The development of efficient methods for the synthesis of polyfunctional N-heterocycles is an important area of research in organic and medicinal chemistry. Pyrazolo[1,5- a ]pyrimidine derivatives are purine analogous of biomedical importance and have been extremely studied for their broad spectrum of biological activities. Recently, they have attracted great interest in materials science owing to their photophysical properties. 3(5)-Aminopyrazoles are extensively utilized in the synthesis of condensed heterocyclic systems, particularly pyrazolo[1,5- a ]pyrimidines via the reaction with 1,3-biselectrophilic reagents. However, the information available in the literature provides little in the way of reasoning their cyclization, particularly the initial attack either by the exocyclic amino group or endocyclic nitrogen. Unfortunately, the relative nucleophilicity of exo- and endocyclic nitrogen atoms in 1-unsubstituted 3(5)-aminopyrazoles is not clear and contradicting. It has been found that other factors can modulate the regioselectivity rather than basicity or steric hindrance for both active sites. The reported studies in the structure–activity relationship revealed that pyrazolo[1,5- a ]pyrimidines having a substitution at fifth, sixth, and seventh positions possess potent biological activities, especially those with an amino group at the seventh position. We here developed a regioselective, high yield synthesis of 7-amino-5-arylpyrazolo[1,5- a ]pyrimidine-3,6-dicarbonitriles by the reaction of N -(5-amino-4-cyano-1 H -pyrazole-3-yl)-benzamide with various cinnamonitriles and enaminones in pyridine at 120°C under controlled microwave heating conditions. All structures of newly synthesized compounds were established by analytical and spectral data as well as single-crystal diffraction and rationalized for their formation.

中文翻译：

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5-氨基-3-苯胺基-1H-吡唑-4-甲腈与肉桂腈和烯胺酮反应的区域选择性：功能取代的吡唑并[1,5-a]嘧啶衍生物的合成

开发合成多官能团N-杂环的有效方法是有机和药物化学研究的重要领域。吡唑并[1,5-a]嘧啶衍生物是具有生物医学重要性的嘌呤类似物，并因其广泛的生物活性而受到了极大的研究。最近，由于它们的光物理特性，它们引起了材料科学的极大兴趣。3(5)-氨基吡唑广泛用于通过与 1,3-双亲电子试剂反应合成稠合杂环体系，特别是吡唑并[1,5-a]嘧啶。然而，文献中可用的信息几乎没有提供推理它们环化的方式，特别是环外氨基或环内氮的初始攻击。很遗憾，1-未取代的 3(5)-氨基吡唑中外环和环内氮原子的相对亲核性尚不清楚且相互矛盾。已经发现其他因素可以调节两个活性位点的区域选择性而不是碱度或空间位阻。已报道的构效关系研究表明，吡唑并[1,5-a]嘧啶在第五位、第六位和第七位具有取代基，具有很强的生物活性，尤其是在第七位具有氨基的那些。我们在这里通过 N -(5-amino-4-cyano-1 H-pyrazole) 的反应开发了一种区域选择性、高产率的 7-amino-5-arylpyrazolo[1,5-a]pyrimidine-3,6-dicarbonitriles 合成方法-3-基)-苯甲酰胺与各种肉桂腈和烯胺酮在吡啶中在 120°C 在可控的微波加热条件下。