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Oxidation reactions benzyllic oxygenation

Peracetic acid specifically labelled with oxygen-18 has been used for the oxidation of (+ )-benzyl-p-tolyl sulphoxide to the (— )-[160180]sulphone46 (equation 15). The reaction gives the required enantiomer in no less than 80% yield. [Pg.974]

In the field of nonheme iron complexes, Miinck, Collins, and Kinoshita reported the oxidation of benzylic alcohols via stable p-oxo-bridged diiron(IV) TAME complexes, which are formed by the reaction of iron-28 complexes with molecular oxygen (Scheme 23) [142]. [Pg.102]

Oxidation of benzyl alcohol catalysed by chloroperoxidase exhibits a very high prochiral selectivity involving only the cleavage of the pro-S C-H bond. The reaction mechanism involved the transfer of a hydrogen atom to the ferryl oxygen of the iron-oxo complex. An a-hydroxy-carbon radical and the iron-hydroxy complex P-Fe -OH form. They may lead to the hydrated benzaldehyde or stepwise with the formation of the intermediate a-hydroxy cation. [Pg.168]

A possible mechanism of oxidation of methylene groups to carbonyl groups involves autoxidation (oxidation by molecular oxygen) at the benzylic position. Autoxidation of arylalkanes is a facile reaction with low activation energies for example, 6.0 kcal/mole for 1,1-diphenylethane and 13.3 kcal/mole for toluene. ... [Pg.309]

The unique chemical behavior of K02 is a result of its dual character as a radical anion and a strong oxidizing agent (68). The reactivity and solubility of K02 is gready enhanced by a crown ether (69). Its usefiilness in furnishing oxygen anions is demonstrated by its applications in SN2-type reactions to displace methanesulfonate and bromine groups (70,71), the oxidation of benzylic methylene compounds to ketones (72), and the syntheses of a-hydroxyketones from ketones (73). [Pg.519]

This section covers the hydroboration-oxidation of alkenes to give alcohols. The author chooses to include this under oxidation since an oxygen atom is introduced into the molecule. This reaction can be performed in a stereocontrolled fashion and it is these methods that are highlighted here. In addition, one similar reductive-oxidation reaction is included, since it is an extremely facile route to benzyl alcohols and a-hydroxyalkanoic acids. [Pg.714]

A range of aromatic alkenes and acrylic acid derivatives have been converted into benzyl alcohols and a-hydroxyalkanoic acids in good yields by a reductive oxidation process. This reaction is accomplished by reaction with oxygen and triethylsilane with a cobalt(II) catalyst, followed by treatment with trialkyl phosphites (equation 30)154. The aromatic olefins may also be converted into the corresponding acetophenone in a modified procedure where the trialkyl phosphite is removed155. In a similar reaction 2,4-alkadienoic acids are converted into 4-oxo-2-alkenoic acids156. [Pg.715]

CuCl, PEG6000-(TEMPO)2, and oxygen are essential for the oxidation of benzyl alcohol into benzaldehyde. The presence of C02 improves the reaction, presumably being ascribed to high miscibility of 02 into compressed C02, thus eliminating interphase transport limitation, and expandable effect of PEG in compressed C02 [63, 64],... [Pg.27]

In related investigations Valderrama et al. [47] studied the reaction of naphthoquinone (40) and juglone (47) with the ketene acetal 51. Using this oxidation state, the oxygen substituent in the product is always preserved at the terminal position of dienes (compare anthracycline chemistry [55]). Thus, the phenol ether 52 a (61 %) and smaller amounts of the phenol 52b were smoothly formed after silica gel-promoted elimination and air oxidation of the primary Diels-Alder adducts. The authors also observed base-catalyzed air oxidation to the ketone 53, analogous to similar oxidations of benzylic carbanions (compare with [56]). [Pg.137]

Toluene was oxidized to a mixture of benzyl acetate (31) and benzylidene diacetate (32) on reaction with oxygen in the presence of a silica supported Pd-Sn catalyst.A reaction run in HOAc/KOAc at 70°C under an atmosphere of oxygen gave a near 3 1 ratio of the monoacetate to the diacetate at 98% conversion (Eqn. 21.40). The two products are formed in parallel reactions as the benzylacetate does not react further under these reaction conditions. Substituted diphenylmethanes were oxidized to the diphenyl ketones by refluxing them in air in a DMF solution containing a copper powder catalyst.""... [Pg.568]

In continuation of this study. Farmer and Welton investigated the selective oxidation of alcohols to aldehydes and ketones by TRAP in conjunction with eithCT A-methylmorpholine-N -oxide or molecular oxygen as oxidants [40]. In the case of molecular oxygen (as oxidant), Cu(I) and a diamine ligand must also be added. Under the optimized conditions, benzylic alcohols were oxidized in good to excellent yields, whereas aliphatic alcohols required longer reaction time and gave poor yield. The reaction products were easily removed from the reaction mixture by extraction with diethyl ether. [Pg.380]

The Co(salophen)/zeolite catalyst was used in the oxidation of benzyl alcohol. The activities of the zeolite-encapsulated catalysts were compared to the free complexes in the oxidation reaction. For this comparison, we were using the same amount of Co(salophen) in both cases, and the oxygen uptake curves are given in Figure 1. [Pg.455]

Allylic oxidation, for example, of cyclohexene to 2-cyclohexenone, and oxidative cleavage of styrene to benzaldehyde are readily accomplished with oxygen such reaction systems contain ALhydrox3fphthalimide and l,4-diamino-2,3-dichloro-9,10-anthraquinone. Aldehydes are converted into carboxylic acids with Pd/C, KOH and catalytic amounts of NaBH4 in the air. Very similar conditions (K2CO3 instead of KOH) are described for oxidation of benzylic and allylic alcohols. ... [Pg.310]

The reaction of oxygen with most radicals is very fast because of the triplet character of molecular oxygen (see Table 11.2, Entries 42 and 43). The ease of autoxidation is therefore governed by the rate of hydrogen abstraction in the second step of the propagation sequence. The alkylperoxyl radicals that act as the chain carriers are fairly selective. Positions that are relatively electron rich or provide particularly stable radicals are the most easily oxidized. Benzylic, allylic, and tertiary positions are the most susceptible to oxidation. This selectivity makes radical chain oxidation a preparatively useful reaction in some cases. [Pg.1024]


See other pages where Oxidation reactions benzyllic oxygenation is mentioned: [Pg.83]    [Pg.83]    [Pg.456]    [Pg.505]    [Pg.380]    [Pg.408]    [Pg.418]    [Pg.432]    [Pg.275]    [Pg.277]    [Pg.77]    [Pg.204]    [Pg.204]    [Pg.351]    [Pg.390]    [Pg.285]    [Pg.35]    [Pg.518]    [Pg.99]    [Pg.583]    [Pg.79]    [Pg.554]    [Pg.60]    [Pg.204]    [Pg.5030]    [Pg.389]    [Pg.81]    [Pg.103]    [Pg.104]    [Pg.491]    [Pg.188]    [Pg.455]    [Pg.937]    [Pg.939]    [Pg.946]    [Pg.19]   


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Benzyl oxidation

Benzyl oxide

Benzylation reactions

Oxidation benzylic

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