1.2.3- Triazolo pyrimidines , chemistry

Pyrazol-3-ones. Part III Reactivity of the Ring Substituents Recent Progress in 1,2,4-Triazolo[1,5-a]pyrimidine Chemistry Organometallic Chemistry of Polypyridine Ligands III Subject Index Pages 257-268... 

With the invention of the aceto-hydoxy-add synthesis inhibitors (AHAS) the dominance of herbiddes that ad as photosynthesis inhibitors was dramatically broken - as it was also by the development of genetically modified herbicide tolerant crops. These especially important areas of research and development, from the 1990s up to now, are exemplified in Chapters 3 and 7. The development of 12 new sulfonyl urea herbicides launched since 1995 and the invention of four development compounds of the same chemical class, after the introduction to the market of twenty compounds already between 1980 and 1995, refleds the importance of this biochemical mode of adion for the herbicide market as well as the different chemistries found to be active at this target, such as imidazolinones, triazolo-pyrimidines, pyrimidinyl-carboxylates, and sulfonylaminocarbonyl-triazolinones. 

The formal derivation of the analogs, described in the foregoing, represents, from the point of view of systematic organic chemistry, a shift to the derivatives of other heterocyclic systems. In the case of pyrimidine aza analogs we arc dealing with derivatives of symmetrical or asymmetrical triazine in the case of purine aza analogs, the derivatives produced are those of imidazo[4,5]-i -triazine and z -triazolo [4,5-d] pyrimidine. 

The 8-aza analogs of purine bases were the first to be studied among all the aza analogs of nucleic acid bases (as early as 1945). Before that time the chemistry of these substances had not been treated in detail from any aspect. Thus the entire chemistry of the u-triazolo [4,5-d]pyrimidines was developed only in connection with the study of antimetabolites of nucleic acid components. Therefore all the papers involved are largely of preparative character and only rarely discuss. theoretical points. 

Tlie chemistry of one of the four possible classes of 1,2,4-triazolopyrim-idiiies, namely l,2,4-triazolo[l,5- ]pyrimidines, was reviewed in 1993 by G. Fischer [93AHC(57)81]. In two previous chapters published in this series we reviewed the chemistry of l,2,4-triazolo[4,3- ]pyrimidines [99AHC(73)131] and their [4,3-c] congeners [99AHC(75)243]. In this chapter we survey the fourth and last class of 1,2,4-triazolopyrimidines. Tlie literature has been inspected to issue number 26, Volume 129(1998) of Chemical Abstracts. 

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