Pyrazolopyrimidines are a privileged class of 5-6 bicyclic systems with three or four nitrogen atoms, including four possible isomeric structures. The significance of this class of compounds is that they can be applied in medical and pharmaceutical fields due to their unlimited biological aptitude, hence it is the basic skeleton of several synthetic drugs. The current review aimed to highlight all the synthetic routes that have been applied to construct the pyrazolo[1,5-a]pyrimidine ring systems up to date. The sections in this study included the synthesis of pyrazolo[1,5- a]pyrimidines by condensation reactions of 5-aminopyrazoles with each of β-diketones, 1,5-diketones, β- ketoaldehydes, α-cyanoaldehydes, β-enaminones, enamines, enaminonitriles, ethers, with unsaturated ketones, unsaturated thiones, unsaturated esters, unsaturated dienones "1,2-allenic", unsaturated aldehydes, unsaturated imines, and unsaturated nitriles. The routes adopted to synthesize this class of heterocyclic compounds were extended for ring construction from acyclic reagents and multicomponent reactions under catalytic or catalyst-free conditions.

中文翻译：

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双环 5-6 系统：吡唑并 [1,5-a] 嘧啶环化的综合合成策略。

吡唑并嘧啶是一类具有三个或四个氮原子的 5-6 个双环系统，包括四种可能的异构结构。这类化合物的意义在于，由于其无限的生物适应性，可以应用于医学和制药领域，因此它是几种合成药物的基本骨架。目前的综述旨在强调迄今为止用于构建吡唑并[1,5-a]嘧啶环系统的所有合成路线。本研究中的部分包括通过 5-氨基吡唑与 β-二酮、1,5-二酮、β-酮醛、α-氰醛、β-烯胺酮、烯胺、烯胺腈、醚、不饱和酮、不饱和硫酮、不饱和酯、不饱和二烯酮”