TV-Oxidation

Chromium (TV) oxide [12018-01 -8], is obtained from the hydrothermal decomposition of mixed oxides of Cr(III) and Cr(VI). A mixed oxide... 

The presence of an TV-oxide group activates the 1,2,4-triazine ring toward electrophilic attack, for instance, in halogenation reactions. Thus, 3-methoxy- and 3-amino(alkylamino)-1,2,4-triazine 1-oxides 16 react easily with chlorine or bromine to form the corresponding 6-halo-1,2,4-triazine 1-oxides 17 (77JOC3498, 78JOC2514). 

The 1,2,4-triazine 4-oxides 55 were synthesized by the reaction of nitrones 158 (generated from a-hydroxylamino ketones and aldehydes) with an excess of hydrazine, followed by the oxidation of the intermediate 4-hydroxy-2,3,4,5-tetrahydro-l,2,4-triazines 159 with lead(TV) oxide (73KGS134). 

Treatment of isoquinoline tV-oxide (55) with sodium hydride in dimethyl sulfoxide results in ring expansion, albeit in poor yield, to the 3//-3-benzazepine 56, along with a trace of naphthalene (0.8%), and much tar.26... 

Dibenz[c,/][1,2]oxazcpine-ll-carbonitrile isomerizes to the TV-oxide acridine-9-carbonitrile 10-oxide on heating in aprotic solvents. Attempted chromatography on silica gel or alumina columns gave a mixture of the oxepino[2,3-6]quinolinecarbonitrile 2, the oxoazepinoindolecarbo-nitrile 3 and the benzo[c]-2-aza-l,6-oxa[10]annulenecarbonitrile 4. Only these types of compounds were isolated when 2,7-dimethylacridine 10-oxide was irradiated.6... 

Carbon black, Chlorinated paraffin, Manganese(TV) oxide... 

Examples P205, diphosphorus pentaoxide or phosphorus(V) oxide Hgj +, mercury ion or dimercury(2+) ion K2[Fe(CN)6], potassium hexacyanoferrate(II) or potassium hexacyanofer-rate(4—) Pb2IPbIV04, dilead(TI) lead(TV) oxide or trilead tetraoxide. 

Mild reaction conditions make it possible for DMD to be used in the formation of optically active nitrones such as (S)-5- hydroxymethyl -1-pyrroline TV-oxide... 

It is relevant to note that only cyclic aldo-nitrones tend to react in oxidative alkoxylations to give a,a-dialkoxy-substituted nitroxyl radicals. However, the only exception is methylene nitrone (215), which on oxidative methoxylation gives the a,a,a-trimethoxy-substituted nitroxyl radical (277). This is due to the proton in methylene nitrone (215), which, as in the case of cyclic nitrones, exists in the cis -position to the TV-oxide oxygen (Scheme 2.104) (517). 

Oxidative Animation of Nitrones to a-Amino-Substituted Nitroxyl Radicals Similar to the oxidative methoxylation reaction, oxidative animation of 4H -imidazole TV-oxides, in amine saturated alcohol solutions, give stable nitroxyl (282), nitronyl nitroxyl (283), imino nitroxyl (284) and (285) radicals with the amino group at the a-carbon atom of the nitroxyl group (Scheme 2.107) (520, 521). The observed influence of substituents on the ratio of animation products at C2 and C5 atom is close to the ratio observed in the previously mentioned oxidative methoxylation reaction. It allows us to draw conclusions about the preference of the radical cation reaction route. 

Oxidative Fluorination of Nitrones to a-Fluorosubstituted Nitroxyl Radicals Formation of nitroxyl radicals by the radical cation route was observed in reactions of various nitrones with xenon difluoride in dry methylene chloride (520, 523). In this reaction, more than 40 nitrones, including 4H -imidazole N,N -dioxides (219), 4H -imidazole TV-oxides (223) and (224), 2H -imidazole N -oxides (225), 2H -imidazole TV,TV-dioxides (226), 3,3,5,5-tetramethylpyrroline N -oxide (TMPO), derivatives of 3-imidazoline-3-oxides (231) and (232), have been examined. ESR spectra of nitroxyl radicals containing one or two fluorine atoms at a-C have been registered (Scheme 2.108) (523). In the case of... 

However, the character of the reaction of 3-nitro-substituted TV-oxide (169) with the C,C triple bond is changed 371. Apparently, the first step affords the normal cycloadduct A, which is successively rearranged into aziridine B. Elimination of the nitronate anion from the latter compound gives rise to ambident cations C and D, which, after quenching with methanol, form dihydrooxazines (170) or (171) depending on the nature of the substituent R. 

The major breakthrough in the catalytic asymmetric dihydroxylation reactions of olefins was reported by Jacobsen et al.55 in 1988. Combining 9-acetoxy dihydroquinidine as the chiral auxiliary with /V-methylmorphine TV-oxide as the secondary oxidant in aqueous acetone produced optically active diols in excellent yields, along with efficient catalytic turnover. 

The formation of iminium ions of 20-epipandoline occurred only under Polo-novski-Potier conditions. Thus on treatment of the TV-oxide of 165 with tri-fluoroacetic anhydride followed by an aqueous solution of KCN, the iminium ion 329 was obtained, readily isolated as the corresponding a-amino nitrile 331 (Scheme 17). The reaction was completely regioselective and no traces of the enamine 332 could be obtained. This made the synthesis of spiroketone 333... 

Indicine IV-oxide (169) (Scheme 36) is a clinically important pyrrolizidine alkaloid being used in the treatment of neoplasms. The compound is an attractive drug candidate because it does not have the acute toxicity observed in other pyrrolizidine alkaloids. Indicine IV-oxide apparently demonstrates increased biological activity and toxicity after reduction to the tertiary amine. Duffel and Gillespie (90) demonstrated that horseradish peroxidase catalyzes the reduction of indicine IV-oxide to indicine in an anaerobic reaction requiring a reduced pyridine nucleotide (either NADH or NADPH) and a flavin coenzyme (FMN or FAD). Rat liver microsomes and the 100,000 x g supernatant fraction also catalyze the reduction of the IV-oxide, and cofactor requirements and inhibition characteristics with these enzyme systems are similar to those exhibited by horseradish peroxidase. Sodium azide inhibited the TV-oxide reduction reaction, while aminotriazole did not. With rat liver microsomes, IV-octylamine decreased... 

Isopulegol, 24 517-519, 526 Isoquinoline. See also Isoquinolines reduction of, 27 201 uses for, 27 206-208 Isoquinoline derivatives. See also Isoquinolines drugs, 27 207—208t synthesis of, 27 201-206 uses for, 27 206-208 Isoquinoline TV-oxide, 27 200-201 Isoquinolines, 27 182, 200-208 alkyl, 27 205... 

Photolysis of nicotine (173) in the presence of oxygen and methylene blue with light wavelengths greater than 300 nm gave the pyrrolidone (174, 30%), nicotyrine (175, 23%) and TV-oxide (176, 7%). Under nitrogen, with eosin as photosensitizer, only nicotyrine (14%) was identified in the photodegraded mixture [112]. 

Intramolecular charge transfer in 4-nitropyridine N-oxide has been investigated by spectroscopic methods and by comparison with AMI and MNDO semi-empirical methods to obtain the vibrational force field225. The results obtained indicate that protic solvents (water, methanol) favour the mesomeric form 97 which is also favoured in the crystal, by an internal interaction between the nitro and TV-oxide groups226. 

Tertiary amine TV-oxides are rapidly deoxygenated by carbon disulphide1112. Oximes are reduced to primary amines by titanium(III) chloride in the presence of sodium cyanoborohydride, NaBTpCN1. The combined action of sodium borohydride and a chiral... 

Hydrogen peroxide, Iron(II) sulfate, 2-Methylpyridine, Sulfuric acid, 4477 Lead(IV) oxide, Carbon black, Chlorinated paraffin, Manganese(TV) oxide,... 

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