Ethers with ozone

Anticipated products from the reaction of sym-dichloromethyl ether with ozone or OH radicals in the atmosphere, excluding the decomposition products formaldehyde and HCl, are chloromethyl formate and formyl chloride (Cupitt, 1980). 

Ozonides. Treatment of a mixture of ketoxime ethers with ozone in the presence of... 

At the same time an important paper (67) appeared in which essentially the same conclusions with regard to the structure of bebeerine were arrived at by a different route. Faltis, Kadiera, and Doblhammer (67) treated the inactive a, a -dimethylbebeerine methine, obtained by a one-stage Hofmann degradation of bebeerine dimethyl ether, with ozone and obtained a mixture of two dimethylamino dialdehydes. These were not isolated but were converted to the chloromethylate derivatives, oxidized with potassium permanganate to the acids, and boiled with dilute alkah to decompose the quaternary bases. Besides trimethylamine, a mixture of two vinyl carboxylic acids were obtained. One of these proved to be 4, 6-dicarboxy-2,3-dimethoxy-5-vinyldiphenyl ether (LIX). The other vinyl carboxylic acid, which was readily separated from LIX by virtue of its low solubility, was first decarboxylated by heating with quinoline and naturkupfer C and then oxidized with potassium permanganate in acetone. This yielded 4-carboxy-2,2 -dimethoxydiphenyl ether (LXIII), the structure of which was proved by direct comparison with the synthetic compound prepared by the Ullmann condensation of o-bromoanisole and vanillic acid. 

As inert as the C-25 lactone carbonyl has been during the course of this synthesis, it can serve the role of electrophile in a reaction with a nucleophile. For example, addition of benzyloxymethyl-lithium29 to a cold (-78 °C) solution of 41 in THF, followed by treatment of the intermediate hemiketal with methyl orthoformate under acidic conditions, provides intermediate 42 in 80% overall yield. Reduction of the carbon-bromine bond in 42 with concomitant -elimination of the C-9 ether oxygen is achieved with Zn-Cu couple and sodium iodide at 60 °C in DMF. Under these reaction conditions, it is conceivable that the bromine substituent in 42 is replaced by iodine, after which event reductive elimination occurs. Silylation of the newly formed tertiary hydroxyl group at C-12 with triethylsilyl perchlorate, followed by oxidative cleavage of the olefin with ozone, results in the formation of key intermediate 3 in 85 % yield from 42. 

The Effect of Mineral Matters on the Decomposition Ethers. Recently, the effect of mineral matters of coal on the coal liquefaction has received much attention. It was shown that small amounts of FeS or pyrite are responsible for the hydro-genative liquefaction of coal. Therefore, it is interesting to elucidate the effect of mineral matters of coal on the decomposition rate and products of aromatic ethers, and so three diaryl ethers were thermally treated in the presence of coal ash obtained by low temperature combustion of Illinois No.6 coal at about 200°C with ozone containing oxygen. 

Photolytic. Photooxidation products reported include 2,2 -dihydroxy-4,4 -dimethylbiphenyl, 2-hydroxy-3,4 -dimethylbiphenyl ether, and 4-methylcatechol (Smith et al., 1978). Anticipated products from the reaction of 4-methylphenol with ozone or OH radicals in the atmosphere are hydroxynitrotoluene and ring cleavage compounds (Cupitt, 1980). Absorbs UV light at a maximum wavelength of 278 nm (Dohnal and Fenclov4, 1995). 

The lignin (50 g) was dissolved in a mixture of dioxane (500 ml) and methanol (1,000 ml), and ozonized at 0°C with an oxygen flow rate of 0.5 ml/min and ozone concentration of 3% as shown in Figure 3. After treatment with ozone, the solution was treated with an excess amount of ether, and the insoluble fraction was filtered off, followed by drying under vacuum. Three samples (No. 1, No. 2, and No. 3) differed in the extent of ozone treatment as shown in Table I. The molar equivalents were based on the ratio of ozone to each phenylpropane (C9) unit. The yield of each sample is also shown in Table I. 

Ethyl Peroxide, Hydrogen Peroxide, and Ozone. — On vigorously shaking 10 cc. of ether with 1 cc. of 1 10 aqueous potassium iodide solution in a completely filled glass-stoppered bottle, neither the ether nor the potassium iodide solution should acquire a color after standing one hour in the dark. 

A portion of the olefin (3.5 grams) dissolved in pentane (10 ml) was treated with ozone at —178°C for 8 hrs. The product was treated with excess LiAlH4 in ether at 0°C and refluxed. After usual work up, benzyl alcohol (1.7 grams) and (—)(S)-2-methyl-l-butanol [1.1 grams [< ]D25 —5.50, op 94.5% (16, 17)] were recovered. An optical purity of 94.5% is attributed to ( + )(S)-l-phenyl-3-methyl-l-pentene having D25 +44.95°. 

Harries et al(Refs 2 3) claimed to prepare the diozonide and the diozonide peroxide of carvone. Their structures were not detd. The diozonide was obtained as a yel oil on treating carvone in CCl4 with ozone, followed by purification with pett ether. It deconpd on standing with formation of formaldehyde. Further treatment of diozonide with ozone yielded diozonide peroxide, which exploded by itself after standing for several hrs in a freezing mixt. It expld almost instantly when treated with warm w or when rubbed with a glass rod Refs l)Beil 7, 153, (101) [l28] 2)Beil 7,... 

Secondary alcohol 11 is first protected as a silyl ether with TBS chloride, after which the terminal double bond is ozonized. The resulting methyl ketone is subsequently converted stereoselectively with a Homer-Wadswonh-Emnions reaction21 into olefin 13. This reaction sequence leads to tram selectivity in the formation of the terminal double bond in 13. 

Beschkov, V., Bardarska, G., Gulyas, H., and Sekoulov, I., Degradation of triethylene glycol dimethyl ether by ozonation with UV irradiation or hydrogen peroxide addition, Water Sci. Technol., 36, 131-138, 1997. 

Some 2-alkoxytetrahydropyrans show a reactivity toward oxidants which parallels the reactivity of polycyclic amines discussed above, and which is in line with the hypothesis that weakening of C-H bonds by hyperconjugation should also increase the rate of C-H bond cleavage. For instance, of the two epimeric pyrans sketched in Scheme 2.15 only that with an axial 2-H is oxidized by ozone [51]. The same selectivity has been observed in the oxidation of methyl a- and /3-glucopyranoside with ozone [52], and in homolytic C-H bond cleavage in cyclic ethers [53],... 

Oxidizing Agents. May explode on contact with anhydrous perchloric acid9 ignites on contact with chromyl chloride10 explodes violently on contact with a mixture of concentrated nitric and sulfuric acids,11 and may react violently with concentrated nitric acid12 simultaneous contact of sodium peroxide with water and diethyl ether causes ignition13 and contact with ozone produces explosive diethyl peroxide.14... 

Fig. 17.32. Oxidative cleavage of an asymmetric ketone with complementary regiose-lectivities. Lactone A is obtained by Baeyer-Villiger oxidation of menthone [2-methyl-5-(l- methylethyl)cyclo-hexanone]. Alternatively, one may first convert menthone into the silylenol ether B and cleave its C=C double bond with ozone to obtain a silyl ester containing an a-methoxyhydroperoxide group as a second functional group (which resembles the unstable structural element of the so-called ether peroxides cf. Figure 1.38). The latter is reduced with NaBH4tothe hydroxylated silyl ester C. The hydroxycarboxylic acid is obtained by acid-catalyzed hydrolysis. It cyclizes spontaneously to give lactone D.

More interesting cases arise when the products of Birch reduction (Chapter 24) are treated with ozone. Here it is the electron-rich enol ether bond that is cleaved, showing that ozone is an electrophilic partner in 1,3-dipolar cycloadditions. If the ozonide is reduced, a hydroxy ester is formed whose trisubstituted bond s Zgeometry was fixed by the ring it was part of (see Chapter 31). 

Oxidation of olefinic side chains with ozone to form aromatic aldehydes gives erratic results and therefore other oxidants are employed. For this purpose, the most widely used oxidant is nitrobenzene in dilute alkali the mixture is allowed to react at moderate temperatures for several hours. Thus, hydroxy benzaldehydes may be obtained from propenyl-phenols, which in turn are readily prepared by the Claisen rearrangement of Oalkyl ethers (method 100). Sodium dichromate in the presence of sulfanilic acid, which removes the aldehyde as it is formed, gives yields as high as 86% in the oxidation of isoeugenol and isosafrole. ... 

Enders and Jegelka [88] have used l,3-dioxan-5-one 122, a protected dihydroxyacetone derivative, to construct enantiomerically pure C5- to C9-deoxycarbohydrates. For example, reaction of 122 with SAMP gives the hydrazone 123, which is deprotonated and alkylated with methyl iodide to yield 124. The monoalkylated hydrazone is then alkylated in the same manner with chloromethyl benzyl ether to form 125. Cleavage of the hydrazone with ozone furnishes the protected ulose 126 (>98% de, >98% ee), which is deprotected to (—)-5-deoxy-L-r/ir o-3-pentulose 127. Reduction of 126 with L-Selectride, followed by deprotection, provides 5-deoxy-D-arabinitol 128 (>95% de, >95% ee) (Scheme 13.46). 

Treatment of S4(NH)4 with ozone converts it into a linear polymer (—SO—NH—) the brown, insoluble material has also been made by treating thionyl chloride with ammonia in the vapour phase. Thionyl fluoride, however, reacts with ammonia to give a volatile ether-soluble amide as the initial product ... 

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