Pyrazine derivatives show a wide range of biological activities. 1-Pyrazin-2-ylethan-1-ones have served as food flavourants, and together with pyrazine-2-carbonitriles have been widely used as intermediates in the synthesis of various heterocyclic compounds. In our laboratory, substituted pyrazine-2-carbonitriles and 1-pyrazin-2-ylethan-1-ones have been used as intermediates for the preparation of potential antifungal and antimycobacterial drugs. Using established methods, a library of pyrazine derivatives was synthesized. Homolytic alkylation of commercially available pyrazine-2-carbonitrile yielded a series of 5-alkylpyrazine-2-carbonitriles which were converted into the corresponding 1-(5-alkylpyrazin-2-yl)ethan-1-ones (5-alkyl-2-acetylpyrazines) via the Grignard reaction. Homolytic acetylation of pyrazine-2-carbonitrile yielded 5-acetylpyrazine-2-carbonitrile. Using the same procedure, 3-acetyl-5-tert-butylpyrazine-2-carbonitrile was obtained with 5-tert-butylpyrazine-2-carbonitrile as a starting material. The hydrophobicity of the compounds was determined both experimentally (RP-HPLC) and by computation (CS ChemOffice Ultra version 9.0, ACD/LogP version 1.0 and ACD/LogP version 9.04), and both the approaches were compared. New hydrophobicity constants π based on experimental results were derived. These constants are markedly different from tabulated constants π valid for benzene rings, and can be widely used in estimating physicochemical properties of new biologically active pyrazines.
吡嗪衍生物展示了广泛的生物活性。1-吡嗪-2-基乙酮已被用作食品香精,与吡嗪-2-碳腈一起被广泛用作合成各种杂环化合物的中间体。在我们的实验室中,取代吡嗪-2-碳腈和1-吡嗪-2-基乙酮已被用作潜在抗真菌和抗分枝杆菌药物的制备中间体。使用已建立的方法,合成了一系列吡嗪衍生物。商业可得的吡嗪-2-碳腈的自由基烷基化产生了一系列5-烷基吡嗪-2-碳腈,这些化合物通过格氏试剂反应转化为相应的1-(5-烷基吡嗪-2-基)乙酮(5-烷基-2-乙酰吡嗪)。吡嗪-2-碳腈的自由基乙酰化产生了5-乙酰吡嗪-2-碳腈。使用相同的程序,以5-叔丁基吡嗪-2-碳腈为起始物获得了3-乙酰-5-叔丁基吡嗪-2-碳腈。这些化合物的疏水性通过实验(RP-HPLC)和计算(CS ChemOffice Ultra版本9.0,ACD/LogP版本1.0和ACD/LogP版本9.04)确定,并进行了比较。基于实验结果得出了新的疏水性常数π。这些常数与对苯环有效的表格常数π明显不同,可以广泛用于估计新的生物活性吡嗪的物理化学性质。