1.2.3-triazolic heterocycles: History, preparations, applications and pharmacological activities.

The 1.2.3-triazole, known since the end of 19(th) century, is a very widely used heterocyclic system present in many synthetic substances and commercial pharmaceutical compounds. In fact. 1,2,3-triazoles show several applications in many areas especially as medicines against many diseases like cancer, AIDS. Parkinson and Alzheimer. Nowadays there is a large variety of known methods to obtain these heterocyclic compounds comprising mainly three synthetic routes. Nevertheless, there is no article that lives an objective overview of the synthetic methods for obtaining these kinds of azoheterocycles. This paper presents a brief history of this class of compounds, and a synthetic discussion concerning the main synthetic methods for its preparation, such as cyclization through hydrazones. concerted cycloadditon [2+3] and pseudopericyclic cyclization - and some others of restricted application. but also important. Finally. this paper also provides a brief overview on pharmacological applications of some 1.2.3-triazoles.