Diazonium special

Primary amino groups attached to azole rings react normally with nitrous acid to give diazonium compounds via primary nitroso compounds. However, the azole series shows two special characteristics the primary nitroso compounds can be stable enough to be isolated, and diazo anhydrides are formed easily from azoles containing ring NH groups. 

Guanyl hydrazones (18) react with diazonium salts to yield a special class of formazans called guanazyls, e.g., 19 (Eq. 1).20 22 The reaction is... 

Coupling reactions in organic solvents are occasionally carried out with masked diazonium compounds e.g., with special diazonium moieties which are incorporated into a larger organic structure [4], for instance in a diazoamino compound (15) or a benzotriazinone (16) ... 

Since many azides may be explosive compounds, investigators planning to work with them should consult the literature and take special precautions. See Volume I, Chapter 15, Diazo and Diazonium Compounds, for additional information about diazo hydrocarbons. 

The Balz-Schiemann synthesis can be applied not only to substituted anilines but also to aminobiphcnyls1,131 or amino-substituted fused polyaromatic compounds, such as naphthalene,1114,119,129 anthracene,136 phenanthrene,1135 acenaphthene,133 fluorene,1,131,134 benzanthracene,130 136 pyrene,136 chrysene,136 fluoranthene,131 fluorenone,1,131 anthra-quinone,1,137,139,140 benzanthrone,1,117,118 phenanthraquinone,138 or xanthone.132 Fluorinated pyridines,1,141"146 methylpyridincs,126,147 149 pyridinecarboxylic acids,150 quinolines,1,151 isoquinolines,152 quinazolone,1 thiazoles,153,154 isothiazoles,156 benzothiazoles,157 thiadiazoles,155 and thiophenes154 can also be obtained from the corresponding aminated heterocycles. Modified Balz-Schiemann methods are recommended for amino nitrogen-containing heterocycles, the diazonium salts of which are rather water-soluble and unstable (a violent explosion was reported for pyridine-3-diazonium tetrafluoroborate).159 These new techniques have also been specially adapted for pyrazol-, imidazol-, or triazolamines which fail to react under classical conditions.158... 

Hydroxybenzenediazonium tetrafluoroborates constitute a special case the meta-isomer has the structure of a true diazonium salt, while the ortho- and para-isomers are in ready equilibrium with the corresponding quinone-diazide dimers which have been isolated as com-... 

Electron-deficient aryl diazonium salts such as the pentafluoro derivative can offer the attractive option to conduct radical arylations as chain reactions with an SrnI mechanism (Scheme 35) [151]. In these special cases, only catalytic amounts of an initiating reductant, such as sodium iodide, are required. In the propagation step, the diazonium salt 92 acts as oxidant for the cyclohexadienyl intermediate 93. Rearomatization of 93 to 94 as well as the generation of a new pentafluorophenyl radical are achieved through this step. 

Specialized diazo transfer reactions have also been reported (Scheme 33 and Equation (18)), but their preparative value is limited. For example, JV-ethylbenzothiazolium azide (164) and 2,6-diaminopyridine affords 5-aminotriazolo[4,5-Z>]pyridine (5p) <78HCA108>. Since the reaction is sensitive to the pKa of the aminoheterocycles employed, the process has limited applicability. The highly specific colorimetric assay for oj-amino acids, which is based on a reaction with quinoline-3-diazonium tetrafluoroborate (166), affords l-substituted-[l,2,3]triazolo[4,5-c]quinolines (167)... 

Replacement of the Diazonium Group by Chloride, Bromide, and Cyanide The Sandmeyer Reaction Copper salts (cuprous salts) have a special affinity for diazonium salts. Cuprous chloride, cuprous bromide, and cuprous cyanide react with arenediazonium salts to give aryl chlorides, aryl bromides, and aryl cyanides. The use of cuprous salts to replace arenediazonium groups is called the Sandmeyer reaction. The Sandmeyer reaction (using cuprous cyanide) is also an excellent method for attaching another carbon substituent to an aromatic ring. 

Nucleophilic substitution of the diazo group is practically the only method for the production of nitro derivatives of tetrazole [392, 436 143], 5-Nitrotetrazole itself was isolated and identified in the form of metallic salts [436-440, 442, 443], The mechanism of substitution of the diazo group by a nitro group in heterocyclic compounds has not been studied specially. As already mentioned, in many cases the reaction takes place as catalytic nucleophilic substitution and does not require the use of a catalyst (copper salts) [392,444], The results from investigation of the kinetics of the substitution of the diazonium group by the nitro group in compounds of the benzene series make it possible to suppose that the diazonitrite is formed intermediately and quickly reacts with a second nitrite anion [392,444], Some difference between the kinetics of the reaction of 3-diazonium-5-carboxy-l,2,4-triazole and 3-diazonium-5-methoxycarbonyl-l,2,4-triazole with sodium nitrite in hydrochloric acid and the analogous process in the benzene series is probably due to prototropic... 

The amine is titrated with hydrochloric acid and sodium nitrite in very dilute solution, and the resulting diazonium salt is coupled with an accurately known amount of a phenol, usually SchaefiFer salt. With other compounds, such as H acid, amino R acid, etc., one sample is diazotized and another is coupled with diazotized aniline or other amine. Under some circumstances it is possible to determine two substances in mixture if one of them reacts much more rapidly than the other. Thus, with a little practice, one can determine quite accurately both G salt and R salt in mixtures of.the two. R salt couples very rapidly with diazotized aniline producing a red dye, while G salt couples more slowly and gives a yellow dye. A large number of other special methods are available which permit the determination of the individual constituents in mixtures. 

Shortly after the discovery of this reaction, a number of observers questioned whether radicals were intermediates or whether the reaction proceeded by purely cationic chemistry by the aryl cation mechanism (Scheme 2). If this were the case, then the formation of products such as the alcohols 4 would proceed equally well in the absence of TTF. The vigor of the effervescence seen immediately on addition of TTF, together with the long-term stability of solutions of the diazonium salts in solution in moist acetone and other solvents in the absence of TTF, immediately disproves this, but additional experiments were performed to show the special character of TTF in the reactions. 

Since volatile, anhydrous hydrogen fluoride is extremely corrosive and toxic, the fluorodediazo-niatron of aromatic amines with this agent require.s special apparatus and. safety conditions, which are not available in most laboratories. Thus, the decomposition of diazonium tclra-fliioro bo rates, which can be readily prepared from aromatic amines and casier-to-handle tetra-fluoroboric acid, is the commonest fluorodediazoniation process, usually referred to as the Balz-Schiemann reaction (see Vol. E 10a, p 705IT). 

The tetrazotization of m-phenylenediamine has been described also, under special conditions (nitrosylsulfuric acid in glacial acetic acid) a similar conversion of the ortho isomer has been accomplished. This procedure has been adaf>ted to the tetrazotization of certain naphthalene diamines. The simultaneous diazotization of two amino groups in the biphenyl series is illustrated by the synthesis of 4,4 -biphenylene-fejs-diazonium chloride and its 3,3 "dimethyl analog. ... 

Generation of a diazonium intermediate (619) from nitrosourea (618) gave products, which are derived from intermediate 620 (equation 161). Surprisingly, in this special case the C(l)-C(2)-bond of the cyclopropane was cleaved. In contrast, diazonium species of a 3-oxa-bicyclo[4.1.0]heptyl or 3,5-dioxabicyclo[5.1.0]octyl system decomposed via an... 

The main uses for steam distillation are to separate a reaction product from a tarry reaction mixture and to separate compounds which for some special reason have a markedly different volatility with steam. For example, the conversion of diazonium salts to phenols and certain Friedel-Crafts reactions lead to tarry by-products which cannot be conveniently removed by distillation or recrystallization. In this case, steam distillation effects a separation of volatile from essentially nonvolatile material. 

Give the reagents and any special conditions necessary to convert p-toluene-diazonium chloride into ... 

Comparisons between diazonium ion reactions and solvolyses involving tertiary alkyl structures are of special interest because both reactions are likely to yield unsolvated carbonium ions. Cannell and Taft (1956) have measTu-ed the ratio of thiocyanate to isothiocyanate obtained when the carbonium ions formed in the solvolysis of t-butyl chloride and the deamination of t-butylamine and isobutylamine in ethanol are trapped with large amormts of added sodium thiocyanate. For the t-butyl... 

In 1966, E. Fischer was granted a U.S. patent ( ) claiming a method for polymerizing cyclic ethers by means of diazonium salts of perchloric acid and perfluorocarboxylic acids decomposed by heat and/or ultraviolet radiation. The storage stability of mixtures of these salts with cyclic ethers was poor, and the handling of diazonium perchlorates would require special consideration before introduction into large-scale coating operations. 

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