One-pot synthesis of fluorinated 2-amino-pyrimidine-N-oxides. Competing pathways in the four-atom side-chain rearrangements of 1,2,4-oxadiazoles
作者:Silvestre Buscemi、Andrea Pace、Antonio Palumbo Piccionello、Nicolò Vivona、Marcella Pani
DOI:10.1016/j.tet.2005.10.071
日期:2006.2
2-(hydroxyamino)-pyrimidine from the reaction mixture evidenced the presence of a competing pathway where the N(4) nitrogen of the oxadiazole is involved in the formation of a regioisomeric pyrimidinium salt. The effect of the trifluoromethyl group on the product distribution is discussed. By X-ray analysis, the crystal structure of two different N-oxide regioisomers has been unambiguously ascertained
通过使3-氨基-5-甲基-1,2,4-恶二唑与三氟甲基-β-二酮在高氯酸存在下反应,然后水解,合成了三氟甲基化的2-氨基-嘧啶N-氧化物。在这种环到环的转化中,最初形成(单)的1,2,4-恶二唑-嘧啶鎓盐,然后在恶二唑部分开环。从反应混合物中分离出2-(羟氨基)-嘧啶证明存在竞争途径,其中恶二唑的N(4)氮参与区域异构的嘧啶鎓盐的形成。讨论了三氟甲基对产物分布的影响。通过X射线分析,两种不同N的晶体结构已经明确地确定了-氧化物区域异构体。