Triazenes

Triazenes are organic compounds that contain the functional group −N(R)−N=N− (where R is H, alkyl, aryl).[2] Some anti-cancer medications and dyes are triazenes.[3] Formally, triazenes are related to the unstable triazene, H2N−N=NH. The relationship is more theoretical than practical.

Dacarbazine is a triazene used in the treatment of melanoma and Hodgkin's lymphoma.[1]

Production

Triazenes are prepared from the N-coupling reaction between diazonium salts and primary or secondary amines.[4] Symmetrical triazenes, for example 1,3-diphenyltriazene (PhN=N−NHPh), are prepared by the partial diazotization of aromatic primary amines, aniline in this example, and the subsequent coupling reaction in the presence of sodium acetate.[5][6] Asymmetrical triazenes, for example (phenyldiazenyl)pyrrolidine (PhN=N−NC4H8), are prepared from the N-coupling reaction between diazonium salts and secondary amines in presence of sodium carbonate[5] or sodium bicarbonate.[4]

Azo N-coupling

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

Bis-triazene analogue of Tröger's base

Tautomerism
Triazenes derived from primary amines engage in tautomerization.

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

Reactions and applications

An important reaction of triazenes is their conversion to diazonium salts.[2] 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.[8]

Triazenes used in the synthesis of thiophenols

Polymeric triazenes are applied as conductive and absorbent materials.[9] Triazenes have been used in the synthesis of cinnoline, functionalized lactams, and coumarins.[8][2]

References
  1. "Dacarbazine". The American Society of Health-System Pharmacists. Archived from the original on 11 September 2017. Retrieved 8 December 2016.
  2. Kimball, D. B.; Haley, M. M. (2002). "Triazenes: A Versatile Tool in Organic Synthesis". Angewandte Chemie International Edition. 41 (18): 3338–51. doi:10.1002/1521-3773(20020916)41:18<3338::AID-ANIE3338>3.0.CO;2-7. PMID 12298030.
  3. Berneth, Horst (2008). "Methine Dyes and Pigments". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a16_487.pub2.
  4. Sengupta, Saumitra; Sadhukhan, Subir K. (2002). "Synthesis of Symmetrical trans-Stilbenes by a Double Heck Reaction of (Arylazo)amines with Vinyltriethoxysilane: trans-4,4′-Dibromostilbene". Organic Syntheses. 79: 52. doi:10.15227/orgsyn.079.0052.
  5. 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. doi:10.1055/s-0032-1316557. S2CID 196805424.
  6. Hartman, W. W.; Dickey, J. B. (1934). "Diazoaminobenzene". Organic Syntheses. 14: 24. doi:10.15227/orgsyn.014.0024.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  7. Kazemostami, Masoud (2017). "Facile preparation of Ʌ-shaped building blocks: Hünlich-base derivatization". Synlett. 28: 1641–1645. doi:10.1055/s-0036-1588180. S2CID 99294625.
  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. doi:10.1055/s-1999-2803.
  9. Khazaei, A.; Zare, A.; Moosavi-Zare, A. R.; Sadeghpour, M.; Afkhami, A. (2013). "Synthesis, characterization, and application of a triazene-based polysulfone as a dye adsorbent". Journal of Applied Polymer Science. 129 (6): 3439–3446. doi:10.1002/app.39069.
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