Hydroxylamines oxidation reactions

The two major methods of preparation are the cycloaddition of nitrile oxides to alkenes and the reaction of a,/3-unsaturated ketones with hydroxylamines. Additional methods include reaction of /3-haloketones and hydroxylamine, the reaction of ylides with nitrile oxides by activation of alkyl nitro compounds from isoxazoline AT-oxides (methoxides, etc.) and miscellaneous syntheses (62HC(i7)i). 

Unsubstituted quinazoline 3-oxide was prepared in an attempt to react quinazoline with hydroxylamine. This reaction gave a product of variable composition, but when an acetone solution was heated in a sealed tube it gave quinazoline 3-oxide. The oxide is more conveniently prepared, in excellent yield, from o-aminobenzaldehyde oxime and ethyl orthoformate. This method appears to be of general use and has been used for the preparation of 4-methylquinazoline... 

Diphenyl-1,2,4-triazine 4-oxide 139 was obtained by reaction of diphenyl-glyoxal mono-2-ethoxymethylenehydrazone 140 with hydroxylamine. The reaction proceeds via formation of an isonitroso intermediate, followed by cyclization to the 1,2,4-triazine 4-oxide 139 (71LA12). 

TS-1 is a material that perfectly fits the definition of single-site catalyst discussed in the previous Section. It is an active and selective catalyst in a number of low-temperature oxidation reactions with aqueous H2O2 as the oxidant. Such reactions include phenol hydroxylation [9,17], olefin epoxida-tion [9,10,14,17,40], alkane oxidation [11,17,20], oxidation of ammonia to hydroxylamine [14,17,18], cyclohexanone ammoximation [8,17,18,41], conversion of secondary amines to dialkylhydroxylamines [8,17], and conversion of secondary alcohols to ketones [9,17], (see Fig. 1). Few oxidation reactions with ozone and oxygen as oxidants have been investigated. 

The cycloaddition, reduction and oxidation reactions emanating from a,/J-unsatu-rated nitroalkenes provide easy access to a vast array of functionalities that include nitroalkanes, N-substituted hydroxylamines, amines, ketones, oximes, and a-substi-tuted oximes and ketones [73-75], Consequently, there are numerous possibilities of using these in situ generated nitroalkenes for the preparation of valuable building blocks and synthetic precursors. 

Direct oxidation of primary amines with peroxide oxidants does not provide appreciable yield of hydroxylamines. As was mentioned above, oxidation of secondary amines usually proceeds smoothly giving moderate to good yields of iV,iV-disubstituted hydroxylamines. Oxidation of sterically hindered secondary amines such as 125 (equation 88) can also be done with peracids . Further oxidation of the resulting Af,A-disubstituted hydroxylamines 126 with an excess of m-chloroperbenzoic acid is known to end up with the corresponding nitroxyl radicals of type 127 (equation 88) ° although the reaction can be stopped at the hydroxylamine stage. 

The Oxidation of Amines and Alcohols The Disproportionation of Hydroxylamine Miscellaneous Reactions... 

Figure 34 Oxidative reactions of amines. Formation of N-oxides from oxidation of tertiary amines and formation of hydroxylamines from oxidation of primary and secondary amines.

Oxidation of secondary hydroxamic acids with performic acid affords the N-alkyl residue as a carboxylic acid (136). A most useful oxidative reaction is that obtained by action of periodate on hydroxamic acids and hydroxylamines (41, 43, 121, 122). Primary hydroxamic acids give ni-... 

Hydroxylamines are commonly postulated as intermediates in diese oxidations, but dey are rarely isolated or detected. Two examples of reactions in which products at the hydroxylamine oxidation level can be isolated bodi involve peroxides. Oxidation of alkylamines (2 R = Bu, Me and niCH2) with arenesul-fonyl peroxides bearing an electron-wididrawing group gave die arenesulfonyloxyamines in good yields (Scheme 6). A similar reaction of primary amines wi dibenzoyl peroxide gave benzoyloxyamines. ... 

The overall reaction is energy yielding, and allows sufficient ATP production to support reverse electron transport for CO2 fixation. However, the first step, oxidation of NH3 to hydroxylamine, requires the input of reducing power. The second step, hydroxylamine oxidation, yields four electrons. These join the electron transport chain at the level of ubiquinone, from which two are shunted back to AMO for activation of NH3. The N oxidation and electron transport pathways in Nitrosomonas are linked in the cytoplasmic membrane and periplasmic space detailed information from the N. europaea genome (Chain et al., 2003) is consistent with the previous biochemical characterizations of the system (Whittaker et al., 2000). Depending on conditions (and enhanced at low oxygen concentrations), nitric oxide (NO), nitrous oxide (N2O) and even dinitrogen gas (N2) have been reported as secondary products... 

The anion radical of 2-methyl-2-nitropropane being formed by reduction with alkali metal or electrolysis fragmentates to tert-butyl radicals and nitrite ions. Thus formation of di-tert-butylaminyloxide is initiated85. Treatment of 2-methyl-2-nitro-propane with sodium phenyl gives tert-butyl-phenylaminyloxide the reaction proceeding through an intermediate hydroxylamine oxide salt 65 which is even isolable86. ... 

Representative and actual examples of nitrogen, sulfur, and phosphorus oxidations are illustrated in Figs. 4A—4D, 5, and 6, respectively. Figures 4A—4C are representative reactions, while Fig. 4D illustrates actual examples of both aliphatic and aromatic nitrogen oxidation reactions. The oxidation of primary amines and in some cases tertiary amines is somewhat common, whereas the oxidation of secondary amines is found less frequently. More common are the oxidative dealkylation reactions of amines that are discussed below. Phentermine is an example of a primary amine that undeigoes oxidation to the hydroxylamine,... 

Direct IV-oxidation of these heterocycles invariably fails (see Section 3.02.7.2.8), making ring synthetic methods the only viable alternative <93CHE127>. Although there has been considerable interest in the chemistry of compounds of this type, there are no new synthetic approaches of a general nature. The most common approach is to react a-oximinoketones with aldehydes and primary amines. With formaldehyde, however, the 2-unsubstituted 1-oxides rearrange to 2-imi-dazolones. Variations on this theme allow synthesis of 1-hydroxyimidazole 3-oxides. Thus, treatment of an a-dicarbonyl compound with an aldehyde and hydroxylamine, or reaction of the aldehyde oxime or aldehyde with a 1,2-dioxime are common approaches <898773 >. Similarly, a-hydroxyamino-... 

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