Ketones, unsaturated with hydrogen peroxide

Oxidation. Ketones are oxidized with powerful oxidizing agents such as chromic or nitric acid. During oxidation, carbon—carbon bond cleavage occurs to produce carboxyHc acids. Ketone oxidation with hydrogen peroxide, or prolonged exposure to air and heat, can produce peroxides. Concentrated solutions of ketone peroxides (>30%) may explode, but dilute solutions are useful in curing unsaturated polyester resin mixtures (see... 

Saturated 5/3- and 4 -unsaturated steroid 3-ketones react with hydrogen peroxide in solution in /-butanol containing hydrochloric acid to form bishydroperoxides (5,6) in good yield. "... 

Methyl ethyl ketone peroxide (MEKPO) is the typical sort of highly reactive chemical. It is used as a catalyst for the room temperature curing of unsaturated polyester resins and an initiator for polymerization reactions. It is manufactured in the oxidation process of methyl ethyl ketone (MEK) with hydrogen peroxide (H2O2) (Liaw et al., 2(XX)). 

Polymeric OC-Oxygen-Substituted Peroxides. Polymeric peroxides (3) are formed from the following reactions ketone and aldehydes with hydrogen peroxide, ozonization of unsaturated compounds, and dehydration of a-hydroxyalkyl hydroperoxides consequendy, a variety of polymeric peroxides of this type exist. Polymeric peroxides are generally viscous Hquids or amorphous soHds, are difficult to characterize, and are prone to explosive decomp o sition. 

As in the case of the steroids, introduction of additional nuclear substituents yields morphine analogs of increased potency. The more important of these are derived from one of the minor alkaloids that occur in opium. Thebaine (14), present in crude opium in about one-tenth the amount of morphine, exhibits a reactive internal diene system that is well known to undergo various addition reactions in a 1,4 manner (e.g., bromination). Thus, reaction with hydrogen peroxide in acid may be visualized to afford first the 14-hydroxy-6-hemiketal (15). Hydrolysis yields the isolated unsaturated ketone (16). Catalytic reduction... 

The benzotriazolyl derivative of acrolein acetal, compound 882, is lithiated, treated with chlorodiphenylphosphine, and the obtained intermediate is oxidized with hydrogen peroxide to phosphine oxide 883 (Scheme 145). The relatively acidic proton in derivative 883 is easily removed by a base, and the obtained anion adds to a carbonyl group of aldehyde or ketone. Subsequent rearrangement and elimination of the phosphorane group generates diene 884. For the derivatives of aldehydes (884, R2 = H), (E)-(E) stereoselectivity of the elimination is observed. Acidic alcoholysis of dienes 884 affords esters of P,y-unsaturated carboxylic acids 885 < 1997JOC4131>. 

As a, (3-unsaturated ketones are electron-poor alkenes, they do not generally give epoxides when treated with peracids. They can be epoxidized with hydrogen peroxide which involves nucleophilic attack by HOO- to give the epoxy ketone (Figure 4.1). 

Thus, the N,N-dibenzyl-protected aminonitrile 55 was prepared via Swern oxidation of N,N-dibenzylaminoethanol 54 followed by treatment with the enantio-pure amine auxiliary (S,S)-53 and HCN, resulting in the formation of a 3 2 epimeric mixture of the aminonitriles 55 in 55% yield, from which the single dia-stereomers could be isolated by chromatography. After lithiation with LDA, addition to the requisite (E)-a, P-unsaturated esters and hydrolysis of the aminonitrile moiety with silver nitrate, the desired a-amino keto esters R)-S6 were obtained with yields of 65-81% and enantiomeric excesses ee of 78-98%, which could be improved to ee > 98% by a simple recrystallization. Since the amino ketone functionality can be cleaved oxidatively, the 5-amino-4-oxo-esters 56 could be transformed to the corresponding succinic half-esters 57 with hydrogen peroxide in methanol in good to excellent yields (68-90%) (Scheme 1.1.15). 

Conjugated dienes can be epoxidized (1,2-addition), although the reaction is slower than for corresponding alkenes, but a,p-unsaturated ketones do not generally give epoxides when treated with peroxyacids.The epoxidation of a,p-unsaturated ketones with hydrogen peroxide under basic conditions is known as the Waits-Schejfer epoxidation, discovered in 1921. This fundamental reaction has been extended to a,()-unsaturated ketones (including quinones), aldehydes, and... 

Allyl phenyl telluriums, prepared from allyl halides and benzenetellurolate, experience oxidative cleavage of the allyl group when treated with hydrogen peroxide, tcrr.-butyl hydroperoxide, sodium periodate, oxygen, or air The allyl group is converted to unsaturated alcohols, aldehydes, and ketones. Before elimination from the molecule the phenyltelluro group is probably oxidized to a telluroxide or a tellurinic ester ... 

TONs up to 9000 [11c]. Of potential interest is the use of ionic liquids which allow recycling of the catalyst (cf. Section 3.1.1.2.2) [33]. SALEN complexes are also eminently suitable for the kinetic resolution of epoxides [12 u] especially promising for commercial applications is hydrolytic ring-opening using Co/ SALEN complexes [34] (42 5). a,jff-Unsaturated ketones can be epoxidized with hydrogen peroxide in presence of a polypeptide catalyst with ee values up to >98% [35]. 

Reaction with enones and quinones. For an a,/3-unsaturated ketone to react with hydrogen peroxide a basic medium is required, the probable function being to... 

C. Bassin, A. Gusso, F. Pinna, G. Strukul, Platinum-catalyzed oxidations with hydrogen peroxide The (enantioselective) epoxidation of a,p-unsaturated ketones, Organometallics 14 (1995) 1161. 

Electrondeficient olefins can be epoxidized by hydrogen peroxide in the presence of bases. This method, known as the Weitz-Scheffer reaction, is used especially for the epoxidation of o,p-unsaturated ketones. Wynberg et al. [4] epoxidized a series of such ketones with hydrogen peroxide in the presence of quaternary ammonium salts of optically active alkaloids. Especially when phase-transfer conditions were used they yielded an e.e. of about 50% (Scheme 3). 

However, as Weitz and Scheffer found,43 <%,/ -unsaturated ketones give epoxy ketones in reaction with hydrogen peroxide in alkaline solution. 

Conversion of ketones into a,(3-unsaturated ketones has been effected by bromination-dehydrobromination, although a better method involves a-phenyl-seleno ketones as intermediates. These are normally obtained by reaction of the enolate of the ketone with a phenylselenyl halide or diphenyl diselenide at low temperature. Oxidation with hydrogen peroxide, sodium periodate or other oxidant gives the selenoxide which immediately undergoes syn p-elimination to form the a, -unsaturated ketone. The process is tolerant of many functional groups, such as... 

For the epoxidation of extremely unreactive alkenes and for the preparation of epoxides which are highly susceptible to nucleophilic attack, Dimethyldioxirane is the reagent of choice. Electron-deficient alkenes such as a, -unsaturated ketones are usually oxidized with Hydrogen Peroxide/base. 

There are similar procedures involving organic selenides. Reaction of ketones and aldehydes with phenylselenyl chloride occurs readily to give the a-seleno derivative, presumably by a mechanism similar to a-halogenation. Alternatively, ketones and esters can be converted to the a-seleno derivatives by reaction of the enolates with phenylselenyl chloride. The a-seleno compounds serve as precursors to a,jS-unsaturated carbonyl compounds because oxidation with hydrogen peroxide leads to spontaneous elimination of PhSeOH. 

Finally, additional multifunctional cleavage strategies are possible. Oxidative cleavage with hydrogen peroxide and sodium hydroxide can be used to generate phenols (Table 1.18, Entry 6) ° while rhodium(I)-mediated 1,2-addition to aldehydes provides secondary alcohols (Table 1.18, Entry 7) and 1,4-addition to a,p-unsaturated ketones yields ketones (Table 1.18, Entry 8). ... 

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