Alkene To epoxide

In general, peroxomonosulfates have fewer uses in organic chemistry than peroxodisulfates. However, the triple salt is used for oxidizing ketones (qv) to dioxiranes (7) (71,72), which in turn are useful oxidants in organic chemistry. Acetone in water is oxidized by triple salt to dimethyldioxirane, which in turn oxidizes alkenes to epoxides, polycycHc aromatic hydrocarbons to oxides and diones, amines to nitro compounds, sulfides to sulfoxides, phosphines to phosphine oxides, and alkanes to alcohols or carbonyl compounds. 

Many other reagents for converting alkenes to epoxides,including H2O2 and Oxone , VO(0-isopropyl)3 in liquid C02, ° polymer-supported cobalt (II) acetate and 02, ° and dimethyl dioxirane.This reagent is rather versatile, and converts methylene oxiranes to spiro-epoxides. ° ° One problem with dimethyloxirane is C—H insertion reactions rather than epoxidation. Magnesium monoperoxyphthalate is commercially available, and has been shown to be a good substitute for m-chloroperoxybenzoic acid in a number of reactions. 

Transition Metal-Catalyzed Epoxidation of Alkenes. Other transition metal oxidants can convert alkenes to epoxides. The most useful procedures involve f-butyl hydroperoxide as the stoichiometric oxidant in combination with vanadium or... 

Catalyst Alkene Oxidizing agent Stage 1 alkene to epoxide Stage 2 epoxide to cyclic carbonate ... 

Other transition-metal oxidants can convert alkenes to epoxides. The most useful procedures involve /-butyl hydroperoxide as the stoichiometric oxidant in combination with vanadium, molybdenum, or titanium compounds. The most reliable substrates for oxidation are allylic alcohols. The hydroxyl group of the alcohol plays both an activating and a stereodirecting role in these reactions. /-Butyl hydroperoxide and a catalytic amount of VO(acac)2 convert allylic alcohols to the corresponding epoxides in good yields.44 The reaction proceeds through a complex in which the allylic alcohol is coordinated to... 

Optically pure (4-)-(5 )-Af-carbo(—)-menthylM-tolylsulfonimidoyl chloride was pre-pared and reacted with 02 " at 0 °C in CH3CN to give the expected optically active sulfonimidoylperoxy intermediate 50, which oxidizes alkenes to epoxides and sulfides to... 

Conversion of alkenes to epoxides The simplest epoxide, ethylene dioxide, is prepared by catalytic oxidation of ethylene, and alkenes are also oxidized to other epoxides by peracid or peroxy acid (see Section 5.7.2). 

Metal-Catalyzed Epoxidation. Hydrogen peroxide is able to convert alkenes to epoxides in the presence of metal catalysts. Several metal oxides (Mo03, W03, Se02, V205) are known to catalyze such epoxidations.2,245,278,279 All these catalysts form stable inorganic peracids, and these peracids are supposedly involved in epoxidation in a process similar to organic peracids. 

The nature of the arsonium substituents also influences the course of the reaction. Gosney et al. (33) studied the reaction between arsonium salts of type 50 and benzaldehyde in THF using -butyllithium to generate the ylide. The results, summarized in Table IX, clearly show that electron-donating substituents at the arsenic atom promote the formation of al-kenes. At one extreme, the reaction of 0) gives a notable yield of stilbene almost to the exclusion of stilbene oxide, whereas at the other, the reaction of (a) yields predominantly stilbene oxide. Table IX shows that electron-donating substituents at arsenic increase the ratio of alkene to epoxide. 

Tungsten(VI)-peroxo complexes such as W0(02)2(HMPA)(H20) are also effective reagents for the selective transformation of alkenes to epoxides. cis-Alkenes such as m-2-butene are exclusively converted to cis-epoxides.123... 

However, attempts to develop similar selective catalysts failed in the case of reactions that require one oxygen atom, like the oxidation of methane, ethane and other alkanes to alcohols, aromatic compounds to phenols, alkenes to epoxides, and many others. These mechanistically simple reactions assume one difficult condition the presence of active sites that upon obtaining two atoms from gas-phase 02 can transfer only one of them to the molecule to be oxidized, reserving the second atom for the next catalytic cycle with another molecule. This problem remains a hard challenge for chemical catalysis. 

The development of simple systems that allow for the asymmetric oxidation of allyl alcohols and simple alkenes to epoxides or 1,2-diols has had a great impact on synthetic methodology because it allows for the introduction of functionality with concurrent formation of one or two stereogenic centers. This functionality can then be used for subsequent reactions that usually fall into the... 

The following examples use m-chloroperoxybenzoic acid (MCPBA), a common epoxidizing reagent, to convert alkenes to epoxides having the same cis or trans stereochemistry. MCPBA is used for its desirable solubility properties The peroxyacid dissolves, then the spent acid precipitates out of solution. 

Peroxyacids (sometimes calledperacids) are used to convert alkenes to epoxides. If the reaction takes place in aqueous acid, the epoxide opens to a glycol. Therefore, to make an epoxide, we avoid strong acids. Because of its desirable solubility properties, meta-chloroperoxybenzoic acid (MCPBA) is often used for these epoxidations. MCPBA is a weakly acidic peroxyacid that is soluble in aprotic solvents such as CH2C12. 

A dinuclear ruthenium complex with both ruthenium in 2+ oxidation states catalyzes the oxidation of adamantane to hydroxy adamantane and alkene to epoxide by dioxygen. Suggest a possible mechanism. 

The Udenfiiend system of 1954 was perhaps the first to be specifically presented as a model of a biological process. In this system, Fe(II) is the catalyst, EDTA the ligand, air is the primary oxidant and ascorbic acid provides the reducing equivalents called for in this monooxygenase system. Arenes can be hydroxylated to phenols, alkanes to alcohols, and alkenes to epoxides, although with modest efficiency. The NIH shift was not observed in the model, however. 

The Sharpless asymmetric epoxidation is an enantioselective reaction that oxidizes alkenes to epoxides. Only the double bonds of allylic alcohols—that is, alcohols having a hydroxy group on the carbon adjacent to a C=C —are oxidized in this reaction. 

Titanosilicalite (TS-1)[165,166], a highly siliceous MFI type zeolite in which 0.1 to 2.5% of the Si atoms are replaced by Ti, is the most successful example for the use of isomorphously substitited zeolites. As a consequence of the high Si/Al ratio of TS-1 the material contains only a negligible concentration of strong Bronsted acid sites. In fact, the presence of acid sites is detrimental to the selectivity of the catalysts, as discussed below. TS-1 has been found to be a selective oxidation catalyst for a wide variety of reactions such as the conversion of alkenes to epoxides [167], alcohols to aldehydes [168], alkanes to secondary alcohols and ketones [169,170], phenol to hydroquinone and catechol [171] and amines to hydroxylamines [ 172]. A schematic representation of the chemistry is given in Fig. 7 which is adapted from ref [17]. 

The conversion of alkenes to epoxides is covered in most introductory organic chemistry texts, often exemplified by the use of m-chloroperoxybenzoic acid (MCPBA) as the epoxidizing reagent. Bradley et al. compared the enantioselective Sharpless epoxidation of geraniol with the classical MCPBA method, which gives a racemic product 21). Hoye and Jeffrey have illustrated a... 

Transition metal catalysts not only increase the reaction rate but may also affect the outcome of the oxidation, especially the stereochemistry of the products. Whereas hydrogen peroxide alone in acetonitrile oxidizes alkenes to epoxides [729], osmic acid catalyzes syn hydroxylation [736], and tungstic acid catalyzes anti hydroxylation [737]. The most frequently used catalysts are titanium trichloride [732], vanadium pentoxide [733,134], sodium vanadate [735], selenium dioxide [725], chromium trioxide [134], ammonium molybdate [736], tungsten trioxide [737], tungstic acid [737],... 

Thallium triacetate, TI(0C0CH3)3 1.5H20 (mp 182 C), like the monoacetate, is used for the stereoselective acetoxylation of alkenes [411] and for oxidations of alkenes to epoxides [412]. 

Iodine and silver oxide oxidize alkenes to epoxides [751], whereas iodine and silver ebromate convert alkenes into a-iodoketones [610]. 

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