One-pot Syntheses Of 1,3,5-Trisubstituted 1,2,4-Triazoles Derivatives Using Microwave Irradiation

Studying the syntheses of heterocyclic compounds and their biological activities is one of the most spirited items in organic chemistry. With the rapid development of heterocyclic chemistry, people found that several biologically active therapeutics contain five-membered ring heterocycles in their chemical structure. A considerable attention has been devoted to the synthesis of 1,2,4-triazole derivatives which possess a broad spectrum of biological activities such as anti-microbial and antibacterial, antifungal, anti-inflammatory, analgesic, antitumorial, antihypertensive, anticonvulsant, antiviral, antidepressant activities.So far, as we known, there are many reports about the syntheses of 1,2,4-triazole using different kinds of compounds as key intermediates, but there are few reports about the using ofα-nitrohydrazones. We provide a new and convenient strategy for the syntheses of 1,2,4-triazole derivatives.There are two parts in this dissertation.The part of summarization made a complete description of the recent reports about the syntheses of 1,2,4-triazoles.The part of experiments reported the syntheses of 22 kinds of 1,3,5-trisubstituted 1,2,4-triazoles.Our study begins with the condensation of arylhydrazine(p-nitrophenylhydrazine or p-chlorophenylhydrazine) and aldehyde in benzene for 12 h, the yields are >98%. The resulting hydrazones were allowed react with a nitrating mixture to finish the in excellent yields of >85%. Finally, the cyclization between amines andα-nitrohydrazones afforded 1,3,5-trisubstituted 1,2,4-triazoles in one-pot sequential and cascade syntheses under microwave irradiation. The yields of 22 compounds range from 34~92%.All the 22 compounds were identified on the basis of their analytical data, such as 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. What's more, we made a great prompt of the syntheses of 1,2,4-triazole derivatives. We provide a more easy and convenient way of the syntheses of 1,3,5-trisubstituted 1,2,4-triazoles by using microwave irradiation, and we got higher yields.