Ketones by oxidation

Difluoroalkenyl boranes, which are prepared in situ, are converted to difluoromethyl ketones by oxidation with hydrogen peroxide m alkaline media [720] (equation 107)... 

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-... 

Ethynyl Ketones by Oxidation of the Corresponding Ethynyl Carbinols with Chromic Add... 

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. 

Aldehydes and ketones By oxidation of the appropriate alcohol. Oxidation... 

Bowden, K., I. M. Heilbron, E. R. H. Jones, and B. C. L. Weedon (1946) Researches on acetylenic compounds. Part I. The preparation of acetylenic ketones by oxidation of acetylenic carbinols and glycols. Journal of the Chemical Society (London), 39-45. 

The reaction of MVL with trialkylboranes gave vinyl borate salts 536, which suffer alkyl migration at room temperature to give salts 537. These compounds can be transformed into vinyl ethers or methyl ketones by oxidation with hydrogen peroxide (Scheme 144)819. 

Acetalization of l-alkenes. The Wacker uinversion of l-alkenes to methyl ketones by oxidation catalyzed by PdCE-CuCl takes a different course when applied to vinyl ketones (1). Thus oxygenation of mixtures of I and 1,3- or 1,2-diols catalyzed by PdCE-CuCl results in cyclic acetals formed by exclusive attaek at the terminal carbon atom. A similar reaction occurs with l-alkenes substituted with COOCH,. 

Cleavage of ketones by oxidation is infrequently used for preparation of monocarboxylic acids. Trimethylacetic acid is made in 75% yield from pinacolone, (CHj)jCCOCHj, by oxidation with chromic anhydride in aqueous acetic acid. Cleavage on only one side of the carbonyl group is possible in this case. 

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. ... 

A special category of ethers are trimethylsilyl ethers. Trimethylsilyl ethers of primary alcohols, on treatment with Jones reagent, give acids [590]. On treatment with A-bromosuccinimide under irradiation, trimethylsilyl ethers yield esters [744]. Secondary alkyl trimethylsilyl ethers are converted into ketones by oxidation with both reagents [590, 744, 981]. Oxidation with Jones reagent is regiospecific the 2-ferf-butyldimethylsilyl 11-Krf-butyldiphenylsilyl ether of 2,11-dodecanediol is oxidized only in the sterically less hindered position [590]. Trimethylsilyl ethers of tertiary alcohols are degraded by periodic acid to carboxylic acids with shorter chains [755] (equations 336-339). 

In general, better results are obtained with Raney nickel catalysts, especially in large-scale reactions. The preferential formation of the thermodynamically most stable product can be used, e.g., in the synthesis of steroids from aromatic precursors such as 1324. Here hydrogenation yields the tram-fused product with a nearly equimolar mixture of the two isomeric alcohols, which can be converted into the corresponding ketone by oxidation with chromium trioxide24. 

The initial compound (9) was prepared by stirring 1,3,5 trimethoxybenzene with 1 -methyl-4-piperidone in glacial acetic acid. The tram alcohol (10) was obtained by hydration of the double bond and the corresponding cis compound (11) then made via the ketone by oxidation then reduction. Treatment with acetic anhydride and an acid catalyst such as boron trifluoride etherate gave (12). Treatment of this compound at room temperature with ethyl benzoate in the presence of sodium metal produced the diketone (13) which was cyclised to (14) by the addition of mineral acid. Final demethoxylation of the chromone hydroxy groups with pyridine hydrochloride was carried out for several hours at 180°. 

In the formation of both aldehydes and ketones by oxidation, the change consists in the removal of two hydrogen atoms a similarity in structure of the two classes of compounds, and, as a consequence, in their reactions might be expected. Such similarity does exist. In the determination of the structure of... 

The most commonly used synthesis of [l,2,3]triazolo[l,5-fl]pyridines remains that from the hydrazones of 2-p) idyl-carboxaldehydes or -ketones by oxidation. Some hydrazones give triazolop) dines when boiled in methanol in the presence of air, but all other reported cases require an added oxidant. The use of the most common oxidants illustrates the versatility of the synthesis. Nickel peroxide, potassium ferrocyanide and bicarbonate, air and a copper-II salt, manganese dioxide or (diacetoxyiodo)benzene have been used (02AHC1). An alternative route from tosylhydrazones of 2-pyridyl-carboxaldehydes or ketones by treatment with base, usually morpholine, has been used for high yields of sensitive materials (02AHC1). 

Ethanol SC Other alcohols, ketones (by oxidation meihods). 

Iodosylbenzoic acid (85) is also a convenient recyclable hypervalent iodine oxidant for the synthesis of a-iodo ketones by oxidative iodination of ketones [88], Various ketones and p-dicarbonyl compounds can be iodinated by this reagent system under mild conditions to afford the respective a-iodo substituted carbonyl compounds in excellent yields. The final products of iodination are conveniently separated from by-products by simple treatment with anionic exchange resin Amberlite IRA 900 HCOs" and are isolated with good purity after evaporation of the solvent. The reduced form of the hypervalent iodine oxidant, 3-iodobenzoic acid (59), can be recovered in 91-95% yield from the Amberlite resin by treatment with aqueous hydrochloric acid followed by extraction with ethyl acetate [88]. 

The best way to initially solve a multistep synthesis is to work backward from the final product. Identify the functional group present in the product—in this case, a ketone. Think how to prepare a ketone—by oxidizing an alcohol. 

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