Diazonium salts Tiffeneau-Demjanov

The formation of diazonium salts from aromatic primary amines by reaction with nitrous acid undoubtedly involves the intermediate formation of V-nitroso compounds. The Demjanov and Tiffeneau-Demjanov ring expansions also involve V-nitroso compounds [2]. Some V-nitroso compounds have been used as sources of free radicals and as blowing agents. 

Semipinacol rearrangements of diazonium salts derived from 2-amino alcohols are sometimes called TIffeneau-DemJanov rearrangements. 

Variations and improvements on the Demanjov and Tiffeneau-Demjanov reaction have been limited. Variations have come in different methods to generate diazonium salts using various acids containing non-nucleophilic counter ions. The use of weaker acids for the Demanjov rearrangement led to diminished amounts of olefmic by-products. Understanding how facile the reaction was at lower temperature also provided higher yield and fewer byproducts. 

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