Amines to azo compounds

Conversion of Amines to Azo Compounds fV-Arylimino-de-dihydro-bisubstitution... 

OxidationThis reagent is similar to barium manganate. It also couples aromatic amines to azo compounds in moderate yield and converts thiols to disulfides in 85-100% yield. 

Methods of oxidation of hydrazo to azo compounds and hydroxylamino to nitroso compounds have been reviewed. Reagents which oxidize aromatic primary amines to azo compounds are also suitable for the oxidation of aromatic hydrazo compounds, since the hydrazo compounds are intermediates in the oxidation of the amines. Thus, manganese dioxide, mercury(II) oxide and lead tetraacetate are all suitable oxidants. Silver carbonate on Celite rapidly oxidizes both diarylhydrazines and acylhydrazines to the corresponding azo compounds in good yield. Another supported oxidant which can convert hy-drazobenzene into azobenzene in high yield is sodium periodate on silica gel. ... 

Sodium perborate, NaBOa dlljO (mp 60 °C dec), is used for oxidations of primary aromatic amines to azo compounds [795] or nitro compounds [194] and of sulfides to sulfoxides and sulfones [794]. This reagent does not affect alcohols and only slightly affects alkenes [794]. 

Barium manganate, BaMn04, is commercially available. The dark-blue crystals are obtained from aqueous solutions of barium chloride and potassium permanganate [552, 555]. It oxidizes alcohols, especially benzylic alcohols, to carbonyl compounds [552, 555] hydroquinone to quinone [555] benzylamines to benzaldehydes [555] aromatic amines to azo compounds [555] and phosphines to phosphine oxides [555],... 

Copper complexes in pyridine solution have been shown to be effective catalysts for the oxidative dimerization of aromatic amines to azo compounds [169]. A thorough treatment of oxidative dimerization reactions is beyond the scope of this review. However, recent reports give evidence for copper peroxo complexes [154] in these systems and for the intermediacy of a species of the type,... 

A review describes the asymmetric epoxidation of allylic alcohols,369 another the role of metal oporphyrins in oxidation reactions.370 jhe TiiOPrMi, catalysed self-epoxidation of allylic peroxides proceeds via an intermolecular mechanism.371 Racemic allyl alcohols can be resolved by asymmetric epoxidation (eq.35).372 a Pd(II)/Mn02/benzoquinone system catalyses the oxidative ring-closure of 1,5-hexadienes (eq.36).373 propenyl phenols are oxidatively degraded to aryl aldehydes and MeCHO in the presence of Co Schiff-base catalysts.374 An Oppenauer-type oxidation with Cp2ZrH2/cyclohexanone converts primary alcohols selectively into aldehydes.375 co macrocycles catalyse the oxidation of aryl liydrazones to diazo compounds in high yields.376 similar Co complexes under CO oxidise primary amines to azo compounds.377 Arene Os complexes in the presence of base convert aldehydes and water slowly into carboxylic acids and H2.378... 

In a related reaction, primary aromatic amines have been oxidized to azo compounds by a variety of oxidizing agents, among them Mn02, lead tetraacetate, O2 and a base, barium permanganate, and sodium perborate in acetic acid, tert Butyl hydroperoxide has been used to oxidize certain primary amines to azoxy compounds. 

While aromatic nitro and azoxy compounds have been reduced to azo compounds with lithium aluminum hydride, aliphatic nitro compounds produced only the corresponding aliphatic amines [65]. The usual technique involves dropwise addition of 1 mole of nitro compound in ether to 1.05-1.15 moles of lithium aluminum hydride in ether solution at Dry Ice temperatures followed by warming to room temperature. If the resulting product is only slightly soluble in ether, hydrolysis should be carried out with dilute sulfuric acid. Then the azo compound simply needs to be filtered off, washed with water, and dried. If the product is ether-soluble, the ether layer is separated, evaporated, and the residue is recrystallized [65, 66]. 

As indicated above (Ohme and Schmitz [38a, p. 339]) primary amines converted into the alkylamides of sulfuric acid can be oxidized with sodium hypochlorite to azo compounds. The reaction appears to proceed by way of an intermediate hydrazine, which is ultimately oxidized [38a], The reaction is suitable for the formation of symmetrically substituted azoalkanes. Highly branched primary aliphatic amines have been oxidized with sodium hypochlorite in an aqueous dioxane medium [77],... 

The bimolecular reduction of aromatic nitro compounds, depending on reaction conditions, may produce azoxy compounds, azo compounds, hydrazo compounds (1,2-diarylhydrazines), benzidines, or amines. Whereas the reduction with zinc and sodium hydroxide leads to azo compounds, zinc and acetic acid/acetic anhydride produces azoxy compounds. Other reducing agents suggested are stannous chloride, magnesium with anhydrous methanol, a sodium-lead alloy in ethanol, thallium in ethanol, and sodium arsenite. 

The oxidation of nonfluorinated aromatic amines with free peracids (not acyl peroxides) proceeded best with the basic amines. The reaction did not pass through the azo stage of oxidation since azo compounds could not be converted under the reaction conditions and hydrazo compounds were oxidized to azo compounds. Under the reaction conditions, p-toluidine was converted only into p-nitrotoluene [31]. 

Oxidation of Amines to Azo or Azoxy Compounds /V-De-bishydrogen-coupling... 

Ready addition of 2-nitrosopyridine to 1,3-dienes gives 3,6-dihydro-1,2-oxazines, e.g. (774) — (773), and condensation with aromatic amines gives azo compounds, e.g. (774) — (775). Nitroso compounds are oxidized by ozone or sodium hypochlorite to the corresponding nitro compounds. 5-Nitrosopyrimidines can be reduced to the 5-amino derivatives or condensed with activated methylene groups. 

Nitrenes have a short lifetime (only several microseconds)86- 8 and undergo stabilization by the following reactions isomerization to imines, dimerization to azo compounds, hydrogen abstraction followed by ring closure to heterocyclic compounds, bimolecular insertion into C-H bonds to secondary amines, addition to solvent yielding ylids, and addition to unsaturated systems yielding heterocyclic compounds. Table 117-106 includes the reaction products and references for the different classes of nitrenes. 

Oxidation. Triphenylbismuth carbonate suspended in CH2CI2 is a heterogeneous oxidant for a variety of functional groups. Allylic alcohols are efficiently oxidized to the corresponding unsaturated aldehydes or ketones, even in the presence of a thiol, which is itself oxidized by this reagent to a disulfide, cis- and Irani-1,2-Glycols are cleaved to dialdehydes hydrazones are oxidized to diazocompounds oximes are cleaved to ketones and 1,2-dialkylhydrazines are oxidized to azo compounds. Phenylhydrazones, semicarbazones, tosylhydrazones, aromatic and aliphatic amines, enamines, and enol ethers are inert to 1. 

Fierz-David and Ziegler (301) first applied this method to azo compounds. Ethyl acetoacetate and various aromatic amines (aniline, o- and p-toluidines, m-xylidine, o-anisidine, and chloroanilines) were convereted to acetoacetanilides and then coupled with diazotized sulfanilic acid. The azo dyes (38) were reduced with stannous chloride in hydrochloric acid to the corresponding aminoaceto-acetanilides (39), which in alkali formed the dihydropyrazines (40). Catalytic reduction of o-hydroxyphenylglyoxal phenylhydrazone in acetic acid over palladium has been shown also to give 2,5-bis(o-hydroxyphenyl)pyrazine (302). Reduction of chemical means has been shown to give... 

Aliphatic azo compounds may be obtained on anodic oxidation of A,A -dialkylhy-drazines amines or their derivatives may be oxidized to azo compounds in some cases. Anodic oxidation at a graphite electrode of rerf-butylamine containing some aqueous sodium perchlorate thus yields 2,2 -azoisobutane together with some azoxy-te Y-butane and minor amounts of nitro-fe/t-butane [83]. 

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