Imines amine oxidation

Nitrones have been generally prepared by the condensation of /V-hydroxylamines with carbonyl compounds (Eq. 8.40).63 There are a number of published procedures, including dehydrogenation of /V,/V-disubstituted hydroxylamines, / -alkylation of imines, and oxidation of secondary amines. Among them, the simplest method is the oxidation of secondary amines with H202 in the presence of catalytic amounts of Na2W04 this method is very useful for the preparation of cyclic nitrones (Eq. 8.41).64... 

I.2. Oxidation of Amines Oxidation of primary amines is often viewed as a particularly convenient way to prepare hydroxylamines. However, their direct oxidation usually leads to complex mixtures containing nitroso and nitro compounds and oximes. However, oxidation to nitrones can be performed after their conversion into secondary amines or imines. Sometimes, oxidation of secondary amines rather than direct imine oxidation seems to provide a more useful and convenient way of producing nitrones. In many cases, imines are first reduced to secondary amines which are then treated with oxidants (26). This approach is used as a basis for a one-pot synthesis of asymmetrical acyclic nitrones starting from aromatic aldehydes (Scheme 2.5) (27a) and 3,4-dihydroisoquinoline-2-oxides (27b). 

The cyclic metabolite 11.169 was also a substrate in further biotransformations, being (V-demethylated to the corresponding endocyclic imine, and oxidized to phenolic metabolites. Very little if any of the secondary amine metabolite (11.168) appeared to undergo direct (V-demethylation to the primary amine, in contrast to many other tertiary amines, presumably due to very rapid cyclization of the secondary amine facilitated by steric and electronic factors. The possibility for the iminium cation (11.169 H+) to become deprotonated (a reaction impossible for the iminium 11.166 in Fig. 11.20) should also drive the cyclization reaction. 

In addition to using amine oxidation products as mediators, anodic oxidation reactions can be used to functionalize amine compounds. These reactions include both - examples that generate imines and nitriles, as well as examples that lead to the addition of nucleophiles to the carbon alpha to the nitrogen. 

The synthesis pathway of quinolizidine alkaloids is based on lysine conversion by enzymatic activity to cadaverine in exactly the same way as in the case of piperidine alkaloids. Certainly, in the relatively rich literature which attempts to explain quinolizidine alkaloid synthesis °, there are different experimental variants of this conversion. According to new experimental data, the conversion is achieved by coenzyme PLP (pyridoxal phosphate) activity, when the lysine is CO2 reduced. From cadeverine, via the activity of the diamine oxidase, Schiff base formation and four minor reactions (Aldol-type reaction, hydrolysis of imine to aldehyde/amine, oxidative reaction and again Schiff base formation), the pathway is divided into two directions. The subway synthesizes (—)-lupinine by two reductive steps, and the main synthesis stream goes via the Schiff base formation and coupling to the compound substrate, from which again the synthetic pathway divides to form (+)-lupanine synthesis and (—)-sparteine synthesis. From (—)-sparteine, the route by conversion to (+)-cytisine synthesis is open (Figure 51). Cytisine is an alkaloid with the pyridone nucleus. 

The subject of Ru-catalysed amine oxidations has been reviewed [1-7]. The first catalytic oxidation (1978) used RuCl3/02/water-toluene/100°C to oxidise primary and secondary amines to nitriles and imines respectively [8]. 

Both aromatic and aliphatic nitroso compounds have been prepared by oxidative procedures. While few of the methods can be considered generally applicable, a sufficient variety of reagents have been proposed that it would appear reasonable to state that virtually any nitroso compound may be prepared by one of these procedures. The organic substrates which have been used are oxaziranes and imines, amines, hydroxylamines, and oximes. A byproduct of the oxidation of 4-methylcinnoline (an azo compound) has also been identified as a dimeric nitroso compound. 

The functions of flavoprotein enzymes are numerous and diversified.151-1533 A few of them are shown in Table 15-2 and are classified there as follows (A) oxidation of hemiacetals to lactones, (B) oxidation of alcohols to aldehydes or ketones, (C) oxidation of amines to imines, (D) oxidation of carbonyl compounds or carboxylic acids to a,(3-unsaturated compounds,... 

Tertiary amines are oxidized to the corresponding nitrogen oxides. Tosyl hydrazones of ketones and aldehydes and imines are oxidized to the corresponding carbonyl compounds. Reactions have been carried out with small molecules and also with molecules that would not diffuse into the pore structure of the titanium silicates. As in the case of C—C bond cleavage, it is possible that these reactions take place on the outer surface of the catalyst crystals. 

Farnum, M., Palcic, M., and Klinman, J. P., 1986, pH dependence of deuterium isotope effects and tritium exchange in the bovine plasma amine oxidase reaction a role for single base catalysis in amine oxidation and imine exchange. Biochemistry, 25 1898n 1904. 

Nitrones, C=N" (R)=0, are generated by the oxidation of N-hydroxyl secondary amines with 5% aq. NaOCl. ° Secondary amines, such as dibenzylamine, can be converted to the corresponding nitrone by heating with cumyl hydroperoxide in the presence of a titanium catalyst. Imines are oxidized to amides with mcpba and BF3 OEt2. ° ... 

The N-hydroxylation reaction is not restricted to o-substi-tuted primary amines such as phentermine. Amphetamine has been observed to undergo some N-hydroxylation in vitro to (V-hydroxyamphetamine.- - /V-Hydroxyamphetamine is, however, susceptible to further conversion to the imine or oxidation to the oxime intermediate. Note that the oxime intermediate arising from this N-oxidation pathway can undergo hydrolytic cleavage to yield phenylacetone. the same product obtained by the a-carbon hydroxylation (carbi-... 

Peroxides [1] e.g. hydrogen peroxide, per acids, diacylperoxides, hydroperoxides, ketone peroxides [1] Under the influence of peroxides aromatic amines (color developer 3) react with phenols to yield quinone imines [1]. Oxidizing agent Aromatic amine -l- 1-Naohthol Quinone imine dyestuff. 

This chapter describes photoreactions of nitrogen containing chromophores which are different from the principal reactions of electronically excited carbonyl compounds. Five groups of substrates were included cyclic and acyclic imines, nitriles, amine oxides, azo and diazo compounds, and enamides. 

Following this initial preparation of a stable material having an ylid structure, a variety of phosphorus, arsenic, and sulfur ylids have been prepared and characterized and their chemistry has been thoroughly reviewed 78>. The chemistry of trimethylamine imine 2> and trimethyl-amine oxide, compounds which are isoelectronic with the ylid, have been reviewed 30,78) and will not be described here. 

Enzymatic oxidations of carbon-nitrogen bonds are as diverse as the substances containing this structural element. Mainly amine and amino acid oxidases are reported for the oxidation of C-N bonds. The steroespecificity of amine-oxidizing enzymes can be exploited to perform resolutions and even deracemizations or stereoinversions (Fig. 16.7-1 A). Analogous to the oxidation of alcohols, primary amines are oxidized to the corresponding imines, which can hydrolyze and react with unreacted amines (Fig. 16.7-1 B). In contrast to ethers, internal C-N bonds are readily oxidized, yielding substituted imines. This can be exploited for the production of substituted pyridines (Fig. 16.7-1 C). Furthermore, pyridines can be oxidized not only to N-oxides but also to a-hydroxylated products (Fig. 16.7-1 D). 

V-(Arylsulfonyl)-3-imino-3,5-dihydro-ll4,2,4,6-thiatriazino[2,3-c7]benzimidazol-l-amines 9 are oxidized only under phase-transfer conditions to the corresponding 1-imine 1-oxides 10.3... 

Deamination of amines to ketones. Dinizo and Watt have reported oxidative deamination by conversion to an imine (1), oxidation to an oxaziridine... 

The changes in the intrinsic oxidation states of thin films of EM base as a function of exposure time in aqueous acid during the protonation-de-protonation cycle have been quantitatively assessed by XPS [85]. Figure 3.8(a) and (b) show the Nls core-level spectra, obtained at photoelectron take-off angles, a s, of 75 and 20°, respectively, of a pristine (as-cast) EM film from N-methylpyrrolidinone CNMP) solution. Depending on the history of the film, such as prolonged extraction with water to remove residual NMP [84], the outermost surface can exhibit a substantially lower intrinsic oxidation state (lower [imine]/[amine] ratio) than the bulk. Figures 3.8(c)-(f) show the respective... 

Aerobic oxidation is not going to be limited to alcohol oxidation. Apparently we are closer to finding suitable catalysts for alcohol oxidation, but oxidation of alkenes, aromatic hydrocarbons, alkylaromatics, imines, amines, sulfur compounds etc. will require much work in the forthcoming years. In some cases, the presence of radical initiators, even though in minor quantities, may serve to promote the oxidation catalyzed by noble metal nanopartides, and gold in particular [56, 108]. Thus, there is no doubt that the next years will witness exciting developments in the field of metal nanopartides for aerobic oxidation. 

Usually, the reaction is poor in yield limited by the imine hydrolysis in the strong acidic conditions used for the cyclization. Two solutions were used to overcome this drawback i. The use of milder acidic conditions (e.g., trifluoroactic acid/boron trifluoride mixture) and ii. Carrying out the cyclization on the amine oxidation state (Bobbit and Jackson variation). 

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