Oxidation by peracid

The oxidation of isoquinoline has also been examined using mthenium tetroxide. In this instance, the surprising observation that phthaUc acid is the only significant product (58%) was made this fact is both important and difficult to explain (145). Isoquinoline is also oxidized to its N-oxide by peracids. Isoquinoline N-oxide [1532-72-5] has also been obtained from 2-(2,4-dinitrophenyl)isoquinolinium chloride [33107-14-1] by refluxing with hydroxjiamine hydrochloride in concentrated hydrochloric acid (146). 

The pH dependence of the rate suggests that nucleophilic attack by the sulphur atom of the sulphoxide on the undissociated hydroperoxide is unimportant while nucleophilic attack by the hydroperoxide anion on the sulphoxide is the preferred reaction under these conditions. Changing the alkyl substituent of the sulphoxide had little effect on the rate and thus the reaction probably proceeds in a similar manner as for oxidation by peracids... 

Peroxomonophosphoric acid (PMPA) oxidizes dimethyl sulphoxide in high yield in water and aqueous ethanol . In neutral solution the reaction mechanism was thought to be very complex but actually occurs by two different mechanisms that are very similar to those for sulphoxide oxidation by peracids in acidic and basic media. In an alkaline medium the mechanism involves nucleophilic attack by a phosphorus-containing species (probably POs ) on the sulphur atom of the sulphoxide, followed by O—O bond scission yielding the sulphone (equation 24). In acidic solution, on the other hand, the sulphoxide is the nucleophilic species as detailed in equation (25). It should be noted however that there is some evidence that these mechanisms are oversimplified since there are other nucleophilic species (such as H2P05 and HPO ") present in aqueous solutions of PMPA over a wide pH range . 

Two new reactive, very powerful organic peroxides, dimethyldioxirane and methyl(trifluoromethyl)dioxirane (4), have been introduced.81-83 The latter is more reactive and can be used more conveniently.84 85 Acyclic alkanes give a mixture of isomeric ketones on oxidation with methyl(trifluoromethyl)dioxirane,84,85 while cyclohexanone is the sole product in the oxidation of cyclohexane (99% selectivity at 98% conversion).85 With the exception of norbomane, which undergoes oxidation at the secondary C-2 position, highly selective tertiary hydroxylations can be carried out with regioselectivities in the same order of magnitude as in oxidations by peracids.85-87 A similar mild and selective tertiary hydroxylation by perfluorodialkyloxaziridines was also reported.88 Oxidation with dioxiranes is highly stereoselective 85... 

Indolones (158 R = aryl) or their water adducts (175 R = aryl, alkyl Nu = OH) are oxidized by peracids, under mild conditions, to benzoxazines (142 R = aryl, alkyl). The reaction is a general one. The reaction may proceed by the intermediate oxirane (120) or by initial addition of the peracid across the azomethine linkage (202).48 Oxidation by aqueous permanganate or dichromate gives iV-acylanthranilic acids (203 R = aryl, alkyl).48"50... 

Triazines (173) without a substituent in the 5-position are oxidized by peracids to... 

Oxidation of 3-methoxy- or 3-phenoxy-1,2,4-triazines (228) with perbenzoic acid converted them into the appropriate 1-oxides (229) (71JOC787). Peracid treatment of 1,2,4-triazin-3-ones with an unsubstituted 5-position (84 R5 = H) gave l,2,4-triazine-3,5-diones (182) (69JHC403), while 5-substituted l,2,4-triazin-3-ones (84) afforded the appropriate 1-oxides (230) (66JOC3914). 3-Amino-l,2,4-triazines with an unsubstituted (86a) or a monosubstituted amino group (86b) were oxidized by peracids to give the 2-oxides (231), while the 3-dialkylamino compounds (86c) afforded the 1-oxides (232) (77JOC546). 

Imines and iminiums salts are oxidized by peracids into oxazidines and oxaziridinium ions, which are good reagents for oxidation of sulfides. The imine or iminium salt can, in principle,... 

Thienotropones 458a-c, on oxidation by peracid, yield normal S,S-dioxides 459a-c and thionaphthene 5,5-dioxides 460a-c and 462 (Scheme 124 84BCJ3156). The latter products result from ring contraction (Section... 

The sulfur in saturated or partly saturated thiazolo derivatives may be oxidized by peracids. 

Berberines are reported to be reduced to dihydroberberines rather than the tetrahydro-compounds by sodium bis(2-methoxyethoxy)aluminium hydride.80 Partial reduction of coralynium salts affords the tertiary dienamine (55), autoxida-tion of which, at pH 8, yields the betaine (56) this can be oxidized by peracids to 6 -acetylpapaveraldine (57), obtainable directly from the dienamine (55) by photolysis in the presence of air. The diketone reacts with hydrazine to give the 1,2-diazine (58).81... 

This hemiacetal type of peroxide has been isolated in fact, a commercial synthesis of peracetic acid is based upon formation of this material (11). These authors state that this peroxide decomposes spontaneously to two molecules of acetic acid and that the decomposition is slow at 0°C. but the rate increases rapidly as the temperature increases. Analogously in polymer oxidation aldehyde could be oxidized by peracid to the hemiperacetal intermediate which then breaks down to form two acid groups. 

Enamines are oxidized by peracids to yield, after hydrolysis, the corresponding a-hydroxy ketones, as shown in Scheme 28 for a steroidal enamine44. 

Baeyer-Villiger oxidation Ketones (RCOR ) are oxidized by peracids (or peroxy acids, RCO2OH) to give esters (RC02R ) and cyclic ketones give lactones. 

Oxidation of codeinone. Codeinone (1) and codeine are oxidized by peracids quantitatively to the N-oxide. However, codeinone can be oxidized in part to the 7,8-oxide (2) by H2O2 (3%) in the presence of NaOH at 0°. The product can be reduced to the 7,8-oxide of codeine (3), which may be a metabolite of codeine. 

The rapid development of chiral phosphine derivatives of ferrocene was undoubtedly due to their application in catalysis. In contrast, chiral sulfur compounds from lithiated iV,iV-dimethyl-l-ferrocenylethylamine were only prepared about 15 years later [140], For the synthesis of such derivatives, the lithiated amine is treated with disulfides as shown in Fig. 4-24, top (and analogously, diselenides [141]). The sulfides obtained are easily oxidized by peracids or NaI04 to the corresponding sulfoxides. As sulfur becomes a new center of chirality by the oxidation, diastereoisomeric sulfoxides are formed in ratios depending on the oxidant [140]. If chiral oxaziridines [106, 142] are used as oxidizing agents, the diastereoisomeric ratio is appreciably... 

While the corresponding cis isomer gave a wine-red color reaction with tetra-cyanoethylene, no color reaction was observed with trans doubly bridged ethylenes. This, together with their lack of reactivity to oxidation by peracids also revealed the inert nature of the central double bonds in these isomers. 

Alkyl- or aryl-1,2,4-triazines without a substituent in the 5-position are oxidized by peracids to 1,2,4-triazin-5-ones, or 1,2,4-triazine-5,6-diones if the 6-position is also unsubstituted. 60,235 Oxidation of 3-unsubstituted and 3-methoxy-1,2,4-triazines with peracids produces the 1-oxides 3 in both cases.236... 

Triazin-3-amines with an unsubstituted or a monosubstituted amino group are oxidized by peracids to give the 2-oxides 4, while the AvV-dialkyl-l,2,4-triazin-3-amines afford the 1-oxides.237 Oxidation of l,2,4-triazin-3-amine 2-oxide (4 R1 = R2 = R3 = H) with hydrogen peroxide in polyphosphoric acid at 24 °C gives l,2,4-triazin-3-amine 2,4-oxide (36%), the first monosubstituted 1,2,4-triazine di-iV-oxide.238... 

Disubstituted 1,2,4-triazine 4-oxides are oxidized by peracids to the corresponding 1,4-dioxides 9. If the 5-position is unsubstituted, the 1,2,4-triazin-5(2//)-one 4-oxides 10 are formed and these are also the products of the oxidation with potassium permanganate.241... 

Cyclohexanones may also be cleaved oxidatively by peracids (18), a rearrangement (19) which has the effect of inserting an oxygen atom into the ring to give a lactone. ... 

Most cyclic a-diazoketones are oxidized by peracids to a-diketones in good yield, but low yields were obtained for oxidation of a-diazocyclo-octanone and a-diazo-cyclononanone because of further oxidation to suberic and azelaic anhydrides, respectively. Since the rate of oxidation is only slightly dependent upon ring size, the conformation of the transition state must be similar to that of the ground state a concerted nitrogen extrusion-oxygen addition mechanism has been proposed. 

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