Synthesis Of 1,3,5-Trisubstituted 1,2,4-TriazolesUsing α-Bromohydrazones As Intermediates Under Microwave Irradiation

Studying the synthesis of heterocyclic compounds and their biological activities is one of the most spirited items in organic chemistry. The 1,2,4-triazole is fascinating in multitudinous heterocyclic by virtue of their special activity and excellent potential.So far, to the best of our knowledge, there are many reports about the synthesis of 1,2,4-triazole derivatives using different kinds of compounds as key intermediates, but there is no report about using theα-bromohydrazones as intermediates under microwave irradiation. Our study is on the basis of former research work. And we develop a new and convenient procedure for the synthesis of 1,2,4-triazole derivatives.There are two parts in this dissertation.The part of summarize made a complete description of the recent reports about the syntheses of 1,2,4-triazoles.The part of experiments reported the syntheses of 20 kinds of 1,3,5-trisubstituted 1,2,4-triazoles. Our study begined with the condensation of arylhydrazines and aldehydes in benzene for 12 h, the yields were >98%. The resulting hydrazones were allowed react with NBS to finish in yields of >58%. Finally, the cyclization between amines andα-bromohydrazones afforded 1,3,5-trisubstituted 1,2,4-triazoles under microwave irradiation. The yields of 20 compounds ranged from 70% to 92%.All the 20 compounds were identified on the basis of their analytical data, such as mp, IR, 1H NMR, 13C NMR and elementary analysis.The results indicate that the strategy we used has significant advantages, such as common available materials, mild reaction conditions, safety operations and high yields.