Oxidation with peracids

Reactive halogen compounds, alkyl haUdes, and activated alkenes give quaternary pyridinium salts, such as (12). Oxidation with peracids gives pyridine Akoxides, such as pyridine AJ-oxide itself [694-59-7] (13), which are useful for further synthetic transformations (11). 

A-Oxidation with peracids (Section 4.04.2.1.3) and the transformation of pyrazoles into 4,4-dihalogeno-2-pyrazolin-5-ones (Section 4.04.2.1.4(v)) have already been discussed. Transformation of non-aromatic 2-pyrazolin-5-ones into the 4-oxo derivatives will be examined in Section 4.04.2.2.l(ii). 

Anions of hydroperoxides may be used to successfully obtain sulphones by the oxidation of sulphoxides in non-aqueous media, without the use of transition metal catalysts. This is in contrast to oxidations with peracids where aqueous media are invariably used. Thus, dimethyl sulphoxide was oxidized by the anion of cumene hydroperoxide in ethanol or benzene solution at room temperature in 90% yield66. The yield is very much dependent on the base used and decreases along the series ... 

A possible extension of the modified Neber reaction would be the synthesis of sulfonyl-substituted 2ff-azirines following the chemistry shown in Scheme 17 [27]. Unexpectedly, the oxime derived from -keto sulfones could not be converted into the oxime tosylate. Therefore, a different route to these requisite starting materials was designed, viz., via the corresponding sulfides 30 which were then oxidized with peracid to the sulfones 31. 

Synthesis of 31 by Method I (107,108) and its conversion to the related anti and syn diol epoxide derivatives (32,33) has been reported (108). The isomeric trans-1,lOb-dihydrodiot 37) and the corresponding anti and syn diol epoxide isomers (38,39) have also been prepared (108) (Figure 19). Synthesis of 37 from 2,3-dihydro-fluoranthene (109) could not be accomplished by Prevost oxidation. An alternative route involving conversion of 2,3-dihydrofluoranthene to the i8-tetrahydrodiol (3-J) with OsO followed by dehydration, silylation, and oxidation with peracid gave the Ot-hydroxyketone 35. The trimethylsilyl ether derivative of the latter underwent stereoselective phenylselenylation to yield 36. Reduction of 3 with LiAlH, followed by oxidative elimination of the selenide function afforded 3J. Epoxidation of 37 with t-BuOOH/VO(acac) and de-silylation gave 38, while epoxidation of the acetate of JJ and deacetylation furnished 39. 

Xanthines substituted at the 8-position with an oxygen or nitrogen atom are oxidized with peracids to 4,5-dihydro-1,2,4-oxadiazoles (200) (Scheme 87) <940PP353>. 

Aliphatic amines have been oxidized with peracids. 

Moreover, the 2-vinyl-l,3-thiazetidine 98a (R1 = R2 = Et) undergoes rearrangement to thiazine sulfone 101 when treated with peracid. A by-product sultine compound 102 was isolated in 6% yield from this reaction. This could be the result of a [2,3]-sigmatropic rearrangement of the sulfone. The reduced 2-vinyl-l,3-thiazetidine 103 is also oxidized with peracid affording the thiazine sulfone 104 but no product corresponding to the sultine was detected (Scheme 30) <1999J(P1)3569>. 

Although a, 3-unsaturated ketones are usually not oxidized with peracid, nmr data point to the formation of a cfs-bisoxirane from 20 with MCPBA (Eq.l 1). ... 

Trimethylsilyl-furans are converted into the butenolide by oxidation with peracid. ... 

Recently, dimethyldioxirane has been found to be very useful for oxidation of thiophenes (Table 6) [45]. The oxidation is carried out under neutral conditions. In addition, workup procedure is very simple since the dimethyldioxirane is converted into acetone. The oxidation is applicable to thiophenes carrying electron-withdrawing substituent(s), which resist oxidation with peracids. The reagent was also successfully applied to the oxidation of thiophenophanes [45]. The authors have succeeded in synthesis and isolation of the thermally unstable, parent thiophene 1,1-dioxide with this reagent [46]. 

In the case of perhydro-l,3-thiazine-2,6-diones (50), oxidation with peracids gives S-oxides (51) (n = 1) and eventually 5,5-oxides (50) (n = 2) (Equation (5)) <84LA1627>. 

Oxidation of quinoxaline with aqueous nitric acid and 2,3-dimethyl-quinoxaline with 20% nitric acid yields 6-nitroquinoxaline-2,3-dione. Quinoxalinediones are also isolated when quinoxalines are oxidized with peracids. Electronegative substituents such as nitro and cyano in the... 

Allylic sulfides 60 were derived from camphor by reacting the enolate with S-allyl thiosulfonates and reducing the carbonyl group with diisobutylaluminum hydride61. Oxidation with peracid leads to the chiral sulfoxides which undergo diastereoselective sigmatropic rearrangements (Section D.7.4.). 

Catalytic reduction of (—)-ll-methoxytabersonine (3) and oxidation with peracid gave l,2-dehydro-16-carbomethoxy-16-hydroxy-ll-me-thoxyaspidospermidine N-oxide (306), which was rearranged by tri-phenylphosphine in acid to a mixture of vincine (307), 16-epivincine (308), and apovincine (309) (173). 

Oxidation with peracids gives epoxides, which can be re-reduced with lithium aluminum hydride (Scheme 5.4.2). Another typical carotene reaction is rapid oxidative or reductive bleaching, which may also occur in the solid state. Cross-linked polymers of unknown structure are formed (see Fig. 5.5.3). With age, fluorescent pigments accumulate in the retinal pigment epithelium. The major chromophore of this particular pigment contains a pyri-dinium ring with two polyene side chains. It can be synthesized from two retinal molecules and ethanolamine via the enamine of retinal and condensation with a second retinal molecule (Scheme 5.4.3) (Eldred and Lasky,1993 Sakai et al.,1996). 

Strong bases hydrolyze nucleic bases slowly and ammonia is released. Acids, however, often stabilize the urea-type heterocycles. The basic lactam oxygen is protonated and converts the bases to aromatic systems (compare with Scheme 8.5.4). The C=C double bonds can usually be removed by catalytic hydrogenation or Michael addition of hydride or other nucleophiles (Scheme 8.5.1). Oxidation with peracids, on the other hand, usually gives N-oxides rather than epoxides (Suhadolnik, 1979 Shabarova and Bogdanov, 1994). 

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