Diazonium halides

Careful observations of the course of iodo-de-diazoniation demonstrate that the detailed pathway of such reactions is still relatively complex. For instance, after adding a solution of KI to a solution of an arenediazonium salt, normally molecular iodine appears to be formed first, followed by a precipitate and evolution of N2. Carey and Millar (1960) isolated the salt ArNJIj- on adding iodide to the diazo-nium salt. Ion pairs (ArNjHlg-), suggested as primary products by Meyer et al. (1979), were identified for diazonium halides (Cl- and Br-) by Israel et al. (1983) as 1 1 complexes on the basis of JOB analyses of visible spectra (Benesi-Hildebrand method). Iodides were, however, not included in that investigation. 

Hantzsch (Ref 1) examined some diazonium halides thiocyanates, which were colored expl compds. He suggested that their color expl props are interrelated and are due to the presence of the "azo-isomer in which halogen or thiocyanate is linked directly to N as in Ar.N.(Br,Cl) = Ar.N... 

The nitro group does not undergo migration of the naphthalene ring during the usual nitration procedures. Therefore, mono- and polynitration of naphthalene is similar to low temperature sulfonation, The nitronaphthalenes and some of their physical properties arc listed in fable 2. Many of these compounds are not accessible by direct nitration of naphthalene but are made by indirect methods, e.g nitrite displacement of diazonium halide groups in the presence of a copper catalysts, decarboxylation of nitronaphtbalcnccar-boxylic acids, or deamination of nitronaphthalene amines. They are nsed in the manufacture of chemicals, dye intermediates, and colorants for plastics. 

Conversion of diazonium halides into chloropyrimidines has employed excess chloride ion or copper(I) chloride. These reactions have been mainly used to make 2- and 4-chloropyrimidines although the 5-chloro derivatives are also available in this way. One drawback is the substantial amount of oxo product formed, especially when 2-aminopyrimidines are... 

The reaction of an aryl diazonium halide with an aliphatic unsaturated compound to yield an a-halo-P-phenyl alkene and alkanes. The reaction is performed in the presence of cupric ious. The presence of an electron-withdrawing group is useful in promoting the reactivity of the alkene. See Kochi, J.K., The Meerwein reaction. Catalysis by cuprous chloride, J. Am. Chem. Soc. 11, 5090, 1955 Morales, L.A. and Eberlin, M.N., The gas-phase Meerwein reaction, Chemistry 6, 897-905, 2000 Riter, L.S., Meurer, E.C., Handberg, E.S. et al, lon/molecule reactions performed in a miniature cylindrical ion trap mass spectrometer. Analyst 128, 1112-1118, 2003 Meurer, E.C., Chen, H., Riter, E.S. et al., Meerwein reaction of phosphonium ions with epoxides and thioepoxides in the gas phase, J. Am. Soc. Mass Spectrom. 15, 398 05, 2004 Meurer, E.C. and Eberlin, M.N., The atmospheric pressure Meerwein reaction, J. Mass Spectrom. 41, 470-476, 2006. 

The catalyzed decompositions of the complex (or double) salts of aromatic diazonium halides and Hg(II) halides, ([ArN2] [HgX3] ), yield organomercurials. Either mono- or diorganomercurials can be produced in these free-radical reactions " ... 

Carbon disulfide is a valuable synthon (see Chapter 9, p. 147) which can be used for the synthesis of thiocarbonic acid derivatives. Thus, carbon disulfide reacts with ammonium polysulfide or hydrogen sulfide to give trithiocarbonic acid (70) or symmetrical esters (73) after reaction with an alkyl halide. With alkoxides or thiolates, carbon disulfide forms xanthates (77) or S-alkyl trithiocarbonates the latter by further treatment with alkyl, acyl or diazonium halides affords the derivatives (74)-(76) (Scheme 39). 

Meenvein reaction [1, 166, before references]. The arylation of olefinic com pounds by diazonium halides with copper salt catalysis was discovered by Meerweit (1939).8 Cupric chloride has been usually employed. Cleland,9 however, prefers cuprous bromide (MCB reagent grade) and recommends that the salt (light green) be washed with acetone until the washings are colorless and then with benzene and then with hexane. The resulting solid is dried at 120° and is only faintly colored. He... 

Both dialkyl- and diaryltrihaloantimony compounds are known, although only a few dialkyl compounds have been described. The trichlorides have been obtained by the chlorination of either dialkylchlorostibines (169) or tetraalkyldistibines (170) with sulfuryl chloride. Dimethyltrichloroantimony [7289-79-4], C2H(5Cl3Sb, is dimeric in the solid state but is monomeric in solution (171). The dimer exists in two different forms, covalent and ionic (172). The covalent form contains bridging chlorine atoms the ionic form possesses the structure [(CH3)4Sb] [SbQJ. The diaryl compounds, both symmetrical and unsymmetrical, are best prepared from a diazonium halide and an aryldihalostibine ... 

Reaction of aliphatic amines1160 or amino carboxylic acids1161 with nitrosyl halides (NOX) leads to halides, and not, as in the analogous reaction of aromatic amines, to diazonium halides. 

Side reactions that occur in this process with diazonium halides and nitrates prevent the diazotization being effected in nitric or hydrochloric acid solution it is necessary to do this in sulfuric acid solution, and the sparing solubility of the sulfates of aromatic amines necessitates certain departures from the usual diazotization procedures. 

Brockmann and Dorlars561 converted diazonium halides into phenols in the presence of phosphoric acid. Treating diazonium fluoroborates with glacial acetic acid gives phenol esters, which can be deacylated in the usual way.562 Diazonium trifluoroacetates are relatively stable and can be converted by warming into phenols in good yield.563... 

The reaction involves the preparation of a solution of the diazonium halide and gradually adding it to a solution of the corresponding cuprous halide. In the preparation of compounds that are volatile, it is essential to employ a reflux condenser. In some cases, the diazo solution is prepared in the presence of the cuprous halide. Under such circumstances, a solution of sodium nitrite is added to a heated acid solution of the amine and copper salt. The diazotization and replacement of the diazo group then takes place in one operation. 

The coupling of diazonium halides with suitable halogenated activated methylene groups is an excellent method of synthesis of a variety of acyl and aroyl hydrazidoyl halides. This method has been used by Favrel and by Dieckmann and Platz to synthesize the acetyl derivative (IV). 

The free carboxylic acid VI is obtained from chloromalonic acid and the corresponding diazonium halide... 

Replacement of diazonium groups by halide is a very valuable synthetic alternative to direct halogenation for preparation of aryl halides. There are three broad types of procedures decomposition of aryl diazonium-halide adducts with expulsion of nitrogen, copper-mediated redox processes, and thermal processes proceeding via aryl radicals. The first type of process is probably involved in the reaction of aryl diazonium salts with iodide ion. Smooth high-yield transformation takes place in the absence of any metal catalyst. The mechanism of the reaction... 

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