Triazenes Explained

thumb|200px|Dacarbazine is a triazene used in the treatment of melanoma and Hodgkin's lymphoma.^[1] 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. Formally, the triazenes are related to the unstable chemical triazene, H₂N−N=NH.

Production

Triazenes are prepared from the N-coupling reaction between diazonium salts and primary or secondary amines.^[3] The coupling reactions are typically mild, using a base such as sodium acetate, sodium carbonate, or sodium bicarbonate.

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.^{[4] [5]} 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.^[6]

Reactions and applications

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.^[7]

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. A strategy for the protection and deprotection of sensitive secondary amines is based on this principle.^[8]

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

Notes and References

1. Web site: Dacarbazine. The American Society of Health-System Pharmacists. 8 December 2016. live. https://web.archive.org/web/20170911072711/https://www.drugs.com/monograph/dacarbazine.html. 11 September 2017.
2. Suleymanov . Abdusalom A. . Severin . Kay . 2021-03-22 . Vinyl and Alkynyl Triazenes: Synthesis, Reactivity, and Applications . Angewandte Chemie International Edition . en . 60 . 13 . 6879–6889 . 10.1002/anie.202011031 . 1433-7851.
3. Synthesis of Symmetrical trans-Stilbenes by a Double Heck Reaction of (Arylazo)amines with Vinyltriethoxysilane: trans-4,4′-Dibromostilbene. Saumitra. Sengupta. Subir K.. Sadhukhan. Organic Syntheses. 2002. 79. 52. 10.15227/orgsyn.079.0052.
4. Kazem-Rostami. M.. Khazaei. A.. Moosavi-Zare. A. R.. Bayat. M.. Saednia. S.. 2012. Novel One-Pot Synthesis of Thiophenols from Related Triazenes under Mild Conditions. Synlett. 23. 13. 1893–1896. 10.1055/s-0032-1316557. 196805424 .
5. Hartman, W. W.; Dickey, J. B.. 1934. Diazoaminobenzene. Organic Syntheses. 14. 24. 10.15227/orgsyn.014.0024.
6. Kazemostami. Masoud. 2017. Facile preparation of Ʌ-shaped building blocks: Hünlich-base derivatization. Synlett. 28. 1641–1645. 10.1055/s-0036-1588180. 99294625.
7. Kimball. D. B.. Haley. M. M.. 2002. Triazenes: A Versatile Tool in Organic Synthesis. Angewandte Chemie International Edition. 41. 18. 3338–51. 10.1002/1521-3773(20020916)41:18<3338::AID-ANIE3338>3.0.CO;2-7. 12298030.
8. Lazny. R.. Poplawski. J.. Köbberling. J.. Enders. D.. Bräse. S.. 1999. Triazenes: A Useful Protecting Strategy for Sensitive Secondary Amines. Synlett. 1999. 8. 1304–1306. 10.1055/s-1999-2803.
9. A.. Khazaei. A.. Zare. A. R.. Moosavi-Zare. M.. Sadeghpour. A.. Afkhami. 2013. Synthesis, characterization, and application of a triazene-based polysulfone as a dye adsorbent. Journal of Applied Polymer Science. 129. 6. 3439–3446. 10.1002/app.39069.