Oximes nitrite oxidation

Another related reaction is the Barton reaction, by which a methyl group in the 0 position to an OH group can be oxidized to a CHO group. The alcohol is first converted to the nitrite ester. Photolysis of the nitrite results in conversion of the nitrite group to the OH group and nitrosation of the methyl group. Hydrolysis of the oxime tautomer gives the aldehyde, for example,... 

A choice between mechanisms (b) and (c) was achieved by photolyzing a mixture of a 14N-nitrite in the pregnane series and the 15N-nitrite (29) to half-completion. Rearrangement of the nitroso dimers thus obtained to a mixture of oximes followed by oxidation of the pure oxime from (29) to the ketonitrile and mass spectrometric analysis indicated the N15/N14 ratio to be 1.15 1.00. Analysis of pure unreacted (29) gave a ratio of 1.00 0.00. These results indicate that mechanism (c) is operative in nitrite photolyses. 

Acenaphthenequinone has been prepared from acenaplithene by oxidation with chromic acid, 1 2 3 with calcium permanganate,4 with air in the presence of catalysts in various solvents,6 6 7 and by the formation of an oxime with amyl nitrite followed by hydrolysis.8... 

Electrophilic substitution of the ring hydrogen atom in 1,3,4-oxadiazoles is uncommon. In contrast, several reactions of electrophiles with C-linked substituents of 1,3,4-oxadiazole have been reported. 2,5-Diaryl-l,3,4-oxadiazoles are bromi-nated and nitrated on aryl substituents. Oxidation of 2,5-ditolyl-l,3,4-oxadiazole afforded the corresponding dialdehydes or dicarboxylic acids. 2-Methyl-5-phenyl-l,3,4-oxadiazole treated with butyllithium and then with isoamyl nitrite yielded the oxime of 5-phenyl-l,3,4-oxadiazol-2-carbaldehyde. 2-Chloromethyl-5-phenyl-l,3,4-oxadiazole under the action of sulfur and methyl iodide followed by amines affords the respective thioamides. 2-Chloromethyl-5-methyl-l,3,4-oxadia-zole and triethyl phosphite gave a product, which underwent a Wittig reation with aromatic aldehydes to form alkenes. Alkyl l,3,4-oxadiazole-2-carboxylates undergo typical reactions with ammonia, amines, and hydrazines to afford amides or hydrazides. It has been shown that 5-amino-l,3,4-oxadiazole-2-carboxylic acids and their esters decarboxylate. 

The benzyl ligand of benzylbis(dimethylglyoximato)pyridine cobalt complex has been selectively converted to 3,5-dibenzyl-l,2,4-oxadiazole by a reaction with alkyl nitrite in the presence of light (426). The reaction proceeds by the in situ formation of an oxime and a nitrile oxide (Scheme 1.44). 

Diazo esters can also be prepared from glycine esters by treatment with nitrous acid [966] or with alkyl nitrites. Further methods include the oxidation of hydrazones, oximes (Forster reaction), and semicarbazones, the base-induced... 

Triketone (57), a key intermediate in the synthesis of 4,4,7,7,11,11-hexanitropentacyclo [6.3.0.0 .0 °.0 ]undecane (61) (Zlj-hexanitrotrishomocubane), has been synthesized independently by both Marchand and co-workers, and Fessner and Prinzach. Marchand and co-workers prepared the trioxime (58) from the corresponding triketone (57). Oxidation of (58) with peroxytrifluoroacetic acid in acetonitrile provides a direct route to the trinitro derivative (59) in 35 % yield, this yield reflecting an efficiency of 70 % for the oxidation of each oxime group. Subsequent oxidative nitration of (59) with sodium nitrite and potassium ferricyanide in aqueous sodium hydroxide yields the target T>3-hexanitrotrishomocubane (61). 

In a communication by Tanimoto and coworkers, ketene O-alkyl O -trunethylsilyl acetals 49 provide either a-nitroso esters 50 or their oximes 51 on reaction with nitric oxide or isoamyl nitrite in the presence of titanium(IV) chloride (Scheme 29). These reactions seem to provide a relatively direct way to introduce a nitrogen substituent at the a-carbon atom of carboxylic esters. 

Nitrosomethane (1) is known to be less stable than its isomer formaldoxime 2 and original attempts to isolate this species failed owing to its facile isomerization to the oxime 2. Already Bamberger and Seligman considered in 1903 that it would be difficult to isolate nitrosomethane after oxidation of methylamine due to its rapid isomerization to 2. Hence, 2 is always present in the synthesis of the nitrosomethane. Nitrosomethane is produced in the pyrolysis or photolysis of tcrf-butyl nitrite and by the reaction of methyl radicals with nitric oxide. Early results were confusing since the final product obtained is dimeric nitrosomethane. It was first isolated in 1948 by Coe and Doumani from the photolysis of gaseous ferf-butyl nitrite according to the overall reaction shown in equation 2. 

The photolysis of nitrites which do not contain g-hydrogen atoms usually results in the elimination of nitric oxide and the formation of hydroxy and carbonyl compounds. When g-hydrogen atoms are present than the product is an oxime or the corresponding nitroso dimer. This reaction is known as Barton S reaction. 

Nitrosation of 2- and 4-alkylpyridines, their quaternary salts and N-oxides, can be effected with an alkyl nitrite and sodamide in liquid ammonia the product is an oxime (Scheme 54) (69AP494, 65YZ451). 

Other examples of an attack on C from an alkoxy radical at C20 are recorded in the literature for instance, in the progesterone series the oxime (7) obtained from the photolysis of the corresponding nitrite was converted to the nitrile (8) J Oxidation and acid hydrolysis of the nitrile (8) gave 3,20-diketo-4-pregnen-18-oic acid (9) identical with a... 

Many compounds have been tested as ignition quality improvers—additives which shorten the ignition delay to a desirable duration. An extensive review in 1944 (6, 43) listed 303 references, 92 dealing with alkyl nitrates and nitrites 61 with aldehydes, ketones, esters, and ethers 49 with peroxides 42 with aromatic nitro compounds 29, with metal derivatives 28 with oxidation and oxidation products 22 with polysulfides 16 with aromatic hydrocarbons nine with nitration and four with oximes and nitroso compounds. In 1950, tests at the U. S. Naval Engineering Experiment Station (48) showed that a concentration of 1.5% of certain peroxides, alkyl nitrates, nitroaikanes, and nitrocarbamates increased cetane number 20 or more units. 

Bromo-3-penten-2-one oxime 111 is converted into 2-hydroxypyrazole 1-oxides 112, when treated first with copper sulfate using pyridine as the solvent and then with butyl nitrite and aq KOH (1994JHC281, 1994JHC1487) (Scheme 34). 

A coozonolysis (two compounds in presence of ozone) is possible if one precursor generates the carbonyl oxide in situ that then reacts with the second compound - the carbonyl. JV-Methyl oximes have been found to be ideal precursors, because they readily react as dipolarophiles in a 1,3-dipolar cycloaddition with ozone. A retro- 1,3-dipolar cycloaddition then leads to the formation of the carbonyl oxide and methyl nitrite ... 

Treatment of 2-butyne with ozone leads to unstable primary ozonides that cleave to cr-oxo-carbonyl oxides these could be trapped in the presence of aldehydes or ketones affording cross- -oxo-l, 2,4-trioxolanes. Subsequent cycloadditions between such cr-oxo-ozonides and cyclohexanone oxide, generated in situ from O-methylcyclohex-anone oxime (which affords methyl nitrite as a side-product), yield cr-diozonides 101 (Scheme 30) <1997J(P1)1601>. 

An improved synthesis7 of aldosterone acetate lb was based on the readily available dienone 30. Conversion to the nitrite and photolysis affords the oxime 31 with no attack on C19. On warming in iso-propyl alcohol this oxime 31, cyclized smoothly to the nitrone 32 with the loss of water. This nitrone is at the right oxidation level to rearrange to the 21-acetoxyimine. The overall yield of nitrone from 30 was 55%. 

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