Reactions of Arenediazonium Salts

The most useful reaction of amines with nitrous acid is the reaction of aryl-amines to form arenediazonium salts. We consider next how these diazonium salts may be used as synthetic intermediates. 

Predict the products from the reactions of the following amines with sodium nitrite in dilute HCI. (a) cyclohexanamine (b) A/-ethyl-2-hexanamine (c) piperidine (d) aniline 

In contrast to alkanediazonium salts, arenediazonium salts are relatively stable in aqueous 

The following flowchart shows some of the functional groups that can be introduced via arenediazonium salts  

These reactions of diazonium salts are extremely useful for solving aromatic synthesis problems. 

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Aldehydes and ketones are formed in reactions of arenediazonium salts with derivatives of carbonyl compounds, e.g., with oximes (Scheme 10-40, Jolad and Ra-jagopal, 1973) or with diacetyl (Scheme 10-41, Citterio et al., 1982b). In most cases yields are mediocre. Better results are obtained with CO, tetraalkyltin, and Pd(OAc)2 as catalyst (Kikukawa et al., 1987). 

Kochi (1956a, 1956b) and Dickerman et al. (1958, 1959) studied the kinetics of the Meerwein reaction of arenediazonium salts with acrylonitrile, styrene, and other alkenes, based on initial studies on the Sandmeyer reaction. The reactions were found to be first-order in diazonium ion and in cuprous ion. The relative rates of the addition to four alkenes (acrylonitrile, styrene, methyl acrylate, and methyl methacrylate) vary by a factor of only 1.55 (Dickerman et al., 1959). This result indicates that the aryl radical has a low selectivity. The kinetic data are consistent with the mechanism of Schemes 10-52 to 10-56, 10-58 and 10-59. This mechanism was strongly corroborated by Galli s work on the Sandmeyer reaction more than twenty years later (1981-89). 

In this section we first discuss photolytic reactions of arenediazonium salts and report on quinone diazides at the end of the section in the context of imaging technology. Diazoalkenes, non-quinonoid diazo ketones, and the Wolff rearrangement are treated in the book on aliphatic diazo compounds (Zollinger, 1995, Chap. 8). 

Connelly et al. (1979) investigated the reactions of arenediazonium salts with cyclooctatetraene (cot) and some of its transition metal compounds. Free cyclooc-... 

In another paper Zakhardin s group investigated the reaction of arenediazonium salts with carboranes in which one of the CH protons was replaced by copper(i). The... 

Heck reactions of arenediazonium salts can be conveniently carried out with [Pd(OAc)2] in ethanol. This method was extended to the one-pot sequential diazotation and allylation of aniUnes (Scheme 6.7). The latter were converted to the corresponding diazonium salts at 0 °C with NaNOa + 42 % HBF4. Ethyl acrylate and [Pd(OAc)2] were added and the reaction mixture was heated on a water bath for 1 h. The corresponding cinnamate esters were obtained in 65-80 % yield [22],... 

Table 23-4 (continued) Summary of Reactions of Arenediazonium Salts ... 

The reactions of arenediazonium salts with (rans-chlorohydrido-bis(triethylphosphine)platinum(II)1 give aryldiimide complexes which are precursors to new arylazoplatinum compounds2 and... 

Wetzel A, Ehrhardt V, Heinrich MR (2008) Synthesis of amino- and hydroxybiphenyls by radical chain reaction of arenediazonium salts. Angew Chem Int Ed 47 9130-9133... 

Mechanism 19-6 Diazotization of an Amine 910 19-17 Reactions of Arenediazonium Salts 911 Summary Reactions of Amines 915 19-18 Synthesis of Amines by Reductive Amination 918 19-19 Synthesis of Amines by Acylation-Reduction 920... 

REACTIONS OF ARENEDIAZONIUM SALTS WITH TETRATHIAFULVALENE AND RELATED ELECTRON DONORS ... 

REACTIONS OF ARENEDIAZONIUM SALTS WITH TETRATHIAFULVALENE AND RELATED ELECTRON DONORS A STUDY OF "RADICAL-POLAR CROSSOVER" REACTIONS Nadeem Bashir, Balaram Patro, and John A. Murphy... 

Reactions of arenediazonium salts (Section 24.8) (a) Nucleophilic substitutions... 

Reaction of arenediazonium salts with arsenic trichloride gives arylarsonic acids in the presence of cuprous bromide (equation 328). ... 

Although these two reactions are similar to the corresponding reactions of arenediazonium salts, aryl radicals are not involved in the reaction of the lead reagents and these reactions are better explained by a ligand coupling mechanism. 

Such a mechanism was unlikely as addition of an external trap, 1,1-diphenylethylene, had no effect on the course of the arylation of p-ketoesters.i l A second approach involved the use of an internal trapping system which had been successfully used in the study of the radical reactions of arenediazonium salts.The internal trap containing reagent, ( rf/io-allyloxyphenyl)lead triacetate (94), can be easily prepared from the corresponding boronic acid. 2 Reaction with various types of nucleophiles, such as ethyl 2-oxocyclopentanecarboxylate (86), mesitol (36), the sodium salt of nitropropane, iodide and azide always afforded the C-arylation products in high yield. No trace of the 3-substituted dihydrobenzofurans, expected in a mechanism involving the intermediacy of free radicals, could be detected. 

The reaction of arenediazonium salts with 5-methyl- and 5-ethylpyrimidine-4,6-diones (489) gives... 

Addition to Olefins.— The arylation of olefins in the presence of various palladium species is of great interest. A further example is the palladium(o)-catalysed reaction of arenediazonium salts with olefins [equation (13)]. Yields are variable but... 

Sengupta, S. and Bhattacharya, S. (1993) Heck reaction of arenediazonium salts a palladium-catalyzed reaction in an aqueous medium. J. Chem. Soc., Perkin Trans. 1, 1943-4. 

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