Alkenes oxidation with hydrogen peroxide

Iron complexes with the pentadentate ligand 3 derived from pyridyl and prolinol building blocks containing a stereogenic center were reported from the group of Klein Gebbink (Scheme 4) [34]. In alkene oxidations with hydrogen peroxide,... 

The conversion of 3-chloropentafluoropropene to 2-(chlorodifluoromethyI)-2,3,3-trifluoro-oxirane (33) can be carried out64 by heating the mixture of the alkene and oxygen in 1,1,2-trichlorotrifluoroethane (CFC-113) in an autoclave.64 The oxidation with hydrogen peroxide in alkaline solution is negatively influenced by the high nucleophilic reactivity of allylic chlorine.65 66 The reaction is performed at very low temperatures that favor the attack of the hydroperoxy anion in competition with the hydroxy anion. Acceptable yields of 31 -38 % are obtained in the presence of a phase-transfer catalyst.66... 

A simple example involves the reaction of the silyl ether 213, made from the corresponding 4-hydroxy-alkene by treatment with (bromomethyl)chloro-dimethylsilane, with tributyltin hydride and a radical initiator. Bromine abstraction and intramolecular cyclization with the double bond leads to the bicyclic 214, which upon oxidation with hydrogen peroxide gives the branched-chain 215 in an overall yield of 73% from the alcohol precursor of 213 (Scheme 21). When the sequence is conducted with the C-4 epimeric starting alcohol, the final product again has the hydroxymethyl group cis-related to the hydroxy group.217... 

Since subsequent oxidation with hydrogen peroxide replaces the boron with a hydroxyl group, the eventual alcohol will be on the least substituted carbon. Furthermore, the addition of the boron and hydrogen atoms takes place such that they are on the same side of the alkenes. This is called syn-addition. 

GeW12C SiW,2C4 > FeW,20 a BW,20 > CoW)20 > CuWi20 [13, 14]. This property is well reflected in their catalytic activities. For cyclohexene oxidation with hydrogen peroxide, the catalytic activity increased in the order B3+ < Si4+ < C44 < P5+ [25, 26]. Cetylpyridinium salts of HPA can be used as phase-transfer catalysts and catalyze epoxidation of alkenes very efficiently in a two-phase system comprising aqueous H202 and CHCI3 [27]. 

P-Nitroselenation of alkenes has been achieved using (i) PhSeBr, (ii) AgN02/HgCl2 in MeCN/THF, -78 to 4-22 C under argon,2 2 and the products oxidized with hydrogen peroxide to give vinylic nitro... 

The reactivity of 120 is much less than that of either a normal alkene or a dithioacetal. Attempts to hydrogenolyze (see Section IV,3) or reduce 120 with Raney nickel, to hydrolyze the dithioacetal (see Section IV,1) with mercury(II) chloride (even in the presence of an overwhelming excess of the reagent), and to ozonize the double bond at —78°, produce only the starting material an analytical sample was prepared by extended treatment of the crude product with a concentrated, aqueous, alkaline solution of potassium permanganate at the reflux temperature.20 Acetolysis, ozonolysis, or brominolysis of 120 at room temperature affords diphenyl disulfide, and extended oxidation with hydrogen peroxide in acetone, with peroxypropionic acid, and with peroxyacetic acid, produces benzene-sulfonic acid, methyl phenyl sulfone, and an uncharacterized explosive, respectively the products occur as intractable mixtures, and the yields are invariably low. 

The hydroboration of alkenes is a very important way to convert alkenes in other organic groups.1 For example, the hydroboration of an alkene followed by the oxidation with hydrogen peroxide and sodium hydroxide produces an alcohol1 in a highly stereo- and regio-selective reaction. 

M. Klawonn, M. K. Tse, S. Bhor, C. Dobler, M. Beller, A convenient ruthenium-catalyzed alkene epoxidation with hydrogen peroxide as oxidant, J. Mol. Catal. A Chem. 218 (2004) 13. 

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. 

The hydroboration-oxidation procedure is a valuable method to hydrate an alkene with anti-Markovnikov orientation and with syn addition of the H and OH groups. ° Addition of BH3 (which may be added to the reaction mixture as diborane, B2Hg) to an alkene occurs readily in diethyl ether, THF, or similar solvent. The hydroboration is strongly exothermic, with a AH of -33kcal/mol per B-H bond that reacts. If stoichiometry and the steric requirements of the alkyl substituents on the boron atom permit, the reaction proceeds until three alkyl groups are attached to each boron atom. The trialkylborane can then be oxidized with hydrogen peroxide in aqueous base to produce the alcohol. 

Sol 1. (b) Selenites on oxidation with hydrogen peroxide (or ozone or m-CPBA) give selenoxides. The latter in the presence of a p-hydrogen undergoes an intramolecular syn elimination to leave behind an alkene and selenenic acid. The diene component is generated in situ by thermal sulfur dioxide extmsion from sulfolene in a reverse reaction and is then trapped by the dienophile in a Diels—Alder reaction. 

Reaction of an alkene with ozone leads to a 1,2,3-trioxolane, which rearranges to a 1,2,4-trioxolane (an ozonide). Subsequent treatment with hydrogen peroxide or with dimethyl sulfide leads to an aldehyde, ketone, or carboxylic acid product. When an ozonide contains a C-H unit, oxidation with hydrogen peroxide leads to a carboxylic acid, but reaction with dimethyl sulfide leads to an aldehyde 51, 52, 53, 54, 78,82,83,117. 

Second, among the newer methods developed to effect the elimination to produce the least substituted alkene is one that involves converting the alcohol to a selenium derivative. In this procedure, a primary alcohol is treated with o-nitrophenyl sele-nocyanate in a suitable solvent such as (THF, oxacyclopentane) in the presence of a phosphine (such as tri-n-butylphosphine [(CH3CH2CH2CH2)3P]) to produce the primary alkyl selenide (Scheme 8.74). Then, in a second step, the primary alkyl o-nitrophenyl selenide is oxidized with hydrogen peroxide to yield the corresponding selenoxide, which readily undergoes elimination to the alkene. Scheme 8.74 shows the application of the sequence of reactions described above to cyclohexylmethanol and the resulting formation of the exo-methylenecyclohexane. 

As a consequence of the above summarized properties of fluorinated alcohols, they are ideal solvents for the generation of cationic or radical-cationic species or reaction intermediates. This eflect has been exploited numerous times, for example, in the investigation of organic radical cations [11]. At the same time, it lies at the heart of the catalysis of alkene epoxidation with hydrogen peroxide and of Baeyer-Villiger-type oxidations of carbonyl compounds. The mechanisms of the latter two reaction types are discussed in more detail in Sections 4.3.1.1 (epoxidation) and Section 4.5.1 (Baeyer-VUliger). 

The first reports on the use of fluorinated alcohols, and in particular of HFIP in oxidations with hydrogen peroxide, can be found in the patent hterature of the late 1970s and early 1980s [19,20]. Typically, 60% aqueous hydrogen peroxide was used in the presence of metal catalysts. A number of reports on alkene epoxidations in fluorinated alcohols, both in the absence and in the presence of additional catalysts, have followed. 

Other Methods.— The palladium-catalysed oxidation of terminal olefins to methyl ketones is very efficient using 30% hydrogen peroxide in acetic acid or t-butyl alcohol. The method offers advantages in that conversions are usually high, aldehyde production is very low, and the method requires only very low concentrations of palladium [20—40p.p.m, as palladium(li) acetate], fi-Hydroxy-o-nitrophenylselenides, or their O-acyl derivatives, on oxidation with hydrogen peroxide undergo elimination to form ketones or enol esters [equation (10)]. The starting materials can be prepared easily from alkenes via their epoxides. 

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