Amines aryl oxides

By this method, different classes of PNs were prepared by replacing chlorine atoms of the polydichlorophosphazene intermediate by primary or secondary amines, alkoxide or aryl-oxide, or organ metallic reagents. " ... 

It was postulated [152, 153] that the aryl amine is oxidized by direct oxygen transfer from Compound I to the substrate. In contrast, for the oxidation of alkaloids, e.g. morphine, codeine and thebaine (Eq. 12), to the corresponding N-oxi-des by hydrogen peroxide in the presence of HRP or crude enzyme preparation from poppy seedlings, a radical mechanism was proposed [154]. 

Asymmetric imidations of aryl alkyl sulfides with [(tosylimino)iodo]ben-zene, catalyzed by various chiral (salen)manganese(III) complexes, have been investigated in some detail [31,32]. The influence of catalyst structure, solvent, temperature, 3°-amine AT-oxides, and the presence of molecular sieves on product yields and the enantioselectivity of imidation with 17 was evaluated. Enan-tioselectivities as high as 90 % ee and 97 % ee with methyl 2-nitrophenyl sulfide and methyl 2,4-dinitrophenyl sulfide, respectively, were achieved. 

Scheme 30. Survey of copper(l l)/amine-mediated oxidative dimerizations of various aryl amines.

Tab. 24. Product distributions from the copper(ll)/amine-mediated oxidative dimerizations of the aryl amines indicated above.

The generally accepted mechanism for the amine arylation is shown in Scheme 1. The catalytic cycle begins with the oxidative addition of the aryl halide (or sulfonate) by Pd (0). The palladium (II) aryl amide can be formed either by direct displacement of the halide (or sulfonate) by the amide or via the intermediacy of a palladium (II) alkoxide [19]. Reductive elimination of the C-N bond results in the formation of the desired arylamine and regeneration of the Pd (0) catalyst [lie,20]. 

Ammonia was oxidized with hydrogen peroxide in the presence of TS-1 first to hydroxylamine and then, further to nitrogen oxides if the hydroxylamine was not trapped. When this reaction was run in the presence of a ketone, the oxime was selectively formed (Eqn. 21.8).33 Oximes were also produced by the oxidation of primary aliphatic amines with TS-1 or TS-2 and hydrogen peroxide at ambient temperature. Linear amines such as n-propyl amine (6) gave the oxime in 73% yield at 32% conversion over the TS-1 catalyst (Eqn. 21.9).3 The isopropyl amine (7) was oxidized with somewhat higher selectivity over the larger pore TS-2 catalyst (Eqn. 21.10).34 Primary aryl amines were oxidized to the symmetrical azoxybenzenes under these conditions (Eqn. 21.11). ... 

Table 3 Pd-catalyzed oxidative cyclization of aryl amines, aryl ethers, and benzanilidc ...

Starting from ort/w-aminoarene imines 1. 4-aryl-substituted condensed 1,2,3-triazines 2 can be obtained.7,8 Using the oximes 3 instead of imines, condensed 1,2,3-triazine 3-oxides 4 can be isolated.7,8,127-129,241 Reaction of ort/io-aminoarenecarbamidoximes 3 (R — NH2) with nitrous acid afforded condensed l,2,3-triazin-4-amine 3-oxides 4 (R = NH2).7,8,195... 

The demonstration of ambident nucleophilic reactivity of aryl oxides in their reactions with nitroaromatics raises the question whether aromatic amines might function similarly. However, TNB does not react with aniline alone to form a stable a complex only a charge transfer or tt complex is formed (33). This result is perhaps surprising because TNB is well-known to form stable a complexes with primary or secondary aliphatic amines (7, 8). 

A possibility for azomethine ylide generation from 4-isoxazolines was first suggested by Baldwin, who demonstrated a thermal N—O bond cleavage of 4-isoxazoline systems (68JA5325). Cycloaddition of N-methylene(t-butyl)-amine V-oxide to dimethyl acetylenedicarboxylate takes place at 0°C, rapidly and quantitatively, to give 4-isoxazoline 146 (R = t-Bu, =R = COOMe), which isomerizes at 80°C into 4-oxazoline 148 (R = f-Bu, R = R = COOMe). The nitrone bearing an N-aryl substituent and the same acetylene directly afford 2-acylaziridine 147 (R = 2,4,6-trimethylphenyl, R = R = COOMe). Reaction of the N-t-butylnitrone with 3-methylbutyn-... 

The insertion of CO into Pd-carbon bonds has also been employed in several tandem/cascade reactions that afford five-membered nitrogen heterocycles [97]. A representative example of this approach to the construction of heterocydes involves synthesis of isoindolinones via the Pd-catalyzed coupling of 2-bromobenzaldehyde with two equivalents of a primary amine under an atmosphere of CO [97bj. As shown below (Eq. (1.57)), this method was used for the preparation of 144 in 64% yield. The mechanism of this reaction is likely via initial, reversible condensation of 2-bromobenzaldehyde with 2 equiv of the amine to form an aminal 145. Oxidative addition of the aryl bromide to Pd° followed by CO insertion provides the acylpalladium spedes 146, which is then captured by the pendant aminal to afford the observed product. An alternative mechanism involving intramolecular imine insertion into the Pd—C bond of a related acylpalladium species, followed by formation of a paUadium-amido complex and C—N bond-forming reductive elimination has also been proposed [97b],... 

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