Department of Medicinal Chemistry, Centro Nacional de Investigaciones Oncológicas, Melchor Fernández Almagro 3, 28029 Madrid, Spain.
Magn Reson Chem. 2010 Aug;48(8):614-22. doi: 10.1002/mrc.2634.
The condensation of malonoaldehyde derivatives with either a 3-amino-[1,2,4]-triazole or a 3,5-diamino-[1,2,4]-triazole precursor was studied. In agreement with previous reports, two different bicycles, namely, bearing the regioisomeric [1,2,4]triazolo[1,5-a]pyrimidine (1) or [1,2,4]triazolo[4,3-a]pyrimidine (2) structural surrogates, could be obtained. We found that, depending on the triazole precursor, only one regioisomer resulted, either of the 1 or 2 series. We also observed that these two structural surrogates could be unambiguously differentiated by indirectly measuring their (15)N chemical shifts by (1)H-(15)N HMBC experiments. The occasional conversion of [1,2,4]triazolo[4,3-a]pyrimidines to the [1,2,4]triazolo[1,5-a]pyrimidine counterparts could be unequivocally determined by (15)N NMR data.
研究了丙二醛衍生物与 3-氨基-[1,2,4]-三唑或 3,5-二氨基-[1,2,4]-三唑前体的缩合反应。与先前的报道一致，得到了两种不同的环系，即具有区域异构[1,2,4]三唑并[1,5-a]嘧啶（1）或[1,2,4]三唑并[4,3-a]嘧啶（2）结构类似物。我们发现，根据三唑前体的不同，只能得到 1 系列或 2 系列的一种区域异构体。我们还观察到，通过（1）H-（15）N HMBC 实验间接测量（15）N 化学位移，可以明确区分这两种结构类似物。[1,2,4]三唑并[4,3-a]嘧啶偶尔会转化为[1,2,4]三唑并[1,5-a]嘧啶的对应物，可以通过（15）N NMR 数据来确定。
