Sandmeyer type reaction

These major routes to quinoxalmecarbonitriles have been covered already by primary synthesis (Chapter 1), by cyanalysis of halogenoquinoxalines (Section 3.2.5), by deoxidative cyanation of quinoxaline N-oxides (Section 4.6.2.2), by cyanolysis of nitroquinoxalines (Section 6.1.2.2), from primary quinoxalina-mines by a Sandmeyer-type reaction (Section 6.3.2.3), from quaternary ammonio-quinoxalines with cyanide ion (Section 6.3.2.4), and by dehydration of quinoxalinecarboxamides (Section 7.4.2). Those remaining preparative routes that have been used recently are illustrated in the following examples. 

Sandmeyer-type reactions are a useful route to polynitroarylenes with unusual substitution patterns. In these reactions an arylamine is treated with a source of nitrous acid to form an intermediate diazonium salt which is readily displaced on reaction with a suitable nucleophile. Many substituents can be incorporated into the aromatic ring via this method, including the nitro group. 

Halogeno-l,6-naphthyridines have also been made by the Meissenheimer reaction from 1,6-naphthyridine N-oxides and by a (copperless) Sandmeyer-type reaction from 1,6-naphthyridinamines. However, neither route has been developed into a practical preparative procedure, as indicated in the following examples. 

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. 

Substitution by diazonium salts (Sandmeyer-type reaction) ... 

The Sandmeyer-type reaction was used to form the aryl diazonium salt intermediate and followed by cyclization to obtain 1,2,3-benzotriazole. 

There have been many reports of reactions that are broadly classified as Sandmeyer-like, yet they do not strictly belong to this specific category. Several groups have reported that triazines of type 12 can be used to mask the diazo, then allow for direct Sandmeyer-type reaction to form the substituted products The iodination of diazoarenes is commonly... 

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