with different acidic solids (rate solid/oxime = 5 1) hydrated (50% r.h.). Reaction conditions 160°C/lh and 130°C/3h. 

On the other hand, we have compared the yield and selectivity in the reactions of acetophenone oxime with Al3 and Cr3 exchanged montmorillonites activated thermically and by microwaves (Fig. 2). From the obtained results, we can deduce that microwaves enhance significatively the conversion rate, being the conversion practically quantitative for only 10 minutes of treatment at 600W. The selectivity of the reaction can be directly correlated with that of the thermal treatment at 160°C. The effect of microwaves could be attributed, as we have previously demonstrated (ref.8) to the rapid... 

Analogous conclusions have been drawn in studying the reaction of acetophenone oxime with acetylene (Scheme 2) leading to 2-phenylpyrrole (3) and 2-phenyl-1-vinylpyrrole (4) (78ZOR1733). 

The dependence of the catalytic activity upon the nature of the hydroxide cation (Tables III and IV) was studied using the same reactions of cyclohexanone and acetophenone oximes with acetylene as an example... 

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-... 

Unknown until recently, 2-(4-ethylthio)- and 2-(4-phenylthiophenyl)-pyrroles (8,9) are formed in a yield of up to 48% by the reaction of 4-ethylthio- and 4-phenylthio-acetophenone oximes with acetylene under atmospheric pressure at 96°C (Scheme 7) [90ZOR(ip)]. 

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... 

Only a minor quantity of 6,8-di phony I-1,2,3,4,5-pentathicpino[6,7-r] pyrrole was detected in the reaction of acetophenone oximes with S2CI2 in the presence of 2-aminophenol <1997BSB605>. 

Pearson et al. (1952) employed this approach to derive a series of substituent parameters for electron-deficient reactions of substituted benzenes. These constants, designated as sigmae, were based on a study of the Beckmann rearrangement of -substituted acetophenone oximes. These authors considered the rates of the rearrangement reaction of the oximes to deviate from the Hammett eq. (1). It is pertinent that, with the sole exception of the yi-OMe group, the deviations were not major. The entropy of activation, AS, for the -anisyl derivative was, however, 20 e.u. different from the essentially constant values for the other substituents. To remedy the deviations, Pearson and his associates suggested the sigmae constants. It was indicated that these constants were more suitable for the correlations of electron-deficient reactions than the conventional cr-values. 

Mechanisms have been suggested for the N-bromosuccinimide (NBS) oxidation of cyclopentanol and cyclohexanol, catalysed by iridium(III) chloride,120 of ethanolamine, diethanolamine, and triethanolamine in alkaline medium,121 and for ruthenium(III)-catalysed and uncatalysed oxidation of ethylamine and benzylamine.122 A suitable mechanism has been suggested to explain the break in the Hammett plot observed in the oxidation of substituted acetophenone oximes by NBS in acidic solution.123 Oxidation of substituted benhydrols with NBS showed a C-H/C-D primary kinetic isotope effect and a linear correlation with er+ values with p = —0.69. A cyclic transition state in the absence of mineral acid and a non-cyclic transition state in the presence of the acid are proposed.124 Sulfides are selectively oxidized to sulfoxides with NBS, catalysed by ft-cyclodextrin, in water. This reaction proceeds without over-oxidation to sulfones under mild conditions.125... 

Acetophenone oxime and its 4-nitro derivative gave with S2Cl2 the l,2,3-dithiazolium chlorides 135. These are analogs of Appel salt 20 which were not isolated but converted to the 5-arylimino derivatives 136 by the reaction with arylamines (Scheme 21) <1997BSB605>. 

The furooxazines (75) react with DBU to form oxazines which can react further under the conditions of the reaction to yield pyridines (76). The compound (75 R = H, R1 = Ph) rearranges under acid catalysis to yield a-(2-furyl)acetophenone oxime (Scheme 4) <79JCS(Pl)249,83JCS(P1)1283, 87JCS(P1)2505>. 

Continuing their work on 1,4-dianions of phenylhydrazone, Hauser and coworkers inspected similar reactions with the 1,4-oxime dianions98. Acetophenone oxime gave the dilithium salt in reaction with /-BuLi and underwent C-alkylation with benzyl chloride and dialkylation with 1,4-dibromobutane (equation 32). 

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