Diazonium salts conversion

The most interesting property of diazonium salts (448 = H) is their conversion into... 

Until recent years the only syntheses of 3-hydroxy quinoline involved multistep processes, the last step of which consisted of the conversion of 3-aminoquinoline to 3-hydroxyquinoline via the diazonium salt. " Small quantities of quinoline have been oxidized to 3-hydroxyquinoline in low yields by using oxygen in the presence of ascorbic acid, ethylenediaminetetraacetic acid, ferrous sulfate, and i)hosi)halc buffer. The decarboxylation of 3-hydroxycinchoninic, acid in boiling nitrobenzene has been re-... 

While the direct halogenation of toluene gives a mixture of isomers that is difficult to separate into the pure isomers, the isomeric o- and /r-nitrotoluenes 6a and 6b, formed by nitration, are easy to separate from each other. Thus reduction of the single o- or /j-nitrotoluene 6 to the o- or /j-toluidine 7a or 7b respectively, followed by conversion into the corresponding diazonium salt 8 and a subsequent Sandmeyer reaction leads to the pure o- or /j-halotoluene 9. 

Conversions of diazonium salts into halogenated derivatives have been reported for compounds of type 128 and 129 [73JCS(P1)2901 80JCS(P 1)2398], Although some 7-substituted pyrazolo[ 1,5-u]pyridines have been made from the lithiated precursors, no halogeno products have been reported (92JOC5538). 

Conversion of Diazonium Salts to Aldehydes, Ketones, or Carboxylic Acids... 

Diazonium salts react with oximes to give aryl oximes, which are easily hydrolyzed to aldehydes (R = H) or ketones." A copper sulfate-sodium sulfite catalyst is essential. In most cases higher yields (40-60%) are obtained when the reaction is used for aldehydes than for ketones. In another method for achieving the conversion ArNj —> ArCOR, diazonium salts are treated with R4Sn and CO with palladium acetate as catalyst. In a different kind of reaction, silyl enol ethers of aryl ketones, Ar C(OSiMe3)=CHR, react with sohd diazonium fluoroborates, ArNj BF4, to give ketones, ArCHRCOAr. " This is, in effect, an arylation of the aryl ketone. 

Entries 7 and 8 illustrate conversion of diazonium salts to phenols. Entries 9 and 10 use the traditional conditions for the Sandmeyer reaction. Entry 11 is a Sandmeyer reaction under in situ diazotization conditions, whereas Entry 12 involves halogen atom transfer from solvent. Entry 13 is an example of formation of an aryl iodide. Entries 14 and 15 are Schiemann reactions. The reaction in Entry 16 was used to introduce a chlorine substituent on vancomycin. Of several procedures investigated, the CuCl-CuCl2 catalysis of chlorine atom transfer form CC14 proved to be the best. The diazonium salt was isolated as the tetrafluoroborate after in situ diazotization. Entries 17 and 18 show procedures for introducing cyano and azido groups, respectively. 

Coupling of 5-aminobenzotriazole 297 with a diazonium salt derived from 4-methoxyaniline generates diazo derivative 298. Conversion of the amino group into maleinimide produces dye 299 (Scheme 45). Diels-Alder cycloadditions of dye 299 to diene tagged nucleotides allows for their efficient labeling <2002CC2100>. 

An alternative approach to developing new reagents for DNA cleavage was founded in the conversion of aryl diazonium salts to aryl halides by the well-known Sandmeyer reaction. The reaction (Eq. 1) is thought to proceed via aryl radicals [7]. These reactions are high yielding and catalytic with respect... 

A secondary reaction yields at the same time phenol ether by the replacement of the diazonium group by alkoxyl. This is clearly analogous to the conversion of diazonium salts to phenols. 

Whilst the conversion of the simple phenyl-syw-diazotate into its isomeride requires strong alkali, the syn-iotms of other diazotates are so labile that, almost instantaneously after formation from the diazonium salts, they change into the anti-iorm and hence can never be obtained in solution. An important example of this change is described under (/), namely, p-nitrophenyldiazotate, which, on coupling with j8-naphthol, yields the much-used dye para-red . 

The profitable conversion of thiouronium salts into dialkyl thioethers (see Section 4.1) is less successful for synthesis of diaryl thioethers. For example, l-chloro-4-nitrobenzene reacts with bis-thiouronium salts of the type (H2N)2CS(CH2) SC(NH2)2+ under soliddiquid and liquidrliquid conditions to produce the desired bis-thioethers, ArS(CH2) SAr, (20-35%), together with the diaryl sulphide, Ar2S (5-15%). Higher yields of the diaryl sulphide are observed under liquiddiquid conditions whereas, under solidiliquid conditions, the diaryl disulphide, (ArS)2, (20%) is also formed [56], Diaryl disulphides are the sole products (>65%) from the stoichiometric reaction of aryl diazonium salts with benzyltriethylammonium tetrathiomolybdate [57],... 

This constitutes a useful method for generating ArC02 , as in the thermolysis of (28) there is a danger of the further decomposition of (29)toAr- -f COj.Cu is also involved in the conversion of diazonium salts, ArN2 Cl , to ArCl + N2 (Sandmeyer reaction), where Ar is very probably formed transiently as an intermediate ... 

Benzenedlazonlum chloride is prepared by the reaction of anUme with nitrous acid at 273-278K. Nitrous acid is produced In the reaction mixture by the reaction of sodium nitrite with hydrochloric acid. The conversion of prlmaiy aromatic amines into diazonium salts is known as diazotisation. Due to its Instability, the diazonium salt Is not generally stored and is used immediately after its preparation. 

The formed mercury dichloride is separated as a crystalline complex with dioxane. Since the starting arylmercury chlorides are easily prepared from diazonium salts, this method allows the conversion of anilines into aryltellurium trichlorides. 

Stannous chloride is used most frequently for the reduction of nitro compounds [177, 178, 179] and of quinones [180, 181], It is also suitable for conversion of imidoyl chlorides [182] and of nitriles [183] to aldehydes, for transformations of diazonium salts to hydrazines [184], for reduction of oximes [f[Pg.30]

Conversion of diazonium salts to hydrazines was achieved by reduction with zinc in acidic medium (yields 85-90%) [59<5], with stannous chloride (yield 70%) [184, and sodium sulfite (yields 70-80%) [253,597]. Nitro groups present in the diazonium salts survive the reduction unharmed [184,253],... 

De Mello et al. [68] have produced several azo-dyes by the conversion of an aromatic amine to a diazonium salt and its reaction with (3-naphtol in a monolithic nanoreactor (Fig. 5). 

Nitration of hydroxypropiophenone (7-1) followed by conversion of the phenol to its methyl ether by means of methyl iodide provides the intermediate (7-2) the nitro group is then reduced to the corresponding amine (7-3) by catalytic reduction. The newly introduced amine is then replaced by a nitrile group by successive conversion to the diazonium salt by means of nitrous acid followed by treatment with cuprous cyanide (7-4). Reaction with aluminum chloride removes the methyl ether to afford the ortho acylphenol (7-5). This is converted to the chromone (7-6) as above by reaction with benzoyl chloride and sodium benzoate. The nitrile is next hydrolyzed to the carboxylic acid (7-7) by means of sulfuric acid. The acid is then converted to its acid chloride by means of thionyl chloride and that treated with 2-(A -piperidyl)ethanol (7-8). There is thus obtained flavoxate (7-9) [8], a muscle relaxant whose name reflects its flavone nucleus. 

Difluorotris(perfluoroalkyl)-25-phosphancs (Rf)3PF2 give stable salts with cesium fluoride, potassium fluoride, sodium fluoride or arenediazonium fluorides, i.e. Cat + [(RF)3PF3] , where Cal+ = Cs +. K+, Na +, ArN2+. The last are difficult to dissolve and they decompose at much lower temperatures (60-90 C) than tetrafluoroborates and hexafluorophosphates. which allows more complete precipitation of diazonium salts from water solutions and their conversion into aryl fluorides 6 without tar formation.6... 

Alkylsulfonyl-5-nitrosamines have an increased stability-range in acidic media and require acids of high concentration (e.g. 80% sulfuric acid) for their conversion into the diazonium salts.86... 

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