Hydrogen peroxide with alkenes

In the same spirit DFT studies on peroxo-complexes in titanosilicalite-1 catalyst were performed [3]. This topic was selected since Ti-containing porous silicates exhibited excellent catalytic activities in the oxidation of various organic compounds in the presence of hydrogen peroxide under mild conditions. Catalytic reactions include epoxidation of alkenes, oxidation of alkanes, alcohols, amines, hydroxylation of aromatics, and ammoximation of ketones. The studies comprised detailed analysis of the activated adsorption of hydrogen peroxide with... 

In 1994, Mansuy and coworkers found that a simple ammonium salt, like ammonium acetate alone, is a very efficient cocatalyst for the metalloporphyrin-catalyzed epoxidation of simple alkenes by hydrogen peroxide ". Bases like sodium carbonate, sodium acetate or tetrabutylammonium hydroxide turned out to promote the porphyrin-catalyzed epoxidation without any other additive. Adducts of hydrogen peroxide (with Na2C03, urea, MesNO, PhsPO), which turned out to be particularly useful for reactions in which the concentration of H2O2 in solution needs to be controlled at a fixed level, have been employed by Johnstone and coworkers. 

A polymeric ja-hydroperoxocopper(II) compound has been prepared from the reaction of hydrogen peroxide with an aqueous solution of copper(II) acetate and has been characterized by spectrophotometric methods and peroxide oxygen determination (equation 257).222 Such copper(II) peroxide compounds have recently been claimed to be active catalysts for the epoxida-tion of light alkenes by dioxygen.223... 

The reactions of hydrogen peroxide with vanadate have been of interest for many years. Much of the early work was concerned with the function of peroxovanadates as oxygen transfer agents. Alkenes and similar compounds such as allyl alcohols can be hydroxylated or epoxidized. Even alkanes can be hydroxylated, whereas alcohols can be oxidized to aldehydes or ketones and thiols oxidized to sulphones or sulphoxides. Aromatic molecules, including benzene, can be hydroxylated. The rich chemistry associated with the peroxovanadates has, therefore, led to extensive studies of their reaction chemistry. To this end, x-ray diffraction studies have successfully provided details of a number of peroxovanadate structures. 

Anti hydroxylation of an alkene is readily achieved with peroxycarboxylic adds. Add-catalyzed ring opening of the irutial produd, an oxirane (epoxide), forms the monoester of a 1,2-diol, hydrolysis of which affords the parent diol. Alternative reagents whi ate often used for anti hydroxylation of alkenes are hydrogen peroxide with oxides of tungsten > 4.2i gj. selenium, 444i and iodine-silver benzoate (Pr6vost reaction).. ... 

Upon treatment with ozone followed by work-up with hydrogen peroxide, an alkene forms formic acid and a compound that shows three signals (a singlet, a triplet, and a quartet) in its H NMR spectrum. Identify the alkene. 

The reaction of peroxides with alkenes is probably the most common method for the preparation of epoxides (oxiranes). Peroxides are a source of electrophilic oxygen when they react with the nucleophilic n bond of an alkene. In Table 3.1, hydrogen peroxide (H2O2) was shown to be a powerful oxidizing agent, with a reduction potential of 1.77 Vl for the following reaction ... 

This general procedure for the synthesis of alkenes from the enamines, when applied to the acyclic enamines derived from the acyclic ketones by modification of hydroboration-elimination procedure, permits a facile, diastereospecific conversion to either (Z)- or (E)-alkene at will (A) The hydroboration of enamine with 9-BBN, followed by treatment with methanol gives (Z)-alkenes of 99% isomeric purity. (B) The hydroboration of the same enamine with borane-methylsulfide, followed by methanolysis and oxidation with neutral hydrogen peroxide gives ( )-alkenes of 99% isomeric purity (Scheme 24.2) [13a]. 

The following is a reaction of hydrogen peroxide with an alkene ... 

Among the hydrogen halides only hydrogen bromide reacts with alkenes by both electrophilic and free radical addition mechanisms Hydrogen iodide and hydrogen chlo ride always add to alkenes by electrophilic addition and follow Markovmkov s rule Hydrogen bromide normally reacts by electrophilic addition but if peroxides are pres ent or if the reaction is initiated photochemically the free radical mechanism is followed... 

Aldehydes are easily oxidized to carboxylic acids under conditions of ozonide hydroly SIS When one wishes to isolate the aldehyde itself a reducing agent such as zinc is included during the hydrolysis step Zinc reduces the ozonide and reacts with any oxi dants present (excess ozone and hydrogen peroxide) to prevent them from oxidizing any aldehyde formed An alternative more modem technique follows ozone treatment of the alkene m methanol with reduction by dimethyl sulfide (CH3SCH3)... 

Hydroboration-oxidation (Sections 6 11-6 13) This two step sequence achieves hydration of alkenes in a ste reospecific syn manner with a regiose lectivity opposite to Markovnikov s rule An organoborane is formed by electro philic addition of diborane to an alkene Oxidation of the organoborane inter mediate with hydrogen peroxide com pletes the process Rearrangements do not occur... 

The alkene is allowed to react at low temperatures with a mixture of aqueous hydrogen peroxide, base, and a co-solvent to give a low conversion of the alkene (29). These conditions permit reaction of the water-insoluble alkene and minimise the subsequent ionic reactions of the epoxide product. Phase-transfer techniques have been employed (30). A variation of this scheme using a peroxycarbimic acid has been reported (31). 

Hydrochlorination. The addition of hydrogen chloride to alkenes in the absence of peroxides takes place by an electrophilic substitution mechanism. The orientation is in accord -with Markovnikov s mle in -which the hydrogen atom adds to the side of the double bond that -will result in the... 

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