Epoxidation ozone

Among the more exotic methods which have been used for the direct epoxidation of steroid olefins are chromic acid, ozone, e.g., (84), and photochemical oxygenation. Ozone is useful for the epoxidation of the unreactive 8,9-olefin, but the results of the other unusual methods can usually be duplicated by the methods of epoxidation discussed above. 

CIS- And trans-1,2-difluoroethylene are oxidized by ozone stereoselectively to a mixture of the corresponding epoxides and ozonides with formyl fluoride The composition of the mixture depends on the solvent used [25] (equation 16)... 

Alkenes are reduced by addition of H2 in the presence of a catalyst such as platinum or palladium to yield alkanes, a process called catalytic hydrogenation. Alkenes are also oxidized by reaction with a peroxyacid to give epoxides, which can be converted into lTans-l,2-diols by acid-catalyzed epoxide hydrolysis. The corresponding cis-l,2-diols can be made directly from alkenes by hydroxylation with 0s04. Alkenes can also be cleaved to produce carbonyl compounds by reaction with ozone, followed by reduction with zinc metal. 

The location of the position of double bonds in alkenes or similar compounds is a difficult process when only very small amounts of sample are available [712,713]. Hass spectrometry is often unsuited for this purpose unless the position of the double bond is fixed by derivatization. Oxidation of the double bond to either an ozonide or cis-diol, or formation of a methoxy or epoxide derivative, can be carried out on micrograms to nanograms of sample [713-716]. Single peaks can be trapped in a cooled section of a capillary tube and derivatized within the trap for reinjection. Ozonolysis is simple to carry out and occurs sufficiently rapidly that reaction temperatures of -70 C are common [436,705,707,713-717]. Several micro-ozonolysis. apparatuses are commercially available or can be readily assembled in the laboratory using standard equipment and a Tesla coil (vacuum tester) to generate the ozone. Reaction yields of ozonolysis products are typically 70 to 95t, although structures such as... 

In contrast with the behaviour of typical vinylphosphonic acid derivatives, the carbon-carbon double bond in the 1,2-oxa-phospholene (167) is remarkably unreactive towards a broad spectrum of reagents including electrophiles, most epoxidizing and organometallic reagents, as well as to dipolar addition reactants. Exceptional reagents are, however, N-bromoacetamide (NBA), ozone, dimethyllithiumcuprate, and sodium-naphthalene. 

Barrett and coworkers have explored hetero-substituted nitroalkenes in organic synthesis. The Michael addition of nucleophiles to 1-alkoxynitroalkenes or 1-phenylthionitroalkenes followed by oxidative Nef reaction (Section 6.1) using ozone gives a-substituted esters or thiol esters, respectively.41 As an alternative to nucleophilic addition to l-(phenylthio)-nitroalkenes, Jackson and coworkers have used the reaction of nucleophiles with the corresponding epoxides (Scheme 4.4).42 Because the requisite nitroalkenes are readily prepared by the Henry reaction (Chapter 3) of aldehydes with phenylthionitromethane, this process provides a convenient tool for the conversion of aldehydes into ot-substituted esters or thiol esters. 

In addition to ozonization, aqueous photolysis of metofluthrin (14) gave the diol derivative possibly formed through epoxidation of the prop-l-enyl side chain in the acid moiety followed by its hydrolysis [56]. 

Chemical/Physical. Ozonolysis of acrylonitrile in the liquid phase yielded formaldehyde and the tentatively identified compound glyoxal, an epoxide of acrylonitrile and acetamide. The reported rate constant for the reaction of acrylonitrile and ozone in the gas phase is 1.38 x lO cm moFsec (Munshi et al., 1989). In the gas phase, cyanoethylene oxide was reported as an ozonolysis product... 

In a simulated atmosphere, direct epoxidation by ozone led to the formation of benzo[a]pyrene-4,5-oxide. Benzo [a] pyrene reacted with benzoyl peroxide to form the 6-benzoyloxy derivative (quoted, Nikolaou et al, 1984). It was reported that benzo [a] pyrene adsorbed on fly ash and alumina reacted with sulfur dioxide (10%) in air to form benzo[a]pyrene sulfonic acid (Nielsen et al., 1983). Benzo [a] pyrene coated on a quartz surface was subjected to ozone and natural sunlight for 4 and 2 h, respectively. The compounds 1,6-quinone, 3,6-quinone, and the 6,12-quinone of benzo[a]pyrene were formed in both instances (Rajagopalan et al., 1983). 

Significant advances in the chemistry of these ring systems over the past 10 years include the first unambiguous detection, and characterization by microwave spectroscopy as 1,2,3-trioxolane, of the primary ozonide from ethene and ozone (cf. Section 4.15.3.2), and the introduction of 1,3,2-dioxathiolane 2,2-dioxides as epoxide equivalents in organic synthesis (cf. Section 4.15.5.3). Advances have also been made in the synthesis and characterization of the chemistry of 1,2,3-trithiolanes and 1,2,3-trithioles. 

Arylidene-,6-ionones, triplet oxygen cycloaddition, 199, 201 Aryl phosphites, ozone adducts, 732 Aryl-substituted olefins, selenide-catalyzed epoxidation, 384-5 Ascaridole... 

Epinephrine, chemiluminescence, 647 6-Epiplakortolide E, synthesis, 256, 257 Epithelial cells, ozone effects, 612 Epothilone B, dioxirane epoxidation synthesis, 1145... 

Uncatalysed cleavage of epoxides has been reported [e.g. tetrahydro-(39)- dihydro-(64 X = OH)]," and oxidation of tetrahydrogeranyl acetate with ozone on silica gel yields dihydro-(65 R = H) predominantly with some 8-acetoxy-6-methyloctan-2-one (cf. Vol. 7, p. 7)." ... 

It should be noted that while the mechanism outlined in this section describes the overall features of 0,-alkene chemistry, there are also other minor paths as well. For example, small yields of epoxides that appear to be formed in the primary reaction have been observed as products of the reactions of some dienes and cycloalkenes (e.g., see Paulson et al., 1992b and Atkinson et al., 1994a, 1994b). The reader should consult the rather extensive ozone literature for further details on both the condensed- and gas-phase reactions. 

Epoxidation of cyclooctene has been shown, using ozone in water where the products were easily recovered by phase separation (Shu et al., 1995). 

Ozonization of lignin forms derivatives of muconic acid that have the unique chemical structure of conjugated double bonds with two carboxyl groups. These derivatives have great potential for chemical modification. The ozonized lignin of white birch was soluble in epoxy resin at 120°C, and the free carboxyl groups were found to react with epoxide. This paper discusses developmental work on the preparation of pre-reacted ozonized lignin/epoxy resins the dynamic mechanical properties of cured resins and preliminary results of the application of these resins as wood adhesives. 

The lignin isolated from white birch after steaming was ozonized. The ozonized lignin was soluble in epoxy resins at 120°C. It was also found that free carboxyl groups (introduced by ozonization) react with epoxide only by heating. Previous developmental work on the blending of lignin with epoxy resin has been reported by Ball and his co-workers (3). They synthesized... 

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