Ketones transition metal oxidation

The mechanisms by which transition metal oxidizing agents convert alcohols to aldehydes and ketones are complicated with respect to their inorganic chemistry The organic chemistry is clearer and one possible mechanism is outlined m Figure 15 4 The... 

Oxidation of Ketones and Aldehydes 12.5.1. Transition Metal Oxidants... 

Tert-butanol and 1-propanol were chosen because a marked difference in reactivity between the two alcohols was expected a priori. Transition metal oxides may also catalyze the formation of ketones or aldehydes by oxidative dehydrogenation providing they have a significant number of basic/acid site pairs [10], With both HY and WZ, the alcohol dehydration to ether and oxidative dehydrogenation pathways were essentially negligible. 

Sections 3.7.A and 3.7.B showed that alkenes are oxidatively cleaved hy transition metal oxidants. With certain reagents, 1,2-diols can also he oxidatively cleaved, usually to aldehydes or ketones. ... 

It was mentioned that oxidation by DDO allows the clean conversion of secondary alcohols into carbonyls under mild conditions. In this transformation the dioxiranes rank high with respect to transition-metal oxidants because of their efficiency, superior versatility, and ease of operations. Based on kinetic data and the application of reaction probes, the oxidation proceeds via a substantially concerted O-insertion by the dioxirane into the C-H bond alpha to the OH functionality generating a ge/w-diol C(0H)2, hence the carbonyl. As shown by the example in eq 36, remarkable chemoselectivity is achieved in the oxidation of epoxy alcohols in that the corresponding epoxy ketones are formed in high yield, while the epoxy functionality remains untouched. The epoxy ketone in eq 36 is a key intermediate in the convergent synthesis of active lQ ,25-dihydroxyvitainin D3 analogs. ... 

Heterogeneous catalytic oxidation of hydrocarbons has been extensively studied for the last century, since a large fraction of high value chemical feed stocks, such as organic aldehydes, acids, ketones, alcohols, etc., are produced by the catalytic partial oxidation of light alkanes and alkenes. Historically, oxidation reactions have always been carried out over either noble metals or transition metal oxides. Noble metals have been almost exclusively applied to complete oxidations, whereas transition metal oxides have been used for both selective and complete oxidations. 

Substituted v-butyrolactones can be prepared by reaction of aldehydes or ketones with tbe dianion (28), and direct condensation of symmetrical ketones with diethyl 2-oxomalonate provides a useful synthetic route to the butenolides (29). A number of initiators have been used previously to promote the free-radical addition of ketones to alkenes now transition-metal oxides have been shown to be effective. Pent-4-enal is cyclized to cyclopentanone by chlorotris(triphenylphos-phine)rhodium(i) through a non-radical pathway. ... 

A very useful group of procedures for oxidation of alcohols to ketones have been developed which involve dimethyl sulfoxide (DMSO) and any one of a number of electrophilic molecules, such as dicyclohexylcarbodiimide, acetic anhydride, trifluoroacetic anhydride, oxalyl chloride, and sulfur trioxide. The initial work involved DMSO and dicyclohexylcarbodiimide. The primary utility of this method is for oxidation of molecules that are sensitive to the more powerful transition metal oxidants. The mechanism of the oxidation involves formation of intermediate A by... 

Eithei oxidation state of a transition metal (Fe, Mn, V, Cu, Co, etc) can activate decomposition of the hydiopeioxide. Thus a small amount of tiansition-metal ion can decompose a laige amount of hydiopeioxide. Trace transition-metal contamination of hydroperoxides is known to cause violent decompositions. Because of this fact, transition-metal promoters should never be premixed with the hydroperoxide. Trace contamination of hydroperoxides (and ketone peroxides) with transition metals or their salts must be avoided. 

Transition metal catalysis in Baeyer-Villiger oxidation of cyclic ketones with formation of lactones 98AG(E)1198. 

The rate of oxidation/reduction of radicals is strongly dependent on radical structure. Transition metal reductants (e.g. TiMt) show selectivity for electrophilic radicals (e.g. those derived by tail addition to acrylic monomers or alkyl vinyl ketones - Scheme 3.89) >7y while oxidants (CuM, Fe,M) show selectivity for nucleophilic radicals (e.g. those derived from addition to S - Scheme 3,90).18 A consequence of this specificity is that the various products from the reaction of an initiating radical with monomers will not all be trapped with equal efficiency and complex mixtures can arise. 

Employing ketones or aldehydes as starting materials, the corresponding silylethers are obtained. Thereafter, the oxidation or hydrolysis of the obtained silylethers gives the corresponding alcohols (Scheme 17). In most cases, a hydride (silyl) metal complex H-M-Si (M = transition-metal), which is generated by an oxidative addition of H-Si bond to the low-valent metal center, is a key intermediate in the hydrosilylation reaction. 

Recently, great advancement has been made in the use of air and oxygen as the oxidant for the oxidation of alcohols in aqueous media. Both transition-metal catalysts and organocatalysts have been developed. Complexes of various transition-metals such as cobalt,31 copper [Cu(I) and Cu(II)],32 Fe(III),33 Co/Mn/Br-system,34 Ru(III and IV),35 and V0P04 2H20,36 have been used to catalyze aerobic oxidations of alcohols. Cu(I) complex-based catalytic aerobic oxidations provide a model of copper(I)-containing oxidase in nature.37 Palladium complexes such as water-soluble Pd-bathophenanthroline are selective catalysts for aerobic oxidation of a wide range of alcohols to aldehydes, ketones, and carboxylic acids in a biphasic... 

Tertiary butylhydroperoxide (TBHP) is a popular oxidizing agent used with certain catalysts. Because of its size, TBHP is most effective with catalysts containing large pores however, it can also be used with small-pore catalysts. Using first-row transition metals, Cr and V, impregnated into pillared clays, TBHP converts alcohols to ketones, epoxidizes alkenes, and oxidizes allylic and benzylic positions to ketones.83-87... 

During the past few years, increasing numbers of reports have been published on the subject of domino reactions initiated by oxidation or reduction processes. This was in stark contrast to the period before our first comprehensive review of this topic was published in 1993 [1], when the use of this type of transformation was indeed rare. The benefits of employing oxidation or reduction processes in domino sequences are clear, as they offer easy access to reactive functionalities such as nucleophiles (e. g., alcohols and amines) or electrophiles (e. g., aldehydes or ketones), with their ability to participate in further reactions. For that reason, apart from combinations with photochemically induced, transition metal-catalyzed and enzymatically induced processes, all other possible constellations have been embedded in the concept of domino synthesis. 

In real systems (hydrocarbon-02-catalyst), various oxidation products, such as alcohols, aldehydes, ketones, bifunctional compounds, are formed in the course of oxidation. Many of them readily react with ion-oxidants in oxidative reactions. Therefore, radicals are generated via several routes in the developed oxidative process, and the ratio of rates of these processes changes with the development of the process [5], The products of hydrocarbon oxidation interact with the catalyst and change the ligand sphere around the transition metal ion. This phenomenon was studied for the decomposition of sec-decyl hydroperoxide to free radicals catalyzed by cupric stearate in the presence of alcohol, ketone, and carbon acid [70-74], The addition of all these compounds was found to lower the effective rate constant of catalytic hydroperoxide decomposition. The experimental data are in agreement with the following scheme of the parallel equilibrium reactions with the formation of Cu-hydroperoxide complexes with a lower activity. 

Ketones are resistant to oxidation by dioxygen in aqueous solutions at T= 300-350 K. Transition metal ions and complexes catalyze their oxidation under mild conditions. The detailed kinetic study of butanone-2 oxidation catalyzed by ferric, cupric, and manganese complexes proved the important role of ketone enolization and one-electron transfer reactions with metal ions in the catalytic oxidation of ketones [190-194],... 

Silicon hydrides can also oxidatively add to low-valent transition metal complexes forming a metal hydride silyl complex which can undergo subsequent insertion reactions. This elementary step forms the basis for the hydrosilylation process for alkenes and ketones. 

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