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31.1.1.5.2.4 Variation 4: Reaction of Diazonium Hexafluoroantimonates

DOI: 10.1055/sos-SD-031-00002

Sandford, G.Science of Synthesis, (20073163.

Although the BalzSchiemann route, involving decomposition of diazonium tetrafluoroborate salts (see Section 31.1.1.5.2.3), has found widespread use in the synthesis of many fluoroarene derivatives, it has some limitations. If the diazonium salt is soluble in water as a result of the presence of hydroxy or carboxylic acid groups, it is difficult to purify and yields are dramatically reduced, while electron-withdrawing groups, such as nitro groups, significantly impede the decomposition process. Other diazonium salts with different counterions can be synthesized, of which hexafluoroantimonate salts 58 are found to be the most effective alternatives to tetrafluoroborate systems (Scheme 32).[‌153‌] Hexafluoroantimonate salts are readily prepared, highly insoluble in water, and decompose at lower temperatures than the corresponding tetrafluoroborates. Consequently, yields of fluoroarene systems 59 bearing electron-withdrawing groups are increased when diazonium hexafluoroantimonates are used instead of the usual tetrafluoroborate precursors.

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