Oxidation reaction with olefin

The reaction mechanisms of these transition metal mediated oxidations have been the subject of several computational studies, especially in the case of osmium tetraoxide [7-10], where the controversy about the mechanism of the oxidation reaction with olefins could not be solved experimentally [11-20]. Based on the early proposal of Sharpless [12], that metallaoxetanes should be involved in alkene oxidation reactions of metal-oxo compounds like Cr02Cl2, 0s04 and Mn04" the question arose whether the reaction proceeds via a concerted [3+2] route as originally proposed by Criegee [11] or via a stepwise [2+2] process with a metallaoxetane intermediate [12] (Figure 2). 

The reaction mechanisms shown in Scheme 2 have been the subject of several computational studies. Of particular interest has been the dihydroxylation by osmium tetroxide,26-29 where the above mentioned controversy about the mechanism of the oxidation reaction with olefins could not be solved experimentally.10,12,13,16,19,22,24,25,35,36... 

Reaction of Unsaturated Compounds with Dialkyl Phosphites The diesters of phosphorous acid are somewhat resistant to oxidation and used as intermediates for the reaction with olefins forming phosphonic acids. The reaction takes place in the presence of free radical initiators, such as di-/-bu-tyl peroxide [104,105]. 

Although nitrile oxide cycloadditions have been extensively investigated, cycloadditions of silyl nitronates, synthetic equivalent of nitrile oxides in their reactions with olefins, have not received similar attention. Since we found that the initial cycloadducts, hl-silyloxyisoxazolidines, are formed with high degree of stereoselectivity and can be easily transformed into isoxazolines upon treatment with acid or TBAF, intramolecular silylnitronate-olefin cycloadditions (ISOC) have emerged as a superior alternative to their corresponding INOC reactions [43]. Furthermore, adaptability of ISOC reactions to one-pot tandem sequences involving 1,4-addition and ISOC as the key steps has recently been demonstrated [44]. 

TS-1 is a material that perfectly fits the definition of single-site catalyst discussed in the previous Section. It is an active and selective catalyst in a number of low-temperature oxidation reactions with aqueous H2O2 as the oxidant. Such reactions include phenol hydroxylation [9,17], olefin epoxida-tion [9,10,14,17,40], alkane oxidation [11,17,20], oxidation of ammonia to hydroxylamine [14,17,18], cyclohexanone ammoximation [8,17,18,41], conversion of secondary amines to dialkylhydroxylamines [8,17], and conversion of secondary alcohols to ketones [9,17], (see Fig. 1). Few oxidation reactions with ozone and oxygen as oxidants have been investigated. 

A few further general examples of zinc catalytic activity or reactivity include the following. Other zinc-containing systems include a zinc phenoxide/nickel(0) catalytic system that can be used to carry out the chemo- and regioselective cyclotrimerization of monoynes.934 Zinc homoenolates have been used as novel nucleophiles in acylation and addition reactions and shown to have general utility.935,936 Iron/zinc species have been used in the oxidation of hydrocarbons, and the selectivity and conditions examined.362 There are implications for the mechanism of metal-catalyzed iodosylbenzene reactions with olefins from the observation that zinc triflate and a dizinc complex catalyze these reactions.937... 

Pd2+ salts are useful reagents for oxidation reactions of olefins. Formation of acetaldehyde from ethylene is the typical example. Another reaction is the formation of vinyl acetate by the reaction of ethylene with acetic acid (16, 17). The reaction of acetic acid with butadiene in the presence of PdCl2 and disodium hydrogen phosphate to give butadienyl acetate was briefly reported by Stem and Spector (110). However, 1-acetoxy-2-butene (49) and 3-acetoxy-l-butene (50) were obtained by Ishii and co-workers (111) by simple 1,2- and 1,4-additions using PdCl2/CuCl2 in acetic acid-water (9 1). 

Wacker cyclization has proved to be one of the most versatile methods for functionalization of olefins.58,59 However, asymmetric oxidative reaction with palladium(II) species has received only scant attention. Using chiral ligand 1,1 -binaphthyl-2,2 -bis(oxazoline)-coordinated Pd(II) as the catalyst, high enantioselectivity (up to 97% ee) has been attained in the Wacker-type cyclization of o-alkylphenols (66a-f) (Scheme 8-24). 

Anodic oxidation of Grignard reagents (5) in the presence of styrene (30), butadiene (36) or vinyl ethyl ether (37) was investigated by Schafer and Kuntzel as an interesting (for preparative use) extension of other anodic reactions with olefins. The electrolysis was carried out at constant current density at Pt, Cu or graphite electrodes. It was found that the products obtained depend on the electrode material, as is seen from the data presented in Table 9. 

Aliphatic nitro compounds are versatile building blocks and intermediates in organic synthesis,14 15 cf. the overview given in the Organic Syntheses preparation of nitroacetaldehyde diethyl acetal.16 For example, Henry and Michael additions, respectively, lead to 1,2- and 1,4-difunctionalized derivatives.14 18 1,3-Difunctional compounds, such as amino alcohols or aldols are accessible from primary nitroalkanes by dehydration/1,3-dipolar nitrile oxide cycloaddition with olefins (Mukaiyama reaction),19 followed by ring cleavage of intermediate isoxazolines by reduction or reduction/hydrolysis.20 21... 

A series of olefin oxidation reactions with H202 and Se02—hydroxylation and oxidation, including cycle contraction, should be noted [53, 54], It is the author s opinion that selenium dioxide catalyzes H202 dissociation to free radicals and, therefore, promotes H202 induction influence on oxidation of olefins. 

Vapor Sttate. Here the situation is much simpler. Ionic species are no longer present, and in the absence of nitric oxide the choice lies merely between nitrogen dioxide and dinitrogen tetroxide. The proportions vary very much with temperature at 21.15° C., the tetroxide is 15.9% dissociated, whereas dissociation to NO2 is complete at 140°. It does not necessarily follow, however, that reaction at low temperatures involves dinitrogen tetroxide, as reaction with olefins clearly shows. 

Wacker-type oxidative reactions of olefins with nucleophiles, reactions of zr-allyl-palladium complexes with nucleophiles, reactions based on chelation, and trans-metallation of organomercury compounds. 

Oxidative Reactions with Pd2 Compounds 2.1 Reactions of Olefins with Nucleophiles... 

The reaction of 3,4-dihydroisoquinoline-/V-oxide (22) with olefins such as allyl alcohol,39 styrene,45 methyl acrylate,36,100 and ethyl acrylate36 gives stereospeciflcally isoxazolidine of type It. 

Solvent appears to have little effect on the rate of reaction of 02 with many classes of chemicals. The rate of reaction with diphenylisobenzo-furan was unchanged in several solvents, excluding water where dimerization may have accelerated its reactivity. However, Young et al. [195] noted that 02 oxidation of some furans showed significant solvent effects (X32), whereas reactions with olefins showed only small effects ([Pg.80]

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