Alcohols, oxidizing reagents ketones

The widely used Moifatt-Pfltzner oxidation works with in situ formed adducts of dimethyl sulfoxide with dehydrating agents, e.g. DCC, AcjO, SO], P4O10, CCXTl] (K.E, Pfitzner, 1965 A.H. Fenselau, 1966 K.T. Joseph, 1967 J.G. Moffatt, 1971 D. Martin, 1971) or oxalyl dichloride (Swem oxidation M. Nakatsuka, 1990). A classical procedure is the Oppenauer oxidation with ketones and aluminum alkoxide catalysts (C. Djerassi, 1951 H. Lehmann, 1975). All of these reagents also oxidize secondary alcohols to ketones but do not attack C = C double bonds or activated C —H bonds. 

Secondary alcohols are oxidized to ketones by the same reagents that oxidize primary alcohols... 

DESS - MARTIN Oxidizing Reagent Oxidation of alcohols to aldehydes or ketones by means of penodinanes. 

Discussion of ketone oxidation has centred around the identity of the molecule undergoing oxidation. This has been clearly resolved in some, but not all, cases, the evidence resting on (i), the relative rates of enolisation and oxidation, (ii) kinetic orders and (ih) isotope effects. A general feature of the oxidations of ketones by one-equivalent reagents is that the rate for a given oxidant exceeds that for oxidation of a secondary alcohol by the same oxidant. The most attractive explanation is that the radical formed from a ketone is stabilised by delocalisation, viz. 

There are many ways to categorize the oxidation of double bonds as they undergo a myriad of oxidative transformations leading to many product types including epoxides, ketones, diols, endoperoxides, ozonides, allylic alcohols and many others. Rather than review the oxidation of dienes by substrate type or product obtained, we have chosen to classify the oxidation reactions of dienes and polyenes by the oxidation reagent or system used, since each have a common reactivity profile. Thus, similar reactions with each specific oxidant can be carried out on a variety of substrates and can be easily compared. 

Hydrogen transfer reactions from an alcohol to a ketone (typically acetone) to produce a carbonyl compound (the so-caUed Oppenauer-type oxidation ) can be performed under mild and low-toxicity conditions, and with high selectivity when compared to conventional methods for oxidation using chromium and manganese reagents. While the traditional Oppenauer oxidation using aluminum alkoxide is accompanied by various side reactions, several transition-metal-catalyzed Oppenauer-type oxidations have been reported recently [27-29]. However, most of these are limited to the oxidation of secondary alcohols to ketones. 

Asymmetric epoxidation of olefins is an effective approach for the synthesis of enan-tiomerically enriched epoxides. A variety of efficient methods have been developed [1, 2], including Sharpless epoxidation of allylic alcohols [3, 4], metal-catalyzed epoxidation of unfunctionalized olefins [5-10], and nucleophilic epoxidation of electron-deficient olefins [11-14], Dioxiranes and oxazirdinium salts have been proven to be effective oxidation reagents [15-21], Chiral dioxiranes [22-28] and oxaziridinium salts [19] generated in situ with Oxone from ketones and iminium salts, respectively, have been extensively investigated in numerous laboratories and have been shown to be useful toward the asymmetric epoxidation of alkenes. In these epoxidation reactions, only a catalytic amount of ketone or iminium salt is required since they are regenerated upon epoxidation of alkenes (Scheme 1). 

The oxidation of a secondary alcohol to a ketone can also occur through the use of a variety of oxidizing agents. Figure 3-22 illustrates the oxidation of a secondary alcohol using Jones reagent. 

Common alcohol oxidation methods employ stoichiometric amounts of toxic and reactive oxidants like Cr03, hypervalent iodine reagents (Dess-Martin) and peracids that pose severe safety and environmental hazards in large-scale industrial reactions. Therefore, a variety of catalytic methods for the oxidation of alcohols to aldehydes, ketones or carboxylic acids have been developed employing hydrogen peroxide or alkyl hydroperoxides as stoichiometric oxygen sources in the presence of catalytic amounts of a metal catalyst. The commonly used catalysts for alcohol oxidation are different MoAV(VI), Mn(II), Cr(VI), Re(Vn), Fe(II) and Ru complexes . A selection of published known alcohol oxidations with different catalysts will be presented here. 

They used this new oxidizing reagent for a rapid and selective oxidation of primary and secondary benzylic alcohols to the corresponding aldehydes and ketones in good to excellent yields. BTPCP was later used for oxidation of various alkylbenzenes under neutral conditions in aqueous CH3CN to the corresponding carbonyl compounds in good yields (equation 34) °. ... 

Any oxidizing reagents, including H2Cr04, Jones reagent or PCC, can be used to oxidize 2° alcohols to ketones. However, the most common reagent used for oxidation of 2° alcohols is chromic acid (H2Cr04). 

An asymmetric synthesis of mevalolactone in over 87% e.e. employs a 1,3-oxathiane as the chiral auxiliary (81TL2859). The reagent (818), easily prepared from (+)-pulegone (81TL2855), was metallated with u-butyllithium and the anion reacted with acetaldehyde. Oxidation of the diastereomeric mixture of alcohols to the ketone (819) and reaction of... 

Uhromic acid, in a variety of acidic media, has been used extensively for the oxidation of primary alcohols to aldehydes Itul. rarely has provided aldehydes in greater than 50% yield.5 Uhromium trioxide in pyridine was introduced as a unique, hniiacidic reagent for alcohol oxidations and has been used extensively to prepare ketones, but has been applied with only limited success to the preparation of aldehydes. While o-metlmxybenzaldehyde was obtained in 89% yield, 4-nitro-beir/.uldehyde and n-heptanal were obtained in 28% and 10% yields, respectively.7... 

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