Reactivity of pyridines bearing EWG with bis-(TMS)ketene acetals. Substituent-induced lactonization reaction
作者:Alejandro Rivera-Hernández、Guillermo M. Chans、Henri Rudler、José G. López Cortés、R. Alfredo Toscano、Cecilio Álvarez-Toledano
DOI:10.1016/j.tet.2014.01.044
日期:2014.3
The nucleophilic addition of bis-(TMS)ketene acetals to pyridines substituted by electron-withdrawing groups, activated with triflic anhydride, leads to their corresponding dihydropyridine carboxylic acids in a first instance. These acids can be efficiently turned into new bicyclic lactones by either of three different methods: first, bicyclic γ-lactones were successfully obtained by an unprecedented
在三氟甲磺酸酐活化下,双-(TMS)乙烯酮缩醛亲核加成到被吸电子基团取代的吡啶上,得到它们相应的二氢吡啶羧酸。这些酸可以通过三种不同的方法有效地转化为新的双环内酯:首先,通过硅胶辅助的前所未有的迈克尔型开环过程成功地获得了双环γ-内酯。第二,通过NBS促进过程获得双环δ-溴内酯。第三,观察到新的羟基γ-螺内酯意外地自发形成。沿着本文介绍的工作,研究了这些内酯化反应的范围,局限性和区域选择性,从而证实了双(TMS)乙烯酮乙缩醛作为1,3-二亲核试剂在此类反应中的应用,