Hydrazines aryl azides

Arylamines and hydrazines react with tosyl azide under basic conditions to yield aryl azides [1] and arenes [2], respectively, by an aza-transfer process (Scheme 5.25). Traditionally, the reaction of anilines with tosyl azides requires strong bases, such as alkyl lithiums, but acceptable yields (>50%) have been obtained under liquidiliquid phase-transfer catalytic conditions. Not surprisingly, the best yields are obtained when the aryl ring is substituted by an electron-withdrawing substituent, and the yields for the corresponding reaction with aliphatic amines are generally poor (-20%). Comparison of the catalytic effect of various quaternary ammonium salts showed that tetra-/i-butylammonium bromide produces the best conversion, but differences between the various catalysts were minimal [ 1 ]. 

The reaction between aryl azides and lithiated aryl amines leads to tetrazenes, which give cyclic silatetrazenes with halosilanes (equation 7)17. Also, the new mono-, bis- and tris-silylamines 15-28 were obtained18-22. The hydrazine 16 was analyzed by electron and X-ray diffraction18. 

Reaction of aryl azides with hydrazine hydrate can result in reductive cleavage of the azido group. Azidobenzene gives a mixture of benzene and aniline when heated with an excess of hydrazine hydrate in ethanol. If there is an acyl or an alkoxycarbonyl group at the ortho position, cyclization products are formed instead for example, methyl 2-azidobenzoate gave indazolinone (13 90%). 

Other examples of photo-induced transformations in monolayers include reduction of p-nitrothiophenol assembled on a silver electrode to p-aminothiophenol initiated by laser radiation (monitored by SERS)350. UV irradiation of a monolayer terminated with aryl azide in the presence of amines results in incorporation of the amines in the monolayer as azepines and hydrazines. No surface attachment takes place without irradiation, and this makes it a convenient method to prepare photopattemed monolayers351. 

Heating aryl azides at reflux in a mixture of hydrazine hydrate and ethanol leads to deazidation. This process appears to be a good method of removing azido groups from aryl systems (particularly in the case of azides bearing ortho substituents) ... 

Aryl Azides from Hydrazines and from Nitrosoarenes... 

Aryl azides can be obtained from A-nitrosation reaction of aromatic hydrazines, using nitrosation reagents such as nitrous acid, dinitrogen tetroxide, nitrosonium tetrafluorobo-rate and nitric oxide in the presence of oxygen (Scheme 3.40). The use of hydrazones is also possible. ... 

Amino-5-aryl-l,3,4-oxadiazoles form stable N-nitrosamines (71c) which are converted into hydrazines (7ld) with zinc in acetic acid. Treatment of the hydrazine (71d) with nitrous acid yields the corresponding azide and with benzaldehyde a hydrazone is formed (B-61MI42300). On heating in benzene or in nitrobenzene, the nitrosamine (71c) undergoes the Gomberg-Bachmann reaction to yield 2,5-diaryl-l,3,4-oxadiazoles (73JCS(P1)1357). 

The free radical products generated by peroxidases are highly reactive species that can, in some instances, covalently modify the heme group of the enzyme (Fig. 5.10). In the case of HRP, the substrates for which this type of reaction has been observed include aryl and alkyl hydrazines [55, 56], the azide anion [57], nitromethane [58], cyclopropanone hydrate [59], and alkyl acids [60]. Free radicals... 

The majority of 2-alkyl-5-aryl-l,3,4-oxadiazoles can easily be cleaved in mineral acid solution to give the corresponding diacid hydr azides. 2- (a-Bromoethyl) - 5-phenyl-1,3,4-oxadiazole is hydrolyzed so easily that even during the synthesis from 1 -a-bromopropionyl-2-benzoylhydrazine, on treating the reaction mixture with water, partial hydrolysis occurs to give the diacid hydrazide or even hydrazine. This can be eliminated in the synthesis by among other means the use of petrol ether in place of water. The 2-bromomethyl-5-aryl-... 

Figure 10.25 Twenty-nine specific toxicophores for mutagenicity as identified by Kazius el al. (Kazius, J-, et al. Derivation and validation of toxicophores for mutagenicity prediction. J. Med. Chem. 2005, 48, 312-320.) (A) Specific aromatic nitro, (B) specific aromatic amine, (C) aromatic nitroso, (D) alkyl nitrite, (E) nitrosamine, (F) epoxide, (G) aziridine, (H) azide, (I) diazo, (J) triazene, (K) aromatic azo, (L) unsubstituted heteroatom-bonded heteroatom, (M) aryl hydroxylamine, (N) alkyl halide, (O) acyl halide, (P) N- or 5-mustard, (Q) polycyclic aromatics, (R) bay-region, (S) K-region, (T) sulphonate-bonded C, (U) unsaturated aldehyde, (V) alkyl A-nitro, (W) diazonium, (X) p-propiolactone, (Y) unsubstituted a,p unsaturated alkoxy, (Z) l-aryl-2-monoalkyl hydrazine, (AA) aromatic methylamine, (AB) aryl hydroxylamine ester, and (AC) polycyclic planar system.

These substrates, like their acid or ester counterparts, furnish 4-aIkyl(or aryl)-2(l/f)-phthalazinones. Although no keto amides have been so used in the more recent literature, some closely related o-acylbenzoyl azides have been employed. Thus o-benzoylbenzoyl azide (97) with hydrazine or phenylhydrazine gave 4-phenyl-l(2f/)-phthalazinone (98, R = H) (PhH, reflux, 2h 60%) or 2,4-diphenyl-l(2f/)-phthalazinone (98, R = Ph) (likewise 65%), respectively analogs were made similarly. ... 

Arylation of a wide range of NH/OH/SH substrates by oxidative cross-coupling with boronic acids in the presence of catalytic cupric acetate and either triethyl-amine or pyridine at room temperature in air. The reaction works for amides, amines, anilines, azides, hydantoins, hydrazines, imides, imines, nitroso, pyrazi-nones, pyridones, purines, pyrimidines, sulfonamides, sulfinates, sulfoximines, ureas, alcohols, phenols, and thiols. It is also the mildest method for NIO-vinylation. The boronic acids can be replaced with siloxanes or starmanes. The mild condition of this reaction is an advantage over Buchwald-Hartwig s Pd-catalyzed cross-coupling. The Chan-Lam C-X bond cross-coupling reaction is complementary to Suzuki-Miyaura s C-C bond cross-coupling reaction. 

Ar-NHNHi toAr-Nj. Aryl and acyl hydrazines are converted to azides in good yields on treatment with an equimolar amount ofNOHS04 orNOBF4 (eq7).l ... 

In addition it may be noted that amides of a, 3-unsaturated adds and of a-hydroxyacids yield aldehydes when allowed to undergo this rearrangement. Aryl-substituted semicarbazides yield azides, and aryl--substituted ureas yield aryl-substituted hydrazines. These reactions are discussed more fully in a subsequent section of this chapter (p. 273). 

Primary Amines—Several new and improved methods for the preparation of aromatic primary amines have been described. " The catalytic reduction of aromatic nitro-compounds to amines with hydrazine hydrate in the presence of iron(iii) oxide hydroxide proceeds smoothly and in high yields. Nitroarenes (1) react with Grignard reagents in the presence of copper(i) iodide, and are alkylated selectively on the aromatic moiety, accompanied by reduction of the nitro-group to the amine (Scheme 1). Both aryl and alkyl azides are rapidly... 

From Thio)carbonohy dr azides. 1,3,4-Thiadiazoles arise in the acidic cyclization of thioacylated (thio)carbonohydrazides. Thioaroylthioacetic acids" convert carbonohydrazide into 1-thioaroylcarbonohydrazides (95 R = H, X = O). 1-Phenyl- and 1-benzylidene-carbonohydrazide react to give similar compounds. All are readily cyclized by mineral acids to 2-aryl-5-hydroxy-l,3,4-thiadiazoles (96), with loss of hydrazine or its appropriate derivative. The action of acetic anhydride produces 2-acetoxy-5-phenyl-l,3,4-thiadiazoles directly, in one stage."... 

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