Progress in the Synthesis of 1,2,4-Triazines by Tandem Cyclization

1,2,4-Triazine compounds are an important class of nitrogen-containing heterocyclic compounds. They have wide applications in the fields of medicine, chemicals and materials. Therefore, green and highly efficient synthesis of 1,2,4-triazine compounds is increasingly attracting the attention of researchers. By tandem cyclization reaction, the post-treatment of intermediate is avoided, and the one-pot synthesis of triazine compounds is the most efficient and direct synthesis method, which conforms to the concept of green chemistry for its step and atomic economy. The formation of C-N bond based on tandem cyclization to give 1,2,4-triazine compounds is reviewed. The synthetic method, reaction mechanism and application of 1,2,4-triazine compounds are introduced under transition-metal and metal-free conditions in the past ten years. The prospects of synthesis of triazine rings are also discussed.