Polysubstituted 3-trifluoromethylpyrazoles: regioselective (3 + 2)-cycloaddition of trifluoroacetonitrile imines with enol ethers and functional group transformations
作者:Greta Utecht、Andrzej Fruziński、Marcin Jasiński
DOI:10.1039/c7ob03126b
日期:——
Non-catalysed addition of trifluoroacetonitrile imines to enol ethers provided fully regioselectively (3 + 2)-cycloadducts, which either spontaneously or via Brønsted acid-induced elimination of ROH molecules led to the formation of 3-trifluoromethylated pyrazoles. In the case of 2,3-dihydrofuran, the respective bicyclic intermediate was isolated and its structure was confirmed by X-ray analysis. Using
三氟乙腈亚胺向烯醇醚的非催化加成可提供完全区域选择性的(3 + 2)-环加合物,这种加合物可自发地或通过布朗斯台德酸诱导的ROH分子消除而导致3-三氟甲基化吡唑的形成。在2,3-二氢呋喃的情况下,分离出各自的双环中间体,并通过X射线分析确认其结构。使用开发的方案,以45%的产率进行了已知的抗肿瘤化合物SC-560的合成。随后通过锂化/加成,交叉偶联反应或通过C(5)对选定的4-(ω-羟烷基)吡唑进行官能化 分子内Pd催化的C–H芳基化使人们可以使用多取代的吡唑,包括以7元环(氧杂环丁烷,硫杂环戊烷和氮杂环庚烷)为中心单元的不寻常的三环系统。