Iodine, diazo group replacement with

The diazonium salts usually decompose when warmed with water to give a phenol and nitrogen. When treated with CuCl, CuBr, KI, the diazo group is replaced by chlorine, bromine or iodine respectively (Sandmeyer reaction). A diazonium sulphate and hydroxyl-amine give an azoimide. The diazonium salt of anthranilic acid (2-aminobenzoic acid) decomposes to give benzyne. ... 

It has been demonstrated that the presence of chlorine or bromine in the nucleus facilitates replacement of the diazo group by hydrogen little or no ether formation occurs.26 Apparently iodine also favors the redudng action of alcohols, but this point has not been investigated carefully.26 27 No attempts to deaminate fluorinated amines are recorded. Representative of the effitiency with which ethanol reduces diazonium salts derived from halogenated amines are the deaminations of m-chloroaniline 26 (87% yield), of 2-bromo-4-methylaniline 28 (67% yield), of 2,4,6-tribfomoaniline 29 (ca. 80% yield), and of 2-carboxy-4-iodoaniline30 (ca. 45% yield) in the biphenyl series the deamination of VIII in 53% yield 31 may be dted. 

The diazo group can be replaced with iodine by reaction with potassium iodide ... 

Other group examples are found in those with formaldehyde (p. 73), in diazo coupling (p. 77), in nitration (p. 80), and in the replacement of halogen by hydrogen (p. 75). The last reaction is of considerable interest its importance was first realized s when 2-bromo-4-ethoxycarbonyl-3,5-dimethylpyrrole in acetic acid was found to oxidize iodide to iodine, being converted into 3-ethoxycarbonyl-2,4-dimethylpyrrole very rapidly ... 

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