Oxidation of olefin

Oxidation of olefins affords interesting oxygenated compounds such as 1,2-dioIs and epoxides. By performing the reaction enantioselectively on prochiral substrates, optically active products can be obtained. 

Recently, a recoverable and reusable catalyst AP-Mg-Os04 was developed by the group of Choudary [44]. It was found that commercially available aerogel prepared AP-MgO has defects sites on the surface, for example Mg sites which are Lewis acids. This situation presents an opportunity to prepare new materials. So, the modified aerogel was prepared via a counterionic stabilization of OSO4 with the 

PEM-MC 0s04 (5 mol%) (DHQD)2PHAL Triton X-405 KjFefCN), KjCOj, HjO 

Of the many substrates which have been oxidized in the presence of transition metal complexes, one of the most extensively studied group of compounds has been olefinic hydrocarbons. The obvious incentive for the pursuit of this research is the identification of catalysts which could convert the abundant olefinic hydrocarbons into more valuable oxygen-containing derivatives under mild conditions in high selectivity. Since hydrocarbon-soluble complexes of the transition metals have been successfully applied to the catalytic addition of other small molecules to olefinic substrates, attempts have been made to activate and catalytically transfer dioxygen to olefins in a similar manner. It has been difficult, however, to exclude other pathways by which oxygen can interact with olefins and to achieve selective reactions. In cases where selective oxidations are achieved it is often hard to decide whether products arise via coordination catalysis or autoxidation pathways. 

Hydroperoxide intermediates are formed wherever possible and free radical reactions usually result. Because of their prevalence during homogeneous catalytic oxidation of olefins the first part of this section will deal with the reactions which hydroperoxides undergo in the presence of metal complexes. Next we will consider 

Epoxides are well known as one of the most valuable intermediates to produce commercially important chemicals such as polyglycols, polyamides, polyurethanes and so many other polymers, chiral pharmaceuticals, pesticides, detergents, agrochemicals, food additives, dyestuffs, flavor and fragrance compounds, surfactants, antistatic agents, corrosion protection agents, textiles, non-toxic PVC plasticizers and stabilizers. They are also valuable additives to lubricants and adhesives. In the last decade, several soluble Schiff base complexes of Cr, Mo, Re, Ni, Co, Mn, V, Cu, Ru, and Ti have been employed as active homogenous catalysts in epoxidation of alkenes. 

Costa et al. also tested their catalytic system based on complex 67, for the epoxidation (reaction 7.9) of cis-cyclooctene, 73, which yielded over 90% conversion within 2 hours at room temperature by TBHP in chloroform. Its chemoselectivity also is shown by the formation of only 1,2-epoxy limonene from limonene as the same condition as cyclooctene. 

In addition, Schuetz et al. have prepared a samarium Schiff base alkox-ide complex, 74, which showed acceptable functionality in epoxidation of trans-chalcone, 75, to 2,3-epoxy-l,3-diphenyl propanone, 76, at ambient temperature by TBHP in THF [57]. 

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Oxidation of olefins and dienes provides the classic means for syntheses of 1,2- and 1,4-difunctional carbon compounds. The related cleavage of cyclohexene rings to produce 1,6-dioxo compounds has already been discussed in section 1.14. Many regio- and stereoselective oxidations have been developed within the enormously productive field of steroid syntheses. Our examples for regio- and stereoselective C C double bond oxidations as well as the examples for C C double bond cleavages (see p. 87f.) are largely selected from this area. 

Another attractive commercial route to MEK is via direct oxidation of / -butenes (34—39) in a reaction analogous to the Wacker-Hoechst process for acetaldehyde production via ethylene oxidation. In the Wacker-Hoechst process the oxidation of olefins is conducted in an aqueous solution containing palladium and copper chlorides. However, unlike acetaldehyde production, / -butene oxidation has not proved commercially successflil because chlorinated butanones and butyraldehyde by-products form which both reduce yields and compHcate product purification, and also because titanium-lined equipment is required to withstand chloride corrosion. 

The most common oxidation states and the corresponding electronic configurations of osmium ate +2 and + (t5 ), which ate usually octahedral. Stable oxidation states that have various coordination geometries include —2 and 0 to +8 (P] The single most important appHcation is OsO oxidation of olefins to diols. Enantioselective oxidations have also been demonstrated. 

T[[dotb]he nature of the initial attack by the water (eq. 10) is a matter of some controversy (205,206). Stereochemical and kinetic studies of model systems have been reported that support trans addition of external water (207,208) or internal addition of cis-coordinated water (209), depending on the particular model system under study. Other paHadium-cataly2ed oxidations of olefins ia various oxygen donor solvents produce a variety of products including aldehydes (qv), ketones (qv), vinyl acetate, acetals, and vinyl ethers (204). However the product mixtures are complex and very sensitive to conditions. 

The highly ionic thaHic nitrate, which is soluble in alcohols, ethers, and carboxyhc acids, is also a very useful synthetic reagent. Oxidation of olefins, a,P-unsaturated carbonyl compounds, P-carbonyl sulfides, and a-nitrato ketones can aH be conveniently carried out in good yields (31,34—36). 

Use of DMF as a solvent for the oxidation of l-o1efins has been reported by Clement and Selwitz. The method requires only a catalytic amount of PdCl2 and gives satisfactory yields under mild conditions. A small amount of olefin migration product is the only noticeable contaminant in the cases reported. The procedure can be applied satisfactorily to various 1-olefins with other functional groups. This useful synthetic method for the preparation of methyl ketones has been applied extensively in the syntheses of natural products such as steroids,macrolides, dihydrojasmone, and muscone. " A comprehensive review article on the palladium-catalyzed oxidation of olefins has... 

From the results of other authors should be mentioned the observation of a similar effect, e.g. in the oxidation of olefins on nickel oxide (118), where the retardation of the reaction of 1-butene by cis-2-butene was greater than the effect of 1-butene on the reaction of m-2-butene the ratio of the adsorption coefficients Kcia h/Kwas 1.45. In a study on hydrogenation over C03O4 it was reported (109) that the reactivities of ethylene and propylene were nearly the same (1.17 in favor of propylene), when measured separately, whereas the ratio of adsorption coefficients was 8.4 in favor of ethylene. This led in the competitive arrangement to preferential hydrogenation of ethylene. A similar phenomenon occurs in the catalytic reduction of nitric oxide and sulfur dioxide by carbon monoxide (120a). 

The fit of these equations to the data is very good, as seen in Fig. 18. These equations are valid to very small values of CO concentrations, where the reaction becomes first order with respect to CO. In a mixture of CO with oxygen, there should be a maximum in reaction rate when the CO concentration is at 0.2%, as shown in Fig. 19. When the oxidation of olefins and aromatics over a platinum loaded monolith is over 99% complete, the conversion of higher paraffins may be around 90% and the conversion of the intractable methane is only 10%. 

R. J. CVETANOVIC AND Y. AmENOMIYA Catalytic Oxidation of Olefins Hervey H. Voge and Charles R. Adams... 

Epoxides such as ethylene oxide and higher olefin oxides may be produced by the catalytic oxidation of olefins in gas-liquid-particle operations of the slurry type (S7). The finely divided catalyst (for example, silver oxide on silica gel carrier) is suspended in a chemically inactive liquid, such as dibutyl-phthalate. The liquid functions as a heat sink and a heat-transfer medium, as in the three-phase Fischer-Tropsch processes. It is claimed that the process, because of the superior heat-transfer properties of the slurry reactor, may be operated at high olefin concentrations in the gaseous process stream without loss with respect to yield and selectivity, and that propylene oxide and higher... 

Reaction of the environment with the starting material The commonest example of this type of interaction is the protonation of the substrate by acids in the electrolysis medium, but pH effects will be dealt with in a later section. There are, however, other chemical interactions which can occur. For example, the mechanism and products of the oxidation of olefins are changed by the addition of mercuric ion to the electrolysis medium. In its absence, propylene is oxidized to the allyl cation (Clark et al., 1972),... 

The major problem encountered in the oxidation of olefins by thallium-(III) acetate is the formation of mixtures of products that are frequently... 

Abstract In this review, recent developments of iron-catalyzed oxidations of olefins (epoxidation), alkanes, arenes, and alcohols are summarized. Special focus is given on the ligand systems and the catalytic performance of the iron complexes. In addition, the mechanistic involvement of high-valent iron-oxo species is discussed. 

RATE PARAMETERS FOR FIRST STAGE OF THE OXIDATION OF OLEFINS BY PERMANGANATE... 

These ions, with the exception of Pb(IV), form complexes with olefins and this process is a preliminary to oxidation when this occurs. A recent review of the action of Pd(II) covers aspects of structure and bonding as well as kinetics, and a similar but older, review exists for Hg(II) . The oxidation of olefins by thallic... 

Cu(rr) compounds are frequently used in conjunction with Pd(I[) in the oxidation of olefins in the Wacker process. Their role has been viewed as that of catalyst for autoxidation of Pd metal back to Pd(II). Dozono and Shiba report the rate of oxidation of ethylene by a PdCl2-CuCl2 couple to be given by... 

In the case of selective oxidation catalysis, the use of spectroscopy has provided critical Information about surface and solid state mechanisms. As Is well known( ), some of the most effective catalysts for selective oxidation of olefins are those based on bismuth molybdates. The Industrial significance of these catalysts stems from their unique ability to oxidize propylene and ammonia to acrylonitrile at high selectivity. Several key features of the surface mechanism of this catalytic process have recently been descrlbed(3-A). However, an understanding of the solid state transformations which occur on the catalyst surface or within the catalyst bulk under reaction conditions can only be deduced Indirectly by traditional probe molecule approaches. Direct Insights Into catalyst dynamics require the use of techniques which can probe the solid directly, preferably under reaction conditions. We have, therefore, examined several catalytlcally Important surface and solid state processes of bismuth molybdate based catalysts using multiple spectroscopic techniques Including Raman and Infrared spectroscopies, x-ray and neutron diffraction, and photoelectron spectroscopy. 

It has been reported that molecnlar oxygen plays an important role in the allylic oxidation of olefins with TBHP (25, 26). Rothenberg and coworkers (25) proposed the formation of an alcoxy radical via one-electron transfer to hydroperoxide, Equation 4, as the initiation step of the allylic oxidation of cyclohexene in the presence of molecnlar oxygen. Then, the alcoxy radical abstracts an allylic hydrogen from the cyclohexene molecnle. Equation 5. The allylic radical (8) formed reacts with molecular oxygen to yield 2-cyclohexenyl hydroperoxide... 

Optically active oxaziridines are useful reagents for the enantioselective oxidation of olefins 37 39). The following three preparative methods to make this reagent available have been reported enantioselective oxidation of an imine by (-)-peroxycam-phoric acid 37,38), photocyclization of a nitrone which has a chiral substituent39), and photocyclization of a nitrone in an optically active solvent 39). However, an... 

The organic substrates in Chart 8 can be divided into two main categories in which (i) the oxidation of olefins, sulfides, and selenides involves oxygen atom transfer to yield epoxides, sulfoxides, and selenoxides, respectively, whereas (ii) the oxidation of hydroquinones and quinone dioximes formally involves loss of two electrons and two protons to yield quinones and dinitrosobenzenes, respectively. In order to provide a unifying mechanistic theme for the seemingly disparate transformations in Chart 8, we note that nitrogen dioxide exists in equilibrium with its dimeric forms, namely, the predominant N—N bonded dimer 02N—N02 and the minor N—O bonded isomer ONO—N02 (equation 88). 

The oxidation of olefins,251 sulfides,252 and selenides253 (denoted as D) involves oxygen-atom transfer from nitrogen dioxide to yield epoxides, sulfoxides, and... 

The ability of complexes to catalyze several important types of reactions is of great importance, both economically and intellectually. For example, isomerization, hydrogenation, polymerization, and oxidation of olefins all can be carried out using coordination compounds as catalysts. Moreover, some of the reactions can be carried out at ambient temperature in aqueous solutions, as opposed to more severe conditions when the reactions are carried out in the gas phase. In many cases, the transient complex species during a catalytic process cannot be isolated and studied separately from the system in which they participate. Because of this, some of the details of the processes may not be known with certainty. 

A similar mechanism of chain oxidation of olefinic hydrocarbons was observed experimentally by Bolland and Gee [53] in 1946 after a detailed study of the kinetics of the oxidation of nonsaturated compounds. Miller and Mayo [54] studied the oxidation of styrene and found that this reaction is in essence the chain copolymerization of styrene and dioxygen with production of polymeric peroxide. Rust [55] observed dihydroperoxide formation in his study of the oxidation of branched aliphatic hydrocarbons and treated this fact as the result of intramolecular isomerization of peroxyl radicals. 

Radical Ph3C" initiates the oxidation of olefins and aldehydes K. Ziegler [63]... 

The attack of peroxyl radicals on 0-CH2 groups produces the same functional groups (hydroperoxyl, hydroxy, oxo) as in the case of subsequent hydrocarbon oxidation. The oxidation of unsaturated acids proceeds similarly to the oxidation of olefins [4,7]. 

The oxidation of nonsaturated esters with double bonds far away from the ester group occurs like the oxidation of olefins (see Chapter 2). Esters like methyl oleate have weak bonds near the double bond. The peroxyl radical attacks these bonds, and the oxidation reaction occurs far from the ester group. The ester group influences the oxidation rate through its solvent properties. 

CATALYTIC OXIDATION OF OLEFINS TO ALDEHYDES 10.6.1 Catalysis by Palladium Salts... 

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