Triazenes

Triazenes are organic compounds that contain the functional group R¹−N=N−NR²R³, where the R are each any of various types of substituent groups.^[2] Some anti-cancer medications and dyes are triazenes.^[3] Formally, the triazenes are related to the unstable chemical triazene, H₂N−N=NH.

Triazenes are prepared from the N-coupling reaction between diazonium salts and primary or secondary amines.^[4] The coupling reactions are typically mild, using a base such as sodium acetate,^[5] sodium carbonate,^[5] or sodium bicarbonate.^[4]

The diazonium reagents are themselves available starting from amines. For symmetrical triazenes derived from primary amines, partial diazotization gives a mixture of the original amine and its diazo derivative that then couple with each other. For example, 1,3-diphenyltriazene (PhN=N−NHPh) can be made from aniline in a one-pot reaction.^[5][6] For asymmetrical triazenes, for example (phenyldiazenyl)pyrrolidine (PhN=N−NC₄H₈), the diazonium salt must be pre-made.

Analogues of Tröger's base containing a symmetric pair of asymmetric triazene side-chains have been obtained similarly.^[7]

Triazenes derived from primary amines engage in tautomerism. In the case of symmetric triazenes, the tautomers are identical.

Triazenes can be converted to diazonium salts.^[8]

Triazenes decompose in the presence of protonating or alkylating agents into quaternary amines and diazonium salts; as such triazenes have been used as an in situ source of diazonium that reacted with sodium sulfide to give the corresponding thiophenols.^[5] A strategy for the protection and deprotection of sensitive secondary amines is based on this principle.^[9]

Polymeric triazenes are applied as conductive and absorbent materials.^[10] Triazenes have been used in the synthesis of cinnoline, functionalized lactams, and coumarins.^[9][8]