Synthesis, Reactivity, and Applications of 4-Amino-3-Thioxo/ Hydrazino-6-Substituted-1,2,4-Triazin-5-Ones and Their Derivatives: A Review

Triazine derivatives have attracted increasing attention due to their diverse applications in medicinal chemistry. They have been reported to be remarkably effective compounds regarding their bioactivities. Therefore, the synthesis and identification of new triazine-derived compounds are of interest for their therapeutic effects. Various approaches have been developed to synthesize triazine derivatives. In this review, a considerable number of studies on the synthesis of 1,2,4-triazine derivatives are investigated with 4-amino-3-thioxo-6-substituted-1,2,4-triazin-ones and 4-amino-3-hydrazino-6-substituted-1,2,4-triazin-5-ones as starting materials. Different types of chemical reactions have been applied to the efficient synthesis of 3-thioxo/hydrazino-6-substituted-1,2,4-triazin-5-ones, such as alkylation, acylation, aroylation, elimination, substitution, acidic/basic hydrolysis, oxidation, cyclocondensation, cycloaddition, phosphorylation, and complexation reactions. Interestingly, a set of compounds is identified to possess various biological activities, such as anticancer antibacterial, antifungal, acaricidal, and molluscicidal properties. Also, some 4-amino-3-thioxo-6-substituted-1,2,4-triazin-5-one derivatives are found to form metal complexes, be used as inhibitor probes for mild steel corrosion, prepare a selective sensor for the determination of gadolinium (III) ions in the soil and sediment samples, and demonstrate antibacterial activities. Finally, 4-amino-3-hydrazino-6-methyl-1,2,4-triazin-5-one was used as an ionophore to develop a chromium (III) ion-selective sensor beside the formation of silver complexes.