Ketones aryl, oxidation

A related reaction involves oe-substituted aryl nitriles having a sufficiently acidic a hydrogen, which can be converted to ketones by oxidation with air under phase-... 

Acyl substituents at the 3- and/or 4-positions result in decreased hydrolytic stability compared with the alkyl and aryl derivatives described above. Despite this constraint most of the usual reactions of the carbonyl group are possible. Aldehydes <9ILA1211> and ketones are oxidized to the carboxylic acid, borohydride reduction affords the expected alcohols, and epoxides are formed on reaction with diazomethane. Oximes and arylhydrazones are formed with hydroxylamine and arylhydrazines, and the products may subsequently undergo monocyclic rearrangement involving the oxadiazole to give the corresponding isomeric furazans and 1,2,3-triazoles (Section 4.05.5.1.4). 

When an aryl alkyl ketone is oxidized, the R remains attached to the carbonyl carbon and Ar is bonded to O of the ester group. 

Oxidative desulfonylation.- Aryl sulfones are converted into ketones by oxidation of the a-carbanion (LDA) with Mo05Py-HMPT in THF at —78 in 50-97% yield. This conversion permits use of phenyl vinyl sulfone as an equivalent of kctcnc in Diels Alder reactions. 

The Dakin Reaction allows the preparation of phenols from aryl aldehydes or aryl ketones via oxidation with hydrogen peroxide in the presence of base. The aryl formate or alkanoate formed as an intermediate is subsequently saponified to yield the substituted phenol product. 

Esters have been prepared in 63-73% yields from several simple cycloalkyl and aryl alkyl ketones by reaction at room temperature with per-benzoic acid. The larger radical of the ketone appears as the alcohol fragment of the ester. Cyclic ketones are oxidized by potassium persulfate and sulfuric acid to esters from which o>-hydroxy aliphatic esters are obtained upon hydrolysis and reesterification. Peracetic acid in acetic anhydride converts salicylaldehyde to o-hydroxyphenyl formate (88%). ... 

NaHCOs, and methanesulfonic anhydride.Dimethyl sulfoxide in 48% HBr oxidizes benzylic alcohols the aryl aldehydes.Note that Swern oxidation of molecules having alcohol moieties, as well as a disulfide, leads to the ketone without oxidation of the sulfur. Sulfoxides other than DMSO can be used in conjunction with oxalyl chloride for the oxidation of alcohols,including fluorinated sulfoxides and a polymer-bound sulfoxide. ... 

A related reaction involves a-substituted aryl nitriles having a sufficiently acidic a hydrogen, which can be converted to ketones by oxidation with air under phase transfer conditions. The nitrile is added to NaOH in benzene or DMSO containing a catalytic amount of triethylbenzylammonium chloride (TEBA). " This reaction could not be applied to aliphatic nitriles, but an indirect method for achieving this conversion is given in 19-60. a-Dialkylamino nitriles can be converted to ketones, R2C(NMe2)CN —> R2C=0, by hydrolysis with Q1SO4 in aqueous methanol or by autoxidation in the presence of r-BuOK. ... 

Aryl ketones. Benzylic oxidation is conveniently carried out with NaBiOj and acetic acid in aqueous acetone. 

Recently, the groups of Mukaiyama [69] and Feng [70] independently demonstrated that aryl oxide anions such as phenoxide [69] or binaphthoxide [70] can be used instead of fluoride to activate (TMS)CF3 as a Lewis base. Several types of aromatic ketones and aldehydes were smoothly trifluoromethylated within a few hours in the presence of cinchona-based quaternary ammonium salts bearing an aryl oxide anion 148 or 149, affording the corresponding product in excellent yields and with moderate to high ee values (up to 87% ee) (Schemes 8.58 and 8.59). 

Hydrogenation of CO. COj (Fischer-Tropsch), olefins, oximes, nitriles, phenols, ben7)4 alcohols, aryl amines, aromatic heterocycles, cyclopentane. aliphatic ketones, nitrobenzenes, oxidation of hydrocarbons Ammonia synthesis... 

Oxidative cleavage is clearer-cut when one of the carbon atoms in -position to the carbonyl group is that of a methyl group (see below) or carries no hydrogen (as in alkyl aryl ketones) the oxidant then attacks only at the side where the -methylene or methine group lies. Ditertiary ketones such as benzo-phenone are therefore almost completely stable against oxidation. 

Oxidation of Carbon Skeletons with IBX. Allylic and benzylic positions are also susceptible to oxidation by IBX. These applications are not limited to the oxidation of compounds containing a pre-existing oxygen functionality but oxidize the hydrocarbon center directly to aldehydes or ketones. These oxidations also proceed via a single-electron-transfer pathway. The oxidation of aryl methyl groups to aryl aldehydes is accomplished with 3 equiv of IBX in DMSO or DMSO/fluorobenzene mixtures at 80-90 The first two equivalents of IBX initiate the single-electron-transfer to generate a benzylic carbocation. Subsequently, the reaction with water affords the alcohol in situ and the third equivalent of IBX completes the conversion to the desired benzaldehyde (eq 13). ... 

A convenient, two-step synthesis of substituted furans fiom readily available aryl alkynes and ketones involves oxidative cyclization mediated by the combination of cerium(IV) ammonium nitrate and potassium bromide.The reaction can also be carried out in an open flask without inert atmosphere protection (14TL5667). 

OSO4-catalysed oxidative cleavage of olefins by H2O2 in DMF and MeCN leads to the formation of corresponding aldehydes and ketones. Aryl olefins were cleaved in good to excellent yield regardless of arene electronics whereas di- and tri-substituted alkyl olefins cleaved in moderate to good yield. ... 

Cheng et al. developed an efficient [CuI(bpy)]2/02-catalyzed intramolecular oxidative C-H amination reaction of 2-aminoacetophenones for the synthesis of various AT-alkyl- or aryl-substituted isatins in moderate to good yields (Scheme 8.38). The 2-aminoglyoxal intermediate may be formed from 2-aminoaryl methyl ketone under oxidation conditions, and it could undergo intramolecular cyclization to give the desired isatins [76]. 

The abihty to perform oxidations without generating species harmful for potential intermediates of further transformations is important to perform multistep synthesis, such as the domino reactions described below (Section 5). In this respect, the use of aryl hahdes as readily available, stable and cheap oxidants (hydride acceptors) is a powerful option due to the production of inert, dehalogenated aryl by-products in anaerobic conditions. Commercially available Pd and Ni complexes with NHC ligands were found to be active in a temperature-controlled domino oxidation/R-ketone arylation with aryl halide. ... 

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