Oxidation of primary amines and

Fig. 27. Oxidation of primary amines and hydrazo compounds with BTMA Br3...

Sn ZSM-11 [85a, 104], V EU-1, V-THETA-1 [101] and Cr-ZSM-5 [106] are reported to catalyze arene side-chain oxidation. Oxidation of primary amine and various arylamines even with electron-withdrawing groups to the corresponding nitro compounds is possible with Cr-ZSM-11 [76a]. Oxidation of secondary amines to nitrones [91] and thioethers to sulfoxides and sulfones is possible with V-ZSM-5 [85a]. 

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,... 

Oxidation of Primary Amines. Goti and coworkers described a one-pot condensation/oxidation of primary amines and aldehydes (eq 46) using UHP as stoichiometric oxidant in the presence of methyltrioxorhenium as catalyst. This reaction leads to nitrones in a simple and regioselective manner. From a sustainability point of view, this one-pot synthesis is simple to perform, takes place under mild conditions, and releases water as the only byproduct. ... 

Rosenblatt etal have examined the effect of structure and isotopic substitution upon the permanganate oxidation of some alky famines (Table 4). The isotope effect of 1.84 is considered to be sufficiently low to be compatible with aminium radical-cation formation, and it is felt that, while C-H cleavage is significant for oxidation of primary amines, the dominant mode of oxidation of tertiary amines is electron-transfer, e.g. 

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). 

Oxidation of primary amines with DMD or other oxidants leads to the formation of a complex mixture of nitroso, oximes, and nitro compounds (76). Utilization of DMD in acetone affords dimethyl nitrone (22). This is likely to be a result of the initial oxidation of primary amine (19) to hydroxylamine (20) with the subsequent condensation of acetone and oxidation of imine (21) (Scheme 2.9) (77). 

FIGURE 4.34 Postulated mechanisms for MAO-catalyzed oxidation of primary amines, (A) SET (B) HAT mechanism, and (C) polar mechanism. 

Nitroxyl mediated electro-oxidation of primary amines also leads to formation of the imine and the further oxidation to the nitrile. In anhydrous acetonitrile containing 2,6-lutidine as a base, the nitrile is formed. In aqueous acetonitrile, hydrolysis of the imine intermediate is fast and good yields of the aldehyde result... 

Oxidation of organonitrogen compounds is an important process from both industrial and synthetic viewpoints . N-oxides are obtained by oxidation of tertiary amines (equation 52), which in some cases may undergo further reactions like Cope elimination and Meisenheimer rearrangement . The oxygenation products of secondary amines are generally hydroxylamines, nitroxides and nitrones (equation 53), while oxidation of primary amines usually afforded oxime, nitro, nitroso derivatives and azo and azoxy compounds through coupling, as shown in Scheme 17. Product composition depends on the oxidant, catalyst and reaction conditions employed. 

Using the selenobiphenol ligand HL mentioned in the previous paragraph, Chaudhuri and co-workers also isolated the trinuclear complex 22 and the dinuclear complex 23 (Scheme 9) [155]. The latter was shown to catalyze the selective aerial oxidation of primary amines with at least one... 

Monoamine oxidase catalyzes the deamination of primary amines and some secondary amines, with some notable exceptions. Aromatic amines with unsubstituted a-carbon atoms are preferred, but aromatic substituents influence the binding of these substrates. For example, m-iodobenzylamine is a good substrate, whereas the o-iodo analog is an inhibitor. The mechanism of deamination is as follows hydrolysis of the Schiff base that results from loss of a hydride ion on an a-proton yields an aldehyde, which is then normally oxidized to the carboxylic acid. Aromatic substrates are probably preferred because they can form a charge-transfer complex with the FAD at the active site, properly... 

Table 14. Comparison of the oxidation of primary amines with the nickel hydroxide electrode and nickel peroxide...

AMI and PM3 calculations reveal that epoxidations by DMDO and TFDO involve peroxide-bond cr at a very early stage and that TFDO is the most reactive dioxirane as the CF3 group in it stabilizes this cr level. In accord with previous calculations a spiro transition state is predicted. Furthermore, allene is predicted to be less reactive than alkenes toward epoxidation by DMDO.192 DFT calculations on the oxidation of primary amines by dimethyldioxirane predict a late transition state with a barrier of 17.7 kcal mol-1 which is drastically lowered by hydrogen bonding to the O—O bond to just 1.3 kcal mol-1 in protic solvents.193... 

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.

Problems can arise at the last stage due to difficulties in die isolation of die aldehyde and/or preferential vinyl sulfide formation. Nonetheless, the method has some potential Sulfoxides are prone to thermal elimination, and this has been used by Trost in his mediod, which can also be used for the oxidation of primary amines (Scheme 14). The procedure is limited to benzylic and allylic bromides. 

The oxidation of aromatic and aUphatic oximes and of tosylhydrazones on TS-1 with excess H2O2 was reported to regenerate corresponding aldehydes [141, 142]. These were obtained also by the one-pot oxidation of primary amines under analogous conditions [143]. 

Oxidation. Potassium ferrate (VI) is a reagent for selective oxidation of primary alcohols and amines to aldehydes and of secondary alcohols to ketones. Double bonds, aldehyde functions, tertiary hydroxyl groups, and tertiary amino groups are resistant to oxidation. The reaction is carried out at room temperature either in water or in aqueous solvents. In fact water is essential for oxidation. The reaction is carried out at an initial pH of 11.5 the final pH is 13.5. In a typical procedure K.2pe04 (0.(X)2 mole)... 

Heterogeneous catalysts such as hydroxyapatite-bound Ru complex [67] and Ru/ AI2O3 [68] can be also used for the aerobic oxidation of primary amines to nitriles (Eqs. 3.32 and 3.33). 

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