1.2.3- Triazolo pyrimidines 8-azapurines , chemistry

Albert, A., 4-Amino-1,2,3-triazoles, 40, 129 The Chemistry of 8-Azapurines( 1,2,3-Triazolo[4,5-d]pyrimidines), 39, 117 Annelation of a Pyrimidine Ring to an Existing Ring, 32, 1 Covalent Hydration in Nitrogen Heterocycles, 20, 117. 

In many cases, the literature since CHEC-I of those systems in class (i) has been extensive, mainly because most are related to the purine nucleus by the inclusion of a further heteroatom for example azapurine derivatives which have shown pharmaceutical or physiological action. The methods of synthesis, except in a few cases, have not changed since the publication of CHEC-I and thus more emphasis has been placed on the physical properties, reactivity, and reactivity of substituents of compounds within these systems. In contrast, in most cases very little literature is available for systems of class (ii) and synthesis has assumed paramount importance. Only two reviews since the early 1980s are applicable to this chapter the conversion of [l,2,5]oxadiazolo[3,4- f]pyrimidines (9) to pteridines <82MI 713-01) and the chemistry and physical properties of 1,2,3-triazolo[4,5-djpyrimidines (7) <86AHC(39)l 17>. The incidence of publications relating to the use of Structures (1)-(50) in such applications as pharmaceuticals, agrochemicals, and even explosives has increased since the publication of CHEC-I and these are discussed in Section 7.13.10. 

The name 8-azapurine, much used in chemistry and universally in biology, is short and self-explanatory. The full replacement name 1,2,3,4,6-pentaazaindene sometimes occurs in publications, and some editors prefer the fusion name [1//, 2H, or 3//]-l,2,3-triazolo[4,5-Chemical Abstracts. Some editors replace the 1,2,3 by v. When described as 8-azapurines (as will be done consistently on this review), the structures 2-6 (inclusive) are numbered as shown in 2. When described as triazolopyrimidines, structures 2-6 are numbered as in 7. 

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