Double bond, oxidation allylic

Naphthalene dioxygenase from P. putida strain FI is able to oxidize a number of haloge-nated ethenes, propenes, and butenes, and d5 -hept-2-ene and cis-oct-2-ene (Lange and Wackett 1997). Alkenes with halogen and methyl substituents at double bonds form allyl alcohols, whereas those with only alkyl or chloromethyl groups form diols. 

Oxidation. The C=C double bond of allyl alcohol undergoes epoxiila-tion by peroxide, yielding glycidol. This epoxidation reaction is applied in manufacturing glycidol as an intermediate for industrial production of glycerol. 

The chemoselectivity of the dioxirane oxyfunctionalization usually follows the reactivity sequence heteroatom (lone-pair electrons) oxidation > JT-bond epoxida-tion > C-H insertion, as expected of an electrophilic oxidant. Because of this chemoselectivity order, heteroatoms in a substrate will be selectively oxidized in the presence of C-H bonds and even C-C double bonds. In allylic alcohols, however, C-H oxidation of the allylic C-H bond to a,/ -unsaturated ketones may compete efficaciously with epoxidation, especially when steric factors hinder the dioxirane attack on the Jt bond. To circumvent the preferred heteroatom oxidation and thereby alter the chemoselectivity order in favor of the C-H insertion, tedious protection methodology must be used. For example, amines may be protected in the form of amides [46], ammonium salts [50], or BF3 complexes [51] however, much work must still be expended on the development of effective procedures which avoid the oxidation of heteroatoms and C-C multiple bonds. 

Both chemical and enzymatic synthetic methods for the asymmetric oxidation of the carbon-carbon double bond have been developed [46], but the area of carbon-carbon double bond oxidations has been shaped by the breakthrough discovery of asymmetric epoxidation of allylic alcohols with the Katsuki-Sharpless method [47]. Catalytic asymmetric synthesis of epoxides from alkenes by Jacobsen... 

The SAE is arguably one of the most important reactions discovered in the last 30 years. The SAE converts the double bond of allyl alcohols into epoxides with high enantioselective purity using a titanium tetraisopropoxide catalyst, Ti(0-iPr)4, chiral additive, either L-(+)-diethyl tartrate [(+)-DET, 7.45] or D-(—)-diethyl tartrate [(—)-DET, 7.46], and tert-butyl peroxide (t-BuOOH, TBHP (f-butylhydroperoxide)) as the source of the oxidant in stoichiometric amounts (see section 1.5, references 28-30 of Chapter 1). 

Acetoxylation of enol thioethers. The reaction of enol thioethers with lead tetraacetate (1,1 equiv.) in THF for 1 hour followed by addition of BFj etherate (or 5 N KOH-ether) results in allylic acetoxylation. The reaction is considered to involve bisacetoxylation of the double bond. Oxidation of sulfur is not observed. Examples ... 

The oxidahon of olefins with aqueous hydrogen peroxide in methanol can produce several products, by different reachon paths double bond epoxidation, allylic H-abstraction, epoxide solvolysis, alcohol and glycol oxidation (Scheme 18.6). Normally, oxide catalysts of Group IV-Vl metals are poorly selechve, because of their acidic properhes, the inhibition they are subject to in aqueous media and homo-lytic side reachons with hydrogen peroxide. The only excephon concerns the epoxidahon of a,(3-unsaturated alcohols and acids, which are able to bind on the... 

Oxyselenenylation-oxidative deselenenylation (oxyselenenylation-selenoxide elimination) sequence provides the double-bond transpositioned allylic alcohols and ethers from alkenes. Oxyselenenylation of alkenes and its asymmetric... 

Hydrogen peroxide attacks the sulfur atom in preference to the double bond in allyl phenyl sulfide and allyl benzyl sulfide to give allyl phenyl sulfoxide (64%) and allyl benzyl sulfone (85%), respectively. Olefinic sulfones may also be obtained by dehydrohalogenation of /3-haloalkyl sulfones prepared by this method. Oxidation of sulfides has been utilized in the preparation of sulfones containing other common functional groups such as the amide, tro, amino, and ester groups. 

Aqueous solutions of bisulfites react with olefins in the presence of oxygen or certain oxidizing agents. Addition of the bisulfite takes place by a free-radical mechanism contrary to Markownikoff s rule. The yields of sulfonates are usually low (12-62%). Styrene gives mainly 2-hydroxy-2-phenylethanesulfonic acid. Bisulfite has also been added to the double bonds in allyl and cinnamyl alcohols. /3-Sulfocarboxylic acids are prepared in this way from a,/3-olefinic acids. /3,/3-Disulfopropionic acid is made in 80% yield by the addition of two molecules of bisulfite to... 

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. 

In the synthesis of an ionophore antibiotic, a bicyclic sulfone made by oxidation of the corresponding sulfide with PhSeSePh/H202 to avoid double bond oxidation was coupled with an allylic bromide in 97% yield and high stereoselectivity. The sulfonyl group was finally eliminated in basic medium to create a trans-dxene (Scheme 66). 

The unsaturated fatty acids in all fats and oils are subject to oxidation, a chemical reaction which occurs with exposure to air. The eventual result is the development of an objectionable flavor and odor. The double bonds and the adjacent allylic functions are the sites of this chemical activity. Oil oxidation rate is roughly proportional to the degree of unsaturation for example, linolenic fatty acid (18 3) with three double bonds is more susceptible to oxidation than linoleic (18 2) with only two double bonds, which is ten or more times as susceptible as oleic (18 1) with only one double bond. Oxidative deterioration results in the formation of hydroperoxides, which decompose into carbonyls, and dimerized and polymerized gums. It is accelerated by a rise in temperature, oxygen pressure, prior oxidation, metal ions, lipoxygenases, hematin compounds, loss of natural antioxidant, absence of metal deactivators, time and ultraviolet or visible light. Extensive oxidation will eventually destroy the beneficial components contained in many fats and oils, such as the carotenoids (vitamin A), the essential fatty acids (linoleic and linolenic), and the tocopherols (vitamin E). 

Asymmetric methoxyselenenylation. A chirally constituted Ar SeBr reagent induces asymmetric addition to double bonds. Chiral allyl ethers are accessible after oxidation and selenoxide elimination. 

The reactions of allyl alcohol are in accord with the structure assigned to it. The presence of a hydroxyl group is shown by the fact that the substance reacts with sodium with the evolution of hydrogen, and by the fact that allyl acetate is formed when it is treated with acetyl chloride. The presence of a double bond in allyl alcohol is shown by the fact that it unites readily with two atoms of chlorine, bromine, or iodine. It shows, in general, the reactions which are characteristic of ethylene and its homologues. The structure of the alcohol follows from the reactions which have been mentioned, and from the fact that by careful oxidation it can be converted into an aldehyde and an acid which contains the same number of carbon atoms as the alcohol. It contains, therefore, a primary alcohol group. 

The oxidation of allylic alcohols has been studied thoroughly using a variety of catalysts. The reactivity of the vanadium-tert-butyl hydroperoxide reagents towards the double bond of allylic alcohols makes possible selecfive epoxidation. Thus, reaction of geraniol with t-BuOOH and vanadium acetylacetonate [VO(acac)2] gave the 2,3-epoxide 33 (5.44). With peroxy-acids, reaction takes place preferentially at the other double bond. 

Next, a hydroxy group was introduced into the terminal methyl group of the AT-substituent of (46) to obtain (47). Several direct allylic oxidations of (46) were examined, but all were unsuccessful, probably due to electron deficiency in the double bond moiety. Allylic bromination with NBS gave the allylic bromide (58) in only 14% yield accompanied by an isomeric mixture of conjugated esters (59) (38%) and dibromide (60) (15%). 

Oxidation of sulfides in the presence of electron-rich double bonds is problematic with many of the traditional oxidants such as MCPBA, NaI04, and oxone because of interference with double bond oxidation (e.g., epoxidation). Koo and coworkers [40] addressed this problem and studied the selective oxidation of allylic sulfides having multiple alkyl substituents. They tested various stoichiometric oxidants and a number of catalytic reactions with 30% aqueous H2O2 as the oxidant. Of all the oxidation systems tested for the sulfoxidation, they found that the use of LiNbMoOg as catalyst with H2O2 as the oxidant gave the best result. With this system no epoxidation took place and a reasonably good selectivity for sulfoxide over sulfone was obtained (Table 8.2). 

The metabolism of A -tetrahydrocannabinol (A -THC, 1) has been studied extensively in recent years and it is evident that a large number of metabolites are formed (1, 2). Three regions of primary biotrans format ion have been described hydroxylation of the 6 and 7 positions allylic to the A -double bond, oxidation of the double bond to an epoxide (3, 5) and hydroxylation of the pentyl side-chain in various positions (6). Each initial reaction may be followed by the introduction of a second hydroxyl group and, in addition, oxidation of one or more of the hydroxyl groups can produce a variety of polar metabolites including aldehydes... 

I se of chromyl chloride in the Collins oxidation does not require large excesses of the reagent however, it is less selective than is Cr03, and tends to isomerize double bonds of allylic alcohols. 

Conjugate addition of vinyllithium or a vinyl Grignard reagent to enones and subsequent oxidation afford the 1.4-diketone 16[25]. 4-Oxopentanals are synthesized from allylic alcohols by [3,3]sigmatropic rearrangement of their vinyl ethers and subsequent oxidation of the terminal double bond. Dihydrojasmone (18) was synthesized from allyl 2-octenyl ether (17) based on Claisen rearrangement and oxidation[25] (page 26). 

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