Sandmeyer reaction hydroxylation

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. ... 

In addition to conversion of existing amino groups to other amino groups, the amino groups also can be replaced by halogen or hydroxyl substituents by diazo-tization followed by the Sandmeyer reaction. 

Hanson, P., Jones, J. R., Taylor, A. B., Walton, P. H., Timms, A. W. Sandmeyer reactions. Part 7.1 An investigation into the reduction steps of Sandmeyer hydroxylation and chlorination reactions. J, Chem. Soc., Perkin Trans. 2 2002, 1135-1150. 

The Sandmeyer reaction is not only useful for the preparation of arylbromides. The Boger group used a Sandmeyer reaction to install both a hydroxyl and chloro substituent in their synthesis of the teicoplanin aglycon (29). Diazotization of 25 followed immediately by hydroxylation with cuprous oxide (halide-free/radical conditions) fiimished phenol 26 in excellent yield, even with several sensitive functionalities present in the molecule. Several steps were then required to convert 25 into aniline 27. At this point, a Sandmeyer chlorination proceeded in moderate yield to furnish the aryl chloride 28. This particular reaction is noteworthy, as the reaction proceeded well, in the presence of a variety of functional groups, many of which were unprotected. 

Modification of substituents in purines generally follows patterns which are similar to substituent modification in typicfd aromatic S5rstems. These include interconversion of hydroxyl, thiol, halogeno, amino and similar groups, and Sandmeyer type reactions involving primary amines although isolation of stable diazonium salts is rarely possible. In addition, transformations and reactions of carboxylic acid derivatives follow standard patterns. 

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