Synthesis of [1,2,4]triazolo[1,5-a]pyrimidine (microreview)

[1,2,4]Triazolo[1,5-a]pyrimidines are very interesting and trend class of fused heterocycles due to their valuable biological properties. Some [1,2,4]-triazolo[1,5-a]pyrimidines possess herbicidal activity,1 also they can act as antifungal,2 antitubercular,3 and antibacterial4 agents. Polycyclic systems containing [1,2,4]triazolo[1,5-a]-pyrimidine moiety are reported as antitumor,5 as corticotropin-releasing factor 1 receptor antagonists6 or calcium channel modulators;7 they can be used for treatment of Alzheimer's disease8 and insomnia.9 Complexes of triazolo-pyrimidines with Pt and Ru are highly active against parasites10 and can also be used in treating cancer.11

The synthetic ways for the preparation of [1,2,4]triazolo[1,5-a]-pyrimidines can be divided into two main groups: annulation of pyrimidine moiety to triazole ring and annulation of triazole fragment to pyrimidine ring. The Dimroth rearrangement of [1,2,4]triazolo[4,3-a]pyrimidines can also be used for the synthesis of [1,2,4]triazolo[1,5-a]pyrimidines. In this review article we have focused on synthetic approaches for the creation of [1,2,4]triazolo[1,5-a]pyrimidine system.