Transannular peroxide

Transaminases Transamination Transannular peroxide Transcat process Transcobalamin II Transcortin... 

A number of chemiluminescent reactions may proceed through unstable dioxetane intermediates (12,43). For example, the classical chemiluminescent reactions of lophine [484-47-9] (18), lucigenin [2315-97-7] (20), and transannular peroxide decomposition. Classical chemiluminescence from lophine (18), where R = CgH, is derived from its reaction with oxygen in aqueous alkaline dimethyl sulfoxide or by reaction with hydrogen peroxide and a cooxidant such as sodium hypochlorite or potassium ferricyanide (44). The hydroperoxide (19) has been isolated and independentiy emits light in basic ethanol (45). 

Chemistry and biological activity of artemisinin (sesquiterpene y-lactone with oxepane fragment and transannular peroxide bridge) and related antimalari-als 99H(51)1681. 

Lithiumalanat4 und Natriumboranat5,6 zeigen gegeniiber Dialkyl-peroxiden deutliche Unterschiede. Wahrend transannulare Peroxide hauptsachlich durch Lithiumalanat auf-gespalten7 werden z.B. ... 

Mechanistic studies were started by Gaffron15-17 in 1926. At this time Moureu, Dufraisse, and Dean18 discovered the direct photooxygenation of rubrene and Windaus and Brunken19 discovered the photosensitized oxygenation of ergosterol. The structures of both the products formed were elucidated some years later and shown to be those of transannular peroxides (endoperoxides).20-23... 

Although thiophene derivatives, e.g., tetraphenylthiophene XXI and XXII70 do not appear to form photoperoxides sulfurated 9,10-diphenyl-anthracenes XXIII and cerothiene XXIV derivatives have been reported to form transannular peroxides of the type A on irradiation in the presence of oxygen.209,210... 

An intriguing group of reactions is known in which oxygen reacts photochemically to yield peroxides. Most of the examples involve cyclic dienoid systems and give transannular peroxides (the reaction is frequently not reversible). 

Figure 4.61 Peroxide and hydroperoxide formation in photo-oxygenation reactions addition of molecular oxygen to anthracene to form the transannular peroxide, and insertion into an olefin...

Photolysis, in the presence of oxygen, of alkenes containing an ally lie hydrogen atom leads to the formation of hydroperoxides. The sensitized process is more efficient, and often yields photoproducts different in structure from those obtained by nonsensitized photooxidation. Cyclohexadiene and related dienes on photolysis in the presence of oxygen yield the transannular peroxides. Thus, on photosensitized oxidation, a-terpinene (410) is converted into ascaridole (411).435 The equivalent process is not, in general, observed in acyclic dienes. Certain polynuclear aromatic hydrocarbons, such as anthracene and naphthacene and including the heterocycles 5,10-diphenyl-1-... 

Photosensitized photooxidation of pyrrole (412) by irradiation in the presence of eosin gives rise to the photoproduct (413), presumably via the intermediate peroxide (414).440 Transannular peroxides are... 

Imidazole reacts very slowly with singlet oxygen to form the imida-zolidone (86)42S through an elimination reaction involving proton loss and cleavage of the oxygen-oxygen bond of the transannular peroxide (87). On the other hand, 4-phenylimidazole forms a hydantoin derivative (88) and V-benzoyl-V -methoxycarbonylurea (89). This... 

These cyclic peroxides are also known as photooxides, transannular peroxides, 1,4-epiperoxides, and epidioxides. 

Transannular peroxides of anthracene and its derivatives, preparation, properties, applications of 90CLY582. 

Kraljic and El Mohsni (1978) developed a method based on bleaching of N,N-dimethyl-4-nitrosoaniline (RNO) by 02 in the presence of imidazole. 02 generated during photolysis reacts with imidazole to form a transannular peroxide that bleaches RNO the bleaching can be monitored spectrophotometrically at 440 nm. Hall and... 

With fused-ring oxazoles of the type 211 imino anhydrides may be isolated in good yields in methanol. However, oxygenation in inert solvents such as methylene chloride takes an entirely different course and results in the formation of u-cyano acids or esters. Photooxidation of fused-ring oxazoles unsubstituted in the 2-position, such as 213, appears to proceed through the intermediate transannular peroxide 214, which then undergoes intramolecular rearrangement178 to form the cyano anhydride (215). Loss of CO from this mixed anhydride of formic acid leads to w-cyano acid (216), the observed product, in 80-90% yields.126... 

Polycyclic aromatic hydrocarbons such as anthracenes, tetracenes, and pentacenes, as well as cyclopentadienes, cyclohexa-l,3-dienes, cyclo-hepta-l,3-dienes, and furans, have been found to be suitable diene systems to which the singlet oxygen adds as a dienophile in a 1,4-cycloaddition reaction. Thus, endoperoxides (transannular peroxides) and, in the case of furans, ozonides of the corresponding cyclobutadienes are the primarily produced, more or less stable addition products (2, 21, 22). 

We have in the past considered another type of hydroxylation mechanism (Reactions 5 and 6) that involves the formation of a hydroperoxide of the substrate as an intermediate, followed by reduction of the peroxide to the hydroxylated product (ii). A similar mechanism involving the formation of a transannular peroxide of the substrate has also been proposed recently for aromatic hydroxylations (iS). 

Experiments with rat liver homogenates and microsomes have provided most of the data on the products of DMBA metabolism. The initial steps in DMBA metabolism are epoxide formation and hydroxylation of each methyl group 49, 257, 426, 502). Evidence has also been presented for enzymatic formation of a transannular peroxide however, this product is also formed nonenzymatically 69). The formation of the 5,6-epoxide of DMBA was demonstrated by crystallization of the radioactive metabolite to constant specific activity, by conversion to a glutathione conjugate, and by hydration to the 5,6-dihydrodiol (257). The other DMBA dihydrodiols presumably result from hydration of epoxides they were not observed in the presence of the epoxide hydrase initiator TCPO 502), The 8,9-dihydrodiol is the major dihydrodiol metabolite of DMBA formed in rat liver. 

Dimethylcyclo-octa-1,5-diene reacts with boron trifluoride diethyl etherate to give 2,5-dimethylbicyclo[3,3,0]oct-2-ene (60%), whereas l,5-dimethylbicyclo[3,2,l] octan-8-ol (156 R = H 50%) and its tosylate (156 R = Ts 70%) are formed on treatment with perchloric acid-aqueous dioxan and toluene-p-sulphonic acid, respectively. Preliminary results indicate that cis,ci -cyclo-octa-l,5-diene and hydrogen peroxide-mercury(ii) nitrate react to give a transannular peroxide. The boron trifluoride diethyl etherate-benzene catalysed cyclizations of the cyclo-octenyl ester (157 R = COjEt) and ketone (157 R = COMe) to the bicyclo[3,3,l]nonanes (158 R = C02Et) and (158 R = COMe), respectively, have been studied further. Possible intermediates in these reactions were synthesized but no cyclized products were obtained. The mechanism that was finally suggested involves protonation of the... 

In a class by itself (Group 5) was the transannular peroxide ascaridole, which reduced at -1.22 V. It showed a linear relationship between diffusion current and concentration in the range 9.2 x 10 to 1.6 x 10 M. 

Reactions of Benzothiazoles with Singlet Oxygen.—Singlet oxygen reacts with 4,5,6,7-tetrahydro-2-methylbenzothiazole in methylene chloride to yield the transannular peroxide (19), which undergoes successive Baeyer-Villiger rearrangement and tautomerism via (20) to the isolable A -acetyl-thio-isoimide... 

A symbolizes the triplet state intermediate formed, as in fluorescence quenching, by interaction with oxygen. In this way transannular peroxides of biochemical interest can be formed. Well-known examples, shown in Fig. 1, are ascaridole, isolated from chenopodium oil (Nelson, 1913), sterol peroxides (Windaus and Drunken, 1928), and a-phillandrene peroxide (Schenk, 1948, and Schenk et al., 1953). 

Fig. 1. The first row shows examples of natural transannular peroxides ascari-dole and a-phillandrene peroxide. The former can be obtained from terpene by diensynthesis with Oj and with chlorophyll or eosin as a photosensitizer. The second row shows sterol peroxide (Windaus and Brunken, 1928) and pentacene (Dufraisse, 1939). The last row illustrates the reversibility of oxygen addition in some cases (Dufraisse and Etienne, 193S).

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