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Synthesis of 2H-1,2,3-triazoles


Recent Literature

Triazoles have been synthesized via a three-component coupling reaction of unactivated terminal alkynes, allyl carbonate, and trimethylsiyl azide under Pd(0)-Cu(I) bimetallic catalysis. The deallylation of the resulting allyltriazoles is described.
S. Kamijo, T. Jin, Z. Huo, Y. Yamamoto, J. Am. Chem. Soc., 2003, 125, 7786-7787.

t-BuOK promoted an intermolecular cycloaddition of tosylhydrazones with nitriles to provide 4,5-diaryl-2H-1,2,3-triazoles in very good yields. Homocoupling of the tosylhydrazones was significantly inhibited by using xylene as solvent.
S. Qiu, Y. Chen, X. Song, L. Liu, X. L. Liu, L. Wu, Synlett, 2021, 32, 86-90.

Reaction of 4-bromo-NH-1,2,3-triazoles with alkyl halides in the presence of K2CO3 in DMF produced the corresponding 2-substituted 4-bromo-1,2,3-triazoles in a regioselective process. Subsequent Suzuki cross-coupling reaction provided an efficient synthesis of 2,4,5-trisubstituted triazoles, whereas hydrogenation furnished an efficient synthesis of 2,4-disubstituted triazoles.
X.-j. Wang, K. Sidhu, L. Zhang, S. Campbell, N. Haddad, D. C. Reeves, D. Krishnamurthy, C. H. Senanayake, Org. Lett., 2009, 11, 5460-5493.

A Cu-catalyzed annulation reaction of azirines and aryldiazonium salts provides fully substituted N2-aryl-1,2,3-triazoles. This regiospecific method allows access to a broad spectrum of products substituted with diverse aryl and alkyl moieties.
F.-F. Feng, J.-K. Li, X.-Y. Liu, F.-G. Zhang, C. W. Cheung, J.-A. Ma, J. Org. Chem., 2020, 85, 10872-10883.

A catalyst-free and regioselective N arylation enables the synthesis of N2-aryl-1,2,3-triazoles in very good yields. This scalable postmodification protocol is effective for a wide range of substrates.
S. Roshandel, M. J. Lunn, G. Rasul, D. S. M. Ravinson, S. C. Suri, G. K. S. Prakash, Org. Lett., 2019, 21, 6255-6258.

Phenyl esters of α-azido acids react with trialkylphosphines in THF/H2O to give 5-substituted 2H-1,2,3-triazol-4-ols in very good yields, whereas their reaction with PPh3 provides amino esters as the major product and no triazoles.
S. D. Taylor, C. R. Lohani, Org. Lett., 2016, 18, 4412-4415.

A palladium-catalyzed and ultrasonic promoted Sonogashira coupling/1,3-dipolar cycloaddition of acid chlorides, terminal acetylenes, and sodium azide in one pot enables an efficient synthesis of 4,5-disubstituted-1,2,3-(NH)-triazoles in excellent yields.
J. Li, D. Wang, Y. Zhang, J. Li, B. Chen, Org. Lett., 2009, 11, 3024-3027.

A Cu-mediated annulation reaction of alkyl 3-aminoacrylates with aryldiazonium salts provides alkyl N2-aryl 1,2,3-triazole-carboxylates rapidly under mild conditions. Furthermore, alkyl 2-aminoacrylates are also viable substrates.
H.-N. Liu, H.-Q. Cao, C. W. Cheung, J.-A. Ma, Org. Lett., 2020, 22, 1396-1401.

The reaction of 4,4-dichloro-1,2-diazabuta-1,3-dienes with sodium azide provides extremely rare 1,1-bisazides. These highly unstable compounds are prone to eliminate N2 to cyclize into 4-azido-1,2,3-triazoles bearing two aryl groups at positions 2 and 5. This reaction enables a highly efficient synthesis of various 4-azidotriazoles. These heterocycles are highly attractive building blocks.
A. V. Shastin, B. T. Tsyrenova, P. G. Sergeev, V. A. Roznyatovsky, I. V. Smolyar, V. N. Khrustalev, V. G. Nenajdenko, Org. Lett., 2018, 20, 7803-7806.