Add time:10/01/2019         Source:sciencedirect.com

Publisher SummaryThis chapter reviews the chemistry, biological significance, and uses of 1,2,4-triazolo- and tetrazolo-[x,y-zl pyrimidines. The arrangement of each ring follows the order of the site of fusion on the pyrimidine ring, denoted by the letter t, and the site of fusion on the triazole ring, denoted by the letters x and y. The classification of the subdivisions is dependent upon the extent of published work. There are four possible isomeric structures: (1) 1,2,4-triazolo[4,3-a] pyrimidines, (2) 1,2,4-triazolo[4,3-c]pyrimidines, (3) 1,2,4-triazolo[l,5-a] pyrimidine, and (4) 1,2,4-triazolo[1,5-c] pyrimidines. A characteristic feature triazolopyrimidines is the ease of a Dimroth rearrangement. 1,2-Diaminopyrimidines are general precursors, and they can be generated from 1-amino or 2-aminopyrimidines. The synthesis of 1,2,4-triazolo[4,3-a] pyrimidines ring system may be achieved by building the triazole onto a preformed pyrimidine ring. The synthesis from pyrimidines, triazoles, reactivity, physicochemical data, uses, and biological properties of all these rings are discussed in the chapter.

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