Epoxidation aldehydes and ketones

The intermediate adduct can be substituted at the a-position by a variety of electrophiles, including acyl chlorides, epoxides, aldehydes, and ketones.79... 

For example, polymers having hydroxyl end groups can be prepared by reaction of polymer lithium with epoxides, aldehydes, and ketones III-113). Carboxylated polymers result when living polymers are treated with carbon dioxide (///) or anhydrides (114). When sulfur (115, 116), cyclic sulfides (117), or disulfides (118) are added to lithium macromolecules, thiol-substituted polymers are produced. Chlorine-terminus polymers have reportedly been prepared from polymer lithium and chlorine (1/9). Although lithium polymers react with primary and secondary amines to produce unsubstituted polymers (120), tertiary amines can be introduced by use of p-(dimethylamino)benzaldehyde (121). 

The procedures in Sect. 4 give some representative examples of metallation of nitriles and isonitriles and reactions of the anionic intermediates with alkylating agents, epoxides, aldehydes, and ketones. Syntheses involving the generation of anionic intermediates (mostly in small concentrations) and their immediate further reaction with an electrophile present in the medium during this generation fall beyond the scope of this book. 

Chapters 7 through 10 cover oxygen functionality in order of the increasing oxidation state of carbon—alcohols and phenols, ethers and epoxides, aldehydes and ketones, and acids and their derivatives. Brief mention of sulfur analogs is made in these chapters. Chapter 11 deals with amines. Chapters 2 through 11 treat every main functional group and constitute the heart of the course. Chapter 12 then takes up spectroscopy, with an emphasis on nuclear magnetic resonance (NMR) and applications to structure determination. This chapter handles the students question How do you know that those molecules really have the structures you say they have ... 

Many aldehydes and ketones react with (12) to give better than 75% yields of epoxides (eq. 23) ... 

The dianions derived from furan- and thiophene-carboxylic acids by deprotonation with LDA have been reacted with various electrophiles (Scheme 64). The oxygen dianions reacted efficiently with aldehydes and ketones but not so efficiently with alkyl halides or epoxides. The sulfur dianions reacted with allyl bromide, a reaction which failed in the case of the dianions derived from furancarboxylic acids, and are therefore judged to be the softer nucleophiles (81JCS(Pl)1125,80TL505l). 

Epoxidation of aldehydes and ketones is the most profound utility of the Corey-Chaykovsky reaction. As noted in section 1.1.1, for an a,P-unsaturated carbonyl compound, 1 adds preferentially to the olefin to provide the cyclopropane derivative. On the other hand, the more reactive 2 generally undergoes the methylene transfer to the carbonyl, giving rise to the corresponding epoxide. For instance, treatment of P-ionone (26) with 2, derived from trimethylsulfonium chloride and NaOH in the presence of a phase-transfer catalyst Et4BnNCl, gave rise to vinyl epoxide 27 exclusively. ... 

The ion 133 also reacts with epoxides to form y-hydroxy aldehydes after reduction and hydrolysis,and with aldehydes and ketones (16-41). Similar aldehyde synthesis has also been carried out with thiazoles " and thiazolines (five-... 

Aldehydes and ketones can be converted to epoxides in good yields with the sulfur ylids dimethyloxosulfonium methylid (60) and dimethylsulfonium methylid (61). For most purposes, 60 is the reagent of choice, because 61 is much less... 

Aldehydes and ketones can also be converted to epoxides by treatment with a diazoalkane,most commonly diazomethane, but an important side reaction is the formation of an aldehyde or ketone with one more carbon than the starting compound (Reaction 18-9). The reaction can be carried out with many aldehydes, ketones, and quinones. A mechanism that accounts for both products is... 

The complex Pd-(-)-sparteine was also used as catalyst in an important reaction. Two groups have simultaneously and independently reported a closely related aerobic oxidative kinetic resolution of secondary alcohols. The oxidation of secondary alcohols is one of the most common and well-studied reactions in chemistry. Although excellent catalytic enantioselective methods exist for a variety of oxidation processes, such as epoxidation, dihydroxy-lation, and aziridination, there are relatively few catalytic enantioselective examples of alcohol oxidation. The two research teams were interested in the metal-catalyzed aerobic oxidation of alcohols to aldehydes and ketones and became involved in extending the scopes of these oxidations to asymmetric catalysis. 

Scheme 7.4 illustrates some of the important synthetic reactions in which organolithium reagents act as nucleophiles. The range of reactions includes S/v2-(ype alkylation (Entries 1 to 3), epoxide ring opening (Entry 4), and formation of alcohols by additions to aldehydes and ketones (Entries 5 to 10). Note that in Entry 2, alkylation takes place mainly at the 7-carbon of the allylic system. The ratio favoring 7-alkylation... 

An alternative to the synthesis of epoxides is the reaction of sulfur ylide with aldehydes and ketones.107 This is a carbon-carbon bond formation reaction and may offer a method complementary to the oxidative processes described thus far. The formation of sulfur ylide involves a chiral sulfide and a carbene or carbenoid, and the general reaction procedure for epoxidation of aldehydes may involve the application of a sulfide, an aldehyde, or a carbene precursor as well as a copper salt. This reaction may also be considered as a thiol acetal-mediated carbene addition to carbonyl groups in the aldehyde. 

V.C.8.1. Alkenes and Alcohol Functions. Although TS-1 and other titanosi-licates oxidize alcohols to the corresponding aldehydes and ketones, the rates are suppressed in the presence of compounds containing C=C bonds. CH3OH, for example, is not oxidized at all during epoxidations of alkene reactants. Higher alcohols, however, are partially oxidized. The oxidation of unsaturated alcohols in the presence of TS-1 is shown in Table XVII (193). 

Sodium borohydride is a much milder reducing agent than lithium aluminium hydride and like the latter is used for the reduction of carbonyl compounds like aldehydes and ketones. However, under normal conditions it does not readily reduce epoxides, esters, lactones, acids, nitriles or nitro groups. 

Alkyl- and aryl-hydrazones of aldehydes and ketones readily peroxidise in solution and rearrange to azo hydroperoxides [1], some of which are explosively unstable [2], Dry samples of the p-bromo- and p-fluoro-hydroperoxybenzylazobenzenes, prepared by oxygenation of benzene solutions of the phenylhydrazones, exploded while on filter paper in the dark, initiated by vibration of the table or tapping the paper. Samples were later stored moist with benzene at —60°C to prevent explosion [3], A series of a-phenylazo hydroperoxides derived from the phenyl-or p-bromophcnyl-hydrazones of acetone, acetophenone or cyclohexanone, and useful for epoxidation of alkenes, are all explosive [4], The stability of several substituted phenylazo hydroperoxides was found to be strongly controlled by novel substituent effects [5],... 

This was the first-described, non-stabilized ylide, obtained by treatment of the corresponding telluronium tetrafluoroborate with hthium 2,2,6,6-tetramethylpiperidide (LiTMP). Epoxides are obtained by reaction with both aldehydes and ketones. ... 

As in the preceding case, the ylide is obtained using LiTMP as the base and gives epoxides with aldehydes and ketones. z... 

Solutions of low-valence titanium chloride (titanium dichloride) are prepared in situ by reduction of solutions of titanium trichloride in tetrahydrofuran or 1,2-dimethoxyethane with lithium aluminum hydride [204, 205], with lithium or potassium [206], with magnesium [207, 208] or with a zinc-copper couple [209,210]. Such solutions effect hydrogenolysis of halogens [208], deoxygenation of epoxides [204] and reduction of aldehydes and ketones to alkenes [205,... 

Examples of the use of dimethylsulfoniurn methylide and dimethylsulfoxonium methylide in the preparation of epoxides are listed in Scheme 2.19. Entries 1-4 illustrate epoxide formation with simple aldehydes and ketones. 

Bhatia KA, Eash KJ, Leonard NM, Oswald MC, Mohan RS (2001) A facile and efficient method for the rearrangement of aryl-substituted epoxides to aldehydes and ketones using bismuth triflate. Tetrahedron Lett 42 8129-8132... 

Sulfur ylides react with aldehydes and ketones to form epoxides (oxiranes) ... 

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