The comprehensive review contains the analysis of literature data concerning reactions of heterocyclization of aminoazoles and demonstrates the application of these types of transformations in diversity-oriented synthesis. The review is oriented to wide range of chemists working in the field of organic synthesis and both experimental and theoretical studies of nitrogen-containing heterocycles.

The present review includes the analysis of known literature data concerning linear and multicomponent heterocyclizations involving pyruvic acids and aminoazoles. In particular, the review demonstrates the approaches to control regio-and chemoselectivity of these types of treatments and their application to solve the matters of Diversity Oriented Synthesis. ________________________________________________________________________________ IntroductionThe significance of pyruvic acid in our life can be hardly overestimated. It plays a vital role as one of the most reactive substances among those of important in cellular metabolism. That is why a conclusion may be made that reactions involving pyruvic acid may help to solve some health problems and assist in finding a cure against various diseases today and in future. However, in this case no clear relationship between the electronic character of the substituents and structure of the reaction products was established.An interesting approach to the synthesis of quinoxaline derivatives via Ugi-type reaction was proposed as well (Scheme 3) [28]. Thus, the four-component reaction of the starting reagents in MeOH yielded the Ugi adducts, which by means of acid catalysis turned into quinoxalinones. Thus, the behavior of 3-amino-1,2,4-triazole (6) in the three-component condensation with aromatic aldehydes 2 and pyruvic acid (1) turned up to be quite the same to the 5-aminotetrazole (4) reactivity [45]. Refluxing 3-amino-1,2,4-triazole (6) and aromatic aldehydes 2 with pyruvic acid (1) in glacial acetic acid allowed to isolate from the reaction mixtures the pure acids 8 with good yields (Pathway B, Scheme 10). At the same time, heating the starting compounds 1, 2 and 6 in DMF led to mixtures of two regioisomeric dihydrotriazolopyrimidines 8 and 9 (Pathway D, Scheme 10). All attempts to separate these mixtures by crystallization or using HPLC were unsuccessful [45, 53].

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