Oxygen donors alkyl peroxides

Peroxides are compounds of great synthetic interest. Especially, alkyl hydroperoxides and hydrogen peroxide have gained more and more importance as cheap and readily available oxygen donors in catalytic oxygenations. Formerly unsafe oxidation procedures (due to the employment of highly concentrated and therefore explosive peroxide solutions) have been optimized or substituted by other and more effective and safe procedures. Over the last two decades, the need for oxidation technologies with enhanced efficiency... 

Technologically, gas-phase processes are more preferable than their liquid-phase counterparts. However, the gas-phase performance usually requires high temperatures and is feasible only with comparatively low-boiling and thermally stable reactants. Therefore, most organic syntheses are conducted in the liquid phase, with the oxidants represented by such active oxygen donors as H202, alkyl peroxides,... 

Equation (33)), which then oxidize substrate. A prominent example of Equations (29), (31), and (32) is formation of a POM-bound oxygen atom donor, which transforms to a POM oxometal intermediate, which then oxidizes the substrate. The last mode (generation of metal-free oxidizing intermediates) can involve oxygen donors, such as iodosylarenes, peroxides (formation of alkyl-peroxy, alkoxy radicals, etc.), or 02 (formation of all the radicals associated with radical chain oxidation or autoxidation ).335-338... 

The oxidation of hydrocarbons by molecular oxygen in the absence of metal complexes has been discussed in Chapter II. The oxidation of hydrocarbons with molecular oxygen, as well as with donors of an oxygen atom (hydrogen peroxide, alkyl hydroperoxides and some other compounds), is a very important field since many industrial processes are based on these reactions [1], In many cases, chain radical non-catalyzed autoxidation of samrated hydrocarbons is not very selective and the yields of valuable products are often low. The use of salts and complexes of transition metals creates great possibilities for solving problems of selective oxidation, as has been demonstrated for a number of important processes. 

Mansuy et al. employed alkyl peroxides and iodosylbenzene as oxygen donors and examined the oxidation products of cyclohexane in the presence of a series of M(TPP) complexes (M=Fe, Mn, Co, Rh, and Cr) [284]. As listed in Table 10, cyclohexanol and cyclohexanone are the major products however, the ratio of the alcohol and ketone was dependent on the oxidant employed. For the oxidation by peroxides, involvement of alkoxy radical (RO ) due to the homolytic 0-0 bond cleavage of R-OO-M was proposed. In order to trap possibly formed radical intermediates. He and Bruice examined the oxidation of cw-stilbene and (Z)-l,2-bis(fran5-2,tran5-3-diphenylcyclopropyl)ethane by iron porphyrin/f-BuOOH system [285]. In separate experiments, AIBN was used as a radical chain initiator for the oxidation of the alkenes by t-BuOOH. According to the product distribution, they concluded the products to be derived from initial combination of t-BuOO, rather than 0=Fe (por)", with olefin. 

Addition of carbon radicals to carbon-carbon double bonds is an important reaction that can be carried out under hydrogen transfer conditions [27], Peroxides are usually used as radical precursors and an application of this chemistry is presented in Scheme 3 (Eq. 3.1). More recently, reduction of alkyl radical by C-H hydrogen donor has been examined in order to find an environmentally friendly alternative to tin hydride. Zard has reported a simple and cheap alternative to tin hydride for Barton-McCombie deoxygenation reactions [80]. Heating of xanthates derived from carbohydrates in 2-propanol in the presence of dilauroyl peroxide affords the de-oxygenated products in good yields (Scheme 17, Eq. 17.1). 2-Propanol functions as... 

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